基于位移梯度法的深基坑桩锚支护结构动态稳定性分析

Dynamic stability analysis of pile anchor support structure in deep pits based on displacement gradient method

滑裂面的搜索模型与安全系数的计算方法是分析深基坑桩锚支护结构稳定性的两大重要内容.本文通过切向位移梯度法搜索最危险滑裂面,并在极限平衡理论的基础上改进了安全系数的计算模型.通过循环以下两步实现滑裂面搜索:搜索切向位移梯度最大的方向作为滑裂面的切线方向;顺着搜索到的切线方向延伸至滑裂面的下一点.在安全系数的计算过程中,通过应力比考虑张拉破坏对土体抗滑力矩的影响.最后,将滑裂面位置及张拉破坏区域代入改进的安全系数公式计算对应工况下基坑的安全系数.通过算例分析发现:切向位移梯度在0°~90°范围内存在极大值;张拉破坏区集中在较浅的土层范围内,且随施工过程动态变化.

The search model of the slip surface and the calculation method of the safety factor are the two important contents to analyze the stability of the pile-anchor support structure of deep foundation pits. In this study, the most dangerous slip surface is searched by the tangential displacement gradient method, and the calculation model of the safety factor is improved based on the limit equilibrium theory. The sliding surface is searched in two steps: searching the direction with the maximum tangential displacement gradient as the tangent direction of the sliding surface;the next point of the sliding surface is determined according to the direction of the maximum tangential displacement gradient. In the calculation of the safety factor, the effect of tensile failure on the anti-sliding moment of the soil is considered through the stress ratio. Finally, the location of the slip surface and the tensile failure area are substituted into the improved safety factor formula to calculate the safety factor of the foundation pit under the corresponding working conditions. Through the analysis of numerical examples, it is found that the tangential displacement gradient has a maximum value in the range of 0° to 90°. The tensile failure zone is concentrated in the shallow soil layer and changes dynamically with the construction process.