软土地基的变形速率及稳定性控制

Deformation Rates and Stability Control of Soft Foundation

为了给软土堆载工程监测提供依据,讨论了工程中常采用的沉降速率10mm·d-1、水平位移速率5mm·d-1作为各类软土地基稳定性控制指标的适用性,并研究了不同加载速率和地基处理方式对软土地基变形的影响。结合上海某工程塑料排水板地基的监测数据,研究了堆载作用下软土地基的变形速率特征,并采用有限元法详细分析了加载速率和地基处理方式(有、无塑料排水板)对软土地基变形速率的影响。研究结果表明:这种采用位移速率为控制指标的方法并不能完全准确反映地基的稳定性,在加载初期安全性较大时位移速率会超过控制标准,而在地基破坏前的位移速率却低于控制标准;加载速率对变形速率有直接影响,加载速率越大地基变形速率也越大;地基的排水性能对变形速率有显著影响,打设塑料排水板的地基比其他类型处理的地基具有更大的变形速率。此外,对于塑料排水板软土地基,软土的固结压密以及排水系统性能的弱化也会造成该类地基的变形速率呈现前期快而后期慢的反常现象。因此,对于塑料排水板软土地基的稳定性控制,这种特殊现象在地基变形监测数据分析中应该予以重视。

To provide a reference for engineering monitor of soft ground under embankment loading,the applicability of commonly used control indicators for the stability of soft foundations with the settlement rate of 10 mm·d-1 and horizontal displacement rate of 5 mm·d-1 in engineering was discussed and the influences of different loading rates and soil treatment methods on the deformation rates of the soft foundation were mainly investigated.According to the field monitor data of a PVD-treated soft ground under embankment loading in Shanghai,deformation rate characteristics of soft ground under the heaped load were investigated,and the finite element method（FEM）was used to analyze the influences of different loading rates and various foundation treatment methods（with or without PVD）on the deformation rates of the soft foundation.The results show that this method based on displacement rate can not accurately reflect the stability of the soft foundation.At the initial loading stage,with high security,thedisplacement rate exceeds the control value;however,before ground failure,the displacement rate is lower than the control value.The loading rate influences the deformation rate directly,and the deformation rate increases with the increase of loading rate.The drainage performance of the foundation has a significant influence on the deformation rate,and the PVD-treated soft grounds have much higher deformation rates than other types of ground.In addition,for PVD-treated soft ground,consolidation and compression of soft ground and weakness of drainage system may result in the abnormal phenomenon that the deformation rate is higher at the initial stage and lower at later stage.Therefore,for the stability control of PVD-treated soft ground,the abnormal phenomenon should be taken seriously in the analysis of monitoring data of foundation deformation.