Experiment of membrane penetration on coarse grained soil

The membrane penetration is the most important factor influencing the measurement of volume change for triaxial consolidated-drained shear tests on coarse grained soil. The volume changes of membrane penetration are deduced from the consolidation tests by the method that iron rods with different diameters are embedded in the triaxial samples. The test results indicate the linear relationship between the sample volume and the displacement. Based on the test results, the penetration volumes are given under each confining pressure. The volume of membrane penetration increases by the increase of confining pressure, however, the increasing speed becomes slow down after 0.8 MPa. The proportion of penetration volume in total displacement can be 31.0%~40.7%. The most used method proposed by Newland and Alley overestimates the penetration volume. Anisotropy of the triaxial sample decreases with the increase of confining pressure. The difference of penetration volume is only 0.22% of volume change when the confining pressure reaches 2 MPa. The analytic solution deduced by Molenkamp and Luger agrees well with the test results among the four analytic solutions. For the coarse grained soil, more tests should be done to establish the relation among the particle breakage rate, the relative density and the coefficient η to correct the analytical solution.