深回填土砂泥岩组合地层桩锚围护基坑的变形规律

Deformation Law of Pile-anchor Retaining Foundation Pit in Deep Backfill Soil Sand-mudstone Composite Stratum

[目的]目前工程界针对基坑的研究大多数基于软土基坑和岩质基坑的经验,重庆地区为深回填土砂泥岩组合地层,需展开基坑变形规律研究。[方法]以重庆轨道交通10号线兰花湖停车场基坑工程为背景,基于现场监测数据,总结围护结构水平位移,围护桩后地面沉降的变化规律,进而围护结构水平位移与桩后地面沉降相关性。[结果及结论]围护桩最大侧移δh变化范围为0.048%H~0.103%H(H为开挖深度),远小于软土地区的统计结果;最大地面沉降δv介于0.033%H~0.220%H,小于卵石和软土基坑,与青岛土岩组合基坑较为接近;基坑开挖影响范围为H~1.5 H;基坑最大地面沉降δv与围护结构最大侧移δh关系可表示为δ_(v)=0.45δ_(h)~2.35δ_(h),均值为1.31δ_(h);地面沉降包络面积和围护结构侧移包络面积比值近似为1.67。

[Objective]At present,most research in engineering field regarding foundation pit is based on the experience of excavations in soft soil and rocky strata.Given that the geological conditions in Chongqing involve deep backfill soil sand-mudstone composite stratum,it is essential to conduct a study on the deformation law of foundation pit.[Method]Taking the foundation pit project of Lanhuahu Parking Lot on Chongqing Rail Transit Line 10 as background,field-monitored data is utilized to summarize the horizontal displacement of retaining structures and the change law of land subsidence behind retaining piles.Additionally,the correlation between retaining structure horizontal displacement and land subsidence behind piles is explored.[Result&Conclusion]The maximum lateral displacementδh of the retaining piles ranges from 0.048%to 0.103%of the excavation depth H,which is significantly smaller than the statistical results observed in soft soil regions.The maximum land subsidenceδv ranges between 0.033%and 0.22%of H,lower than that observed in gravel and soft soil excavations,and closer to the results observed in Qingdao soil-rock composite foundation pit.The influence range of foundation pit excavation extends from 1 to 1.5 times the excavation depth H.The relationship between the foundation pit maximum land subsidenceδv and the retaining structure maximum lateral displacementδh can be expressed asδv=0.45δ_(h)~2.35δ_(h),with a mean value of 1.31δh.The ratio of the enveloped area of land subsidence to the enveloped area of retaining structure lateral displacement(S_(w)/S_(p))is approximately 1.67.