车辆荷载作用下软土地基塑性变形的计算

对于低路堤公路，合理地预测车辆荷载引起的地基塑性累积变形对于低路堤公路的设计有着重要的意义。从机制上讲，可将地基的塑性应变分为塑性体积应变和塑性剪切应变。其中对于塑性体积应变，提出采用不排水条件下的残余孔压模型与一维固结理论相耦合进行计算；对于塑性剪切应变，考虑了塑性体积应变引起的土体硬化，提出了修正的塑性剪切应变计算模型。然后基于所提模型，对萧山黏土的不排水与排水条件下的动三轴试验进行模拟，初步验证了所提模型的有效性。对于实际工程问题，首先运用数值的方法求得车辆荷载在地基中引起的附加应力，然后运用所提模型计算各土层的塑性应变，再结合分层总和的方法求得地基的累积塑性变形。以日本佐贺机场1号测点为例，说明了模型在工程边值问题中的有效性。

Calculation of vehicular load-induced plastic deformation of soft subsoil

For a low embankment road, the reasonable prediction of vehicular load-induced plastic deformation plays an important role in the road design. According to the mechanism of vehicular load-induced plastic strain, the plastic strain comprises two parts: plastic volumetric strain and plastic shear strain. In the calculation of plastic volumetric strain, the dissipation equation with a source term, which couples Terzaghi’s consolidation theory with the experimentally-achieved cumulative pore pressure model under undrained condition is adopted. While in the calculation of plastic shear strain, the hardening factor of plastic volumetric strain is taken into consideration. The validity of the model is verified by the dynamic triaxial test results of saturated clay under undrained and drained condition. For practical problems, the vehicular load-induced stress is calculated by the numerical method firstly; then the plastic strain can be calculated by the proposed model. Finally, the plastic deformation is obtained by the layer summation method. The calculation example of the point NO.1 on Saga Airport access road is analyzed to illustrate the validitity of the model in a pratical boundary value problem.