黄土地层地铁暗挖隧道地表纵向沉降规律及其预测分析方法

地铁隧道施工过程中，地表纵向沉降槽最大倾斜率及其出现的时机对地面和地下建筑物的安全评价非常重要。针对目前采用累积概率曲线描述纵向沉降曲线的不足，依据黄土地区地铁隧道暗挖施工引起地表纵向沉降槽特征的研究，寻求一种能反映地表纵向沉降规律的函数，引入掌子面地表位移释放率和地表纵向沉降最大斜率2个特征值，提出基于特征值的地表纵向沉降预测方法。研究结果表明，黄土地区暗挖法地铁隧道施工过程，老黄土-古土壤地层掌子面地表位移释放率和地表纵向沉降最大斜率均较大，饱和软黄土地层的较小。经过数学严密推导，提出一种考虑掌子面地表位移释放率和地表纵向沉降最大斜率的地表纵向沉降预测分析方法，分析了其随着特征值的敏感性，验证了预测方法的可靠性和合理性。研究成果对于分析和预测地铁隧道施工引起地表不均匀沉降对地面与地下建筑的影响具有重要的意义。

Surface longitudinal settlement induced by subway tunneling in loess and its prediction analysis method

During the construction process of subway tunnel, maximum inclination rate of surface longitudinal settlement and release rate of surface settlement on the excavated face are significant for safety assessment of surface and underground building. Cumulative probability curves can not completely describe the characteristics of longitudinal settlement. Firstly, the characteristics of the surface longitudinal settlement caused by covered digging of subway tunnel in loess are researched. Secondly, a new function is sought to reflect the characteristics of surface longitudinal settlement. Thirdly, the maximum inclination rate of surface longitudinal settlement and the release rate of surface settlement on the excavated face are analyzed in the different regions of loess. Finally, Predicting method of surface longitudinal settlement is put forward based on the two characteristic values. The results indicate that during the construction process of subway tunnel by covered digging in the region of loess, the two characteristic values in the paleosol strata are both maximum, but on the contrary in the saturated soft loess strata. Through the rigorous mathematical derivations, a predicting analysis method is proposed considering maximum inclination rate of surface longitudinal settlement and release rate of surface settlement on the excavated face. Its sensitivity with characteristic values is analysed; and rationality of these methods is verified based on the monitoring data. It has a significant meaning to analyze and predict the influences that differential settlements on the surface have an effect on the ground and undergroud building.