ABSTRACT: The design of many engineering structures require foundation systems to resist vertical uplift or horizontal pullout forces. These types of structures, which may include transmission towers or earth retaining structures, are commonly supported directly by soil anchors. To date the design of these anchors has been largely based on empiricism. As the range of applications for anchors increases, to include the support of more elaborate and substantially larger structures, a greater understanding regarding their behaviour is required. This paper presents the numerical results obtained for the ultimate pull-out capacity of horizontal and vertical strip anchors in sand using the upper and lower bound methods of limit analysis. Results are presented in the familiar form of break-out factors based on various soil strength profiles and geometries. INTRODUCTION During the last thirty years various researchers have proposed approximate techniques to estimate the uplift capacity of anchors in sand. A large proportion of this past research has been experimentally based and, as a result, current design practices are largely based on empiricism. Although a number of numerical studies have been undertaken to estimate the capacity of sand anchors, very few of them can be considered rigorous. The existing numerical studies of anchors in sand have typically utilised simple analytical approaches such as limiting equilibrium, cavity expansion, and limit analysis. These can be found in the works of Meyerhof and Adams (1968,1973), Murray and Geddes (1987,1989), Neely et al (1973), and Yu (2000). The most rigorous numerical study appears to be by Rowe and Davis (1980). In this study, results were presented for both horizontal and vertical strip anchors embedded in sand. An elasto-plastic finite element analysis was used incorporating a soil structure interaction theory at the soil/anchor boundary. Numerical analysis and laboratory testing will be performed on anchors in both clay and sand.

ABSTRACT: A new method for analysis of size, shape and roughness of aggregates based on a 3-D-laser-digitising technique is presented. Measurements of aggregate particles are carried out by a system consisting of a laser sensor and a co-ordinate-measuring machine; the accuracy of the system is ±50 mm. Scanned data are processed to create a digital image of aggregates to be employed in further analyses. Size, shape and volume analysis of particles has been conducted in two ways. A so-called geometrical analysis is based on simple applications of analytical geometry. Another method consists of the Fourier transform analysis of the topography of the two halves of the sample defined by a plane intersecting its mass center. Three-dimensional spectra are obtained as a function of two frequencies along the co-ordinate axes. The cross-sections of the spectrum are then investigated and the pattern of the power spectra gives the dimensions and shape of the particles. When comparing the results from these two methods, a very good agreement is obtained. From the spectrum, the texture component can be identified, which gives the roughness of the particles' surfaces. The new technique by Fourier transform analysis is promising giving repeatable results and performing a combined shape-size-texture analysis of the aggregate particles. INTRODUCTION Aggregates' size, shape and surface texture can be characterized from a strictly geometric point of view. The particles are three-dimensional objects thus; their size should be described by at least three parameters. The volume would be the most natural parameter quantifying the size of a certain particle, but it cannot be directly correlated with the shape. Therefore some authors (Jansson & Muhr, 1995; Wang et al. 1996) suggested to utilize typical lengths obtained by circumscribing the particle or its images on a picture with simple Euclidean shapes.

ABSTRACT: Rock mass classification systems for rock engineering have gained widespread acceptance since their introduction in the mid-60''s. Their widespread use can be attributed to the ease with which they employ simple measurements and observations to provide a quantitative index of rock mass quality. It is then possible to link this index to specific engineering objectives such as predicted stand-up time, maximum size of stable excavation, choice of support etc. Improvements in rock mass classification systems and their application have been based on more quantitative field measuring techniques, improvements to the weightings assigned to the different parameters, and better links to design. The widespread use of classification systems for design has resulted in a significant increase in case histories linking classification to rock mass behaviour, under a wide variety of conditions. Consequently this has contributed to the statistical validity of design recommendations. More recently there has been a trend to link different classification systems to avoid collecting the required field data to quantify the additional classification values. INTRODUCTION Rock mass characterization is an integral part of any design process in mining, even though most classification systems now in use have their origin in underground civil engineering applications. Project duration, scale, access, even tolerance of risk, can contribute to developing different engineering strategies for civil and mining applications. CLASSIFICATION AND DESIGN The results of rock mass classification are routinely used to estimate rock mass behaviour as well as provide guidelines for underground mine design. Documented case studies can provide an extraordinary amount of knowledge and experience that can be used for design purposes. There has been a tendency to also use the resulting empirical ratings to determine the constitutive laws as well as failure criteria now employed with the majority of numerical models.

ABSTRACT: A new type of soil nailing, called sand anchors, was developed to stabilise old retaining walls. Sand anchors bear without grout due to the constrained dilatancy of a dense granular material between anchor rod and borehole wall. They protect the environment, preserve old monuments, provide additional drainage, the load can be applied immediately, they are removable and the cost is low. Their bearing effect is explained with the following example. The stabilisation of an old retaining wall with sand anchors, in co-operation with the company Bausanierungstechnik GmbH, is presented together with results of pullout tests. Finally some recommendations for applications of sand anchors in soil are given. INTRODUCTION Sand anchors can be applied in rock using sand and in soils using gravel, Wehr (1999). In both cases they may be installed as anchors or as nails, however only the application soil nailing is described herein. The name Ôsand anchorÕ will be kept. Old retaining walls often show large deformations. It may be concluded, that the wall does not have the required safety and is no more usable with increasing risk of further deformations. The installation of sand anchors stabilises the wall safely and cost effectively. Soil nailing of retaining walls was introduced in Germany some 15 years ago. Generally tensionless or pre-stressed rods are used in the soil to ensure the required safety of the wall and soil system against sliding or slipping. Sand anchors are part of the so-called "hidden soil nailing" with an enlarged nail head, which acts as load distribution element behind retaining walls. The main advantage is that the soil nail is not connected to the old retaining wall, which then just carries its own weight. The design uses the same safety philosophy as ordinary soil nailing, Gudehus (1990).

ABSTRACT: Rock mass is heterogeneous, anisotropic and discontinuous. When civil engineering structures like dams are founded on rock, they transmit normal and shear stresses to the joints of the rock mass. For a realistic assessment of the stability of a structure, estimations of the shear resistance of a rock mass both along any desired plane of potential shear and along the weakest discontinuity are essential. To quantify the influence of the rock material and of the roughness on the strength of joints, various researchers have proposed different equations and correlations to estimate strength parameters. This paper briefly describes a new approach to characterize the three-dimensional morphology of rough joint surfaces and proposes a new equation to evaluate the peak shear strength. INTRODUCTION The shear strength of rock joints is markedly influenced by the roughness of the joint surface, as well as by the nature of the rock material itself. Since over twenty years, various attempts have been made to quantify these effects. Most of such attempts either relied on experimental testing to derive empirical parameters, or on numerical models based on a discontinuous approach (distinct element codes). The major difficulty in dealing with these latter models appears to be the proper choice of the input data set of parameters (joint stiffness and strength). Patton (1966) quantified the roughness by defining the dilatation angle and developed a theory for the shear strength of rock joints based on such a measure of roughness. Ladanyi & Archambault (1970) developed a model for the shear strength of rock joints, assuming that two modes of failure occur simultaneously. Although the idea behind their model is excellent, it is difficult to determine the parameters used. To determine the JRC Tse & Cruden (1979) converted Barton's table into equations.

ABSTRACT: Recently the first full face tunnel boring machines were used in the Netherlands. Several problems have been encountered in tunnelling projects in the Dutch soft soils. One was the adherence of stiff clays to the TBM cutting wheel, mixing chamber and the pipelines, which transport the clay from the front. Adherence of clay can be described in terms of adhesion and adhesive friction. Parameters which influence these two factors are on one hand the mineralogy, texture, the (over)-consolidation ratio and composition of the clay and on the other hand the type of steel and the textural state and condition of the steel surface. To study the adherence of clay, two types of clays were tested. Tests have been performed on Speswhite, which consists mostly of kaolinite and on Boom clay, which is a mixture of quartz, illite and kaolinite. Samples were prepared from clay powders. The adherence behaviour of clay was investigated by measuring the shear stress required to shear the clay over a steel surface in a direct shearbox. Results show a great influence of the steel roughness, contact time and mineral type. This is in accordance with practical experience and previous literature. The shearbox test gives a good quantitative impression of the adhesive shear strength, however it is expected that other devices like the simple shearbox and the ring shearbox are better suited to study the parameter variation during the tests. INTRODUCTION As traffic activity is growing in the Netherlands, more infrastructure is needed to ensure public transport. Since little space is still available in the Netherlands, the Dutch are forced to increasingly use the underground. Recently, the Tunnel Boring Machine (TBM) has been used in tunnelling projects. This technique has several advantages compared to the cut and fill method.

ABSTRACT: Piles socketed into hard rock are frequently used in Ireland but much uncertainty exists on appropriate design procedures for the piles. The results of twenty four pile tests at twelve sites located throughout Ireland have been backanalysed in order to produce estimates of mobilised skin friction. It is shown that the existing design methods, which are based primarily on correlations with unconfined compressive strength, are not appropriate for Irish rock socketed piles. Mobilised ultimate skin friction values are shown to be highly dependent on fracture spacing. It is suggested that this parameter is more appropriate for pile design in hard Irish rocks. The Rocket '97 approach, which uses basic rock and pile parameters and allows for the effects of roughness along the pile shaft, is shown to give encouraging results for Irish conditions. INTRODUCTION The recent period of sustained economic growth in Ireland has led to an increase in the use of rock socketed piling due to the requirements for higher structural load capacities and the development of previously marginal sites. Some previous papers (Long and Collins, 1998 and 1999) have described the development and current state of the art of the piling techniques available in Ireland and have described the current design methods. Results of pile loading tests from eighteen sites located widely around the country were analysed, using Fleming's (1992) hyperbolic function approach in order to examine the behaviour of the piles and to review the validity of the current design process. It was shown that the piles behaved largely by transferring the applied structural load to the rock mass in skin friction. From this work it became clear that rock quality and the nature of discontinuities in the rock mass has an important influence in the behaviour of the piles.

ABSTRACT: The succesful drilling of the continental deep borehole (KTB) will be dependent on knowledge of the causes of borehole instability. In addition to secondary KTB research and development projects in this field the drilling of the KTB pilot borehole, a series of overlapping caliper logs was run at intervals of only a few days. This enabled the study of borehole diameter changes on a time dependent basis. The caliper log data were processed using a statistical method to elaborate characteristic parameters of the borehole geometry in 25 m sections. Important characterization variables are borehole roughness, elongation and ellipticity. The time dependence of these parameters was correlated to changes in the circulation. The data shows the successful application in the KTB pilot borehole of increased use of the complex bond-forming viscosifier Dehydrill in the fluid circulation to practically stop all borehole enlargement at all depths. This factor shows the primary influence of circulation conditioning on borehole stability. Over virtually the entire borehole it was observed that enlargement took place in the direction of dip of foliation, which is undoubtedly due to the presence of hydraulic permeability along paths forming preferentially in the direction of steeply dipping foliation. 1. INTRODUCTION A large number of overlapping caliper logs run at relatively short time intervals during drilling of the KTB pilot borehole make statements of a previously unknown degree of accuracy possible when describing the time dependent behaviour of borehole geometry. Literature on the subject of borehole stability (CHEATHAM, 1984, GUENOT, 1987- see also summary by BORM, 1988) makes It clear that the majority of authors used stationary models in their interpretation of borehole instabilities. The initial logging data acquired from the KTB pilot borehole made it soon apparent (KESSELS, 1988) that borehole instability in this case displays a clear dependence upon time, a fact confirmed in the subsequent borehole logs. It is then necessary to include non-steady-state mechanisms in a realistic description of borehole instability. In addition to these effects caused by inhomogenity of the structure (KESSELS, 1987) other observable effects are due to chemical interaction with the drilling fluid and the drilling activity itself, both non-steady state processes. When comparing caliper logs taken at different times it should be borne in mind that technical reasons will cause a four-arm caliper log to supply differing data on a second run through the same borehole geometry than on a first, because the orientation of the tool in the borehole cannot be fixed unequivocally. In general it is, therefore, assumed that one pair of arms will tend to run in the direction of the longitudinal axis of borehole ellipticity, as shown in figure 1. That this assumption is justifiable is confirmed by a large number of caliper log runs in which, by employing the relative bearing angle (RB), it is possible to show that the caliper log maintains a stable position in an enlarged section, whereas, in a smooth section of the borehole, cable tension leads to axial rotation (KESSELS, 1988).

ABSTRACT: The results are reported of a study of elastic-wave propagation and permeability measurements on a slate before cracking and after oriented sets of cracks had been introduced. Three loading cycles on a servo-controlled testing machine were performed on the rock sample in order to create the cracks in planes parallel to the sample axis. Compressional - and two shear-wave velocities, having particle motion parallel and perpendicular to sets of cracks, were determined concurrently with permeability measured in the same direction. Significant changes in both permeability and elastic-wave velocity, due to stress-induced cracks, were observed after each loading cycle. The velocity magnitudes conformed basically to the predictions of Hudson's theory. A near-linear relationship between the velocity of shear waves polarized perpendicular to the stress-induced cracks and the logarithm of the measured permeability exist. This indicates an encouraging means of monitoring permeability variation in a fractured reservoir rock by using seismic data. INTRODUCTION The elastic behaviour of the crust is significantly affected by the presence of cracks, joints and fractures. King (1969) and Anderson, Minster and Cole (1974) reported that a preferred orientation of microcracks has a marked effect on elastic-wave velocities, with a major reduction in velocity when particle motion is perpendicular to the plane of microcracks. Many authors (e.g. Crampin 1984, 1985) have shown that an isotropic solid permeated by aligned cracks or fractures will behave in an anisotropic manner. It is generally found that the microcracks, joints, fractures and faults are aligned by tectonic stresses (Nur and Simmons 1969, Babuska and Pros 1984, Engelder 1982) perpendicular to the direction of the minimum principal stress. Crampin (1984) therefore suggests that the azimuthal anisotropy in the crust, particular at shallow depths, is frequently the result of the alignment of cracks or other inhomogeneities. The use of seismic data to monitor the occurrence of cracks and other discontinuties is of particular interest to geophysicists, petroleum engineers and rock mechanics engineers. In earlier studies, crack parameters were only estimated from observation of the P-wave anisotropy (Crampin and Bamford 1977, Bamford and Nunn 1979, Crampin, McGonigle and Bamford 1980). However, when it was realised that shear wave velocities were more sensitive to changes in crack parameters of a cracked body (Crampin 985), attention was drawn to the importance of studies of polarized shear waves and shear-wave birefringence. King, Myer and Rezowalli (1986) studied acoustic velocities of P and S waves in a jointed basaltic rock mass and observed a very strong seismic anisotropy, approximately 18% for P waves and 25% for S waves. Besides the velocity information provided by shear waves, the polarisation of shear waves provides important information about crack geometry. This is because the faster shear wave is always polarized parallel to aligned cracks. Roberts and Crampin (1986) employed shear-wave polarizations to monitor the natural stress-aligned microcracks and artificial hydraulic fractures at the Hot Dry Rock Geothermal Project in Cornwall, England, and found that the orientation of hydraulic fractures could be predicted from polarizations of shear waves.