硬-软互层层厚构造影响隧道围岩开挖损伤研究

研究目的:在实际地质环境中,隧道开挖所表现出来的各种变形破坏都是各种因素综合影响的产物。但顺层构造由于其分层特性和结构形式的特点决定了在这样的地质环境中开挖隧道,其围岩受力之后的变形和破坏具有一定的特殊性。本文以拟建某高铁宝云隧道为例,就硬-软互层顺层构造作用下隧道围岩开挖损伤变形开展数值模拟分析评价,主要研究不同岩层厚度影响下的隧道围岩变形、围岩屈服渐进性及稳定性,并给出强度折减至极限状态时硬-软互层组合隧道的变形破坏模式。研究结论:(1)薄层弯曲变形是不同岩层厚度构造作用下硬-软互层顺层隧道开挖的主要变形形式,厚层围岩虽体现出了较明显的滑移,但变形量值较小,隧道支护设计时应考虑岩层厚度控制的该变形特点;(2)硬软互层组合屈服区主要沿顺层面向软岩展布,层厚越小,屈服范围越大,以0.2 m层厚顺层向屈服区为典型,层厚超过0.4 m后,拱腰顺层面屈服区迅速减小,且随厚度增大,两个方向屈服区不断减小;(3)强度折减条件下,层厚超过1.5 m后,稳定安全系数趋于定值,围岩强度主要受软岩自身控制,受硬-软组合结构影响程度降低;(4)岩层厚度较小时,隧道围岩变形模式以岩层弯曲为主,随岩层厚度的不断增大,变形模式逐渐转变为顺层滑移为主、滑移与弯曲并存;(5)本研究成果对促进该高铁的顺利建设具有理论意义和工程价值。

Research on the Influence of Hard-soft Interlayer Thick Structure on Tunnel Surrounding Rock Excavation Damage

Research purposes:In the actual geological environment,all kinds of deformation and failure of tunnel excavation are the result of comprehensive influence of various factors.However,due to the layered characteristics and structural form of bedding structure,tunnel excavation in such geological environment is determined,and the deformation and failure of surrounding rock after stress have certain particularity.Taking Baoyun Tunnel of a high-speed railway as an example,this paper carries out numerical simulation analysis and evaluation on damage and deformation of tunnel surrounding rock under the action of hard-soft interbedded bedding structure.The deformation,progressive yield and stability of tunnel surrounding rock under the influence of different rock thickness are studied.The deformation and failure modes of hard-soft interbedded composite tunnels are given when the strength is reduced to the limit state.Research conclusions:(1)Thin-layer bending deformation is the main deformation form of hard-soft interbedded bedding tunnel excavation under the action of different rock thickness structures.Thick-layer surrounding rock shows obvious slip,but the deformation value is small.The deformation characteristics controlled by rock thickness should be considered in tunnel support design.(2)The yield zone of the hard-soft interbedded combination mainly distributes along the bedding to the soft rock.The smaller the thickness of the interbedding,the larger the yield range.The yield zone of 0.2 m bedding is typical.When the thickness of the interbedding exceeds 0.4 m,the yield zone of the arch waist along the bedding decreases rapidly.With the increase of the thickness,the yield zone of the two directions decreases continuously.(3)Under the condition of strength reduction,when the thickness of stratum exceeds 1.5 m,the stability safety factor tends to be fixed.The strength of surrounding rock is mainly controlled by soft rock itself,and the influence of hard-soft composite structure is reduced.(4)When the thickness of strata is small,the deformation mode of tunnel surrounding rock is mainly rock bending.With the increase of the thickness of strata,the deformation mode gradually changes to bedding sliding,and both sliding and bending coexist.(5)The research results have theoretical significance and engineering value to promote the smooth construction of the high-speed railway.