26A experiments. Pore crushing occurs even under fully saturated conditions and leads to stress wave attenuation and liquefaction of the rock. 921196 Geosynthetic drains against liquefaction Watari, Y: Fujiwara. T Proc 4th International Conference on Geotextiles, Geomembranes and Related Products, The Hague, 28 May-I June 1990 V1, P327-332. Publ Rotterdam: A A Balkema, 1990 Loose sandy soils which are susceptible to earthquake induced liquefaction can be stabilised by installing drains. A board drain of section 155mm by 12.6mm, constructed of PVC and geotextile and containing 14 drainage channels, has been developed for this purpose, Large scale shaking table tests were used to optimise layout of the board drains. Emplacement methods and equipment have been developed which allow the drain to be easily and quickly installed. 921197 Exfoliation phenomena in pre-stressed rock Muhlhaus, H B Proc 2nd International Symposium on Rockbursts and Seismicity in Mines, Minneapolis, 8-10 June 1988 P101-107. Pub/ Rotterdanl: A A Balkema, 1990 A simple strain softening model for brittle rock which has been developed in the framework of the Cosserat theory is presented. The Cosserat theory considers a material point to have three rotational and three translational degrees of freedom. The problem of surface buckling of a semi-infinite strip under surface compression is examined by finite element analysis, with particular interest in whether the tensile stresses developed are sufficient to cause exfoliation. 921198 Effect of repeated loading on the strength of Mexico City clay Diaz Rodriguez. J A Soil Dynamies and Liquefaction, Proc 4th International Conference on Soil Dynamics and Earthquake Engineering, Mexico Cio', 23-26 October 1989 P197-208. Publ Southampton: Computational Mechanics Publications, 1989 Stress controlled cyclic triaxial tests followed by static loading to failure were used to investigate the effect of dynamic loading on undrained static shear strength of Mexico City clay. The main loading parameter controlling cyclic stress strain behaviour at a given OCR was cyclic stress ratio (R). For R below 83%, there was practically no change,but above this value shear strength reduced drastically. Anisotropically consolidated samples are less deformable than isotropically consolidated ones, but equivalent damping ratio is little affected. 921199 Behavior of silt under monotonic and cyclic Ioadings Shen, C K; Jeong, S; Wang, Z L; Dafalias, Y F Soil Dynamics and Liquefaction, Proe 4th International Conference on Soil Dynamics and Earthquake Engineering, Mexico City, 23-26 October 1989 P209-223. Publ Southampton: Computational Mechanics Publications, 1989 Drained and undrained monotonic and cyclic compression and extension tests were carried out on a pure (non-plastic) silt in an automated triaxial testing apparatus to further understanding of the material behaviour under seismic and storm wave loading. Results have been analysed within the framework of the hypoplasticity model of granular soils. A computer aided calibration procedure was used to optimise parameter determination. The validation of the constitutive model against laboratory results is demonstrated.
Identification and classification 921200 Probabilistic simulation of rock quality designation (RQD) Elsayed, E A; Sen, Z lnt Assoe Engng Geoi Bull V43, April 1991, P31-40 Discontinuities have a fundamental influence on the properties of rock masses. Many attempts have been made to use statistical or empirical analytical methods to describe the discontinuities quantitatively. Here, RQD parameter distributions are obtained, using Monte Carlo simulation techniques, to describe the percentages of rock classified from excellent to very poor. Intact length distributions are chosen as negative exponential or log-normal. RQD distributions are shown for different average numbers of discontinuities. The advantages of the probabilistic description over average RQD classification are discussed.
921201 Mathematical representation of jointed rock masses and its application Sadagah, B H; Sen. Z: de Freitas, M H Proc International Conference on Mechanics o f Jointed and Faulted Rock, Vienna, 18-20 April 1990 P65-70. Publ Rotterdam. A A Balkema, 1990 Rock Quality Designation (RQD) is widely used as a quantitative assessment of rock fracturing in engineering applications. No measure exists to describe the certainty that a RQD obtained in a certain direction accurately reflects the range of RQDs in that direction. Two new parameters, Rock Quality Risk (RQR) and Rock Quality Percentage (RQP),are presented which reflect the extent to which a given RQD satisfactorily describes the amount ofjointing in a given direction and the risks related to allocating that value of RQR to the rock. Field examples are shown.
In Situ Stress Causes and nature of in situ stress See. 921250
Measurement of in situ stress 921202 Determination of the stress tensor in a rock mass through local stress relief at the bottom of a borehole (In French) Mazzoleni, G; Gouin. T: Richard, J C Bull Liaison Labs Ponts Chaussees N172. March-April 1991, P121-132 A method for determining the stress tensor in a rock mass using an overcoring technique with a cell containing multiple strain gauges is described. Principles of the method are outlined. The stress tensor is evaluated from the measured deformations using a transfer function, which has been established using the finite element code CESAR. Laboratory and field results for application of the method are presented.
"~ 1992 Pergamon Press plc. Reproduction not permitted