土岩组合深基坑桩撑式支护结构抗倾覆稳定性研究

Study on overturning stability of pile-strut support for deepfoundation pit in soil-rock combination formation

为了探究围护桩插入比和见岩面深度对土岩组合二元地层桩撑式深基坑围护结构抗倾覆稳定性的影响,结合金华地区某地铁站深基坑土压力和支撑轴力的实测数据,采用有限元软件Midas GTS NX进行数值模拟,针对不同桩插入比及不同见岩面深度的模拟结果进行分析。研究结果表明:开挖面位于见岩面以上时,土压力呈三角形分布;开挖面位于见岩面以下时,土压力呈近R形分布;桩撑式基坑抗倾覆稳定性与见岩面深度呈负相关;抗倾覆稳定性与桩插入比呈正相关,桩插入比存在某个转折点,到达转折点后抗倾覆稳定性系数趋于稳定,见岩面深度和桩插入比均是抗倾覆稳定性的重要影响因素。对相同地质条件下见岩面深度较浅的桩撑式深基坑工程,可采取适当降低围护桩插入比的方法来降低施工成本。本研究所得数据能为土岩组合二元地层桩撑式基坑围护结构设计和施工提供一定的指导。

In order to explore impacts of the insertion ratio of retaining piles and the geotechnical interface depth on the anti-overturning stability of the retaining structure of the pile-strut deep foundation pit in soil-rock combination binary strata,in combination with the measured data of soil pressure and supporting axial force of a deep foundation pit in a subway station in Jinhua,the finite element software Midas GTS NX was used for numerical simulation,analyzing the simulation results regarding different pile insertion ratios and different geotechnical interface depths.The results show that when the excavation face is located above the geotechnical interface,the soil pressure is distributed triangularly;when the excavation face is below the geotechnical interface,the soil pressure is distributed roughly in the R shape.The anti-overturning stability of foundation pit is negatively correlated with the geotechnical interface depth h,while the anti-overturning stability is positively correlated with the pile insertion ratio δ.Theδhas an inflection point where the anti-overturning stability coefficient tends to be stable.Thus,both h andδare important factors influencing the anti-overturning stability.For the pile-strut deep foundation pit projects with shallower geotechnical interface under the same geological conditions,the construction cost can be lowered by appropriately reducing the insertion ratio of retaining piles.The data can provide some guidance for the design and construction of the retaining structure of the pile-strut foundation pit in soil-rock combination binary strata.