【作者】 范永慧；

【导师】 戴俊；

【作者基本信息】 西安科技大学 ， 桥梁与隧道工程， 2011， 硕士

【摘要】 在浅埋破碎岩层地段进行隧道掘进时,为了克服地层稳定性差对隧洞施工的不利影响,往往需要在开挖前对工作面前方地层施加预支护,以保证围岩稳定。本课题在相关领域已有研究成果的基础上,开展浅埋破碎岩层隧道小导管预支护技术研究,主要研究内容与结论如下:(1)阐述了浅埋破碎地层条件下隧道围岩特性,指出破碎岩体的抗剪强度主要受软弱结构面或软弱夹层所控制;(2)对小导管预支护的加固机理及作用效应进行分析,表明预支护能够改善工作面前方围岩的应力状态,提高围岩稳定性。通过建立小导管预支护系统的串并联模型,可以明确预支护各单元间的相互关系,只有当各单元之间达到最佳匹配时,整个系统才能发挥最佳效用;(3)对隧道预支护原理进行深入研究,预支护力由围岩自承能力和支护结构承载力共同组成,它是隧道“围岩—支护”结构体系的承载力,要保证隧道围岩稳定,预支护力就要始终大于施工前保持岩体稳定平衡的原始内力;(4)通过比较不同工况对拱顶竖向位移的影响,表明小导管注浆支护在控制拱顶沉降、维持围岩稳定上发挥了重要作用。进一步探讨了小导管管径、环向间距、注浆管长、开挖步长、隧道埋深等因素对小导管预支护作用效果的影响,得到以下结论:①在管体不注浆情况下,不论改变管径、管长还是环向间距对拱顶竖向和拱肩水平位移的影响都不大;②小导管注浆管长存在合理长度;③在同一隧道埋深下,管体注浆长度对拱顶位移的影响是有限的,当埋深增大到一定值后,小导管预支护已不能满足控制围岩变形的要求,这时需要提高小导管预支护参数或改用其他支护方式。更多还原

【Abstract】 When tunneling in shallow broken rock sections, in order to overcome the disadvantageous impact of unstable strata, supportive measures are often taken prior to excavation in the front of the working face to ensure the stability of surrounding rock. This thesis summarizes previous works and conducts in-depth study on technology of mall duct pre-supporting. The main research contents and achievements are as follows.(1)It describes the characteristics of surrounding rock under shallow broken geological conditions and points out that the shear strength of broken rock is mostly determined by weak structural plane or weak intercalation;(2)It analyses the reinforcement mechanism and action effect of small duct pre-supporting and demonstrates that pre-supporting helps improve the stress state of the surrounding rock in front of the working face and increases the stability of surrounding rock. The interrelationship among various pre-supporting units can be clarified by building the serial parallel connection model of small duct pre-supporting system. Only when each unit matches in the optimum can the overall system work the best;(3)It explores the tunnel pre-supporting principle in depth and points out that the pre-supporting force is composed of the self-bearing capacity of surrounding rock and the bearing capacity of supporting structures. As the bearing force of the tunnel Surrounding Rock and Supporting structure, pre-supporting force, in order to ensure stable surrounding rock in tunnel, is always supposed to be greater than the initial internal force that maintains stable rock masses before construction;(4)By comparing the impact on vertical displacement of vault under different working conditions, it illustrates that small duct grouting support plays an important role in controlling vault settlement and maintaining the stability of surrounding rock. In addition, It discusses the influence of the diameter of small duct, the annular space, the duct length, the excavation step, the tunnel depth, etc on the effect of small duct pre-supporting and reaches the following conclusions:①Without grouting, neither changing the diameter and the length of small duct nor the annular space would affect the displacement of working face;②The optimal length of small duct exists;③With a given tunnel depth, the influence of grouting length on vault displacement is limited; when the tunnel depth reaches an certain amount, small ducting pre-supporting can not meet the needs to control surrounding rock deformation, which requires increasing some parameters of small duct pre-supporting or changing some other supporting methods.更多还原