黄河冲积互层深基坑围护桩插入比优化分析

济南西北部为黄河下游冲积黏-砂互层地质结构,深基坑稳定性受地层条件影响较大,土层质量直接影响围护桩插入比的取值。以山东省会文化艺术中心深基坑为工程背景,通过理论计算和数值模拟对桩体在不同插入比下的稳定性进行分析。研究发现:土层质量参数与插入比存在线性关系,可引入土压力折减系数计算围护桩入土深度;通过实际工程数值分析得到最佳插入比为0.55;根据现场0.58插入比实测数据对数值模拟进行验证,结果发现桩顶侧向位移最大值为0.05%H(H为基坑深度),沉降最大值为0.04%H,基坑结构足够稳定且有相当大的安全储备,因此,可减小插入比以降低工程造价,缩短施工工期,实现工程的绿色建设。研究成果对济南特殊的黄河冲积层地区深基坑建设具有借鉴意义。

Optimizing Insertion Ratio of Supporting Pile in Deep Foundation Pit in Yellow River Alluvium

The stability of excavation pit in northwest Ji'nan,which locates in alluvial clayey-sand interbedded zone of downstream Yellow River,is greatly affected by soil strata.The pile insertion ratio (defined as the pile length above excavation bottom to the length below excavation bottom) is directly affected by soil strata quality.In this article,the stability of support piles with different insertion ratios are analyzed through theoretical calculation and numerical simulation.The excavation pit at the Shandong Provincial Cultural and Arts Center is taken as engineering background.Research results reveal that parameters of soil strata quality are in linear relations with insertion ratio.By introducing the earth pressure reduction coefficient into the calculation of embedded depth of pile,we found that the optimum insertion ratio is 0.55.According to measured insertion ratio 0.58,the numerical result is verified.The maximum lateral displacement of pile top is 0.05％ of the pit depth (H),and maximum settlement 0.04％H,indicating that the excavation structure is stable enough with sufficient safety reserve.Therefore,the insertion ratio in the study case can be reduced to cut project cost and shorten construction period.The research results are of reference value for excavation pit construction in special alluvial areas of the Yellow River.