节理化炭质页岩地层隧道围岩大变形及控制技术研究

Research on large deformation and control technology of tunnel surrounding rock in jointed carbonaceous shale strata

某高速铁路XHS隧道穿越节理化炭质页岩地层,在施工过程中围岩大变形、失稳坍塌现象显著,现场采用强支护和仰拱加深等措施后围岩变形控制效果不佳。针对XHS隧道节理化炭质页岩地层地质条件,结合现场监测手段、离散-连续耦合数值模拟分析围岩大变形及破坏特征,基于数值模拟提出以采取地层预加固为主的围岩变形控制措施,并通过现场试验探讨该控制措施的应用效果。研究结果表明:隧道开挖后,围岩变形具有变形量大、变形速率快的特点,围岩拱部沉降量大于水平收敛量且变形具有非对称的分布特征;受三台阶法多次开挖扰动影响,围岩卸荷范围动态发育并不断向全环扩展,松动区逐渐由浅部围岩向深部转移,并呈现出非对称的破坏特征,最终引发围岩大变形;采取地层预加固后,模型中围岩变形和松动区范围明显减小,围岩非对称变形破坏也得到了有效控制;在采用地层预加固、管棚超前支护、三台阶临时仰拱法开挖的控制措施后,围岩变形得到控制,施工效果良好,隧道恢复正常施工,保证了隧道的顺利贯通;以地层预加固为主的控制措施是此类节理化炭质页岩地层围岩变形控制的有效手段。

A high-speed railroad XHS tunnel which crosses through the jointed carbonaceous shale stratum shows significant large deformation and collapse of the surrounding rock.The control effect is not good after adopting measures such as strong support and deepening of the tunnel invert.For the geological conditions of jointed carbonaceous shale stratum in XHS tunnel,the large deformation and damage characteristics of the surrounding rock were analyzed by combining on-site monitoring means and discrete-continuum coupled numerical method.Based on the numerical simulation,the control measures of surrounding rock deformation which mainly focused on pre-reinforcement of stratum were proposed,and the application effect was explored through on-site test.The results show that the rock mass deformation after tunnel excavation is characterized by large volume and fast rate,the crown settlement value is larger than the horizontal convergence value,and the deformation has asymmetric distribution characteristics.Under the influence of multiple excavation disturbances,the unloading area dynamically develops and continuously expands to the whole ring,and the loosening area gradually transfers from the shallow rock mass to the deep and presents asymmetric damage characteristics,which eventually causes the large rock mass deformation.After taking pre-reinforcement measures,the sizes of deformation and loosening areas in the numerical model are obviously reduced,and the asymmetric deformation damage is effectively controlled.With the control measures of pre-reinforcement of the stratum,combined with over-supporting of the pipe shed and three-bench excavation method with temporary invert,the deformation is controlled and the construction effect is good.The tunnel resumes normal construction,and these measures also ensure the tunnel completion.The control measures which are mainly based on pre-reinforcement of the stratum are effective means to control the surrounding rock deformation in this type of jointed carbonaceous shale stratum.