By using a simple shear apparatus that is developed from RMT-150B,a series of simple shear tests of interface between saturated sand and structure under high normal stress were carried out to study constitutive law and shearing stiffness of interface to provide some theoretical evidences for design and calculation of projects concerned with mechanical problem of interface. In test, sand was consolidated in upper shearing box firstly,then,shear was started and testing data was recorded under high and constant normal stress. During the process, sand can deform relatively freely. It is shown that the relation curve between shear stress and shear displacement under high normal stress in simple shear tests is different from that in direct shear tests,and the complete shearing deformation process of interface under high stress can be described as a nonlinear elastic-perfect plastic form; Weibull distribution with three parameters can overcome the mathematical deficiencies of hyperbola in NEPP. The new model which is established by substituting Weibull distribution for the hyperbola of NEPP better agrees with the testing data. The regressive results of the initial shearing stiffness demonstrate that the linear function is slightly better than power function to express the relation between the initial shearing stiffness and normal stress. Based on the new interface model,the formula of tangential shearing stiffness is proposed,meantime,the change trend oftangential shearing stiffness of the new model is compared with that of NEPP.%利用改装自RMT-150B试验系统的单剪试验仪进行饱和砂土与结构界面单剪试验,研究高应力条件下界面本构模型及界面剪切刚度变化趋势,为高应力状态下涉及到界面力学问题的工程设计、计算提供理论依据.试验中,首先对剪切盒中的砂土进行固结,然后法向应力恒定在高应力水平上开始界面剪切,并记录试验数据,剪切时保证砂土能相对自由的变形.试验结果表明:高应力下界面剪应力-剪切位移关系曲线呈现非线性弹性-理想塑性特征,不同于直剪试验条件下二者呈现的双曲线关系；三参数威布尔分布曲线能克服NEPP模型中双曲线的缺陷,其取代双曲线形成新的非线性弹性-理想塑性模型能更好地拟合试验数据.界面初始剪切刚度的回归结果表明,相对于幂函数,线性函数更适合描述界面初始剪切刚度同法向应力之间的关系.基于新的界面模型给出了界面切线剪切刚度的公式,同时比较了2种模型的界面切线剪切刚度随剪切位移的变化趋势.
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