RESEARCH ON DEFORMATION AND STRENGTH CHARACTERISTICS OF SANDS AND SOFT ROCK GROUND UNDER HIGH PRESSURE CIRCUMSTANCE.

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A series of experimental and analytical examinations was carried out to investigate the effects of several influencing factors, such as stress state, primary properties of sand particles, physical and mechanical properties of sands, on the deformation-strength behavior of sands and soft rocks.For sands, 200 kind of sand samples with different primary properties were prepared.The relationships between the index properties, such as grain density, shape and size distribution were investigated, It was proven, that some index properties such as maximum and minimum void ratio, crushability characterize physical property of sands.The significant influence of the primary properties on the deformation-strength characteristics was also clarified, From the test results, the relationships of deformation-strength properties of sands with index physical properties are discussed ; the significant influence of grain shape, grading and crushability on the mechanical behaviors are presented.To investiga … More te the strength-deformation characteristics of soft rock, samples from horizontal and vertical directions were secured from the dam construction site, where strata were folded by horizontal thrust. Interesting information on the anisotropic characteristics of permeability, failure and residual triaxial strength, and yielding confining pressure were obtained. Significant effects of stress history on the mechanical behavior of soft rock, were pointed out.Deformation and failure mechanism of soft rock ground were investigated by several series of loading tests on model circular footing on artificial soft rock grounds. The effects of geometry of ground, footing size, mechanical properties of ground materials and relative position of footing from the top of slope were examined in connection with the type of failure mode ; general shear mode or large deformation with punching failure mode.Modified slice method was proposed and applied to the calculation of the ultimate bearing capacity of circular footing beside slope. While 2-dimentional calculation gave unacceptable under estimate, 3-dimentional calculation gave the reasonable estimate for the variation of ground material, slope angle, and the vicinity of the footing to the slope. Less