华坪隧道围岩稳定性离心模型试验研究

发布时间：2018-07-28 21:33

【摘要】：华坪隧道是丽攀高速公路仅有的穿越于攀西地区昔格达地层的隧道,也是所有昔格达地层中仅有的高速公路隧道。华坪隧道围岩稳定性研究不仅可以对隧道施工设计提供参考,同时其研究成果也可应用到其他昔格达地层中的公路隧道。因此,课题组有必要对华坪隧道的围岩稳定性进行深入的分析和研究。本文以丽攀高速公路华坪隧道为研究对象,首先通过收集资料、野外勘查及室内土工试验,掌握了隧道的工程地质背景,进而开展了对昔格达地层隧道围岩稳定性的离心模型试验研究。课题采用模型试验方法,用离心力代替山体应力,模拟隧道开挖后可能出现的围岩变形破坏及地质病害。本课题共进行了三组对比试验,通过布设观测点、应变数据曲线分析、数据插值分析,研究不同岩性、岩层结构、节理发育情况及支护措施对围岩稳定性的影响,进而探索围岩变形破坏规律,预测隧道变形情况和可能产生的地质病害,为在施工过程中及时采取措施应对地质病害提供了理论支持。主要研究内容及成果如下：(1)离心力模拟山体自重应力作用于模型洞室围岩,当洞室开挖后,围岩原有应力平衡状态被打破,形成围岩应力重分布,在新的围岩应力状态下,围岩产生松胀变形。(2)隧道模型围岩聚集大量能量,呈向内挤压趋势；且愈向自由表面(洞室周边)接近,能量愈集中,至洞室周边处达到最大值；其中洞壁拱顶位置能量最为集中,应变最大。(3)主应力分异效应使得拱顶表现为拉应力集中,边墙表现为切向压应力集中围岩应力释放,使围岩各质点向洞室内部回弹变形。当拱顶围岩应力大于抗拉强度时,产生张裂塌落现象。(4)由于洞壁围岩应力集中,当隧道围岩发育软弱结构面时,不利于围岩的稳定性,易发生坍塌。特别在断层影响带,岩体发育有倾向于掌子面外的结构面时,易沿结构面产生掌子面滑塌,发育为结构面控制型的围岩变形破坏。(5)锚杆加固围岩使其整体性增强,层间摩阻力增大,抗拉强度增大,从而增加围岩稳定性,缩小围岩塑性区范围,减小围岩应变。实验结果表明现场锚杆参数以取长度4.5m,间距0.75cm为宜。(6)昔格达地层华坪隧道围岩范围为2倍洞径,超过2倍洞径应变很小。洞室间距为2倍洞径时,围岩之间无明显的相互影响。(7)由于采用钢拱架支护可以起到环形封闭的作用,避免出现掉拱等拱架失稳现象的发生。因此,在施工工程中,建议采用钢拱架支护围岩,根据实验中围岩掉块的结果,说明钢拱架间距设置应取0.5米为宜。
[Abstract]:Huaping Tunnel is the only tunnel in Lifan Expressway that passes through Xigeda formation in Panxi area, and it is also the only highway tunnel in Xigeda formation. The study of surrounding rock stability of Huaping tunnel can not only provide reference for tunnel construction design, but also be applied to other highway tunnels in Xigeda formation. Therefore, it is necessary to analyze and study the surrounding rock stability of Huaping Tunnel. In this paper, the Huaping Tunnel of Liupan Expressway is taken as the research object. Firstly, the engineering geological background of the tunnel is grasped by collecting data, field exploration and indoor geotechnical test. The centrifugal model test of surrounding rock stability of Xigeda formation tunnel is carried out. In this paper, the model test method is used to simulate the deformation and failure of surrounding rock and geological diseases after tunnel excavation by using centrifugal force instead of mountain stress. Three groups of comparative tests were carried out in this paper. By setting up observation points, analyzing strain data curve and data interpolation analysis, the effects of different lithology, rock structure, joint development and supporting measures on the stability of surrounding rock were studied. Furthermore, the rules of surrounding rock deformation and failure are explored, and tunnel deformation and possible geological diseases are predicted, which provides theoretical support for timely measures to deal with geological diseases in the construction process. The main research contents and results are as follows: (1) the centrifugal force simulates the gravity stress of the mountain body acting on the surrounding rock of the model cavern. When the tunnel is excavated, the original stress balance state of the surrounding rock is broken, and the stress redistribution of the surrounding rock is formed, under the new surrounding rock stress state, (2) the surrounding rock of the tunnel model accumulates a large amount of energy and tends to squeeze inward, and the closer the free surface (surrounding the cavern) is, the more concentrated the energy is, and the maximum energy is reached to the periphery of the tunnel. Among them, the energy concentration is the most concentrated and the strain is the largest in the arch roof. (3) the main stress differentiation effect makes the arch roof appear as tensile stress concentration, and the side wall shows tangential compression stress concentration surrounding rock stress release, which makes the surrounding rock particles rebound to the interior of the cavern. When the stress of the arch roof wall rock is greater than the tensile strength, the phenomenon of tensile crack collapse occurs. (4) because of the stress concentration in the wall rock of the tunnel, when the tunnel wall rock develops a weak structural plane, it is unfavorable to the stability of the surrounding rock and prone to collapse. Especially in the fault influence zone, when the rock mass develops the structural plane which tends to be out of the face, it is easy to collapse along the structural plane and develop into the deformation and failure of the surrounding rock controlled by the structural plane. (5) strengthening the surrounding rock with anchor rod to enhance its integrity. With the increase of interlayer friction resistance and tensile strength, the stability of surrounding rock is increased, the range of plastic zone of surrounding rock is reduced, and the strain of surrounding rock is reduced. The experimental results show that the parameters of anchor rod in the field are 4.5m in length and 0.75cm spacing. (6) the surrounding rock area of Huaping tunnel in Xigeda formation is 2 times diameter, and the strain over 2 times diameter is very small. There is no obvious interaction between the surrounding rock when the space between the caverns is 2 times the diameter. (7) because the steel arch support can play the role of annular closure, the phenomenon of arch instability such as falling arch can be avoided. Therefore, in the construction project, it is suggested that the steel arch frame should be used to support the surrounding rock, and according to the results of the surrounding rock falling in the experiment, it is suggested that the distance between the steel arches should be set at 0.5 meters.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U451.5

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