桩土接触面力学特性大型剪切试验

Large-scale shear test on mechanical characteristics of interface between pile and soil

土与混凝土接触面力学特性直接影响到桩侧摩阻力的发挥,相关研究对抗拔桩设计及应用至关重要。采用大型剪切系统,设计试验剪切模型箱,通过将预制混凝土板置于剪切装置中,以模拟抗拔桩的实际受力情况,分别从剪应力-剪切位移曲线、接触面剪切强度及剪缩剪胀性3个角度进行对比分析。结果表明:剪应力达到峰值强度后随剪切位移的增加线性递减,且在不同法向应力作用下,减小速率近似相等;接触面最大剪应力随着法向应力的增大而增大,两者呈良好的线型关系,但随含水率的增大而减小;接触面抗剪强度随含水率的增大而逐渐减小,相同法向应力下其值远低于土体抗剪强度;当法向应力较小,土样含水率较低时,土体发生剪胀现象,而在其他条件下均为剪缩,法向应力越大,其剪缩量越大。

The performance of the lateral frictional resistance can be directly affected by the mechanical characteristics of soil-concreteinterface. Thus corrsesponding research is essential for the design and application of uplift pile.Based on the existing large-scales hear system and self-designed shear box,the precast concrete slabs were placed in the shear device to simulate the actual stress of pile body.Then,the test results were presented in aspect of shear stress-strain curves,interfacial shear strength and dilatancy characteristics. The results showed that the shear stress decreased linearly with the increase of shear displacement after reaching the peak value,and the decrease rate was approximately equal under different normal stresses. Further more,the maximum shear stress of the interface increased with the increase of normal stress and shows great linearity,but it decreased with the increase of water content.In addition,the shear strength of the interface decreased with the increase of water content,which was much lower than the soil shear strength under the same normal stress.Shear dilatancy occurred under smaller normal stress and lower water content,and under other conditions,it showed shear contraction. It can also be obtained that the higher normal stress can offer the larger shear contractions.