临近既有线基坑支护影响因素的正交分析

以既有线的轨道水平作为控制标准, 对基坑尺寸、既有线形式与支护形式等影响因素进行正交优化分析, 并与现场沉降结果进行对比。根据极差和方差分析方法, 确定了临近既有线轨道水平的影响因素的重要性顺序, 分析了是否考虑渗流影响下的的轨道水平。分析结果表明: 临近既有线轨道水平的影响因素的重要性顺序依次为基坑宽度、既有线路基高度、既有线股道数量(路基面宽度)、基坑深度、支撑点位置、支撑强度、桩长和基坑距坡脚距离; 在支护参数中, 第1道支撑点位置是主导因素; 当考虑渗流后, 轨道水平将大大增加。建议在施工过程中, 优先考虑基坑宽度因素, 且临近既有线的开挖必须在止水条件下进行, 应采用优化参数的结构形式, 使得轨道水平在3.0mm范围内。

Orthogonal analysis of influence factors for foundation pit support approaching existing railway line

The track level of existing railway line was taken as control standard, the influence factors including foundation pit size, existing railway line form and support form were orthogonally analyzed, and the calculation results and field settlement situation were compared. Based on the analysis methods of range and variance, the importance order of influence factors on track level approaching existing railway line was determined, and the track levels were analyzed with and without seepage.Analysis result shows that the importance order of influence factors on track level approaching existing railway line are the width of foundation pit, the subgrade height of existing railway line, the track number of existing railway line (the width of subgrade surface), the depth of foundation pit, support point position, support strength, pile length and the distance from foundation pit to slope toe.For support parameters, the first support position is dominant influence factor.When seepage is considered, the railway track level increases greatly.It is suggested to consider the width of foundation pit preferentially in construction process.The excavation approaching existing railway line should be done under sealing condition.The structure type with optimized parameters should be used to make railway track level less than 3.0 mm.