管片衬砌配合碎石可压缩层与锚杆的支护型式研究

Study on a new type of support structure of segment lining combined with compressible crushed stone and anchor bolt

摘要:

针对深埋地层中修建盾构隧道,特别是围岩表现蠕变特性,研究一种管片衬砌配合压缩层与锚杆的联合支护技术.采用有限差分与离散元的耦合计算方法,进行了管片衬砌壁后注浆、管片衬砌壁后填充碎石可压缩层、管片衬砌配合碎石可压缩层和高强预应力锚杆的支护效果对比研究.从围岩塑性区发展、沉降随时间变化、管片衬砌弯矩和轴力分析了联合支护效果.从碎石可压缩层的压缩变形路径、锚固围岩的位移矢量等角度揭示了联合支护的细观作用机理.研究结果表明:仅采取管片衬砌配合碎石可压缩层的让压支护手段无法维持管片衬砌的长期稳定；联合支护结构型式既可以提高围岩自身承载能力,也能够有效吸收围岩的蠕变变形.联合支护的作用机理由两部分构成:碎石可压缩层的让压作用与高强预应力锚杆加固围岩作用.其中,碎石可压缩层的让压机理主要通过颗粒间相互嵌挤和错动移位作用调减管片衬砌壁后接触力；高强预应力锚杆的加固机理是由锚杆形成的锚固区控制了蠕变变形的过大发展.研究结果对未来盾构工法修建深部高地应力、强蠕变隧道的支护型式设计具有一定参考价值.

Abstract:

A new type support structure combined with compressible crushed stone and high-strength pre-stressed anchor cable is proposed which is suitable for deep inclined shaft construction using shield method with great depth. Different conditions in terms of liner combined with crushed stone and high-strength pre-stressed anchor were simulated. The effect of the combined support was studied by analyzing the plastic zone development of surrounding rock, convergence of surrounding rock and internal force of segmontal lining. Moreover, the support mechanism of combined support was revealed from movement characteristics of the crushed stone and displacement vector of the anchored surrounding rock. The results show that only the yielding effect of crushed stone cannot promise the safety of the liner, especially when the creep effect of surrounding rock was considered. The combined support can not only improve the bearing capacity of the surrounding rock, but also effectively absorb the creep deformation of the surrounding rock. The support mechanism of combined support consists of two parts: the yielding effect of crushed stone and surrounding rock reinforcement of anchor cable. The yielding effect of crushed stone was attributed to the mutual squeezing effect and movement effect, while the support mechanism of anchor cable was attributed to reinforcement effect of anchor cable on the surrounding rock. The results have a certain reference value for the design of support structure of shield constructing deep tunnel in the future.