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

Analysis of Force and Deformation Characteristics of Pile-anchor Support System for Ultra-deep Foundation in Hard Rock Strata

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,依托于崂山公卫中心基坑支护工程,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。

To investigate the stress and deformation evolution of the deep foundation pit pile-anchor support system in hard rock formations,relying on the support project of Laoshan public health center foundation pit,real-time monitoring was conducted on the prestressed anchor bolt axial force,horizontal and vertical displacements of the completed area of the south side support.The mechanical performance of the pile-anchor support system under these geological conditions was analyzed,and the factors influencing the rapid decrease of anchor bolt axial force and the increase of horizontal displacement of the foundation pit were discussed.The results show 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.