【作者】 赵强；

【导师】 周晓军；

【作者基本信息】 西南交通大学 ， 建筑与土木工程（专业学位）， 2022， 硕士

【摘要】 我国铁路隧道围岩分级是以单线铁路隧道围岩稳定性为基础而建立的,并以岩石坚硬程度和岩体完整程度两个基本指标将围岩划分为六个等级。但大量的工程实践表明,隧道的开挖断面参数如跨度和扁平率等对围岩的力学特性和变形具有重要影响,而现行的铁路隧道围岩分级方法并未考虑这些因素。因此,研究隧道断面参数如跨度和扁平率等对围岩稳定性的影响具有实际意义。本文基于正交试验原理采用数值分析法、层次分析法和强度折减法,对影响隧道围岩稳定性的断面参数如开挖跨度、扁平率和支护参数初支厚度等的敏感性、大跨度铁路隧道围岩力学特征与变形机理、大跨度铁路隧道的扁平率合理取值以及跨度对围岩基本质量指标BQ值的修正方法进行了研究,主要得出了如下结论。(1)基于正交试验原理通过数值模拟方法,采用极差分析法对特定跨度和扁平率下的各级围岩隧道拱顶竖向位移进行计算与分析,定性地揭示了开挖跨度、扁平率、初支厚度等参数对隧道围岩稳定性影响的重要性次序;通过回归分析,定量地分析了3个因素对拱顶竖向位移的贡献大小。(2)利用有限差分法,就不同扁平率下的隧道在不同围岩级别下的施工过程进行数值模拟,结合施工过程中引起的围岩位移、应力、塑性区,以及初期支护结构的安全性,得到了不同断面型式下的围岩力学特性与变形机理。(3)综合考虑四线大跨铁路隧道的围岩稳定性、初期支护结构的安全性以及隧道工程的经济性,利用层次分析法对Ⅰ级～Ⅴ级围岩条件下的四线大跨铁路隧道的断面型式进行多目标优化,得到了各级围岩条件下的四线大跨铁路隧道的扁平率合理取值,其分别为:Ⅰ～Ⅱ级围岩时取0.625,Ⅲ级围岩时取0.65,Ⅳ～Ⅴ级围岩时取0.675。(4)利用强度折减法计算得到了不同跨度、不同围岩级别条件下的铁路隧道毛洞开挖时围岩的剪切安全系数,并以小跨度铁路隧道在不同工况下的安全系数指标与其对应的围岩基本质量指标BQ值建立了围岩分级的定量化标准;通过回归分析,建立了安全系数、BQ值、跨度三者之间的数学关系式,进而得到了基于跨度的围岩质量指标修正方法。更多还原

【Abstract】 The classification of surrounding rock of railway tunnel in China is based on the stability of surrounding rock of single-track railway tunnel,and the surrounding rock is divided into six grades by two basic indexes of rock hardness and rock integrity.However,a large number of engineering practices shows that the tunnel excavation section parameters such as span and flatness have an important impact on the mechanical properties and deformation of surrounding rock,and the existing classification method of railway tunnel surrounding rock does not consider these factors.Therefore,it is of practical significance to study the influence of tunnel section parameters such as span and flatness on surrounding rock stability.In this thesis,based on the principle of orthogonal experiment,numerical analysis,analytic hierarchy process and strength reduction method are used to study the sensitivity of section parameters such as excavation span,flat rate and initial support thickness of support parameters affecting the stability of surrounding rock of tunnel,the mechanical characteristics and deformation mechanism of surrounding rock of large-span railway tunnel,the reasonable value of flat rate of large-span railway tunnel and the correction method of span to the basic quality index BQ value of surrounding rock.The main conclusions are as follows.(1)Based on the principle of orthogonal experiment and numerical simulation method,the vertical displacement of vault of surrounding rock tunnel at different levels under specific span and flat rate is calculated and analyzed by range analysis method,and the importance order of the influence of excavation span,flat rate and initial support thickness on the stability of surrounding rock is qualitatively revealed.Through regression analysis,the contribution of three factors to the vertical displacement of vault is quantitatively analyzed.(2)The finite difference method is used to numerically simulate the construction process of tunnels with different flat rates under different surrounding rock levels.Combined with the displacement,stress,plastic zone of surrounding rock caused in the construction process and the safety of primary support structure,the mechanical properties and deformation mechanism of surrounding rock under different section types are obtained.(3)Considering the surrounding rock stability of the four-line long-span railway tunnel,the safety of the initial support structure and the economy of the tunnel project,the multiobjective optimization of the section type of the four-line long-span railway tunnel under the condition of grade I-V surrounding rock is carried out by using the analytic hierarchy process.The reasonable flat rate of the four-line long-span railway tunnel under the condition of surrounding rock at all levels is obtained,which are 0.625 for I ～ II rank surrounding rock,0.65 for III rank surrounding rock,0.675 for IV ～ V rank surrounding rock.(4)The shear safety factors of surrounding rock during the excavation of railway tunnels with different spans and different surrounding rock levels are calculated by using the strength reduction method,and the quantitative standard of surrounding rock classification is established based on the safety factor index of small-span railway tunnels under different working conditions and the corresponding basic quality index BQ value of surrounding rock.Through regression analysis,the mathematical relationship among safety factor,BQ value and span is established,and then the correction method of surrounding rock quality index based on span is obtained.更多还原