基于非饱和黏性土桩土界面剪切特性试验研究

Experimental Research on Shear Characteristics of Pile-soil Interface in Unsaturated Clayey Soil

通过自制的大型恒刚度直剪仪对非饱和黏性土进行桩土界面剪切试验,探讨了非饱和黏性土桩土界面剪切特性及受黏性土饱和度的影响规律。试验和研究结果表明:在分析了非饱和黏性土桩土界面土压力和孔隙水压力的变化规律后,得到桩土界面剪应力峰值和剪切破坏位移随黏性土饱和度的增大而降低的结论,同时还受界面粗糙度和法向应力的影响,界面粗糙度和法向应力越大,桩土界面剪应力峰值和剪切破坏位移越大,在法向应力不同时最大剪切破坏位移相差9.81~12.23 mm;桩土界面黏聚力在饱和度80%~90%时最大,摩擦角随着饱和度的增大呈衰减趋势,因此在桩基设计中需要考虑黏性土饱和度对桩土界面抗剪强度参数的影响,否则会使设计结果过于安全。

In order to study the shear characteristics of the pile-soil interface in unsaturated clayey soil and influence of clayey soil saturation,direct shear test of pile-soil interface in unsaturated clayey soil was conducted on the large constant normal stiffness pile-soil interface direct shear apparatus.The test and research results indicate that after analysis on the variation of soil pressure and pore water pressure of pile-soil interface in unsaturated clayey soil,shear stress peak and shear failure strain of pile-soil interface would decrease with the increase of clayey soil saturation is obtained.Shear stress peak and shear failure strain of pile-soil interface would increase with the increase of roughness and normal stress,the difference between maximum shear failure strain reaches to 9.81~12.23 mm under the different normal stresses.The cohesion of pile-soil interface reaches the maximum while the saturation is80%~90%,friction would go down slowly with the increase of saturation.Considering the influence of clayey soil saturation on shear strength parameters of the pile-soil interface in pile foundation design is necessary,otherwise the design results are too conservative.