硬岩地层超深基坑桩锚支护体系受力与变形特性实测分析

为探究硬岩地层超深基坑桩锚支护体系随基坑开挖的受力与变形演化规律,依托于崂山区某基坑支护工程,对南侧支护完成区域基坑的预应力锚索轴力、基坑水平和竖向位移进行了实时监测,分析桩锚支护体系在该地质条件下的力学性能,探讨锚索轴力急速下降与基坑水平位移增大的影响因素。研究表明：预应力锚索轴力持续、急速的下降与基坑紧邻原状山体的土压力和北侧后挖区域的持续施工有关,工程中采取预应力锚索2次补偿张拉适用效果良好；基坑最大水平位移为19.98 mm,最大竖向位移为12.11 mm,南侧支护完成区域基坑支护体系的变形受后续施工区域的影响明显；桩锚支护体系在硬岩及土岩二元地层超深基坑中具有较好的适用性和可靠性。类似工程支护结构设计应重视周边地质环境、邻近区域持续施工等因素的影响。

Analysis of force and deformation characteristics of pile-anchor support system for ultra-deep foundation in hard rock strata

In order to investigate the evolution law of force and deformation of pile-anchor support system of ultra-deep foundation pit in hard rock stratum with excavation of foundation pit, based on a foundation pit support project in Laoshan District, real-time monitoring of prestressed anchor cable axial force, horizontal and vertical displacement of foundation pit in the completed area of south side support was carried out to analyze the mechanical performance of pile-anchor support system in this geological condition and explore the influencing factors of rapid decrease of anchor cable axial force and increase of horizontal displacement of foundation pit. The study shows that the continuous and rapid decrease of the axial force of the prestressing anchor cable is related to the earth pressure of the foundation pit adjacent to the original mountain and the continuous construction of the back excavation area on the north side, and the project takes 2 times of compensatory tensioning of the prestressing anchor cable to apply good effect; The maximum horizontal displacement of the foundation pit is 19.98 mm and the maximum vertical displacement is 12.11 mm. The deformation of the foundation pit support system in the completed area of the south side support is obviously influenced by the subsequent construction area; The pile-anchor support system has good applicability and reliability in ultra-deep foundation pits in hard rock and soil-rock binary strata. The design of support structure of similar projects should pay attention to the influence of surrounding geological environment and continuous construction in neighboring areas.