深埋隧道锚岩体力学参数综合取值研究

深埋岩石工程勘察设计阶段中岩体原位试验工作困难,针对深埋复杂岩体力学参数选取问题,提出在岩体地质分析基础上,综合原位试验和Hoek-Brown准则的岩体力学参数取值方法。该方法首先依据勘探成果分析岩体地质特征,对工程区岩体进行分类,应用Hoek-Brown准则确定各类岩体力学参数并采用经验参数核对校正,确定设计阶段岩体力学参数。最终根据施工开挖揭示地质信息和原位试验,校正设计阶段岩体力学参数。该方法应用于川藏高速公路泸定大渡河特大桥隧道锚区域蚀变二长花岗岩岩体力学参数确定,实例分析表明:岩体原位试验成果离散性大,试验成果难以代表大范围复杂岩体力学参数;Hoek-Brown准则估算岩体内摩擦角与原位试验基本一致,黏聚力则偏高较多,需要采用经验参数校正;复杂岩体力学参数的选取,需在地质分析基础上综合采用各种方法相互验证。

Study on Comprehensive Selection of Mechanical Parameters of Rock Mass in Deep-buried Tunnel Anchor

In-situ rock mass test of deep-buried rock engineering is difficult in the investigation and design stage. Aiming at selecting mechanical parameters of complex rock mass with large buried depth, a method of selecting rock mass mechanical parameters based on rock mass geological analysis is proposed, which combines in-situ test and Hoek-Brown criterion. Firstly, classify the rock mass in the engineering area according to geological characteristics based on the exploration results. Secondly, determine the mechanical parameters of various rock masses by the Hoek-Brown criterion, then check and correct them by the empirical parameters. Finally, according to geological information of the excavation face and in-situ test, verify and correct the rock mechanics parameters in the design stage. The method was applied to determine the mechanical parameters of altered monzonitic granite rock mass in the tunnel anchorage area of Luding Dadu River super-large bridge on the Sichuan-Tibet expressway. The case study shows that the results of the in-situ rock mass test are discrete and difficult to represent the mechanical parameters of the large-scale complex rock mass. The Hoek-Brown criterion is consistent with the in-situ test in estimating the internal friction angle of the rock mass, while the cohesion is higher, which needs to be corrected by empirical parameters. The selection of mechanical parameters of complex rock mass needs to be verified by various methods on the basis of geological analysis.