非饱和直剪仪改造及砂土-结构剪切试验

Modification of unsaturated direct shear instrument and sand-structure shear test

土与结构相互作用问题涉及实际工程的多个方面,研究土-结构接触面力学特性是解决该问题的基础。通过对常规非饱和直剪仪进行改造,并利用改造的非饱和直剪仪进行非饱和砂土-结构接触面剪切试验,研究了基质吸力、结构面类型和净法向应力对接触面抗剪强度的影响。结果表明:基质吸力对非饱和砂土-结构接触面的界面黏聚力影响较大,对界面摩擦角影响较小;随着基质吸力的增加,非饱和砂土-混凝土接触面的抗剪强度先增大后减小,存在峰值效应;基质吸力对非饱和砂土-钢接触面的抗剪强度影响较小,基质吸力不变的条件下,随着净法向应力的增加,砂土-钢接触面的抗剪强度呈非线性增长;净法向应力对非饱和砂土-结构接触面对应基质吸力的界面摩擦角(δb)的影响较小。最后,建立了基于峰值效应的非饱和砂土-混凝土接触面抗剪强度公式。

The study on the mechanical properties of soil-structure interface is the basis to solve the problem of soil-structure interac⁃tion,which involves many aspects of practical engineering.By modifying the conventional unsaturated direct shear apparatus and using the modified unsaturated direct shear apparatus,the shear tests of unsaturated sand-structure interface were carried out,and the effects of the matrix suction,the structural interface type and the net normal stress on the shear strength of the interface were stud⁃ied.The experimental results show that the influence of matrix suction on the interface cohesion of unsaturated sand-structure inter⁃face is great,while that on the interface friction angle is small.With the increase of matrix suction,the shear strength of unsaturated sand-concrete interface increases first and then decreases,indicating a peak effect.The shear strength of unsaturated sand-steel inter⁃face was less affected by matrix suction.Under the condition of constant matrix suction,the shear strength of sand-steel interface increases nonlinearly with the increase of net normal stress.The influence of net normal stress on the friction angle(δb)correspond⁃ing to matrix suction is little.Finally,a shear strength formula of unsaturated sand-concrete interface was established based on peak effect.