深基坑开挖影响下深厚软土路基变形规律研究

Study on the Deformation Law of Deep Soft Soil Subgrade under the Influence of Deep Foundation Pit Excavation

深厚软土区域地下空间开发形成的深基坑环境影响与控制一直是业界关注重点。为研究排桩支护深基坑开挖卸荷下深厚软土路基变形的影响因素与规律,以横琴深度合作区近邻某软土路基的深基坑工程为例,利用HS模型确定真空联合堆载预压处理后软土参数,建立考虑路侧原状软土的数值模型,并与现场实测结果相互验证,得到如下结论:(1)受路侧原状软土影响,浅层开挖阶段软土路基远基坑侧的深层水平位移大于近基坑侧;(2)随开挖深度增加,最大深层水平位移慢慢发展至开挖面附近且达到了40.5 mm,最终水平位移整体形态在远基坑侧表现为倾斜,近基坑侧为开挖面附近的“鼓出”;(3)路基沉降同时受路基顶面荷载和基坑开挖卸荷影响,其中路基顶面荷载引起的沉降占到了累计值的64.4%;(4)基坑开挖第一阶段和第二阶段数值计算和实测结果吻合度高,而受软土流变影响,深层水平位移持续发展,开挖第三阶段实测值显著大于数值计算。研究成果可为深厚软土区域基坑环境影响的变形预测与控制提供科学依据。

The environmental impact and control of deep foundation pit formed by underground space development in deep soft soil area has always been the industry focus.In order to study the influencing factors and laws of soft soil subgrade deformation under the excavation and unloading of deep foundation pit supported by row piles,taking the deep foundation pit project adjacent to a soft soil subgrade in Hengqin New Area as an example,the soft soil parameters after vacuum combined surcharge preloading are determined by HS model,and a numerical model considering the undisturbed soft soil on the roadside is established,and then the results are verified with the field measured results.The following conclusions are obtained:(1) Affected by the lateral pressure of undisturbed soft soil on the roadside,in the stage of shallow excavation,the horizontal displacement of soft soil subgrade far from the foundation pit is greater than that near the foundation pit;(2)With the increase of excavation depth,the maximum horizontal displacement slowly develops to 40.5 mm near the excavation surface.Finally,the overall shape of horizontal displacement is inclined at the far side of the foundation pit,and "bulging" near the excavation surface.(3) The subgrade settlement is affected by pavement load and foundation pit excavation at the same time,among which the settlement caused by the pavement load accounts for 64.4% of the cumulative value.(4) The numerical calculation of the first stage and the second stage of foundation pit excavation are in good agreement with the measured results.Due to the influence of soft soil rheology,the horizontal displacement will continue to develop,and the measured value of the third stage of excavation is significantly greater than the numerical calculation.The research results can provide a scientific basis for the deformation prediction and control of the environmental impact of foundation pit in deep soft soil area.