为了探究岩锚体锚碇变形破坏机理,以西堠门公铁两用特大桥岩锚体锚碇为研究对象,在桥址区按1∶10比例建造4 m×6.2 m×4.84 m(长×宽×高)的岩锚体锚碇实体模型,施加载荷直至模型锚碇失稳破坏。加载过程中观测模型锚碇位移及破裂演进过程,结合数值模拟反演分析,研究超载作用下模型锚碇位移-破裂-整体失稳的变形破坏过程。载荷为1P时(P=3 243.46 kN)位移0.085 mm,后锚板上部岩体局部初始拉裂;超载至7P时位移3.63 mm,后缘拉裂面向地表扩展贯通,两侧侧裂面追踪陡倾节理面拉剪破坏贯通,底滑面受拉剪应力作用沿缓倾角节理开始剪切错动,形成整体失稳破坏的雏形;超载至9P时底滑面拉剪破裂贯通,至11P时模型锚碇整体失稳破坏。超载作用下,模型锚碇变形破坏受拉剪应力状态、岩体拉剪强度、节理产状等多因素影响和控制,概化为初始拉剪破裂阶段(0~1P)、拉剪破裂扩展贯通阶段(1P~7P)、追踪节理拉剪整体滑移失稳破坏阶段(7P~11P)的渐进破坏模式,具有明显的后缘岩体拉裂、侧裂面及底滑面追踪原生节理拉剪破裂的渐进破坏特征。

[Objective] The aim of this study is to explore the deformation and failure mechanism of rock anchor body anchorage. [Methods] Engineering geological analysis, in-site rock anchor body anchorage entity model testing, and finite difference numerical simulation were adopted to systematically study the distribution of stress and deformation, rock mass fracture process, and failure mode of jointed rock mass rock anchor anchorage. The displacement and fracture evolution process of the model anchorage were observed during the loading process. Combined with numerical simulation inversion analysis, the deformation and failure mechanism of the model anchorage displacement-fracture-overall instability under overload was investigated. [Results] In-site entity model test results show that when the load is 1P (P=3 243.46 kN), the deformation of rear anchor plate is the largest, with a displacement of 0.085 mm, and the upper part of the rock mass of the rear anchor plate experiences local initial tensile cracking. When the overload reaches 7P, the displacement of the rear anchor plate is 3.63 mm, and the trailing edge tensile fracture surface extends and penetrates the surface. The two side fracture surfaces track the steeply inclined joint surface and undergo tensile shear failure. The deep rock mass at 5.7 m below the surface begins to undergo displacement deformation, and the bottom sliding surface is subjected to tensile shear stress and begins to shear along the gently inclined joint, forming the embryonic form of overall instability and failure. When overloaded to 9P, the displacement of the rear anchor plate is 8.73 mm, and the crack width of the trailing edge tensile fracture surface continues to increase. The crack width of the steeply inclined joint surface tensile shear failure on both sides continues to expand outward, and the bottom sliding surface tensile shear fracture penetrates. The deep rock deformation at a depth of 3.7 m below the surface reaches 0.8 mm. When overloaded to 11P, the displacement of the rear anchor plate was 22.013 mm, and the bottom sliding surface continued to expand and rupture due to tensile and shear stress. The deep rock mass below the surface of the ground had a displacement deformation of 8.5 mm, and the overall model anchorage was unstable and failed. The load displacement full process curve, tensile and shear stress distribution, and plastic zone development results revealed by numerical simulation of model anchor anchorage are in good agreement with the spatiotemporal relationship of overload rupture evolution in in-site entity model tests. [Conclusions] Under the action of overload, the deformation and failure of the model anchorage are affected and controlled by many factors including tensile shear stress state, tensile shear strength of rock mass, and joint occurrence. It is generalized into the initial tensile shear failure stage (0-1P), the tensile shear failure expansion and penetration stage (1P-7P), and the tracking joint tensile shear overall slip instability failure stage.