桩-海洋黏土界面剪切性状试验研究

桩-土界面剪切性状制约着桩基受力特性,对研究桩-土相互作用机理具有重要意义。利用改进后的直剪仪,进行海洋黏土与钢板、混凝土板的界面剪切试验,研究不同含水率、不同固结时间的海洋黏土与钢、混凝土界面的剪切应力-剪切位移关系。结果表明:界面剪切应力-剪切位移关系表现出较好的弹塑性关系,可用双曲线模型表示;随着法向应力增大、含水率减小和固结时间增长,界面峰值剪切应力增大,所需峰值剪切位移增加,峰值剪应力的增加集中在固结开始后的14 d内;界面摩擦角和界面黏聚力随含水率增加而减小,界面摩擦角受固结时间影响不大,集中在20°～23°范围内,界面黏聚力随固结时间增加而增大,且集中在固结开始后的14 d内。研究成果可为海洋桩基工程沉桩阶段阻力估算及数值模拟提供参考。

Experimental Study on Shear Behaviors of Interface Between Pile and Marine Clay

The mechanical behaviors of pile foundation are restricted by the shear behavior of pile-soil interface which is of importance for the study of pile-soil interaction mechanism. In this research, shear tests on marine clay-steel interface and marine clay-concrete interface were conducted via an improved direct shear apparatus to investigate the relationship between shear stress and shear displacement of interface with varied water content and consolidation time. Results indicate that relationship between shear stress and shear displacement of interface displayed good elastic-plasticity which can be expressed by hyperbolic model. The peak shear stress and displacement of interface increased with the climbing of normal stress, the declining of water content and the extension of consolidation time. The increment of peak shear stress concentrated within 14 days after consolidation. Moreover, the friction angle and cohesive force of interface decreased with the climbing of water content. Consolidation time had little influence on the friction angle of interface which concentrated in the range from 20 degrees to 23 degrees. The cohesive force of interface increased with the increasing of consolidation time, and such increment concentrated within 14 days after the initiation of consolidation. The research findings provide reference for estimating the resistance during the pile driving stage and for numerical simulation of marine pile foundation engineering.