入岩基坑桩锚支护结构在爆破振动作用下的弱化及失效机理研究

There is much less research of blasting vibration effects on pile-anchor supporting structure during the excavation process of urban rock pit foundation. This project will be carried out through theoretical analysis, field test, physical and numerical simulation in order to solve the potential safety problem in urban rock pit foundation engineering. First, monitoring components and sensors will be laid in pile-anchor supporting structure and peripheral rock at the test site, so that the deformation and stress characteristics of the structure can be easily analyzed by the monitoring data during the pit foundation construction. At the same time quality inspection will be carried out by sonic prospecting before and after the blasting process. Second, according to the characteristics of blasting seismic wave, bearing capacity test of the pile-anchor supporting structure under blasting vibration will be carried out on large-scale shaking table to study the weakening effects of anchorage force due to circle vibration. Finally, the interaction between pile-anchor supporting structure and rock foundation will be analyzed using forward and backward numerical methods, and the calculation parameters will be adjusted for numerical backward analysis work according to data of field test and physical simulation test. The study will reveal the weakening mechanism and failure evolution of pile-anchor supporting structure in a circular scrolling way, and present an evaluation method of slopes reinforced by pile-anchor retaining structure under blast vibration in rock pit foundation, which will provide reliable, practical theory basis for the design and construction of foundation pit and slope engineering.

当前对桩锚支护结构在入岩基坑下挖过程中遇到的爆破振动影响问题研究尚属空白。本项目采用理论分析、现场试验、物理和数值模拟试验相结合的研究方法进行研究，以解决入岩基坑工程中存在的施工安全问题。首先，通过在施工现场对桩锚支护结构及周边岩体埋设监测元器件，监测和分析桩锚支护结构在施工全过程的变形和受力特性，并在爆破前后采用声波测试等检测手段对桩锚支护结构进行质量检验。其次，结合爆破地震波特点，在振动台上对桩锚支护结构进行承载性能试验，以研究由于循环振动影响带来的锚固力弱化问题。最后，采用数值模拟研究桩锚支护结构与岩土体的相互作用，通过与现场试验资料、物理模拟成果相比较，调整计算参数进行数值反分析工作。本项目以循环滚动方式研究桩锚支护结构在爆破振动作用下的弱化及失效机理，提出爆破振动作用下采用桩锚支护结构的基坑边坡稳定性评价方法，为基坑及边坡工程设计和施工提供可靠、实用的理论依据。

针对桩锚支护结构在入岩基坑工程受到的爆破振动影响问题，本项目采用理论分析、室内试验、现场试验以及数值模拟计算相结合的研究方法，以解决入岩基坑工程中存在的施工安全问题。. 在室内试验中，通过物理模型试验揭示桩锚结构的受力特性及坡体变形破坏特征，分析支护桩水平位移和锚索轴力的演化规律；以锚固界面为研究对象，开展桩-锚体系嵌（锚）固围岩的流变特性研究，分析各流变阶段特征。. 以厦门某典型基坑工程为研究案例，首先建立三维静力、二维动力数值模型，模拟不同岩土体开挖、预应力锚索支护以及爆破加载步骤下的支护桩以及预应力锚索的变形及受力演化过程，研究支护桩桩身水平位移、支护桩内力、支护桩损伤效应、预应力锚索拉力及内力以及桩锚结构的爆破振动响应。与现场监测数据对比完善后数值计算分析表明：①深基坑开挖爆破可诱发支护桩损伤的产生和发展；②爆破加载作用在波阻抗较小的岩土体边界上，易使岩土体与支护桩的交界面产生受拉损伤，在有岩层分界面处产生损伤的风险更大；③爆破加载通过扰动岩土体应力使岩土体水平应力降低，使得各排预应力锚索的拉力出现重新调整。. 提出基于多态模糊贝叶斯网络的桩锚支护基坑工程多参量稳定性评价方法，实现了爆破开挖前和爆破开挖施工过程中实际故障状态两种不同的方式计算失稳风险发生的概率，根据敏感性分析结果辨识关键致险因子，通过反向推理获得各根节点的后验概率以进行故障诊断及进一步预测系统状态。.项目研究成果可为基坑及边坡工程设计和施工提供可靠、实用的理论依据。