An Experimental Investigation of the Flow–Stress Coupling Characteristics of Soil–Rock Mixture Under Compression

Abstract

The aim of this work is to investigate the flow–stress coupling characteristics of soil and rock mixture (SRM) with different rock block percentage, under a series of triaxial flow–stress tests with various confining pressures. Self-developed servo-permeable testing system was used to carry out the flow–stress coupling test. Cylindrical SRM specimens (50 mm diameter and 100 mm height) with staggered rock block proportions (20, 30, 40, 50, 60 and 70 % by mass) were produced by compaction test with different count hammers to roughly insure the same void ratio of soil matrix. From the test results, the structural controlled mechanism of flow–stress coupling characteristics of SRM is discussed. Permeability coefficient of SRM presents decreasing trend with the increase in axial stress at triaxial stress path, the relationship between permeability coefficient and axial stress follows negative exponential function, and the correlation coefficients are greater than 0.85 for all studied SRM specimens. In addition, the stress–strain curve presents strain-hardening characteristic at different confining pressure. However, morphology of strain–permeability coefficient curve is different for specimens with various rock block percentage. For specimens with high rock blocks of 50, 60, and 70 %, the strain–permeability coefficient curve presents fluctuation drop trend. Test results also show that permeability coefficient increases with the increase in hydraulic gradient; however, axial stress presents variety trend for specimens with different rock block percentage.