饱和软黏土地基竖井施工扰动效应分析与评价

由于挤土效应,饱和软黏土地基中竖井施工会产生附加扰动,并导致井周土体强度与渗透系数降低。基于修正剑桥模型的屈服准则,应用圆柱形孔扩张理论对不排水圆孔扩张过程中土体应力状态进行分析。根据超静孔压和径向应力的分布规律,在确定了扰动区范围的基础上,提出一种修正的基于饱和软黏土灵敏度考虑的原位扰动函数FD,并结合已有文献中室内模型试验与现场竖井施工扰动引起的固结指标变化规律的结果,验证了修正的原位扰动函数的合理性。施工扰动的合理评价有助于准确计算竖井地基的固结沉降。

Analysis and assessment of disturbance effect by the installation of vertical drain in saturated soft clay ground

Due to the squeezing effect,additive soil disturbance induced by the installation of vertical drains results in reduction of the in situ consolidation index of soft deposits in the immediate vicinity of the drains.An attempt was made to analyze the stress state during the undrained expansion of a cavity,and the cylindrical expansion theory for soft clay was employed to obey the modified Cam clay model.The analysis results indicate that the excess pore pressure and radical stress generate when installation decreases logarithmically as the radical distance from the centre of vertical drains increase.Based on the analysis above and determination of the disturbed zone extent surrounding vertical drains,a modified field disturbance(FD) function is proposed considering the sensibility of saturated soft clay.The proposed disturbance function is verified through the laboratory tests on samples collected from field and model experiments from the available literature.Furthermore,the reasonable assessment of construction disturbance effect on soft clay is helpful to exactly calculate the consolidation settlement of the ground with vertical drains.