软弱围岩的蠕变损伤特性及最佳支护时间

从岩体的蠕变全过程、长期强度和能量耗散的角度,分析软弱围岩的蠕变损伤特性。围岩的蠕变损伤是内部新裂纹产生和不断扩展的结果,是变形损伤与时间损伤效应的耦合。当围岩内应力水平低于其长期强度时,表现为时间损伤效应;当围岩内应力水平高于其长期强度时,表现为变形损伤效应。根据软弱围岩的蠕变损伤特性,选择合理的支护时间,使围岩的蠕变变形不至达到加速蠕变阶段,围岩强度不低于其长期强度,则可以有效避免围岩的失稳破坏。运用西原模型引入蠕变损伤变量,采用粘弹塑性理论研究软弱围岩的蠕变变形规律,提出通过位移反分析或蠕变试验方法确定模型中的蠕变参数,进而确定软弱围岩二次支护最佳时间的方法。工程实践证明该方法是合理的。

Creep Damage Characteristics and Decision of Optimum Support Time for Weak Surrounding Rock

From the point of whole creep process,long-term strength and energy dissipation,this paper analyzes the creep damage characteristics of wreak surrounding rock.Creep damage of surrounding rock is the result of the emergence and development of new internal fractures,and it is the deformation damage and time damage coupling.When the stress level in surrounding rock is lower than long-term strength,it presents time damage effect.When the stress level in surrounding rock is higher than long-term strength,it presents deformation damage effect.To choose rational support time according to creep damage characteristics of weak surrounding rock can avoid stable failure damage effectively,which prevents creep deformation from accelerated creep state and prevents the strength in surrounding rock from being lower than long-term strength.Using the creep model of Xiyuan and introducing the creep damage variable,the creep deformation regularities are studied through Visco-Elastic-Plastic theory.A rational method to determine the creep parameters of the model by displacement back analysis and creep test is put forward in this paper through which to determine the research clue of the optimal supporting time for the weak surrounding rock tunnel is found.And this proposed method is proved rational by practice.