粗粒土与结构接触面三维力学特性的直剪试验研究

运用80t三维多功能土工试验机,对粗粒土与人造粗糙钢板接触面的三维力学特性进行试验研究,包括常法向应力条件下单调剪切试验(法向应力σ=200kPa、400kPa、700kPa、1000kPa)及十字、单向圆形和往返圆形路径下循环剪切试验(σ=400kPa)。结果表明:在单调和循环剪切时接触面均产生了明显的剪切体变,循环剪切时可分为遵循不同规律的可逆和不可逆两部分;不同剪切路径下接触面切向应力-应变关系曲线有很大差别,但主剪应力-主切向位移关系类似;随循环剪切的进行,接触面在逐渐剪切硬化,主剪应力-主切向位移曲线形式均由双曲线形式向理想弹塑性模式转变;接触面抗剪强度具有各向同性,其与法向应力关系符合摩尔-库伦准则;法向应力对接触面单调力学特性影响显著,剪切路径对其循环力学特性(剪切体变、切向应力-应变关系及破坏状态等)有重要影响。

Large-scale direct shear test investigation of the 3D behavior of a gravel-structure interfaces

Using a new device,the 3-D monotonic and cyclic behaviors of a gravel-structure interfaces were investigated through a series of interface tests under constant normal stress condition.The tests include four monotonic shear tests at normal stress of 200,400,700 and 1000 kPa and three cyclic shear tests in two-way cross,one-way circle and two-way circle shear paths.The volumetric change is obviously induced by monotonic and cyclic shearing,and can be divided into reversible and irreversible components.The relationship between shear stress and tangential displacement in x-or y-directions is different in various shear paths,but similar between principal shear stress and principal tangential displacement.The interface becomes stiffer due to cyclic shear application,and the principal shear stress vs.principal tangential displacement relationship transfers from hyperbolic to elastic-perfectly plastic.The interface is isotropic in shear strength and behaves in accordance with the Mohr-Coulomb strength criteria.The normal stress has significant influence on the monotonic behavior of the interface,and the shear paths affect its 3D cyclic behavior,including volumetric change,shear stress-strain relationship and failure state,etc.