饱和软土路基长期沉降计算研究

Permanent settlement of subgrade of saturated soft soils

在车辆荷载作用下,公路路面会产生长期沉降。尤其对于长三角地区,路基多为饱和软黏土,在长期循环荷载作用下其强度和刚度均发生衰减,并有超静孔压的累积。基于现有试验结果提出新的刚度衰减模型,建立了考虑孔隙水压力的刚度衰减系数与循环次数的关系,并提出有效应力计算公式。同时与工程实用的分层总和法相结合,对某低路堤公路长期沉降进行了预测。计算结果表明:在交通荷载作用初期,沉降迅速增加,随后趋于稳定;由于路面结构层的刚度很大,其压缩量很小,沉降主要由第④层淤泥质黏土产生,由于土层中应力扩散,第⑤层粉砂层受到很小的竖向动偏应力,因而其沉降也很小。

Under vehicle loads, the permanent settlement of highway pavement is induced, especially in the Yangtze River Delta area, the traffic loading induces the degradation of the strength and stiffness and the accumulation of the excess pore pressure. Based on the former cyclic triaxial test results, a new degradation of stiffness model is proposed, which is expressed by the effective stress increment compared with the initial condition divided by the corresponding deformation, and a formula for the effective stress is established. Moreover, by combining with the layer-wise summation method, a method is suggested to estimate the long-term settlement of soft ground caused by traffic loads. The calculated results show that the settlement increases rapidly in the early phase, then tends to stable. Because the stiffness of the pavement layer is very large, the compression deformation is very small, and the settlement of road surface is mainly composed of the deformation of the 4th layer of silt clay. Due to the stress dispersion, the vertical dynamic deviator stress of the 5th layer of silt is small, so its settlement is very small.