地铁车站浅埋暗挖法施工引起地表沉降规律研究

STUDY ON GROUND SETTLEMENT INDUCED BY SHALLOW METRO STATION CONSTRUCTIONS

通过大量现场监控量测数据的统计分析,研究北京地区黏性土与砂性土互层的特定地质条件下,地铁车站浅埋暗挖法施工引起地表沉降的一般规律。分析结果表明:约占69.8%的暗挖地铁车站,地表沉降值小于60 mm,大于相应沉降值的累计发生频率曲线符合正态分布。地表沉降槽宽度参数的取值范围与施工方法密切相关,对洞桩法而言,该值为0.61～0.82;而对中洞法而言,该值则为0.40～0.65。不同施工方法引起的地层损失率也有差异,对洞桩法而言,该值为0.39%～1.41%,均值为0.93%;而对中洞法而言,该值为0.49%～1.03%,均值为0.69%。所得结论可用于初步判断车站施工引起的最大地表沉降,并可为地铁车站施工环境影响(包括桥桩、建筑和管线等)预测提供依据。

For studying the effects of ground movements on pipelines and structures, prediction of ground settlement induced by tunneling is always a hot issue. A regression analysis of the field measurements of ground settlements induced by shallow metro station constructions in Beijing is conducted to acquire empirical estimations of the relevant characteristic parameters. The ground conditions include silty sand, silty clay, clayey silt, silty fine sand, medium and coarse sands, cobble and gravel, which are typical of soil compositions in Beijing area. About 69.8% of the maximum ground settlements induced by the station constructions are less than 60 mm. The accumulative frequency curve of maximum surface settlement fits well with the accumulative normal distribution curve. The parameter of settlement trough is dependent on the construction method： 0.61 - 0.82 for drift-PBA method, and 0.40 - 0.65 for central drift method. The ground loss ratio is 0.39% - 1.41% for drift-PBA method： and the average loss ratio is 0.93%. For central drift method, the ground loss ratio is 0.49% - 1.03%, and the average is 0.69%. These results are useful for predicting the magnitude and influential range of ground settlement.