麻崖子不同级别围岩隧道结构受力特性分析与安全性评价

发布时间：2018-11-25 10:47

【摘要】：本文依托麻崖子隧道，主要研究III、IV、V级围岩隧道结构受力特性与安全性评价：首先，通过现场的地质预报与地质素描，认识不同级别围岩性质，成功预报出Ⅴ级围岩地段的断层破碎带和涌水地质灾害；介绍规范中BQ围岩分级，BQ分级法关键在于得出围岩的单轴饱和抗压强度RC与围岩的完整性系数KV，借助现场试验室测定岩石单轴抗压强度，通过统计裸露掌子面突起部位得到节理数，介绍BQ分级方法，使我们能迅速准确地分辨围岩的级别，及时调整开挖与支护参数。其次，，通过对III、IV、V级围岩地段各选择5组断面进行周边收敛与拱顶下沉测试得出：其变形值随围岩级别的增大而增大，收敛时间与岩性、节理等因素有关；以极限位移值与位移速率为标准对围岩变形做出评判，判定隧道的安全性；基于监控量测数据运用位移反分析得出围岩的力学参数，并结合设计规范给出的围岩参数，从而确定有限元模拟时所用围岩参数。再次，通过在IV、V级围岩地段埋设测试元件（包括压力盒、钢筋计、表面应变计和混凝土应变计等），对围岩和隧道结构受力进行量测试验；基于对测试结果的对比与分析，找出隧道初支与二衬分担的荷载比例，隧道衬砌内力变化规律、受力状况和受力薄弱部位；通过受力分析和监控量测，对支护时机的选择做出判断；对V级隧道的围岩与初支、初支与复拱、复拱与二衬分别所承担的荷载比进行了对比。最后，通过结合反位移法得出的参数和规范规定的参数，得出各级围岩的模拟参数。使用有限元对其结构与围岩进行整体模拟，得出位移云图和应力云图。利用提取的拱顶下沉值、周边收敛值、锚杆轴力图与现场测试进行校核，来分析变形趋；分别求出各级围岩中，各施工工法所引起的周边收敛与拱顶下沉的比例，找出各级围岩隧道开挖中最不利工序；提取衬砌轴力、弯矩、锚杆轴力、初支剪力，求得初支与衬砌的安全系数，进而评价隧道的安全性。
[Abstract]:Based on Mayazi Tunnel, this paper mainly studies the structural stress characteristics and safety evaluation of III,IV,V class surrounding rock tunnel. Firstly, through the field geological prediction and geological sketch, we know the nature of different grade surrounding rock. The fault fracture zone and water gushing geological hazard of grade V surrounding rock are successfully predicted. This paper introduces the classification of BQ surrounding rock in the code. The key point of BQ classification method is to obtain the uniaxial saturated compressive strength of surrounding rock RC and the integrality coefficient of surrounding rock KV, to measure the uniaxial compressive strength of rock with the help of field laboratory. By counting the joints in the protruding part of the exposed face, the paper introduces the BQ classification method, which enables us to quickly and accurately distinguish the grade of surrounding rock and adjust the excavation and support parameters in time. Secondly, through the test of peripheral convergence and arch roof subsidence of 5 groups of sections selected for III,IV,V grade surrounding rock, it is concluded that the deformation value increases with the increase of surrounding rock level, and the convergence time is related to lithology, joints and other factors; Based on the limit displacement value and displacement rate, the deformation of surrounding rock is evaluated and the safety of tunnel is determined. Based on the monitoring data, the mechanical parameters of the surrounding rock are obtained by using the displacement back analysis, and the parameters of the surrounding rock are given in the design code, so as to determine the surrounding rock parameters used in the finite element simulation. Thirdly, the test elements (including pressure box, steel bar gauge, surface strain gauge and concrete strain gauge) are embedded in the surrounding rock of IV,V class to measure the stress of surrounding rock and tunnel structure. Based on the comparison and analysis of the test results, the paper finds out the load ratio of the first branch and the second lining, the law of the change of the tunnel lining internal force, the force condition and the weak position of the tunnel lining. Through the force analysis and monitoring measurement, the choice of supporting opportunity is judged, and the load ratio of surrounding rock and initial branch, initial support and double arch, double arch and second lining of V class tunnel are compared. Finally, the simulation parameters of surrounding rock at all levels are obtained by combining the parameters obtained by the reverse displacement method and the parameters specified in the specifications. The finite element method is used to simulate the structure and surrounding rock, and the displacement cloud map and stress cloud map are obtained. The deformation trend is analyzed by using the extracted dome subsidence value, peripheral convergence value, anchor shaft force and field test. The ratio of circumjacent convergence and dome subsidence caused by each construction method in surrounding rock of all levels is calculated, and the most unfavorable procedure in excavation of surrounding rock tunnel at all levels is found out. The axial force of lining, moment of bending, axial force of anchor rod and shear force of initial support are extracted, and the safety factors of initial support and lining are obtained, and the safety of tunnel is evaluated.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U452.12

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