移动荷载作用下土岩组合基坑吊脚桩变形分析

以青岛地区特有的土岩组合地质条件为背景,采用现场监测和Plaxis有限元模拟相结合的方法,研究了土岩基坑中吊脚桩在龙门吊移动荷载作用下的变形规律及动力响应。结果表明:桩身变形模拟结果与实测值吻合较好,基坑的变形主要发生在基坑上部软弱土层,吊脚桩嵌岩处产生应力集中;在龙门吊移动荷载作用下,桩顶水平位移较大,但其动力响应最小,而嵌岩处水平位移较小,但其动力响应最大;嵌岩处、桩身最大正弯矩处及最大负弯矩处的土压力动力响应较大,且移动荷载刚经过时刻影响最大。研究成果可为类似土岩结合地区深基坑支护设计提供参考。

Deformation analysis for the end-suspended piles in the combined soil-rock foundation pits under moving loadings

Based on the unique feature of the combined soil-rock geological conditions in Qingdao, Shandong province, the deformation and dynamic responses of the end-suspended piles for foundation pits in the combined soil-rock foundation pits under gantry crane moving loads are studied by using the finite element code, Plaxis, and field monitoring. The results indicate that the numerical predictions agree well with the measured deformations of the pre-bored pile shaft, and the major deformation of foundation pit occurs in the soft soil strata in rocky area, whereas the stress concentration occurs at the rock-socketed part of the end-suspended piles. In addition, under the gantry crane moving loads, the horizontal displacement of the pile head is larger, and its dynamic response is the least pronounced, whereas the horizontal displacement of the rock-socketed part is smaller and its dynamic response is the most significant. At the rock-socketed part, maximum positive bending moment part and maximum hogging moment part, the dynamic responses of earth pressure are the most pronounced, and the largest response occurs as a moving load passes by. The results can provide reference for the deep foundation pit supporting design in similar geological conditions.