粗颗粒土橡皮膜嵌入试验研究

对于粗颗粒土三轴固结排水剪试验,橡皮膜嵌入是影响试验体变测量的最重要因素。通过在中三轴试样中埋置不同直径铁棒的方法进行等向固结试验来推求橡皮膜嵌入量。试验表明,试样土体体积与排水量呈较好的线性关系,基此给出了各个围压下的膜嵌入量。指出随着围压的增大,膜嵌入量逐渐增大,约0.8 MPa后,嵌入量的增速变缓,嵌入量占实时总排水量的比例可达31.0%~40.7%。由于粗颗粒土的各向异性,目前所用最多的Newland和Allely所提出的方法总体略高估了膜嵌入的大小,随着围压的增大,各向异性减弱,围压为2 MPa时嵌入量差异仅有0.22%的体变。最后,对比4种解析解发现Molenkamp和Luger的解析解最为接近试验值。针对粗颗粒土,需要进行更多的试验来建立颗粒破碎率和相对密度等与系数η的关系来修正解析解。

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.