软土地区基坑开挖诱发邻近盾构隧道水平位移的简化算法

A Simplified Calculation Method for Horizontal Displacement of Adjacent Shield Tunnel Caused by Excavation in Soft Soil Area

为探究软土地区基坑开挖对于邻近隧道水平位移的影响,首先,分析了软土地区基坑开挖卸载引起盾构隧道水平位移的变形机理;其次,收集了国内软土地区邻近地铁盾构隧道开挖基坑的工程实例,利用随机森林算法对影响隧道最大水平位移的因素进行了重要度排序,并对影响因素进行了统计分析,提出一相对简便且方便广大工程从业人员使用的半经验公式,可直接用于隧道在邻近基坑开挖下的最大水平位移的预测.通过与所收集到文献中已发表的工程实际案例实测数据的对比,对经验公式进行了验证,验证了所提公式的准确性与适用性.参数分析表明:隧道最大水平位移随基坑开挖体量的增大近似呈对数增大,增速逐渐放缓.隧道水平位移受基坑围护结构水平位移影响较大,两者之间近似呈线性正相关.隧道最大水平位移与基坑隧道间距离呈负相关关系,当距离小于两倍开挖深度时,基坑开挖对隧道的影响较大.基于提出的公式,对基坑开挖对隧道的影响范围进行了分区,结果可为类似工程提供一定的理论指导.

To explore the effect of excavation on the horizontal displacement of adjacent tunnels in soft soil area,firstly,the deformation mechanism of horizontal displacement of adjacent tunnels in soft soil area due to excavation is analyzed.Secondly,project cases on excavation of adjacent tunnels in soft soil area are collected.The importance of the factors affecting the maximum horizontal displacement of the tunnel is ranked by the random forest algorithm.Through analyzing the influencing factors statistically,a semi-empirical formula,which is relatively simple and convenient for engineering practitioners,is proposed.It can be directly used to predict the maximum horizontal displace-ment of the adjacent tunnel under excavation.The accuracy and applicability of the proposed empirical formula is verified by comparing with the measured data of the actual engineering cases published in the collected literature.Parameter analysis shows that:with the increase of excavation geometry,the maximum horizontal displacement of the tunnel increases in an approximate logarithmic relation,but the increasing speed gradually slows down.The horizontal displacement of tunnel is greatly affected by the horizontal displacement of retaining structure.It is approximate linearly correlated with the horizontal displacement of retaining structure.The distance between the excavation and the tunnel has a negative correlation with the maximum tunnel horizontal displacement.Furthermore,when the distance is less than twice the excavation depth,the influence of excavation on the tunnel is greater.Based on the proposed formula,the effect range of excavation on the tunnel is divided into zones,and the results can provide certain theoretical guidance for similar projects.