162A IN SITU STRESS:MEASUREMENT region of the North East of England. Generally the superficial deposits consist of glacial materials. These data are being assessed to allow a model to be developed of the geological and geotechnical processes that have taken place. In this paper the results of a simple statistical study of the classification and strength data are presented. (Authors) 954096 Geoteehnicai characterization of blended coal tailings for construction and rehabilitation work B. Indraratna, Quarterly Journal of Engineering Geology, 27(4), 1994, pp 353-361. Coarse and fine refuse is produced by various coal processing equipment. The relatively wet fine railings have limited use in construction activities and they are generally pumped as slurries into tailings ponds. The coarse rejects have a greater engineering applicability and are utilized in the construction of railings dams and mine access roads as well as for landfill and ballast. This study investigates the fundamental engineering properties of blended tailings, whereby appropriate fractions of flotation tailings are mixed with cyclone rejects to produce an acceptable construction or rehabilitation fill. In particular, a practical procedure to optimize the blended ratios, is proposed on the basis of fundamental geotechnical testing. The applications of relevent tests are described, including Proctor compaction, California Bearing Ratios, triaxial and consolidation tests. The results confirm that blending of fines with coarse rejects enables enhanced dry densities associated with reduced permcabilities, higher shear and compressive strengths, lower consolidation settlements and increased bearing capacities. The addition of a small quantity of cement (2-5%) further improves the engineering properties of the blended matrix. (from Author) IN S I T U STRESS Causes and nature of in situ stress 954097 Numerical simulation of roadway maintenance by stress control method (in Chinese) Ju Wenjun, Journal - China Coal Society, 19(6), 1994, pp 573-580. Based on a complete stress-strain curve of the rock, an elastoplastie formula describing rock deformation failure is established. An FEM program is used to investigate the mechanism for maintaining roadways by stress control. The layout of weakened zone and the effect of parameters relevant to weakened zone on roadway maintenance is also studied. The results show that after local weakening of the rock, the stress concentration area in the roadway moves to the depths of the surrounding rock, and the stability of rock is greatly improved. The layout of weakened zone and its parameters will be determined by rock conditions of the roadway and stress environment. (English summary) Measurement of in situ stress 954098 Monitoring stress changes in three dimensions using a solid cylindrical cell A.-P. Bois, G. Ballivy & K. Saleh, International Journal of Rock Mechanics & Mining Sciences, 31(6), 1994, pp 707-718. Presents a mathematical analysis of an inclusion device to carry out long-term strain-stress variation monitoring. The device consists of a solid cylinder grouted into a borehole. Analysis of the influence of the Young's moduli of the sealing grout and of the surrounding material revealed that a thin layer of grout should be used to seal the cylinder and that rigid cells should not be considered for monitoring strainstress variations in three dimensions. (from Authors) 954099 Stresses around a circular opening in an elastoplastic porous medium subjected to repeated hydraulic loading Y. Wang & M. B. Dusseault, International Journal of Rock Mechanics & Mining Sciences, 31(6), 1994, pp 597-616. Stresses near a circular borehole under repeated interior loading are analyzed. In a porous material which is capable of plastic deformation, the stresses and strains adjacent ot a borehole depend on the loading history. Varying loadings inside a circular opening are imposed to simulate the nonmonotonic pressure changes that arise during drilling and injection in a borehole. Plastic yielding related to different yielding modes is explored. Stages in the development of such stress states are analyzed, and the stress states in different zones under various circumstances are calculated separately and summed. The solutions presented can be used to understand stress development around boreholes, and can also be used to interpret hollow cylinder test results. (from Authors) 954100 Back analysis of stress measurement of anisotropic rock mass (in Chinese) C a t Wengui & Y a n Ronggui, Journal of China Coal Society, 19(2), 1994, pp 122-130. As soon as distribution of 3D stress and strain around a homogeneous borehole is established, 3D stress measurement by using a single borehole becomes successful in in-situ stress measurement in homogenous rock mass. Due to the difficulty in establishment of stress and strain distribution around a borehole anisotropic rock mass by mathematic methods, the authors introduced a back analysis method, and found a solution by means of 3D FEM. It was verified by an example. (from English summary) 954101 Back analysis of initial stresses in rock masses (in Chinese) Zhu Bofang, Shuili Xuebao/Journal of Hydraulic Engineering, 10, 1994, pp 30-35. Two methods are given for the back analysis of the initial stresses in rock masses. By using the first method, the initial stresses in rock masses in a small area are determined from the displacements observed during the process of tunnelling. By using the second method, the initial stress field in the rock masses in a large area are determined from the observed in situ stresses. The number of variables of regression is reduced and the accuracy of computation is improved due to the use of these methods. (English summary) 954102 Confidence intervals for in situ stress measurements A. J. Jupe, International Journal of Rock Mechanics & Mining Sciences, 31(6), 1994, pp 743-747. Walker et aL proposed a method of evaluating confidence intervals for in situ stress measurements which employed the Monte-Carlo sampling of the normal probability distribution function estimated from a number of independent overcoring measurements taken within one borehole. This note discusses an alternative means of evaluating confidence intervals from overcoring data and compares the technique with that of Walker et al.. As with their method, the technique makes use of random sampling to simulate a repetition of the overcoring experiment. However, rather than using the Monte-Carlo approach, it makes use of the statistical technique known as Jacknifing. (from Author)
