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Proceedings Papers

Paper presented at the ISRM International Symposium, November 19–24, 2000

Paper Number: ISRM-IS-2000-327

... grout, soil type, stress history of the soil, stress state,

**boundary**conditions and rate of injection. Because of the complex behaviour of grouting in soils, a conceptual modelling of compensation grouting in clayey soils is necessary. Upstream Oil & Gas specimen grout viscosity grout...
Abstract

ABSTRACT: Compensation grouting is an effective way to reduce surface settlement induced by construction activities in urban areas. However, the long-term behaviour of the compensated area is still not known very well. Grout injection in clayey soils was performed in the laboratory to measure both short and long-term deformation of the clay around the grout and to investigate the fundamental behaviour of the compensation grouting process, which includes hydraulic fracture and cavity expansion mechanisms. The experimental results indicate the growth of a fracture plane in soil in a very fast manner both in normally and overconsolidated clays. Finite element analyses of compensation grouting have been performed to assess its ability to model the complex behaviour of compensation grouting observed in the laboratory. The finite element analyses clearly show that the long-term behaviour of compensation grouting is greatly dependent on the overconsolidation ratio of the clay. The finite element analysis agreed reasonably well with the long-term behaviour of the grouted clay in the experiments INTRODUCTION In recent years, compensation grouting has been applied successfully in many major tunneling projects to limit ground settlement (e.g. Mair, 1994). For example, during tunnel construction projects in Lisbon and for the underground construction of the Jubilee Line Extension Project in London, extensive compensation grouting systems were applied to protect the surface structure around the area influenced by tunneling construction activities (Harris et al, 1996; Schweiger and Falk, 1998). Compensation grouting can involve two different modes; compaction grouting and fracture grouting. The possible factors that affect the occurrence of different modes of behavious are: type of grout, soil type, stress history of the soil, stress state, boundary conditions and rate of injection. Because of the complex behaviour of grouting in soils, a conceptual modelling of compensation grouting in clayey soils is necessary.

Proceedings Papers

Paper presented at the ISRM International Symposium, November 19–24, 2000

Paper Number: ISRM-IS-2000-515

... package. Not only the outflow was permitted through the left-hand side

**boundary**, but also the inflow was permitted across the right-hand side**boundary**. Both were specified as constant head**boundaries**. The surface**boundary**condition was one of constant flux specified so as to represent infiltration or...
Abstract

ABSTRACT: Field and laboratory investigations as well as slope hydrodynamic simulations were carried out to observe the mechanism of landslide at Puncak Area in West Java, Indonesia. Monitoring on water level fluctuations in piezometers were conducted to calibrate the simulation results. It was found that the inducement of landslide was started from the lower part of middle slope. The seepage from upper slope as well as back-up migration of saturation front in response to rainfall played an important role in triggering the slope failure. Indeed, the largest increment of pore water pressure occurred in blue clay under the lower part of middle slope in which the failure surface developed. INTRODUCTION Landslide occurred at Puncak area in West Java, Indonesia (Figure 1) in February 1984 after the heavy rainfall and destroyed a highway section as well as several houses. Such landslide was located at the lower part of Mount Megamendung (Figure 2) and resulted in the translational movement of colluvial deposit (clay - silt layer), and sand layer (Figure Ib). These deposits were underlain by blue clay which was investigated as the failure surface (Sugalang, 1989). Such clay was montmorillonite and interpreted as the lake deposit, originated from tuffaceous sediments (Karnawati 1999). FACTORS ENCOURAGING PUNCAK LANDSLIDE According to field observation as well as the evaluation on geological data and rainfall record, the interaction of rain precipitation, morphology, geology, hydrogeology, and existing landuse conditions were considered as factors encouraging landslide. The landslide occurred on a gentle slope which was only about 15 0 (Figure 5), when the monthly precipitation was high (exceeding 770 mm as illustrated in Figure 3). This gentle slope should be stable, however it was located on the foot of mountains which was surrounded by higher mountainous and hilly morphology (Figure 2).

Proceedings Papers

Paper presented at the ISRM International Symposium, November 19–24, 2000

Paper Number: ISRM-IS-2000-410

... film time-dependent change liquefaction

**boundary**coarse sand deposit Figure 1. Slope in dewatered trench excavated for soil investigation WATER FILM MECHANISM IN SEISMICALLY INDUCED LAND AND SUBMARINE SLIDE Takeji Kokusho1 and Tetsuro Kojima2 ABSTRACT Site investigation in sandy soil sites...
Abstract

ABSTRACT: Site investigation in sandy soil sites demonstrates extensive soil layering in actual sand deposits. One-dimensional liquefaction tests are carried out for several types of layered sand models, which indicates that water films develops beneath impermeable sublayers in layered sand. The mechanism for the water film generation is clarified. Thus the significant effect of water film on land and submarine slides due to seismic liquefaction is demonstrated. INTRODUCTION In past earthquakes, landslides in alluvial sand deposits or lateral flow took place in coastal or river-side areas as in Alaska and Niigata. Submarine slides have also been triggered seismically worldwide. Nom1ally the slope of the sliding surface in those slides is not steep, being much gentler than the intemal friction angle ofthe soil. In land areas, liquefied sand deposits often experienced lateral spread or flow not only during but also after earthquake shaking. The magnitude of flow distance sometimes reached more than several meters even in a very gentle slope ofless than a few percent. In Niigata city, a famous lateral flow occurred in the Meikun High School along the Shinano River where a rather large area of250m by 150m moved towards the river a maximum of 7 meters (Kawakami and Asada 1966). Pictures taken by a high-school student demonstrated that mud water started to come out violently and fissures gradually expanded after the end of shaking. Soil profiles in this area consisted not only of sand but also of sublayers ofsilts or clays (Kishida 1966). In Greece, on the occasion of the 1995 Aegion earthquake, a similar post-earthquake submarine slide involving coastal land with the slope of 12% occurred. The soil profile at the failure site was characterized by a continuous interchange between silty sand and clay layers (Bouckovalas et al. 1999).

Proceedings Papers

Paper presented at the ISRM International Symposium, November 19–24, 2000

Paper Number: ISRM-IS-2000-050

... better with the test result than the prediction result. Upstream Oil & Gas explosion test preexisted stress fluid modeling Engineering computational model test result Reservoir Characterization field explosion test charge chamber

**boundary**equation of state formula jointed rock...
Abstract

ABSTRACT: A field explosion test is conducted to investigate the shock wave propagation in jointed rock masses. The coupled method of UDEC and AUTODYN-2D is applied to predict the rock mass response due to the explosion. Comparing the prediction result with the field explosion test result and empirical formulas, it is evident that the numerical method is capable of modelling explosion problems with high reliability. The prediction result is calibrated by involving the test condition modifications and the dynamic equation of state of the rock. It is shown that the calibration result is in a better agreement with the test result than prediction result, indicating that inputting dynamic parameters is very important to obtain reliable results. INTRODUCTION The software package UDEC has been widely used to model static problems in jointed rock masses (Cundall 1980; Hart and St. John 1986; Fairhurst and Pei 1990; Barton et al. 1994; Shen and Barton 1997). However, only few studies on UDEC modelling of explosion problems have been presented because the explosion load is very difficult to be determined (Lemos 1987; Brady 1990; Rosengren 1993; Senseny and Simons 1994). Chen and Zhao (1998) proposed a coupled method of UDEC and AUTODYN-2D to model the explosion problems, in which the explosion load is provided by the AUTODYN-2D modelling and then applied to the UDEC modelling to simulate the wave propagation in jointed rock masses. In this study, a field explosion test is conducted to investigate the shock wave propagation in jointed rock masses. Comparing the modelling results with the test result and empirical formulas indicates that the numerical method is capable of modelling explosion problems with high reliability, especially at near field, and that the calibration result agrees better with the test result than the prediction result.

Proceedings Papers

Paper presented at the ISRM International Symposium, November 19–24, 2000

Paper Number: ISRM-IS-2000-241

... soils due to lateral spreading. strength clean sand

**boundary**flow potential residual strength void ratio range sandy soil deposit Ishihara relative density SPT blow count steady state line deformation fine content no-flow condition flow deformation FLOW POTENTIAL OF SANDY SOILS...
Abstract

ABSTRACT: The flow deformation or strain softening of saturated sand in undrained shear is discussed in this paper. When evaluating flow of field deposits, the prime issue to be addressed is whether a given soil at its in situ state has a potential to develop flow or not. This paper presents a rational method for such assessment to be made and highlights the effects of grain-size distribution and fines content on the flow potential of sandy soils. On the basis of existing laboratory test results on sandy soils, a flow potential formulation was developed within the framework of the state concept. To facilitate the flow assessment of field deposits, the formulation is also presented in terms of the SPT resistance. It is shown that sands with a large (emax - emin)- value have high flow potential indicating that fines-containing sands are more susceptible to flow than clean sands. INTRODUCTION Undrained behaviour of sandy soils under monotonic shearing can generally be characterized by three types of response, as outlined in Figure 1. Very loose sand shows fully contractive behaviour where following the peak stress the sand strain softens until the steady state is reached at large strains. This strainsoftening phase of the response resembles a flow-type behaviour and therefore it is commonly referred to as flow or flow deformation. If the density of the sand is somewhat higher, then the strain softening is followed by strain hardening in which the sand recovers its strength and restores stability. In this case, the flow takes place over a limited range from the peak stress to the point of phase transformation where dilative behaviour is initiated. During earthquakes, flow-type behaviour may be triggered by seismic forces resulting in flow slides or movement of large masses of soils due to lateral spreading.

Proceedings Papers

Paper presented at the ISRM International Symposium, November 19–24, 2000

Paper Number: ISRM-IS-2000-254

... spectral characteristics of microtremor and earthquake ground motion were examined, comparing with theoretical characteristics of Rayleigh wave and S wave. Fig.2 shows a test site ground condition. At this site, soft surface soil layers are exists until upper

**boundary**of engineering bedrock appears at the...
Abstract

ABSTRACT: In order to estimate characteristics of ground motion and underground structure, spectral ratios between horizontal and vertical component (H/V spectrum) based on the microtremor records is used. First, properties of H/V spectrum for microtremor and strong ground motion are examined at the site where the underground structure had been clarified. As a result, it is confirmed that H/V spectrum for microtremor represents the amplitude ratio between horizontal and vertical motion of Rayleigh wave including higher modes. Based on it, we investigate relationship between the shape of H/V spectrum for microtremor and underground structure in Nagoya City. The depth of earthquake and engineering bedrock are also estimated from the predominant periods of H/V spectrum for microtremor. INTRODUCTION Among various kinds of geological exploration using microtremor records, the H/V spectrum is especially noticed recently. The H/V spectrum only requires observation at one point, which is much easier than the array observation for the F-K spectrum and the SPAC method. However, the meaning of the H/V spectrum with its theoretical background is not sufficiently clear. In this paper, on the basis of microtremor observation at over 300 sites in Nobi plain and Nagoya municipal area, the potential effectiveness of the H/V spectrum for the investigation of deep and shallow soil structure is discussed. The meaning of the H/V spectrum is also examined theoretically. MICROTREMOR OBSERVATION Fig. 1 shows a map of microtremor observation sites in Nagoya City, which includes 341 sites. Moving coil type 3-dimensional velocity sensors with 5second natural period are used. 23 minutes record was obtained at each site, using 14 – 16 bit AD converter with 100Hz sampling and low-pass filter (fc=10Hz). By selecting suitable eight parts of 163.84seconds from the observed record, Fourier spectra for 3 components are calculated with ensemble averaging.

Proceedings Papers

Paper presented at the ISRM International Symposium, September 10–12, 1990

Paper Number: ISRM-IS-1990-037

... Reservoir Characterization reservoir simulation

**boundary**element model metals & mining Upstream Oil & Gas fundamental solution**boundary**condition**boundary**displacement reservoir geomechanics element method time step Artificial Intelligence displacement excavation equation...
Abstract

ABSTRACT: This paper describes an application of a numerical technique for computing the dynamic displacements and stresses induced by mining in an assumed infinite, homogeneous, isotropic, linearly-elastic rock mass. A two-dimensional direct boundary integral method is used as the basis for the numerical model, which determines the solution in a two-stage process. In the first stage, the static state of stress around the existing excavation in the region of interest is found by using a computer model for elastostatics. Then, in the second stage, an elastodynamics computer model is used to remove the appropriate "initial" stresses from the locations of the newly excavated boundary to create the required traction-free boundary condition for the enlarged excavation. By superimposing the static and dynamic solutions, one can compute the displacements and stresses at any location in the rock mass, at any time. An example is given to demonstrate the efficacy of the numerical model and to illustrate the dynamic effects that can occur when an underground excavation is enlarged by blasting. INTRODUCTION Many important practical problems in rock mechanics and mining engineering involve dynamic phenomena. For example, the response of an underground excavation Subjected to transient loading caused by an explosion, a rockburst, or an earthquake cannot be quantified without Considering dynamic effects. In mining, blasting is the most frequently used means to extract ore from the host rock and to excavate shafts and stopes. The stress waves generated by blasting will reflect from these openings and refract around them, creating a potential for spalling of the supporting walls. In addition, these dynamic events may cause separation or slip along pre-existing geologic discontinuities within the mined area. This paper is concerned with the development and application of a boundary element method for two-dimensional elastodynamics problems. For linear elastodynamics problems in the absence of body forces, this method requires only a surface discretization of the region of interest. Thus the spatial dimension of the problem is reduced by one as compared With "domain-type" techniques (e.g., the finite element method) which require a discretization of the interior as well as the boundary. For problems involving an infinite domain, the boundary element method automatically satisfies the correct boundary conditions at infinity, thus eliminating the need for special transmitting boundaries to avoid spurious reflections at the extremities of a finite domain model. In this study two boundary element methods are combined to simulate numerically the dynamics of mining. First, a static method is used to compute the stress field surrounding an initially excavated stope. A dynamic method (Crouch and Tian 1988) is then used to simulate the dynamic process of blasting by applying dynamic incremental tractions to the newly excavated boundary in a suitable fashion which eventually satisfies the traction-free boundary condition. Finally, the sum of the static and incremental dynamic results gives the total elastodynamic response at any spatial location and time during the entire process. GOVERNING EQUATIONS Let V denote the volume occupied by a homogeneous

Proceedings Papers

Paper presented at the ISRM International Symposium, August 30–September 2, 1989

Paper Number: ISRM-IS-1989-158

... not frequently analysed, that one part of the rock decay, the rock dis- integration is proceeded through the gra- dual decrease of cohesive energy on the grain

**boundaries**until the complete dis- integration. The bonding properties of the solid rocks are representing a very narrow layer of the size of...
Abstract

ABSTRACT: For rock behaviour and rock genesis the energetic surrounding may be of first importance; the energy-content characterizing strength and durability is in close dependency on it. The paper deals with the energetic conditions of the rock-forming elements, following an established petrophysical rock model and with the energetic evolution of each genetic rock family. RESUMÉ: L'entourage energetique est de premiere importance pour le comportement et le genèse des roches; la teneur en energie, caracterisant la resistance mecanique et la durabilite des roches suive ses changements. Le rapport s'occupe des conditions energetiques des elements, composants des roches, selon un modèle petrophysique, specialement construit et de l'evolution energetique des familles genetiques de petrographie. 1. INTRODUCTION The properties of rocks, as heterogeneous and following the sophisticated rules of petrology compound bodies depend in a hierarchic manner on properties and changes of different rock-forming elements. Analysis of these rock-forming elements has been often effectueted in the applied petrophysics and rock mechanics, but the interdepences were generally not deeply treated. Therefore for an overview and interpretation of the correlations, the rock-forming elements have been summarized in a so called rock model (Galos-Kertesz, 1983., Galos et al. 1988.) It is to establish from this rock model (Table 1.) that the rock forming elements are from different sizes and they may be both, spatial and superficial. We can state too, that the behaviour of each spatial model-element is composed from the behaviour of a spatial model-element of smaller size and of a -- often negligible -- superficial element. This rock model gives the basis of the further discussion and is appropriate for a correct overview of be behaviour, as well as of the genetic and changing conditions of rocks. Rocks are formed through geologic processes, they change later through natural and artificial processes: for all these processes the thermodynamic laws are effective (too), whose most important characteristic is the strive for equilibrium. The equilibrium means in this case also the homogeneous distribution of the intensive thermodynamic quantities (f.i. energy-density) in the examined system (e.g. in spatial element of the Earth's crust). The processes are in the same way processes of energy- -equalization. The direction of the natural geologic processes is determined by the direction of the diminution of the inhomogeneity. The so observable interaction is a geologic one in the manner, that the succeeding (e.g. structural, crystallographical) physical states are one after the other more probable (perfect) than the previous one, until as long as the equilibrium is not established or the energy-conditions are not disturbed through a new energy-source. These processes are generally spontaneously carried out until obtaining the entropy-maximum, in some cases instable states may also conserved with an only local maximum in entropy; the spontaneous process is this way interrupted and may be only continued after an activation. All geologic matters -- f.i. minerals, rocks -- are situated in an intermediate or final (equilibrium) state, the artificial effects may be superimposed on them, therefore it seems to be opportune to discuss their energy-conditions. 2. ELEMENTS OF THE ROCK MODEL AND THEIR ENERGY-CONDITIONS The properties of the continuous rock blocks are determined by the elements of the rock model, that means by the rock-forming consituents and the joints between them; in the discontinuous rock bodies the elements of the discontinuity-system may playa technically important role too. Among this, less clear and accepted in the science are characteristics and role of the joints (bonds). Fracture mechanics deals detailed with fissures and discontinuities, but less usual is the analysis of the energy-reducing effect of discontinuity-systems in rock masses.

Proceedings Papers

Paper presented at the ISRM International Symposium, August 30–September 2, 1989

Paper Number: ISRM-IS-1989-167

...) au external or overburden stress Ri Initial radius (excavated tunnel) Rc Radius of tunnel after convergence Rb

**Boundary**between intact and broken coal ub Displacement of this**boundary**ab Radial stress on this**boundary**Rr, Rrr Dimensions of injected area. ar, arr Radial stress on Rr and Rrr· 3. The...
Abstract

Abstract: At the coal-mine of "Les Houilleres de Blanzy", France, extraction galleries are constructed at a depth of approximately 700 m, entirely in coal of very poor mechanical properties. To understand the problem of the severe convergence that occurs in these galleries a mathematical simulation is made, using a simplified shape (cylindrical tunnel) of the underground opening. The material model is described as follows: Linear elasticity up to a linear Mohr-Coulomb failure criterion. After reaching the Mohr-Coulomb criterion the material fails with a sudden volume increase. The broken material then behaves following soil-mechanics with no further volume change. The given mathematical simulation is an exact solution of the above problem. The thus calculated deformations are in good agreement with the convergence observed underground. The presence of a large zone of broken material around the gallery is verified by in situ observations and measurements. Therefore, it can be concluded that the simplifications made are acceptable. It is obvious that man-made measures are necessary to avoid or limit the problems related to the strong convergence. Some experiments carried out are described shortly. As a preparation to an underground experiment, the possibility of injecting the broken coal with resin is analyzed. A circular area around a gallery could be injected. A material model is described for injected coal (Mohr-Coulomb envelope with a small cohesion) and again an exact solution is found for the stress distribution and deformations. Calculations show that only a small improvement of the material property, by means of injection, already gives a strong stabilizing effect on the galleries. It remains to be seen if this is applicable in practice. 1. Introduction The underground coalmine of "Les Houilleres de Blanzy" is located in the coal basin of Blanzy, between Rozelay and Montceau les Mines. This formation belongs to the north-east section of the Massif Central, France. The Blanzy formation is generally folded in the north-east/south- west direction. The basin is a depression of 100 Km long, 10 Km wide with a minimum depth of 1500 m, see fig. 1. The coal found in this region belongs to the upper carbon period. The coal was subjected to tectonic movements and metamorphism at low pressures and high temperature. The result of this geological history is that coal seams occur of thicknesses up to 40 m which are of very poor mechanical properties. The production method used in this mine (a special retreating longwall caving method) requires that extraction galleries are constructed entirely in the coalseam and are maintained until the face has passed. During this period (0.5–2 years) strong convergence occurs in the galleries and up to five reopenings are required. In the past, several attempts are made to avoid or reduce the problems related to this strong convergence. See [1] and [2]. Extremely strong arches were constructed and coal was extracted from between those arches to limit the pressure on them. In principle this method worked but it was much to laborious.

Proceedings Papers

Paper presented at the ISRM International Symposium, August 30–September 2, 1989

Paper Number: ISRM-IS-1989-108

... occurred, the pore pressure is nearly constant due to the higher diffusivity. At the

**boundary**of the failed or disturbed zone, pressure causes flow of condensed water into the virgin reservoir. The magnitude and timing of the pressure responses at observation wells can be used to estimate the size of the...
Abstract

ABSTRACT: Initial heating of heavy oil reservoirs by steam injection requires high pressures which disturb the matrix. This disturbance creates regions of enhanced porosity and permeability which can impact the subsequent conformance of heat distribution and bitumen depletion. Pressure observations at injection wells and offset wells during first cycle steam injection have been made at Cold Lake. Injection can occur at pressures less than the minimum in situ stress and when this happens tensile parting cannot be the dominant failure mode. Instead, shear failure of the uncemented sands, coupled with the resulting dilatant behaviour, can account for the observed injection behaviour. Extreme asymmetry and anisotropy characterize the shape of the failure zone. Disturbed zones in the reservoir initiated from horizontal fractures have aspect ratios as extreme as 1:10 and have typically propagated to distances exceeding the well spacing after injection of a fraction of the scheduled steam. They are two to three times as extensive on the up-dip side of the well as on the down-dip side. By the end of injection only a small fraction of the water equivalent steam volume injected has leaked outside the pore volume of the disturbed zone in the reservoir. 1 INTRODUCTION The process of bitumen recovery which has been commercialized at Cold Lake is Cyclic Steam Stimulation (Mainland et al, 1983, Rodgers, 1987, Vittoratos et aI, 1988). In each well, steam injection is alternated with bitumen and water production for as many cycles as economic conditions permit. Steam is injected into the reservoir to provide sufficient temperature to reduce the bitumen viscosity and allow its flow to the well. Observations of heat distribution in the reservoir have shown it to be complex (Vittoratos, 1986), but knowledge of it is critical to predicting performance of the recovery process. For all cycles except the first, there is already in place a heated portion of the reservoir with significantly more mobile fluids than in the unheated reservoir. The evolution of the distribution of heat in cycles after the first will be determined by this existing zone of mobile pore fluids. In particular, the horizontal extent of the heated reservoir, the areal conformance, is strongly influenced by the template formed by steam injection during first cycle. At Cold Lake, Esso Resources Canada Limited drills directional wells clustered on a central surface location called a pad to minimize surface disruption. Steam injection into a single well prior to the operation of any other wells was performed. This represented a unique opportunity to study the nature of the controls on the distribution of steam during injection. Stress determinations were used to characterize the initial stress state in the reservoir. High-rate water injection tests were conducted on a number of wells to assess the behaviour of the reservoir material in response to injection without the complexity of the thermal responses due to steam injection. Offsetting wells were used to observe pressures in the reservoir due to steaming a single well.

Proceedings Papers

Paper presented at the ISRM International Symposium, August 30–September 2, 1989

Paper Number: ISRM-IS-1989-057

... Mech stiffness aperture experiment

**boundary**Witherspoon permeability tensor Rock at Great Depth, Maury & Fourmaintraux (eds), © 1989 Balkema, Rotterdam. ISBN 90 61919754 Permeability of rock masses at great depth Permeabilite des massifs rocheux a grande profondeur Durchlassigkeit des Gebirges...
Abstract

Abstract: Rock masses, which commonly contain a large number of discontinuities like joints, are treated as homogeneous, anisotropic porous media. The corresponding permeability tensor k, is formulated in terms of a symmetric, second-ran k tensor pij, which is dependent not only on the geometry of related joints (density, size, orientation and aperture of joints) but also on the earth pressure at any depth. Two case studies are carried out; that is, the ventilation drift at Stripa Mine, Sweden, and the underground cavern for an oil storage at Kikuma Test Plant, Japan, where the large scale hydraulic conductivity tests have been done together with the extensive survey of joints. It becomes clear that a statistical interpretation on the joint data collected from an in-situ rock mass provides a powerful tool to determine the permeability tensor. The mean permeabilities of the both sites accord well with the theoretically predicted ones. On the basis of this study, the permeability at great depth is considered. 1 INTRODUCTION In the recent topics of rock hydraulics, much attention is focused on ground water flow through various geological discontinuities to solve some problems concerning the geothermal energy, earthquake and deep underground burial of high level nuclear waste. For example, the repository of high level nuclear waste will be buried about 300 m to 1000 m below the surface in rock masses (e.g. Runchal and Maini, 1980). One of the most serious problems to be solved is the isolation of the high level nuclear waste form the biosphere. Ground water flow through geological discontinuities (called cracks) is believed to be the most significant way of radionuclide migration. Field tests can be a practical solution to overcome the present difficulty. Large scale hydraulic conductivity tests were carried out to investigate the hydraulic properties of a low-permeable, jointed granue, for example, at Stripa mine in Sweden (Wilson, Witherspoon, Long, Galbraith, Dubois and Mcpherson,]983) and at Kikuma in Japan (Hoshino, 1983 and 1984). In addition to such field tests, many theoretical (or numerical) studies were also done to give a sound basis for predicting the overall permeability of rock masses; e.g., Parsons (1966), Snow (1969), Wilson and Witherspoon (1974), Long, Remer, Wilson and Witherspoon (1982), and Robinson (]984). Among others, Oda, Hatsuyama and Ohnishi (1987) have also proposed a theory in which discontinuous rock masses are treated as homogeneous, anisotropic porous media. By extending the previous study, we will propose a set of equations which make it possible to predict the permeability of jointed rock masses at great depth. 2 HYDRAULIC PROPERTIES OF DISCONTINUOUS ROCK MASSES 2.1 Permeability tensor In order to formulate a permeability tensor for discontinuous rock masses, the following idealization was accepted (Oda, et al., 1987): Any crack has a shape similar to a penny, with a diameter r and a uniform aperture t, whose orientation is identified by a unit vector n normal to the principal plane. Her, r, t and n are random variables.

Proceedings Papers

Paper presented at the ISRM International Symposium, August 30–September 2, 1989

Paper Number: ISRM-IS-1989-073

...

**boundary**dyke equation of state calculation coefficient nonreversible shear strain gradual shear failure reservoir geomechanics displacement great depth korotkov gradual failure Reservoir Characterization explosion porosity application tensile stress brittle parameter Rock at GreatDeplh...
Abstract

ABSTRACT: At great depth stresses are approximately equal to the strength of rock. That is why failure develops near such underground excavations. But this failure may not be entire because its value depends not only from stresses but also depends from strains. On the basis of experiments on compression specimens of rocks in rigid presses, particular on decreasing the cohesion with increasing the strains it was formulated the model of gradual shear failure of rocks. Models with constant parameters in the Coulomb formule for the cohesion do not reflect the real decreasing of cohesion and lead to diminish displacements of rock near underground openings. On other case models with instant decreasing the cohesion leads to essential greater displacements because unjustified diminish the cohesion in calculations. It was revealed when the model has been used to one-dimensional static problem of compression rock with circular hole. Also it has been calculated the dynamic problem of burst in rock. Another application of the model has been made to two-dimensional problem about influence the gradual failure of rock into geological break or dyke, which appear near underground opening on formation dangerous vertical tensile stresses. THE MODEL OF GRADUAL SHEAR FAILURE OF ROCKS Rocks contains many strucktural defects, holes and cracks. If stresses change through the distance much larger than the interval between structural defects, then such rocks may be regarded as a continuous medium. The main effect of structural defects and cracks consists in two main phenomena: in decreasing of a cohesion and in increasing of a crack porosity. These two phenomenon a develop simultaneously but gradually while the nonreversible shear strains increases. It follows from numerous experiments of Karman (1911),Byerlee (1968),Stavrogin and Protosenya (1985) and others, and have been used in developed by author the model of gradual shear failure of rocks (Korotkov (1980,1987,1989)).. The model consists of several main equations. In the beginning of failure of rocks there are some strengthening during small increasing of nonrevercible shear strains; it defines as prefailure. Further increasing of nonlinear shear strains causes the intensive decreasing of shear strength. This region defines as post failure. These effects may he described by the loading surface depending from nonreversible shear strains also pressure and temperature. The value of YP calculated only in the region of failure where pressure is not too high, usually less then 10 kbar, because at more high pressure the rock deforms without loss of compressive strength. The full volume is divided in two parts. It consists reversible part of solid framework and nonreversible volume of crack porosity. For the framework the equation of state was accepted with the consideration of effective value of pressure. Earlier theories used only one-term for description of nonreversible porosity, such as Rudnicki and Rise (1975) included only one term for description of dilatancy in rock. Other theories for granular material also used one term for description the dependence porosity from pressure. The model of gradual shear failure used more general description with including both mentioned terms.

Proceedings Papers

Paper presented at the ISRM International Symposium, August 30–September 2, 1989

Paper Number: ISRM-IS-1989-070

... region equation

**boundary**Strength Criterion tunnel Rock at Greatoepth, Maury & Fourmaintraux (eds), © 1989 Balkema, Rotterdam. ISBN 90 61919754 Effects of non-linearity and strength reduction of rocks on tunnel movements Effets de la non-linearite et de la perte de resistance des roches sur les...
Abstract

ABSTRACT: A theoretical method to calculate ground stresses, strains and displacements around a circular tunnel under initially hydrostatic in situ stress field is newly presented. In the analysis, peak and residual strength criteria for rocks are proposed, and new boundary conditions between the peak and the residual strength regions are introduced in order to satisfy experimental results on failure strains and failure stresses. The influence of a non-linearity of stress-strain relationships, brittle-stress reduction, internal pressure and post-peak dilatancy on movements of the tunnel is analytically investigated. 1 INTRODUCTION Stresses and displacements in a rock surrounding a tunnel are fundamentally important in planning the tunnel and support systems, and which depend on stress-strain relationships, ground failure criteria, initial stresses of the ground and executive conditions. There are many literatures for calculation of ground response, most of which give closed form solutions to problems with hydrostatic initial stresses and circular geometry but some use numerical approaches such as a finite element method (FEM), a boundary element method (BEM) and a coupling method of FEM and REM, to solve problems involving more complex two or three dimensional tunnel geometry and stress fields[l-5]. Generally, stress-strain relationships for a rock show non-linearity, and mechanical parameters involved in the stress-strain relationships are affected by confining pressure. Also, under a high initial stress state, the strength of the rock surrounding the tunnel decreases from its peak strength to residual one and volumetric change in residual strength region gives big influence on tunnel displacements and support system. Experimental results show that the rock failure criterion can be expressed by stresses but there is a unique relation on failure strains. Yoshinaka and Yamabe[6] showed that the failure of rocks occurs nearly at the same strain regardless confining pressure. The failure condition of a rock surrounding a tunnel should satisfy the both experimental results on failure stresses and failure strains. If a linear stress-strain relationship in the peak strength region is used in the tunnel analysis, the residual strength region is determined only by using stress conditions at the boundary between the peak and the residual regions. In other words, the failure strains at this boundary is automatically determined from the stress conditions, and which do not coincide with experimental failure strains. Namely in this linear analysis, there is no way to satisfy the both conditions on failure stresses and failure strains. In order to make tunnel movements clear by taking into account the realistically mechanical behavior mentioned above and to contribute to practical tunnel engineering, this paper presents solutions to a simple axisymmetric tunnel problem. The influence of the non-linear stress-strain relationships, non-linear criteria, brittle stress reduction, internal pressure on tunnel movements is investigated. 2 ROCK MASS MODEL 2.1 Stress-Strain Behavior The hyperbolic stress-strain equation was proposed by Kondner[7] to model the stress-strain curves of soils subjected to axial deformation. In this analysis, a generalized hyperbolic stress-strain relationship in octahedral space is employed until the stress reaches to the peak strength.

Proceedings Papers

Paper presented at the ISRM International Symposium, August 30–September 2, 1989

Paper Number: ISRM-IS-1989-072

... Upstream Oil & Gas Griffith criterion initiation structural geology microcrack failure zone Computation

**boundary**rock specimen propagation fracture surface tunnel Reservoir Characterization strength mechanism stress state rock mass fracture brittle fracture rockburst Rock at Great...
Abstract

ABSTRACT: This paper describes the rockburst phenomena around circular tunnels excavated in limestone formation; analyses the failure mechanism of surrounding rock of the tunnel caused by rockburst, the stress condition leading to rockburst and the relation between rockburst intensity and stress state; indicates the possibility of predicting the occurrence and intensity of rockbursts using FEM on the basis of the above analysis and gives an engineering case. 1 INTRODUCTION The Tianshengqiao two stage hydropower station is situated in the lower reaches of the Nanpanjiang River at the juncture of Guizhou and Guangxi provinces in the Southwest of China. It has a low dam, long headrace tunnels and an installed capacity of 1.32 million kilowatts. The three tunnels are straight, each has a length of 10 km, and run parallel to one another in the river bend area on the right bank (Fig. 1). The tunnels are excavated by TBM and drilling-and-blasting method. Three construction adits are excavated among which the adit no. 2 is located at the transitional part of Nila anticline and Zhongshanbao syncline with its axis subparallel to the fold and has a length of about 1.3 km. The adit no. 2 and a part of the tunnel in limestone formation upstream from it are constructed by TBM while the others by drilling-and- blasting method. The adit no. 2 constructed by TBM is circular in cross section and 10m in diameter, just like the tunnels. The average buried depth is about 400m, with a maximum of 760m. The tunnel line runs through an area of limestone and dolomitic limestone in the upper reaches of Yachagou Brook (Fig. 2). The compressive strength of limestones ranges from 60 to 100 MPa. This segment of tunnel line is about 7 km long and is rockburst prone. In the lower reaches of Yachagou Brook, the formation consists of sandy shale which is fractured and no rockburst occurred there. The main geological structure is the Nila anticline with its trend turning from NWW to NE in this area. Palaeotectonic stress field in this area is perpendicular to the anticline axis while the present one acts in NW-SE direction. In the valley area of Nila anticline and the edit no. 2, geostresses are measured at the points shown in Fig.l. 2 ROCKBURST PHENOMENA OBSERVED IN-SITU Rockburst occurred first at the roof and floor of edit no. 2 at a buried depth of about 200–250m, and then in the major tunnel in limestone many times. In edit no. 2, the extent and depth of failure in the surrounding rock and burst intensity increase with increasing buried depth of the edit. The observed data show that the initial stress in rock mass is not necessarily the gravitational stress field. Therefore, the dip angle of principal stress in the rock mass in edit no. 2 can be inferred from the location of surrounding rock failure caused by rcckburst. Moreover, it is known that the rockburst intensity is related to the magnitude of stress.

Proceedings Papers

Paper presented at the ISRM International Symposium, September 12–16, 1988

Paper Number: ISRM-IS-1988-008

... method is suggested for estimating the stress-strain state of rock foundations weakened by periodic systems of parallel oblique joints. The method is bas ed on the analytical solution of the relevant

**boundary**problem of the elasticity theory. Different types of rock foundation models are considered. A...
Abstract

ABSTRACT: A method is suggested for estimating the stress-strain state of rock foundations weakened by periodic systems of parallel oblique joints. The method is bas ed on the analytical solution of the relevant boundary problem of the elasticity theory. Different types of rock foundation models are considered. A procedure is developed for determining pliability and crack resistance of rock foundations and stress intensity factors at the joint tips. Rock foundations of hydraulic structures constitute rock masses which, in their natural condition, comprise a number of discontinuities in the form of joints or various geomechanical defects. Rock jointing can be of different nature but in many cases rock masses are found to be heavily weakened by systems of parallel or nearly parallel joints (Goodman, 1987). Construction of large dams on rock foundations, excavation of large underground cavities and driving high-pressure tunnels suggest an ever increasing employment of strength and deformation properties of the rocks (Sapegin et e. l, 1972). Optimum utilization of rock mechanical pro- Perties, provision for safety and stability. of the structures to be built, their cost-effectiveness are impossible without comprehensive studies on strength and deformability of rock masses. The object of this paper is to develop a method for calculating the stress-strain state of a rock mass weakened by a peri- odic system of Oblique joints and for finding stress intensity factors at the joint tips. The paper considers a possible model of jointed rock masses, i.e. an elastic range weakened by a system of parallel oblique joints. The calculation procedure described below is based on the analytical solution obtained by Sapegin et al. (1987). The latter is the solution of a mixed elasticity theory problem for the elastic isotropic plane XY with Poisson's ratio v and shear modulus G weakened by a periodic system of semi-infinite parallel tight joints. The joint tips fallon the same straight line, the joints being inclined to the line at an angle of x 0 < x≤ π The adjacent joints are spaced at a distance of 2 (Figure 1) (Figure in full paper) Thus, as distinguished from the continu- ous foundation, the jointed foundation features horizontal pliability from vertical loads and vertical pliability from horizontal loads. The combined use of the elasticity theory boundary problem solutions for the Plane with the foregoing periodic system of joints at periodic load and the analytical solution of a similar boundary problem received by Kamysheva & Nuller (1979) for non-periodic load has made it possible to consider the following models of jointed rock foundations: (Equation in full paper) is considerably lower than, which enables us to employ the solutions of the periodic and non-periodic problems on deformation of an elastic plane weakened by a periodic system of oblique semi-infinite joints. Applied to the upper boundary of the foundation is the distributed load б y = − q, q > O. 1.1. Let us assume that the strips are resting on the non-deformable foundation. In this case normal displacements of the strip faces are taken to be equal to zero.

Proceedings Papers

Paper presented at the ISRM International Symposium, September 12–16, 1988

Paper Number: ISRM-IS-1988-066

... Region. The problem is thus much more simple in the transformed field, since the

**boundaryes**there are all rectangular, and the computation in the transformed field thus is 536 regardless physical ofon a square grid the shape of the**boundaries**. Several transformed region configurationsmay be obtained rut...
Abstract

ABSTRACT: A code for numerical generation of boundary-fitted curvilinear coordinate systems on fields containing any number of arbitrary two dimensional bodies have been developed. Both algebraic generation systems and partial differential equations procedures have been used. For this paper many grids for several situations with differents purpose are generated and the best grid configuration is interactively obtained. 1 INTRODUCION A numerically-generated grid is understood here to be the organized set of points formed by the intersections Of the lines of a boundary- Conforming curvilinear coordinate system. The procedure for the generation of curvilinear coordinate systems used here is the numerical solution of partial elliptic differential equation. Those of poisson and/or laplace. An algebric interpolation has been used to provide the first approximation to the numerical solution of the partial differential equation. In the section which follows. the conception of the curvilinear coordinate system and the grid generation system are discussed. The next two sections discover about the equations of the generation system and the implementation procedure. Finally. a sample solution showing some of the implemented program's facilities is presented. The extension of the program capabilitiescan be seen else where. 2 BASIC CONCEPTS Here the generation of the curvilinear coordinate system may be treated as follows: With the curvilinear coordinates specified on the boundaries. e.g., ~ (x.y) and T) (x.y).on the boundary B and A (this specification amounting to a constant value for either ~ or T) on each segment of B and A, with a specified monotonic variation of the other coordinate over the segment), generate the values, ~(x,y) and n(x,y), in the field bounded by Band A. This is thus a boundary value problem on the physical field with the curvilinear coordinate (s,n) as the dependent variables and the cartesian coordinates (x.y) as the independent variables, with boundary conditions specified on curved Figure 1: Physical Region. The problem may be simplified for computation, however, by first transforming so that the physical cartesian coordinates (x,y) become the dependent variables, with the curvilinear coordinates (s, n) as the independent variables. Since a constant value of one curvilinear coordinate, with monotonic variation 'of the other, has been specified on each boundary segment, it follows that these boundary segments in the physical field will correspond to vertical or horizontal lines in the transformed field. Also, since the range of variation of the curvilinear coordinate varying along a boundary segment has been made the same over opposing segments, it follows that the transformed field will be composed of retangular blocks. The boundary value problem in the transformed field then involves generating the values of the physacal.cartesian coordinates x (s, n) and y (E;" n), in the transformed field from the specified boundary values of x I["n) and y ([" n) on the retangular boundary of the transformed field, the boundary being formed of segments of constant S or n, i.e vertical or horizontal lines. Within = constant on a boundary segment, and the increments in S taken to be uniformly unity, this boundary value specification is implemented numerically by distributing the points as desired along the boundary segment and then assigning the values of the cartesian coordinates of each successive point as boundary values at the equally spaced boundary points on the botton (or top) of the transformed field.

Proceedings Papers

Paper presented at the ISRM International Symposium, September 12–16, 1988

Paper Number: ISRM-IS-1988-042

... of several to a dozen meters. When the tunnel is full of water, the high pressure water unavoidably fill in these open fissures. As a new kind of load they act on the

**boundary**of such fissures which may cause further stretching and so called hydro-splitting may happen. 2.1 The modelling of the...
Abstract

ABSTRACT: Use of unlined pressure tunnels can save materials, accelerate construction procedure and lower cost of hydropower project. Several of this kind have been employed in Norway, U.S.A. and UK •• The design criteria varies from one to another, which are all based on the assumption that rock is homogeneous and linear elastic body. But the stratified or jointed rock is often encounted in practical cases. BEN have been applied in modelling the hydraulic splitting of stratified or jointed rock with which we draw the tunnel layout curves under different water levels in stratified or jointed rock for two slopes. Our conclusions are that the steeper the river slope is, the more serious the influence of joints parallel to the river bank on the curves; and that, the Norwegian FEM charts, after proper modification, can also be used in the above cases. Finally, some suggestions have been proposed for the design and construction of the unlined pressure tunnels in stratified or jointed rock masses. INTRODUCTION: Construction cost will be greatly reduced if the steel lining section of the pressure inclined shaft in water convey system of hydropower station is ommited. Now, steel penstocks in pressure inclined shafts are adopted in almost all the underground power stations in China. China is planning to construct about 100 hydropower stations before the year 2000, the installed capacity of which totals 1.1 billion kw, among them 42% are underground. 1£ unlined pressure tunnels are used, construction cost thus reduced will be ennormous, and naturally benefits the development of the hydropower in China. Many unlined pressure tunnels have been constructed in Norway, U.S.A., and UK., most of which are successful. But some problems arose, such as Byrte Station, Askara Station, Bjerka station in Norway, etc. It's obvious from the failures of this examples that: Design criterion of unlined pressure tunnel is a basic criterion; the layout of unlined pressure tunnels must first Satisfy the demands of the FEM chart. The present criteria are all based on the assumption that rock mass is homogeous and linear elastic body without Considering the influence of the structure of stratification or joints of rock. Many researchers are engaged in the study of influence of stratification and joints of rock on unlined pressure tunnels. Ming Lu calculated the capacity of jointed rock to resist the internal water pressure by studying the cross sections of the tunnels. But few researchers studied logitudinal section along the tunnel as the Norwegian did in FEM charts, surly that they did not take into account the case with high pressure water filling in joints and stratification plane. CALCULATION OF CRITICAL WATER LEVEL OF STRATIFIED AND J0INTED ROCK WITH BEM: The capacity of the unlined pressure tunnels in jointed rock to endure the internal water pressure are mainly influenced by the following factors: Mechanical properties of rock; The extents and orientations and dip of joints and fissures; The normal stresses on the structure planes.

Proceedings Papers

Paper presented at the ISRM International Symposium, August 31–September 3, 1986

Paper Number: ISRM-IS-1986-053

..., intragranular cracks and cracks along grain

**boundaries**. Rock have been subjected to a series of complex processes as rock-genesis, metamorphosis, tectonics, sedimentation and erosion. The process of rock genesis was accomplished under various complex diffusional and shear transformations with changes of volume...
Abstract

SUMMARY: This report presents a theoretical analysis of rockbursts. Cracks, internal stresses, heterogeinity and anisotropy are fundamental features of rocks and coals. The influences of high stress concentrations, internal stresses, the conversion of potential to seismic energy, the multiple reflections of seismic waves and the local magnification of the energy and dynamic stresses are fundamental factors in the mechanism of rockbursts. An analysis of catastrophic rockbursts and some suggestions for their prevention and mitigation is presented. RÉSÚMÉ: Ce report présente un analyse theorétique des "rockbursts". Les fissures, contraints internes, Ie heterogeneité et l''anisotropie sont des traits fundament aux des roches et charbons. L''influence des contraints concentrés, contraints internes, la conversion de L''energie potential en energie sismique, les reflections multiples des ondes sismiques et la magnification locale de L''energy et des contraints dynamiques sont des facteurs fundamentaux dans Ie mechanism des "rockbursts". L''auteur presénte un analyse des "rockbursts" catastrophiques et quelques suggestions pour leur contróle. ZUSAMMENFASSUNG: Diese Verhandlung bietet eine theoretishe Analyse der Gebirgschläge. Die Risze, eingefrorene Spannungen, Heterogenität und Anisotropie, sind Hauftkenmerke der Fels und Kohlen massen. Der Einflusz der hohen Spannungs-Koncentrationen, interne Spannungen, die Umverwandlung von potentia Ie Energie zu dynamische Energie, die vielfache Reflexionen von seismische Wellen und die lokale Vergröszerung der dynamische Energie und Spannungen sind Hauptfaktoren in das Mechanismus der Gebirgschläge. Der Schreiber gibt eine Analyse der Katastrophale Gebirgschlägen und bietet einige Vor- Schläge für Ihre Verhütung und Abschwächung. 1. INTRODUCTION In China the excavation of mines, underground constructions is rapidly increasing in order to meet the big progress in industrialisation. With the ever increasing scale of mining and the deepening of mines the danger of rockbursts becomes progressively more pressing. The Chinese engineers have much experience in dealing with rockbursts, and have studied eagerly from their foreign colleagues; but as the problem is very intricate we have not yet found an efficient way to treat rockbursts. Rockbursts are known already since 1900 in the Witwatersrand (Salamon 1983) and the Kolar Gold Fields (Krishna Murti 1983). The percentage of total fatalities due to rockbursts in South Africa from 1926–1975 was increasing and in the ten years from 1926–1975 rockbursts amounted to 55.7% of the total fatalities. In severe cases the mining induced seismic events can damage underground excavations, costly surface structures, haulage roadways, pumping stations etc. On the basis of his study of Chinese and foreign experiences the author is of opinion that three fundamental factorsin addition to stress concentrations, stress strain relations mode of fracturing etc-which are neglected, must be studied carefully; locked in stresses and conversion of potential strain energy to seismic energy the Multiple reflections of seismic waves which can lead to local energy and stress magnification. Although experience is very valuable the need is pressing to study this complicated problem from more basic theories. This report is a first modest attempt to study it on the basis of rheology and dynamic fracture theory. 2. MICRO ANALYSIS OF ROCKS AND COALS In order to get an insight into the mechanism of rock and coal bursts we now present a prelude on the microstructure of rocks and coals. Rocks are complicated materials from any aspect. They are composed of grains of various sizes, shapes and mineral compositions, which are firmly welded together, the grains having different physico chemical and mechanical properties. Generally micro flaws can be easily detected as intergranular cracks extending over many grains, intragranular cracks and cracks along grain boundaries. Rock have been subjected to a series of complex processes as rock-genesis, metamorphosis, tectonics, sedimentation and erosion. The process of rock genesis was accomplished under various complex diffusional and shear transformations with changes of volume and shear. Due to the different anisotropic thermal and mechanical properties of the crystals this rock genesis resulted in a non homogeneous stress distribution which is frozen or locked in within the material. Furthermore, misfits of atoms in semi-coherent interfaces readily occured, leading to the creation of born in dislocations within the grains and grain boundaries. ''The motion of these dislocations along sliding surfaces could account for a partial relaxation of the intragranular and intergranular stresses. Metamorphosis lead to further recrystallisation and phase transformation and heterogeneous straining. In general the grains will not undergo a general strain in comformity with the applied stress and imposed constraints from the neighbouring grains. Thus incompatible straining occured which resulted in the cleavage of grainboundaries and splitting of individual grains,thus the creation of cracks and voids. In Coal which are known to be brittle, cracks were created during the tectonic history. In this way a part of the concentrated stresses was released, however a part of these stresses is retained in the form of locked in stresses. Hence born in dislocations, cracks, locked in stresses, inhomogeneity anisotropy are fundamental features inherent to rocks arid coals.

Proceedings Papers

Paper presented at the ISRM International Symposium, May 26–28, 1982

Paper Number: ISRM-IS-1982-059

... strength calculation

**boundary**plastic zone Upstream Oil & Gas criterion lining excavation reservoir geomechanics volumetric strain water pressure shaft Rock Mech Reservoir Characterization displacement rock mass tunnel Ladanyi circumferential determination pressure shaft...
Abstract

SUMMARY: A major factor hindering the detailed application of the method of characteristic lines in underground excavation design is the difficulty of determining realistic rock mass properties and allowing for them in the calculations. A new method of making rock-support interaction calculations for plane strain, axi-symmetric pressure shaft and tunnel problems is presented. This method uses non-linear peak and residual rock mass strength criteria, allows for strain-softening and the development of plastic volumetric strains, calculates the distribution of groundwater pressures by allowing the permeability of the fractured rock mass in the plastic zone to vary with the square of the volumetric strain, and evaluates the influence of water pressure subsequently applied inside the lined excavation. ZUSAMMENFASSUNG: Ein Hauptfaktor der die ausfuerliche Anwendung der Methode der charakteristischen Linien im Untertage Ausgrabung Entwurf verhindert, ist die Schwierigkeit die reele Felsmasse Elgenschaften zu bestimmen und in die Berechnung zu beruecksichtigen. Eine neue Methode die die Fels-Unterstutzung Aufeinanderwirkung fuer ebenen Zwang axialsymmetrische Druckschachte-und Trunnelprobleme berechnet ist dargestellt. Diese Methode wendet nicht- lineare Bruch-und Restfestigkeit Felsmasse Kriteria an, beruecksichtigt den Festigkeits a b fall und die Entwicklung von plastischen Volumetrischen Formanderungen, berechnet die Verteilung des Grundwasserdrucks bei ermöglichen die Durchlassigkeit der gebrochenen Felsenmasse in die plastische Zone mit dem Quadrat der Volumetrischen Formanderung zu verandern und den Einfluss des nachtraglich an der Innenseite der verschalenen Ausgrabung aufgelegenen Wasserdrucks abzuschatzen. RESUME: La utilisation de toutes les possibilitees de la methode des characteristiques est empechee par des difficultes au niveau pratique presentees par la determination de la loi de comportement global du massif fissure, et par des difficultes au niveau mathematique de tenir compte de ce comportement lors du calcul, On presente ici une nouvelle methode d''analyse de l''interactillnentre une structure de soutenement et le massif, pour le cas de contraintes planes tel qu''un tunnel, et pour le cas axisymmetrique d''un puit. Cette methode permet l''utilisation des criteres non-lineaires de resistance maximale et residuelle, et elle permet de tenir en compte les phenomenes de l''anti-ecrouissage et de l' evolution de la dilatation plastique. La variation de la pression d''eau souterraine se calcule a partir de l''hypothese qu''a l''interieur de la zone plastique, le permeabilite des roches fissurees est proportionelle à la deformation volumetrique au carre, et on tlent compte lors du calcul de l''influence de la pression interne sur Ie paroi de la cavite souterraine. INTRODUCTION The development of stresses and displacements in the rock surrounding tunnels and shafts and in the lining or support elements has long been studied using ground support interaction analyses. The use of what is known as the method of characteristic lines or the convergence-confinement method produces ground-support interaction diagrams which show the inter-relationships between the rock mass properties, the in-situ stresses, the type and stiffness of the lining or support and the timing of its installation. The general principles elucidated by this approach are now widely understood and applied in practice, particularly in conjunction with field measurements as in the New Austrian Tunnelling Method (Rabcewicz, 1964). Despite these advances in general under st.anoi.ng, the basic concept s of ground-support interaction have not, as yet, been incorporated into a widely applied method of making pre-excavation design calculations. This can be attributed, in the main, to two major factors: the difficulty of adequately predetermining the range of rock mass properties required for use in such calculations; and The analytical and computational difficulties associated with solving other than axi-symmetric problems taking into account realistic rock mass properties which generally involve non-linearities and strain-softening post-peak behaviour. This paper considers the models of rock mass behaviour that have been previously used in rock-support interaction calculations, and proposes a new model of the relevant rock mass properties. The application of this model is illustrated through the solution of an axi-symmetric pressure shaft problem in which the distribution of water pressures throughout the problem domain is taken into account.

Proceedings Papers

Paper presented at the ISRM International Symposium, May 26–28, 1982

Paper Number: ISRM-IS-1982-134

... tunnel or a compressed air surge chamber among others. The idealized geometry of the cavern and the distance to a

**boundary**equipotential, which may be the groundwater table, determines the value of a geometry factor appearing in the flow rate formulas. One formula applies to water flow in completely...
Abstract

SUMMARY: Straightforward approximate formulas are presented for the estimation of flow rates of air (gas) and water (incompressible liquid) from a cavern in a permeable mass; the cavern acting as a source or a sink. The mass may be soil or fractured rock and the cavern may be a drill "vole, a tunnel or a compressed air surge chamber among others. The idealized geometry of the cavern and the distance to a boundary equipotential, which may be the groundwater table, determines the value of a geometry factor appearing in the flow rate formulas. One formula applies to water flow in completely water saturated media and a slightly different formula to air flow in dry media. Special emphasize is given to the application of the formulas in questions regarding design of unlined compressed air surge chambers in jointed rock. ZUSAMMENFASSUNG: Vereinfachte, approximative Formeln sind fuer die Bestimmung der Stömungsgeschwingigkeit von Luft (Gas) and Wasser (unzusammendrueckbarer Fluessigkeit) aus einer Kaverne in durchlassiger Materie prasentiert, wo die Kaverne als eine Quelle oder Senke fungiert. Die Materie könnte Erde oder klueftiger Fels sein, and die Kaverne könnte ein Bohrloch, ein Tunnel oder ein geschlossenes Wasserschloss das mit Druckluftpolster arbeitet sein, u.a. Der in den Strömungsformeln auftretende Geometriefaktor wird durch die ideale Geometrie der Kaverne and durch den Abstand von einem Randàquipotential (z.B. dem Grundwasserspiegel) bestimmt. Die eine Formel ist fuer die Wasserströmung in wassergesattigten Böden anwendbar, and eine àhnliche Formel fuer die Luftstrimung in trockenen Baden. Besondere Betonung wird our die Anwendung der Formeln in den Fragen der Konstruktion unausgekleideter geschlossener Wasserschlösser mit Druckluftpolstern in zerklueftetem Fels gelegt. RESUME: Des formules approximatives et directes pour estimer les vitesses d''ecoulement de l''air (gaz) et de l''eau (liquide incompressible) à partir d''une caverne dans une masse permeable sont presentees; la caverne agissant comme source ou comme drain. La masse peut être un sol ou un roc fracture et la caverne peut être un trou de fourage, un tunnel ou une chambre d''equilibre a air comprime entre autres. La geometrie idealisee de la caverne et la distance à une equipotentielle limite, qui peut être la nappe d''eau souterraine, determine la valeur d''un facteur de geometrie apparaissant dans les formules de vitesse d''ecoulement. Une première formule s''applique à l''ecoulement de l''eau dans un medium complètement sature d''eau et une autre formule, legèrement differente, à l''ecoulement de l''air dans un medium sec. Un accent special est mis sur l''utilisation des formules en question pour le calcul des chambres d''equilibre à air comprime sans recouvrement interieur dans un roc comprenant des joints. Fig. 2. Geometry in an idealized flow problem(figure in the paper). INTRODUCTION The planning of closed air surge chambers in Norway in the early seventies called for methods to predict air loss from caverns located in fractured rock. The work undertaken by the- present authors (1973) was directed towards the development of appropriate formulas for estimating rock mass permeability from borehole tests(Lugeon tests) and measurements of water flow into tunnels and caverns. Furthermore to develop formulas for estimating water and air flow from a cavern knowing the effective permeability of the rock mass. Fig. 1(Figure in the paper). Closed air surge chamber in a fractured rock mass (not in scale). Fig. 1 shows the typical problem; an air surge chamber partially filled with compressed air. Under air pressure higher than, or even slightly below the original water pressure at the chamber location, compressed air will migrate into the rock joints intersecting the chamber. The air loss must be compensated for by compressors. One crucial question is the compressor capacity needed. The analysis of flow problems in fractured rock is difficult for several reasons. The flow taking place in hard rock suitable for the location of air surge chambers is exclusively limited to fissures and joints. The spacing, distribution and openings of such are likely to be most irregular. Considering even a single joint parallel plate theory may not be correct as the flow may take place in channels. In the theory to be presented the medium in which flow takes place is considered homogenous. Thus the theory itself is not developed particularly for flow problems in fissured rock. The flow equations to be presented applies to soils and other permeable media as well. In the present paper emphasize is, however, given to the application of the flow equations to inhomogenous rock. The combined flow of air and water (two fluid system) is hard to analyse. Much easier is the analysis of water (liquid) flow in a completely water saturated porous medium and the analysis of air (gas) flow in a dry porous medium. When able to handle the latter problem at least an upper limit of the air flow in a mixed air-water flow problem is given. The theory to be presented is limited to single fluid flow, but some emphasis is given to the application of the results to the mixed flow problem of an air surge chamber.