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Proceedings Papers

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

Paper Number: ISRM-IS-2000-322

... of patented concrete constructions . The results of model tests (method of equivalent material) and

**computer**calculations (Finite Element Method 2D, Limit Equilibrium Method 3D), confirm high efficiency of proposed approach. INTRODUCTION Due to wide use of reinforced soil technology in recent...
Abstract

ABSTRACT: The paper discusses the possibility of using the principles of bionics for designing reinforced earth embankments. Practical usage and novelty of proposed approach are shown on the example of number of patented concrete constructions. The results of model tests (method of equivalent material) and computer calculations (Finite Element Method – 2D, Limit Equilibrium Method – 3D), confirm high efficiency of proposed approach. INTRODUCTION Due to wide use of reinforced soil technology in recent years the problem established of effective methods for optimization of the structures and reduction of cost of construction has become real. PRINCIPLE OF EQUALITY IN STRENGTH Stressed-strained state (SSS) of the embankment is characterized by high irregularity both in longitudinal and transversal directions. In this state the strength properties of the materials in different parts of the embankment are used to various degrees. In this case the principle of equality in strength requires to select materials (soil and reinforcement) in such a way that their spatial arrangement should provide uniform SSS and should allow full use of their strength. In general, the solution of this problem is associated with many difficulties and it should be divided into several stages. Improvement of equality of strength as far as the height of the embankment is concerned (plain task, cross section) In order to work out the recommendations as far as rational distribution of reinforcement along the height of the embankment is concerned we have carried out three series of computations using "ARMDAM" program (finite element method, plain deformed state, written by the authors). In the first series of computations the criteria of evaluation of reinforcement efficacy were determined. For this purpose the height position of one layer of reinforcement has been changed and the embankment SSS has been analysed.

Proceedings Papers

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

Paper Number: ISRM-IS-1989-135

... stress borehole diameter length change matrix Rock Deformation inverse problem initial stress field formula contour algorithm field measurement parallel borehole rock mass equation length change

**Computation**Poisson initial stress Rock at Great Depth, Maury& Fourmaintraux (eds), © 1989...
Abstract

ABSTRACT: The paper suggests an algorithm for determining characteristics of the initial stress field in an intact rock mass based on the interpretation of field measurements of cross-section diameter length changes of a circular borehole (or opening). When designing underground structures constituting with the surrounding rock mass a single deformable system the results obtained are essentially influenced by the characteristics of the initial stress field in the intact rock which are used as input - the principal stress value N1, the ratio of the principal stresses Λ= N2/N1 and the slope of the main axes of the initial stresses to the vertical and horizontal lines. These characteristics determine to a considerable degree the qualitative character of distribution of normal and tangential contact stresses (loads) along the perimeter of the support cross-section and therefore stresses and forces in the support sections. If, given the rock sale weight, the slope of the main axes γ = 0, the vertical principal initial stress N1 = H (- rock weight per unit volume, H - excavation depth), and rock lateral pressure coefficient can be approximately derived from the Academician A.N. Dinnik's formula λ = V o/(1-V), where Vo - Poisson's ratio of or the rock, then to design a support in a rock mass subjected to the action of tectonic forces the above characteristics should be determined from field measurements. One of the measuring procedures in current use is the method of parallel boreholes consisting in measuring changes in the lengths of the diameters of the cross-section of a circular unsupported borehole (opening) when excavating a parallel one near it, which causes additional displacements of the surface points. In order to interprete the results of the measurements performed by the method of parallel boreholes the authors use the solution of the plane problem of the elasticity theory for a medium weakened by two unequal circular holes (Fig. 1) and having the initial stresses б x(o), б y(o), τ(o). The problem is stated as an inverse one and consists in determining, from the known changes in diameter length of one of the holes caused by the presence of another hole the initial stresses б x(o), б y(o), τ(o) as well as the principal initial stresses N1, N2 and the slope of the greater principal stress to the line of the centres. If one of the principal stresses (N1 or N2) is known (e.g. N1 = H), the above solution can be used to determine the rock deformation modulus E o. In the primal problem the basic formulas for determining displacements of the points of the borehole cross-section contour are derived by D.I. Sherman's method using the theory of analytical functions of complex variable and the apparatus of complex series. In treating the inverse problem the increments of the diameter length changes caused by the influence of the second hole, i.e. the differences Δ d = Δ d2- Δ d1 are used as initial data rather than the changes themselves (Δd2).

Proceedings Papers

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

Paper Number: ISRM-IS-1989-072

... order to predict rockbursts, the cross- section marked as 6+550 which was excavated by the TUM is selected and anal- ysed

**computationally**. From the buried depth of this section and ()v=oH, it is obtained that O"v=12.1L1MPA. It has already been known from back analysis that a'H =1.1-1.7 a'v. In...
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-1988-032

... models and design proce- dures for linings are realized as

**computer**programs enabling one to perform multivariant designs of un- derground structures. Reliability of the mathematical models and design procedures for li- nings is ensured both by qualitative and quantitative correspondence of the design...
Abstract

ABSTRACT The paper deals with mathematical modelling of interaction of hydraulic tunnel linings with the surrounding rock mass with different kinds of static loads and earthquake seismic effects, as well as design methods for linings regarded as elements of a single deformable "liningrock" unit subject to loads and other effects. INTRODUCTION The principle of interaction treating the rock mass and the lining as elements of a single deformable "lining- rock" unit sensitive to all external loads and actions is assumed as a basis for mathematical models and design procedures for linings of underground structures. According to the above principle the design scheme (physical problem statement) for an underground structure (hydraulic tunnel) is a pattern of contact lining-rock interaction. The scheme can serve as a basis for a mathematical model of an underground structure (analytical solution) or for a numerical experiment (using the finite element method). The scheme of lining-rock interaction can be also realized in the form of a physical model of an 'underground structure of optically active (photoelastic method) or equivalent materials. The most important feature of the contact interaction schemes is that stresses at the lining-rock contact (loads, pressure acting on the lining) are not given a priori, but are determined in the course of analysis (modelling). Schemes of contact interaction of linings (supports) of underground structures with rock masses are studied within the scope of underground structure mechanics - a scientific discipline developed in the Soviet Union (Bulychev 1982). The paper discusses mathematical models simulating the rock mass by a linearly deformable medium including viscoelastic one. So each mathematical model is the result of analytical solution of the corresponding plane problem of the elasticity theory. The models and design procedures for linings are realized as computer programs enabling one to perform multivariant designs of underground structures. Reliability of the mathematical models and design procedures for linings is ensured both by qualitative and quantitative correspondence of the design values to the results of model experiments and in situ measurements. In addition, these mathematical models enable one to solve inverse problems using in situ measurements of stresses or displacements in linings. ARBITRARILY SHAPED TUNNEL LININGS The design scheme for tunnel linings (Fig. 1) is one of the contact interaction of an arbitrarily shaped elastic ring, with one axis of symmetry, having the characteristics EI (modulus of deformation), VJ (Polsson's ratio), simulating the Iining and supporting a hole in a linearly deformable homogeneous medium having the characteristics E, V, and simulating the rock mass The mathematical model considers rock rheologic characteristics within the scope of 269 H Figure 1.

Proceedings Papers

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

Paper Number: ISRM-IS-1982-106

... SUMMARY:

**Computer**calculations concerning a nuclear waste repository will require a high accuracy in the predictions of the deformations and the stability of the repository over very long times and therefore a hight level of sophistication in geomechanical modeling. For the Waste Isolation...
Abstract

SUMMARY: Computer calculations concerning a nuclear waste repository will require a high accuracy in the predictions of the deformations and the stability of the repository over very long times and therefore a hight level of sophistication in geomechanical modeling. For the Waste Isolation Pilot Plant (WIPP) project near Carlsbad, New Mexico a benchmark II problem was stated in order to cornpare various computer codes with respect to their capability for calculating the thermal mechanical response of a hypothetical drift configuration for nuclear waste experiments and storage demonstration. Structural computations were made with ANSALT, a new FEM-code, especially developed for the analysis of thermomechanical processes related to the storage of heat producing radioactive wastes in rock salt. The computed results are illustrated and discussed. ZUSAMMENFASSUNG: Stabilitatsberechungen fuer ein Endlagerbergwerk fur nukleare Abfalle erfordern geomechanische Modelle und Rechenverfahren, die es erlauben, zuverlassige Vorhersagen ueber thermomechanische Auswirkungen der Einlagerung auch ueber sehr lange Zeitraume zu machen. Fuer das "Waste Isaolation Pilot Plant (WIPP)" project in New Mexico, U.S.A., wurden Vergleichsberechnungen mit verschiedenen Rechenprogrammen durchgefuehrt, um die Möglichkeiten, die Genauigkeit und Leistungsfahigkeit der verschiedenen Rechenprogramme zu untersuchen. Im Rahmen dieser Studie wurden Berechnungen auch mit dem von der BGR in Zusammenarbeit mit CD nach neuesten Erkenntnissen der Salzmechanik und der Rechentechnik entwickelten FEM-Programm AN SALT durchgefuehrt. Die Berechnungsergebnisse fuer eine hypothetische Lagerstrecke fuer warmeentwickelnden radioaktiven Abfall unter Zugrundelegung einer differenzierten geologischen Situation werden dargestellt und erlautert. RESUME: Les calculs de stabilite pour des installations souterraines d''enfouissement requièrent des modèles geomecaniques aussi que des procedes de calculs permettant de faire, meme sur de très lonques periodes, des pronostics sûrs en ce qui concerne les consequences thermomechaniques d''enfouissement. Pour Le "Waste IsoIation Pilot Plant (WIPP) ", Projet a New Mexico, U. S.A., ont ete effectues des calculs de comparaison, avec differents programmes de calcul afin d''etudier les possibilites, l''exactitude et le rentement des differents programmes de calculs. C''est dans le cadre de cette tude que les calculs ont ete realises avec egalement le FEMProgramm ANSALT, mis au point par le BGR en collaboration avec le CD d''apres les theoris les plus recentes de la mecanique du sel et de la technique de calcul. On y decrit et y expliquer les resultats de calculs concernant une qalerie pour des dechets radioactifs thermogenes en prenant pour base une situation geologique differenciee. INTRODUCTION The design of a nuclear waste repository is based on a multiple barrier storage concept taking into account a system of sequential or interconnected natural and technical barriers (Albrecht et al 1980) The natural barrier provided by a rock salt formation could act as an encapsulated system due to the very low permeability and the high ductility of rock salt contrary to other host rock types. However, the assessment of the integrity of the rock salt mass over very long times among other things requires a thorough understanding of the long-term thermomechanical process taking place due to the decay heat of high level waste. In the framework of the US!FRG bilateral agreement on cooperation in research and development for nuclear waste management the BGR, Hannover, in cooperation with CD, Hamburg, had the chance to participate in the second benchmark problem for.the Waste Isolation Pilot Plant(WIPP) initiated by Sandia National Laboratories, Albuquerque NM in order to compare different thermal-structural computational codes. The purpose of the WIPP project is to investigate the feasibility of storing defence transuranic waste in the bedded salt formation of Southeastern New Mexico and to perform experiments with defence high level waste (Hunter 1979). Structural calculations are used for reliable and detailed predictions for the WIPP experiments and storage demonstration as well as for extrapolating the longterm behavior of the repository to hundreds or thousands of years needed for nuclear waste isolation. GEOMECHANICAL MODELING Model and code requirements It is obvious that geomechanical modeling of an underground structure can only reach a certain level of accuracy because the rock mass itself will always remain unknown up to a certain extend. Beyond that all input data for a computer calculation like the material properties, the loading and the boundary conditions may vary within the investigated system, whereby the exact variability of those values will not be known. The engineer''s approach to overcome this general difficulties is a continuous improvement to the model appropriate to the improved knowledge of the input data within an integrated cycle. The features of this cycle are the establishment of a constitutive modei for the material behavior, the quantification of site relevant input data, the prediction and monitoring of the structural response and from that the necessary feedback to check the validity of the constitutive law, input data and modeling process in an iterative manner.

Proceedings Papers

Paper presented at the ISRM International Symposium, September 21–24, 1981

Paper Number: ISRM-IS-1981-116

...(3) is employed. strain-softening mite element analysis

**Computation**excavation equation strength loading surface stress-strain relationship procedure loading uniaxial compression test greenstreet Phillips tensile stress finite element method stress-strain curve reversal...
Abstract

INTRODUCTION For the construction of large-scale underground openings such as tunnels, underground power stations, petroleum storages, etc., analysis of stress and deformation of the rock under excavation is important and indispensable. Nowadays, for the prediction of rock stability or the decrease of the bearing capacity around the opening, the finite element method has been successfully applied. However, most conventional finite element analysis limits itself to be within the range of strain-hardening analysis. The ground rock under excavation is characterized by the fact that it itself is an important member with respect to load bearing capacity as well as the object to be excavated. Namely, strain- softening is favorable for the object to be excavated but unfavorable as a load bearing member. In the rock material to be excavated practically, the stress-strain relation curve shows the so-called strain-softening behavior if the loading condition exceeds the maximum strength. The analysis such as On fall of rock or expansion of side wall', etc., can be carried out if the strain- Softening characteristics can be dealt with within the stress-strain relationship. The practical repeated compression test indicates that the loading even lower than the maximum strength produces the accumulation of permanent plastic strains and finally causes the fracture of the material if loaded cyclically. For analysis of this Phenomenon, it is necessary to include the function so as to be able to treat the cyclic loading condition. The finite element method presented in this paper can analyze the repeated loading, with consideration given to the strain-softening stress-strain relationship. Basic idea of elastic plastic constitutive equation is the concept of loading surface which is presented by Green-street and Phillips('), The stress-strain curve isassumed to be given from the relation between equivalent stress and equivalent plastic strain. For the practical function form, exponential function is successfully used to express the strain-softening. CONSTITUTIVE EQUATIONS To express constitutive relationship between stress and strain, the concept of closed loading surface introduced by Green-street and Phillips is utilized in this paper (Fig. 1). In this analysis, it is assumed that there is no yield surface, which encloses the elastic region. Namely, plastic strain is assumed to be always produced immediately after the initial loading The loading surface passes through the stress point. The loading surface grows larger as the loading proceeds. A stress rate is assumed to be directed toward the outside of loading surface. In the case of loading reversal, new loading surface with new stress-strain relationship will be introduced. After that, if loading increases once again, then the former loading surface will decrease and new loading surface will be produced. (Fig. 2) (Figure in full paper) Where p, f i , Vi are density, body force and displacement, respectively. The finite element method can be applied to equations (11)~(14) following the standard approximation procedure. For the interpolation relation of displacement, linear interpolation equation based on the triangular finite element is used. As the basic procedure for the nonlinear iteration, the stress transfer method(3) is employed.

Proceedings Papers

####
Geomechanical Parameters **Computed** From Instrumentation Measurements at Agua Vermelha Dam Fonundation

Paper presented at the ISRM International Symposium, September 27–29, 1978

Paper Number: ISRM-IS-1978-013

... SUMMARY This paper deals with the

**computation**of the geomechanical parameters of the basaltic foundation of Aqua Vermelha concrete dam, from the deformation measurements of the multiple position rod extensometers and joint measurement devices. These extensometers were installed in the...
Abstract

SUMMARY This paper deals with the computation of the geomechanical parameters of the basaltic foundation of Aqua Vermelha concrete dam, from the deformation measurements of the multiple position rod extensometers and joint measurement devices. These extensometers were installed in the beginning of the construction period, thus allowing the computation of the deformation moduli of different rock layers and the normal stiffness moduli of a major joint with silt or clay infilling between two basaltic lava flows, during the construction of the dam.

Proceedings Papers

Paper presented at the ISRM International Symposium, September 27–29, 1978

Paper Number: ISRM-IS-1978-022

... wellbore integrity discontinuous rock mass assumption rock mass Wellbore Design principal plane

**Computation**rock material Reservoir Characterization Upstream Oil & Gas plane Poisson reservoir geomechanics strip load equation physical property data Kulhawy exploratory adit...
Abstract

SUMMARY A geomechanical, model is proposed for estimating the settlement of long dams on discontinuous, rock masses. It is shown. that orthogonally discontinuous rock masses can be analyzed as orthotropic media, and a discussion is included on evaluating the properties for the rock materials and the discontinuities. Settlements are evaluated with solutions for strip loads on orthotropic media, with appropriate corrections for varying dip of the principally planes of orthotropy. Example computations are included.

Proceedings Papers

Paper presented at the ISRM International Symposium, September 27–29, 1978

Paper Number: ISRM-IS-1978-018

...) and Canelles (archdam). safety coefficient geomechanical model discontinuity dam foundation plastic condition mathematical model rock mass deformability

**Computation**fracture Upstream Oil & Gas resistance gallery coefficient earthfill dam Artificial Intelligence abutment...
Abstract

SUMMARY In a dam it is important to be familiar with the foundations when either all or at least part are under plasticity conditions; that is, when the loads are greater than those which correspond to the elastic limit. Such an analysis is always necessary when we wish to know the margin of safety which exists under normal load conditions. In this paper some considerations are given to the means of determining the stress-strain state in accordance with the type of -dam and its application to a number of practical examples such as the following dams: Canales (rock fill) Mequinenza (gravity) and Canelles (archdam).