软弱围岩浅埋偏压隧道围岩稳定性控制技术

发布时间：2018-11-21 17:07

【摘要】：隧道施工中,由地表坡度引起的浅埋隧道偏压现象,使得隧道在开挖过程中,支护结构受力及变形不对称,严重时会引起塌方、冒顶等灾害现象,影响隧道围岩的稳定性。本文以娄邵铁路改扩建工程陈家湾隧道为工程背景,采用强度折减法结合突变理论,对软弱围岩浅埋偏压隧道稳定性等问题进行分析研究。根据陈家湾隧道现场量测数据,采用BMP系统,对隧道围岩物理参数进行反演,并参考现行铁路隧道设计规范,综合确定隧道围岩物理参数。以所得围岩物理参数,采用有限元强度折减法进行数值模拟,分析围岩塑性区随强度折减系数的变化趋势,找到围岩潜在破坏面,结合突变理论,给出洞周典型位置的临界折减系数及位移值。分析结果表明,软弱围岩浅埋偏压隧道的潜在破坏面与现行铁路、公路规范中所假定的破坏面形式不同,围岩破坏形式不仅仅是从坡顶向坡底的整体滑动,浅埋侧拱顶贯通至地表的塑性区也影响了支护结构的受力情况。对不同横坡坡度及不同岩体性质条件下的浅埋偏压隧道进行数值模拟,采用前述研究方法,分析不同横坡坡度及岩体性质对围岩稳定性的影响,比较洞周典型位置的临界折减系数。结果表明,随着坡度的增大,围岩潜在破坏面出现的时间越来越早,围岩稳定性降低;随着围岩等级的提高,潜在破坏面出现的时间越来越晚,甚至不出现,围岩稳定性增加。采用数值模拟的方法对台阶高度及台阶长度进行工法参数优化,通过比较不同台阶高度及长度对隧道结构变形、支护结构内力及围岩塑性区的影响,综合分析,确定合理的台阶高度及台阶长度。最后,从超前支护、地表沉降控制等方面,给出相应的施工改进措施,使其对相似工程具有借鉴意义。
[Abstract]:In the tunnel construction, the phenomenon of shallow tunnel bias caused by the slope of the surface causes the asymmetry of the force and deformation of the supporting structure in the course of excavation, which will cause disasters such as collapse and roof fall when serious, which will affect the stability of the surrounding rock of the tunnel. Based on the Chenjiawan tunnel of Loushao railway reconstruction project, this paper analyzes and studies the stability of shallow buried bias tunnel in weak surrounding rock by using strength reduction method combined with catastrophe theory. Based on the field measurement data of Chenjiawan Tunnel, the physical parameters of surrounding rock of the tunnel are inversed by BMP system, and the physical parameters of surrounding rock of the tunnel are determined synthetically with reference to the current design code of railway tunnel. Based on the physical parameters of surrounding rock, the finite element strength reduction method is used to simulate the plastic zone of surrounding rock. The change trend of plastic zone with strength reduction coefficient is analyzed, and the potential failure surface of surrounding rock is found, which is combined with catastrophe theory. The critical reduction coefficient and displacement value of typical position around the hole are given. The results show that the potential failure surface of shallow buried bias pressure tunnel with weak surrounding rock is different from that of the existing railway and highway code, and the failure form of surrounding rock is not only sliding from the top of the slope to the bottom of the slope. The plastic zone from the shallow arch roof to the surface also affects the stress of the supporting structure. Numerical simulation of shallow buried bias tunnel with different slope gradient and rock mass property is carried out. The influence of slope degree and rock mass property on the stability of surrounding rock is analyzed by using the above-mentioned research method. The critical reduction coefficient of typical position around the hole is compared. The results show that with the increase of slope, the potential failure surface of surrounding rock appears earlier and the stability of surrounding rock decreases, and with the increase of surrounding rock grade, the time of occurrence of potential failure surface becomes more and more late, or even does not appear, and the stability of surrounding rock increases. The method of numerical simulation is used to optimize the working parameters of step height and step length. By comparing the influence of different step height and length on the deformation of tunnel structure, the internal force of supporting structure and the plastic zone of surrounding rock, the comprehensive analysis is made. Determine the reasonable height and length of the steps. Finally, from the aspects of advance support, surface subsidence control and so on, the corresponding construction improvement measures are put forward, which can be used for reference for similar projects.
【学位授予单位】：石家庄铁道大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U451.2;U455

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