高速铁路路基帮宽工程复合地基有限元分析方法探讨

Discussion on Finite Element Analysis Method of Composite Foundation for High Speed Railway Subgrade Widening Engineering

路基帮宽工程势必引起既有路基沉降,在高速铁路建设过程中,高效开展复杂工况下多个路基断面的沉降计算并获得更精确的沉降预测值十分重要。目前常规使用的二维简化计算模型,由于较少深入研究简化理论,存在精度不足误差较大的问题,而大型的三维计算模型,存在建模工作量大,计算收敛困难等问题。基于有限元软件ABAQUS,分别建立典型路基帮宽工程的二维和三维模型,推导三维至二维的群桩弹性模量和重度转化公式,并讨论土体弹性模量和重度的加权平均计算方法,转化后的二维与三维模型计算结果差异率小于2%。通过沉降计算结果,研究了桩土接触面摩擦系数设置对沉降结果的影响,其对附加沉降值的变化影响率小于1%;开展桩基弹性模量的参数分析工作可以得出,对于路基复合地基处理措施,当桩基模量大于1 GPa时,对附加沉降的控制效果明显减弱。

Subgrade widening is bound to cause the settlement of existing railway. In the process of high-speed railway construction, it is very important to efficiently calculate the settlement of multiple subgrade sections under complex working conditions and obtain more accurate settlement prediction value. At present, the conventional two-dimensional simplified calculation model has the problem of insufficient accuracy and large error due to less in-depth study of simplification theory. However, there are many problems such as large modeling workload and difficult convergence in large 3d computing models. In this paper, the two-dimensional and three-dimensional models of typical subgrade widening engineering are established respectively based on the finite element software ABAQUS, the transformation formulas of elastic modulus and weight of pile group from three-dimensional to two-dimensional are derived, and the weighted average calculation method of elastic modulus and weight of soil is discussed. The difference rate between the calculation results of two-dimensional and three-dimensional models is less than 2%. Based on the settlement calculation results of finite element model, the influence of the friction coefficient of pile-soil contact surface on the settlement results is studied, and the influence rate of the additional settlement value is less than 1%.The parameter analysis of elastic modulus of pile foundation shows that the effect of subgrade composite foundation treatment measures on the control of additional settlement is obviously weakened in case that the pile modulus is greater than 1 GPa.