法向刚度对土与结构接触面三维特性影响的试验研究

运用80 t大型三维接触面试验机，对不同法向刚度下粗粒土与结构接触面三维静动力学特性进行了试验研究，重点分析了法向刚度对接触面力学特性的影响规律。法向常刚度条件下，接触面在单调剪切时均先剪缩再剪胀、法向应力先减小后增大；循环剪切时接触面不可逆性剪切体变呈单调增长、可逆性剪切体变峰值逐渐减小后趋于稳定，切向应力峰值不断减小，抗剪强度逐渐减小，主应力比峰值则基本保持不变。法向刚度主要影响剪切体变、可逆性剪切体变、切向应力、主剪应力等接触面力学性能参数的大小；法向刚度越大，单调剪切时法向应力变化越大、切向应力峰值越大、剪缩和剪胀量越小；循环剪切时不可逆性剪切体变增长越慢、最终值越小，抗剪强度减小越快、达到0时对应的循环周次越少。法向刚度对剪切体变、可逆性剪切体变、主剪应力、主应力比等性能参数与切向位移的关系形式及接触面摩擦角基本没有影响。

Influence of normal stiffness on 3D monotonic and cyclic behaviors of a gravel-structure interface

Applied with a new large-scale interface apparatus, the influence of normal stiffness on 3D monotonic and cyclic behavior of the gravel-structure interface was investigated in detail. Under constant normal stiffness condition, the interface contracts first and then dilates, and the normal stress accordingly reduces and then increases during monotonic shearing. The irreversible volumetric change of the interface grows continuously, the normal stress, peak shear stress, shear strength of the interface decreases overall due to cyclic shearing while the peak resultant stress ratio remains invariable despite of shear cycle. It is indicated that the normal stiffness plays a vital role in 3D monotonic and cyclic behavior of the interface. With larger normal stiffness, the normal stress and the peak shear stress increase more during monotonic shearing; the irreversible volumetric change accumulates more slowly and its ultimate value is accordingly smaller. Meanwhile, the shear strength of the interface decreases faster to zero and the corresponding cycle number at which the shear strength becomes zero is smaller. The normal stiffness has a markable impacts on the value of performance parameters of the interface such as the irreversible and reversible volumetric change, shear stress, resultant shear stress, except the friction angle. In addition, good consistency exists in the relationship pattern between volumetric change, reversible volumetric change, resultant shear stress and resultant stress ratio versus tangential displacement, regardless of normal stiffness.