半正弦循环交通动载下加筋砾性土动力特性研究

Dynamic characteristics of reinforced gravelly soil under semi-sinusoidal cyclic traffic dynamic load

为研究交通荷载下加筋砾性土的动力特性,以土工格栅为加筋材料,开展了多级长期循环荷载下无筋、平铺、环形竖向及环形立体组合加筋等不同加筋形式的半正弦循环荷载下加筋饱和砾性土动三轴试验,同时也进行了半正弦循环荷载下土体阻尼比计算公式的推导,并研究了加筋层数和围压对环形立体组合加筋砾性土阻尼比、骨干曲线等动力特性的影响规律。试验结果表明:多级循环荷载下砾性土试样的阻尼比呈现前期增大随后减小的规律,阻尼比在动应变达到1%左右达到峰值,且加筋能够减小砾性土试样的阻尼比;Hardin-Drnevich模型适用于描述加筋砾性土的骨干曲线,且模型参数a、b与围压和加筋层数之间分别存在线性关系和指数关系,基于此提出适用于不同围压、不同加筋层数下环形立体组合加筋砾性土的骨干曲线方程。

Here,to study dynamic characteristics of reinforced gravel soil under traffic load,taking geogrid as reinforcement material,dynamic triaxial tests of reinforced saturated gravel soil under half sinusoidal cyclic load with different reinforcement forms under multistage long-term cyclic load,such as,unreinforced,tiled,annular vertical and annular 3D combined reinforcement were conducted.At the same time,the calculation formula of soil damping ratio under half sinusoidal cyclic load was deduced.Effects of number of reinforced layers and confining pressure on dynamic characteristics of annular 3D composite reinforced gravelly soil,such as,damping ratio and backbone curve were studied.The test results showed that damping ratio of gravelly soil sample increases in early stage and then decreases under multi-stage cyclic load,damping ratio reaches peak value when dynamic strain reaches about 1%,and reinforcement can reduce damping ratio of gravelly soil sample;Hardin-Drnevich model is suitable for describing backbone curve of reinforced gravelly soil,and there are linear and exponential relations between model parameters a,b and confining pressure and reinforced layer number,respectively,based on these relations,backbone curve equations of annular 3D composite reinforced gravelly soil under different confining pressures and different reinforced layer numbers are proposed.