薄层破碎硬质岩隧道群施工的压力拱效应及荷载理论模型研究

发布时间：2018-01-03 19:10

本文关键词：薄层破碎硬质岩隧道群施工的压力拱效应及荷载理论模型研究　出处：《西南交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：我国交通建设的蓬勃发展,为隧道及地下工程的发展带来了机遇与挑战。薄层破碎硬质岩多分布在沉积岩及岩溶地区,我国云贵川地区的地下工程施工中将可能遇见这种特殊的围岩,然而目前对其工程特性开展的研究并不多。本文采用离散元软件,对该围岩条件下的地下洞室开挖进行数值分析研究,并通过一定的现场实测数据进行验证,得出如下结论：(1)薄层破碎硬质岩内部贯通的层理与错开分布的节理这几组软弱结构面决定了其主要的工程性质：易于沿层理发生顺层滑移：可以承受一定的弯矩作用；软弱结构面的变形将对整个地层产生最主要的影响。地下洞室开挖后,洞周的围岩将由近及远的逐层张开、剥离变形。节理张开变形所引起的洞周收敛位移较顺层滑移引起的变形位移量更大,但后者的影响范围更广。这两种位移相互垂直,使得薄层破碎围岩地下洞室开挖后位移云图呈“十字形”分布,且“十字”偏斜的角度与贯通的层理面倾角相一致。(2)洞室埋深大于临界埋深时,薄层破碎硬质岩地下洞室开挖后洞周围岩将产生压力拱效应。提出以不同范围内的围岩的切向应力增加量与该路径上围岩总切向应力增加量的比值来确定该范围内围岩对压力拱成拱作用的贡献,并据此划分压力拱效应的主要区域界限。对比计算了不同倾角、不同结构面参数下不同埋深、不同跨度的地下洞室开挖后洞周围岩的压力拱效应：当软弱结构面力学性质远差于岩块的力学性质时,软弱结构面的粘聚力和摩擦角对整体围岩开挖后力学状态影响不大；层理面倾角较缓时,压力拱高度随层理面倾角的变化不明显,当层理面倾角超过某个阈值时,压力拱范围随层理面倾角的增大而显著增加：隧道埋深大于临界埋深时,洞室埋深的增加对压力拱范围的影响不明显；洞周压力拱范围与洞室跨度呈线性递增关系。根据这些结论拟合出特定工况下的薄层破碎硬质岩地下洞室开挖压力拱高度公式。(3)考虑薄层破碎硬质岩的特性修改了普氏塌落拱理论与岩柱理论使其更好的适用于该围岩条件。发展了压力拱承载结构理论计算围岩荷载的方法,并对比现行铁路隧道设计规范、修正塌落拱理论与压力拱承载结构理论,提出各自的适用范围。(4)结合贵阳龙洞堡机场隧道的现场实测数据与离散元软件数值模拟计算结果,分析该并行近接段施工的围岩力学状态。后行隧道的开挖将破坏先行隧道形成的压力拱效应,形成联合压力拱或拱形梁效应,对围岩受力状态及地表沉降位移产生决定性影响。当近接隧道中岩柱厚度小于8.5m时,近接隧道间中岩柱可能发生失稳,应予以注意并采取一定措施以避免发生事故。(5)通过数值模拟结果与现场实测数据、已有研究成果对比,表明离散元方法可以较为准确地模拟薄层破碎硬质围岩条件的地下洞室开挖状况。
[Abstract]:The vigorous development of China's transportation construction, brings opportunities and challenges for the development of tunnel and underground engineering. The thin broken hard rock distributed in sedimentary rock and karst area, Guizhou and Sichuan area in China during the construction of underground engineering can meet the special rock, however there is little research on the engineering characteristics of in this paper. Using the discrete element software, the surrounding rock of the underground cavern excavation is numerically analyzed, and verified by field test data, draw the following conclusions: (1) the thin broken hard rock bedding and staggered through internal distribution joints these groups of weak structure plane determines the main engineering properties: easy along the bedding slip layer: can be influnced by moment; weak structure surface deformation will have a main effect on the whole stratum. Underground excavation, tunnel The rock layer will open, the deformation of joints. Peeling from the near to the distant convergence around the tunnel caused by the displacement of deformation is along the displacement caused by the slip layer is larger, but the scope of the latter is wider. These two kinds of vertical displacement, the thin layer of broken surrounding rock of underground cavern excavation displacement was "cross" the distribution, consistent with the cross deflection angle and through the bedding plane angle. (2) the depth of the tunnel is larger than the critical depth, thin broken hard rock after excavation of underground cavern surrounding rock will produce pressure arch effect. The surrounding rock in different range of the tangential stress increases with the path the total amount of surrounding rock increase ratio to stress to determine the range of surrounding rock pressure arch effect, the main regional boundaries and accordingly divided into pressure arch effect. Compare the calculation of different angles, different structural plane parameters In different depth, the arch effect of the surrounding rock pressure of underground caverns of different span after excavation: when the mechanical properties of structural plane is far worse than the weak mechanical properties of rock, little weak structure of the cohesion and friction angle on the impact of the overall mechanical state of surrounding rock after excavation; bedding plane angle is gentle, the pressure arch height change with the bedding plane angle is not obvious, when the bedding angles exceeds a certain threshold, increasing the pressure arch with bedding angles and increase the buried depth of the tunnel is larger than the critical depth, the depth of the tunnel affected by the increase of pressure arch is not obvious; the tunnel pressure arch tunnel span range and linear the relationship between increasing. According to these conclusions fit thin specific conditions of underground cavern excavation of hard rock crushing pressure arch height formula. (3) considering the properties of thin broken hard rock modified collapsing arch theory and rock pillar The theory of making it better for the development of the surrounding rock. The rock pressure calculation method of load bearing arch structure theory, and compared to the existing railway tunnel design specification, revision of arch collapse theory and pressure bearing arch structure theory, put forward the application scope of each. (4) numerical simulated calculation results with measured data of tunnel and Guiyang Longdongbao Airport the discrete element software, analysis the parallel construction of the adjacent rock mechanics. After excavation tunnel will destroy the first tunnel formation pressure arch effect, the formation of joint pressure arch or arch effect on surrounding rock stress and surface subsidence displacement have a decisive impact. When approaching the tunnel rock pillar thickness is less than 8.5m, near the middle rock pillar between the tunnel instability may occur, should pay attention to them and take some measures to avoid the accident. (5) through the numerical simulation results and field measured data, The comparison of the existing research results shows that the discrete element method can accurately simulate the excavation condition of the underground cavern in the thin layer of hard rock.

【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U451.2

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