竖井施工对软土地基的扰动效应研究

Study on disturbance effect on soft soil ground during vertical drain construction

为了分析竖井施工扰动对竖井排水效果的影响,基于圆柱形孔扩张理论,并考虑土体自重应力的影响,采用Mohr-Coulomb屈服准则,得到了弹塑性交界处土体位移、塑性区半径以及最终挤土应力等理论计算公式.对塑性区沿深度的变化规律作了仔细分析,分析表明塑性区呈上大下小的漏斗形,半径大小与埋深、土体参数等密切相关.在塑性区分析的基础上,进一步指出传统竖井固结理论认为涂抹区与深度无关的假设跟实际不符,对不同竖井的涂抹区范围取值不加区别也不甚合理,所建议的涂抹区范围对于袋装砂井来说偏小,宜根据土质、竖井类型等来选择涂抹区范围.

In order to analyse the disturbance influence during vertical drainage construction, based on the column cavity expansion theorem and considering the influence of the soil gravidity stress, the radius of the plastic zone, the ultimate crowding stress and the soil displacement in the intersection of plastic and elastic areas were deduced when Mohr-Coulomb yield criterion was adopted. The characteristics that the plastic area changed with the depth were studied carefully. The analysis results showed that the plastic area looking like a funnel, wide at the top and narrow at the bottom, had radius value closely related with the depth and parameters of soil. Based on the analysis on plastic area, it was further pointed out that the assumption of traditional vertical drain system consolidation theorem that smear area was unrelated with the depth cannot live up to the reality, and the suggested smear zone was unreasonable not to distinguish different vertical drains, and also was small for sand drain. The smear zone shoud be determined by soil type, vertical drain type, and so on.