考虑成层土变异性的等效基床系数分析

ANALYSIS OF EQUIVALENT COEFFICIENT OF SUBGRADE REACTION CONSIDERING VARIABILITY OF LAYERED SOILS

基床系数是利用荷载–结构法求解工程问题的关键。为研究具有变异性成层土地基的等效基床系数的分布特征及统计参数,基于最终沉降量一致原理推导以压缩模量为参数的等效基床系数计算方法,利用Monte Carlo方法考虑地层的变异性。在此基础上,借助Matlab软件实现求解,并将计算结果应用于港珠澳沉管隧道工程中,建立基于荷载–结构法的二维分析模型。主要得到如下结论:(1)典型断面K9+843处的等效基床系数近似符合正态分布,均值为985 kPa/m,变异系数为0.265;(2)考虑地基变异性得到的沉降量近似符合对数正态分布,且差异显著;(3)断面沉降量与地层–结构法三维有限元模型计算结果接近,证明上述计算方法是合理的。

Determination of coefficient of subgrade reaction is the key to solve the engineering problems with load-structure method. In order to study the distribution characteristics and statistical parameters of layered soils foundation with variability,a calculation method with the compression modulus of each layer soil as the input parameter was derived based on the principle of consistent final settlement,and the variability of soil was considered with the aid of Monte Carlo method. Besides,the proposed method was realized by using Matlab software. The results were applied to the Hong Kong-Zhuhai-Macao immersed tunnel,and a two-dimensional analytical model was established based on the load-structure method. The following conclusions can be drawn:(1) The equivalent coefficients of subgrade reaction of the typical section K9+843 approximately obey normal distribution. The mean value is 985 kPa/m,and the coefficient of variation is 0.265.(2) The settlements of this section approximately obey logarithmic normal distribution when taking the variability of soils into consideration,which has a significant difference.(3) The settlements of this section are close to those obtained from three-dimensional analysis model based on stratum-structure method under the same condition,which validates the rationality of the proposed method to calculate the equivalent coefficient of subgrade reaction.