膨胀土路堑全封闭基床结构型式及其动力模型试验

Structure and Dynamic Model Test of Fully-closed Railway Subgrade in Swelling Soil Cutting

对膨胀土地区新型铁路路堑全封闭基床结构进行室内足尺模型试验,得到循环振动荷载作用下基床的动力特性。结果表明：新型全封闭基床结构中动应力沿深度的衰减规律呈指数型,速度和加速度沿深度的衰减规律成二次曲线型,说明在基床表层底面铺设半刚性结构层使振动速度和加速度的影响深度增大;基床底层底面的最大动应力、振动速度、加速度以及路基面最大动变形波动区间分别为4.09-6.13kPa、1.72-3.15 mm/s、0.082-0.085m/s2和0.30-0.43mm,均小于高速铁路基床相应动力指标限值,验证了新型膨胀土路堑全封闭基床结构设计的可行性和合理性。

A full scale indoor dynamic model test for the structure of fully-closed railway suhgrade in swelling soil area was conducted to obtain the dynamic characteristics of the subgrade under cyclic vibration load. The results indicated that the dynamic stress in the fully-closed subgrade attenuated in the form of exponential decay in the vertical direction, hut velocity and acceleration attenuation curves could be fitted by quadratic polynomi- al. The laying of the semi-rigid waterproof layer under the surface of the subgrade could increase the influence depths of vibration velocity and acceleration. The maximum fluctuation interval values of dynamic stress, vi- bration velocity and acceleration on the bottom of the subgrade were 4.09-6.13 kPa, 1.72-3.15 mm/s, and 0. 082-0. 085 m/s2 respectively, while the maximum deformation fluctuation interval value of the subgrade surface was 0.30-0.43 mm. These dynamic parameters are all less than the corresponding dynamic index lim- its of high-speed railway subgrade, validating the feasibility and rationality of the structure design for new fully-closed subgrade in swelling soil cutting. Key words： expansive soil; model test; subgrade; high-speed railway