京津城际路基沉降数值模拟与原位观测对比分析

Comparison and Analyses of Numerical Simulation and in Situ Observed Data of Subgrade Subsidence of Beijing-Tianjin Intercity Railway

研究目的：京津城际轨道交通工程天津段内广泛分布软土，其成因类型主要为冲积、海积，局部为湖沼堆积；岩性为各类黏性土、粉土、砂类土等，夹淤泥、淤泥质黏土、淤泥质粉质黏土。上述土体含水量、孔隙比较大，所以在路堤荷载及列车荷载作用下的沉降变形较大。为满足无砟轨道对路基工后沉降的要求，路基基底采用CFG桩复合地基进行加固。由于复合地基受力状态复杂，对其进行工后沉降预测较为困难，本文采用数值模拟和原位数据对比分析的方法对路基的工后沉降进行预测。研究结论：（1）采用数值模拟及原位测试数据对比分析复合地基的沉降变形规律，得出桩问土的压缩主要发生在桩长下部的1／4—1／6桩长范围内，桩端的刺入量占总沉降值的20％～30％；（2）由实测的沉降-深度分布曲线可以得到，桩端以下土体压缩层厚度为桩平面分布宽度的1倍左右；（3）有限元计算所得的最大沉降量和工后沉降量，与观测值相比较为接近，采用有限元计算结果推断的工后沉降差异，小于根据实测值采用经验公式得到的推断值，因此在沉降计算中应推广有限元方法。

Research purposes： There are a lot of soft soils in the Tianjin section of Beijing - Tianjin Intercity Railway. The main reasons for the soft soil formation are the alluvion and accumulation of lake marsh. According to the lithologic classification, most of these soft soils are clay, silt and sand soil and a few of them are sludge and mucky soil. As the soils contain much water with big void ratio, the subsidence of subgrade subsidence is large under the loads of the embankment and the train. For satisfying the requirement of ballastless track for the construction -post subsidence of subgrade, the subgrade base is reinforced with CFG pile. As the stressed situation of composite subgrade is complicated, it is difficult to predict the construction - post subsidence of subgrade. In this paper, the construction - post subsidence of the subgrade is predicted by making the comparison and analyses of numerical simulation and in situ observed data. Research conclusions：（ 1 ） The numerical simulation and in situ observed data are used to compare and analyze the subsidence law of composite subgrade and it can be seen that the compression of soil between piles appears in 1/4 - 1/6 ranges of the pile bottom and the entry volume of pile end is up to 20% - 30% of the total subsidence volume. （2） It can be seen from the subsidence - depth distribution curve that the compression depth of the soil body under the pile end is one tine of plane distribution width of pile. （ 3 ） The max. subsidence volume and construction - post subsidence calculated with finite element method are very close to the observed data and the difference of construction-post subsidence predicted with finite element method is smaller than that with experience formula. So the finite element method is worth using widely in calculation of subsidence.