大型地下洞室对穿预应力锚索失效形式与耦合模型

以锦屏二级水电站地下厂房与主变室之间中隔墙的多根对穿预应力锚索失效实例为背景，首先总结对穿预应力锚索失效的多种现场表现形式，采用现场取证和室内试验再现的方式论证锚索钢绞线断裂的拉破坏模式。将对穿锚索视为弹脆性体，被锚固围岩视为黏弹性体，提出描述对穿预应力锚索与被锚固围岩之间相互作用关系的锚索-围岩耦合元件模型，并据此分别阐明在洞室开挖卸荷阶段和围岩时效变形阶段中预应力锚索的力学响应机制和荷载变化规律。最后，在现场调研、室内试验和机制分析基础上，综合分析导致锦屏二级水电站地下厂房与主变室之间对穿锚索失效的主要原因，并探讨对穿预应力锚索与被锚固围岩之间对立统一的矛盾关系以及大型洞室群预应力锚索支护时机问题。

Failure format and interactive mechanism of prestressed thru-anchor cable in a large underground caverns

This paper pays main attention on the failure performance and excavation induced interaction of prestressed thru-anchor cable by a case study. In-situ investigation had shown that there were several failure formats of prestressed thru-cable in the Jinping II underground powerhouse. The observed proof also indicated that this kind of break of thru-cables belongs to tensile failure due to unloading deformation and time-dependent rheology of underground caverns. Thus, a new cell model is purposed to describe the interactive relation between thru-anchor cables and reinforced rock. This cable-rock cell model has special structure, i.e. an elasto-brittle cell is employed to representing the mechanical behavior of thru-anchor cables, and a viscoelastic Kelvin-Hooke cell is employed to representing the mechanical response of host rock. Based on this coupled model, several mechanical parameters which influence the cable’s load are discussed, including elastic modulus of cable, elastic modulus of rock, viscoelastic modulus of rock and coefficient of rock viscosity, etc. This discussion can help us to recognize the ambivalent relationship between thru-anchor cable and reinforced surrounding rock.