非等向固结压缩量对土体刚度影响试验研究

Experimental study of compression deformation effects on soil stiffness under anisotropic consolidation

采用动三轴弯曲元联合试验方法,对兰州原状黄土进行了均等固结与偏压固结下剪切波速测试,实测偏压固结下与均等固结下剪切波速比值远大于按Hardin公式计算值,验证了以往相关试验现象的可靠性。并且,不同于以往共振柱仪器不能测试试样变形,动三轴试样轴向变形结果表明,偏压固结比均等固结下黄土试样轴向变形大很多,偏压固结下剪切作用使土体骨架产生相对于均等固结更大的压缩量,并且改变了土颗粒间的接触行为,致使土体剪切波速最终产生了一个超过Hardin公式平均主应力所描述的增长。回顾以往研究结果,砂土密度及级配状况等决定土体压缩性的因素,同时也决定着固结比对剪切模量的影响程度,证实了压缩性是决定固结比对土体刚度影响的重要因素。

Using cyclic triaxial apparatus along with bender element system,shear wave velocity of Lanzhou loess under isotropic and anisotropic consolidation were tested. The ratio of measured V_s under anisotropic consolidation to measured V_s under isotropic consolidation,which is significantly larger than that calculated by Hardin ＇s formula. The reliability of previous experiments is verified. Furthermore,the resonant column instrument used in previous studies can＇t test soil sample deformation,but samples axial deformation tested by cyclic triaxial apparatus in this study show that loess axial deformation under anisotropic consolidation is much larger than that tested under isotropic consolidation. Anisotropic consolidation causes soil shear stress,which will compress the soil skeleton and alter the contact behavior between soil particles,and finally results in a more growth of shear modulus than that described by mean principle stress in Hardin ＇s formula. Reviewing previous studies,sand density and gradation which influence soil compressibility,would also decide the influence degree of consolidation ratio on shear modulus,confirmed that soil compressibility is an important factor of the problem about consolidation ratio effect on shear modulus.