北京地区浅埋暗挖法下穿施工既有隧道变形特点及预测

 城市地下工程建设中，新建隧道近距离下穿施工对既有隧道造成的扰动不可避免。正确分析及可靠预计既有隧道变形成为目前地下工程建设的热点问题。在预测隧道开挖引起的地表位移的经验法中，Peck公式最简便，应用也最为广泛。搜集北京地区10个近接下穿工程23组数据，对既有隧道实测变形进行拟合，发现绝大多数符合Peck公式分布规律。拟合得到地层损失率为0.116%～1.183%，沉降槽宽度系数为0.93～6.76。讨论新建隧道施工工法、辅助施工方法、新建隧道与既有隧道的埋深、既有隧道刚度、新建隧道双洞间距、变形缝位置等因素对经验参数的影响，给出经验参数的修正公式。将经验参数修正公式与Peck公式相结合，为北京地区受新建隧道下穿施工影响的既有隧道变形提供一个简便、快捷的预测方法，并通过工程实例验证了预测方法的有效性。研究成果可对未来北京同类工程和其他地区近接工程设计和施工提供参考，同时对丰富同类工程数据库具有重要意义。

DEFORMATION CHARACTERISTICS OF EXISTING TUNNELS INDUCED BY EXCAVATION OF NEW SHALLOW TUNNEL IN BEIJING

The existing tunnels deform inevitably due to the excavation of a new tunnel nearby in the urban underground engineering construction. Correctly analyzing and predicting the deformation of the existing tunnel has been an important issue in underground engineering. Peck equation is one of the most popular used methods to predict the soft ground movement induced by the shallow tunneling. 23 sets of measured data from 10 projects in Beijing were found to fit well with Peck equation. The ground loss ratios fit by Peck equation are from 0.116% to 1.183%，and the width parameters of the settlement trough are from 0.93 to 6.76. The effects of the construction method of new tunnels，the auxiliary construction method of new tunnels，the burial depths of both the new tunnels and the existing tunnels，the flexural rigidity of the existing tunnels，the distance between two new tunnels and the position of the deformation joints of the existing tunnels on the fitting parameters were analyzed. Empirical formulae of fitting parameters were thus derived. Combining Peck equation with the empirical formulae of parameters，a simple and convenient method of prediction on the deformation of the exiting tunnels in Beijing area was obtained. The validity of the method was confirmed in an engineering case study.