基于敏感性分析的围岩力学参数反演方法研究

Study on Inversion Method of Mechanical Parameter of Surrounding Rock Based on Sensitivity Analysis

由于影响隧道变形的围岩强度参数和变形参数较多,现有的反分析研究主要集中在算法的优化上,因而忽略了工程应用的便利性和实用性。针对这种状况,以南京某隧道工程为依托,结合数值模拟,提出了基于敏感性分析的反演方法。根据工程实际,将围岩和支护结构综合考虑分为初始围岩区(简称Z1),松动圈与锚杆锚固共同作用区(简称Z2)以及钢支撑和喷射砼等效作用区(简称Z3);通过安排试算初始值,利用FLAC3D程序计算并分析不同的力学参数对不同隧道变形的敏感性,从而确定反演流程;根据反演流程结合各测点的实测变形值获取合理、准确的围岩力学参数。研究结果表明:与常规的反演方法相比,通过敏感性分析确定隧道不同变形的主控因素,以此变形来反演该主控因素参数在很大程度上提高了工程应用的效率与可靠度;拱顶下沉受Z1区弹性模量E1、Z2与Z1区弹性模量比值n的影响较大,受围岩泊松比μ1的影响相对较小;隧道收敛受E1、n、μ1三者的影响都较大;围岩力学参数反演结果为E1=362.6 MPa、n=0.62、μ1=0.30;现场应用证明了该方法的有效合理性。

For there are too many intensity and deformation parameters of surrounding rock that affect the deformation of tunnel, existing back analysis researches almost concentrate on optimizing algorithm, and neglect the convenience and practicability of engineering application. Due to this situation, taking a tunnel in Nanjing as the ba- sis, combined with numerical simulation, a method of parameter back analysis of surrounding rock based on the sensitivity of itself is obtained. Based on the engineering reality with comprehensive considering of surrounding rock and supporting structure, to divide them into three zones： initial surrounding rock zone（Z1 for short） , the loose circle and anchor grappling coefficient zone （Z2 for short）and steel and shotcrete equivalent zone（ Z3 for short） ; By confirming the initial value of mechanical parameters, the FLAC30 software is used to simulate and analyze the different sensitivity of every parameter to different deformations, and then the procedure of inversion is determined ; On the basis of this procedure, the mechanical parameter of surrounding rock is acquired by combining it with the measured value. The results show that ： the main influence factor of different deformations can be acquired by sensitivity analysis, compared with common inversion methods, inverting the main factor parameter can improve the efficiency and reliability in engi- neering application based on the deformation ; the main influence factors on crown settlement are El （ elastic modulus of Z1 ） and n（ the elastic modulus ratio between Z2 and Z1 ）,μ1（ Poisson＇ s ratio of surrounding rock）; the main influ-enee factors on tunnel convergence are E1,n,μ1 ;the meehanical parameter value according to back analysis is as follows, E1 =362.6 MPa,n =0.62,μ1 =0.30;this method is effective and rational verified by field applications.