软土深基坑组合开敞式支护数值模拟与监测分析

以某沿海地区深基坑工程为背景,介绍了软土地区采用分级卸荷、重力挡墙和桩锚组合的开敞式基坑支护型式。通过建立三维有限元模型模拟基坑开挖过程,对比数值模拟和现场监测结果,分析了基坑支护桩水平位移和锚杆力的变化规律。结果表明:支护桩变形和锚杆力的模拟值与监测结果趋势一致,实测结果与预测值的整体偏差在15%以内,基坑工程处于安全稳定状态;三维有限元模型可以较好地考虑基坑在组合支护情况下重力挡墙和空间效应对桩锚结构受力的影响,具有较高的可信度;对于软土基坑,将重力挡墙和桩锚组合,并结合分级卸荷,改变了支护结构上的土压力分布规律,能够有效控制基坑变形,确保支护结构稳定。应用成果可以为同类工程提供参考。

Numerical simulation and monitoring analysis of composed open-typed support for deep soft soil foundation pit

By taking a deep foundation pit project in coastal area as the case，the open-typed support system composed by staged unloading，gravity retaining wall and pile-anchor for the foundation pit adopted in soft soil area is introduced herein． Through establishing the relevant 3-D finite element model for simulating the construction of the foundation pit，the results from the numerical simulation and the in situ monitoring are compared，and then the variation laws of the horizontal displacement of the supporting pile and the force of the anchor bolt for the foundation pit are analyzed as well． The results show that the trends of the simulated values of the deformation of the supporting pile and the force of the anchor bolt are coincided with those of the monitoring results，while the overall deviations between the measured results and the predicted values are within 15%，thus it is indicated that the foundation pit project is in a safe and stable status． The 3-D finite element model can better consider the influences from the gravity retaining wall and space effect on the pile-anchor structural stress under the condition of the foundation pit being supported by the composed support，and then has a higher credibility． For the soft soil foundation pit，combining gravity retaining wall with pile-anchor and integrating stage unloading can change the distribution law of the soil pressure on supporting structure and then effectively control the deformation of foundation pit for ensuring the stability of the supporting structure． The application results can provide references for the similar projects concerned．