硬脆性岩石强度演化特征与深埋岩体长期强度研究

The time effect of the hard brittle rock has been payed more and more intension as the engineering construction going deeper and deeper. Making the Jinpin Ⅱ power station as background, this project will take the marble common in the power station to do the creep test under different confining pressure conditions aiming to the laws of the rock material’s strength varies with the load time and load state. First of all, the creep test with the marble under different confining pressure will be carried out in four strengths level that are 90%, 80%, 70% and 60% of failure strength, and also four lengths of time that are respectively the time of completely destroyed, 1/3, 1/2 and 2/3 of completely destroyed time. The different damage variables will be obtained by the CT images of every marble sample after the creep test for determining the damage caused by the strength level and the length of time. Then the time effect evolution model based on the damage degree of the hard brittle rock’ strength will be established by the function of time、stress state expressed by YAI and damage degree obtained from experimental data. Finally, the numerical analysis research on the long-term strength of the underground workshop and tunnels deep buried in the Jinpin Ⅱ power station will be taken, and the accurate advice of the long-term stability of the engineering will be given.

随着工程建设不断向地下深入，人们对硬脆性岩石的时间效应越来越重视。针对岩石材料的强度随着加载时间以及加载状态不同而变化的规律，本项目将以锦屏二级水电站为工程背景，选取工程中常见大理岩开展不同围压条件下蠕变试验研究。首先，针对性的开展大理岩不同围压条件下，在破坏强度的90%、80%、70%和60%四个加载级别下加载时间分别为完全破坏所需时间、破坏时间的1/3、1/2和2/3四个加载时长的蠕变试验，并且利用CT扫描图像测定每个岩样的损伤变量，以确定应力的大小以及加载时间对岩石损伤所造成的影响。然后，利用所获得的试验数据建立时间、应力状态与损伤程度的函数关系以获得基于损伤变量的硬脆性岩石强度时效性演化模型。最后，利用该模型对锦屏二级水电站中引水隧洞以及地下厂房的长期强度进行数值分析，以对工程的长期稳定性给出准确意见。

在交通、采矿以及水利水电工程中，对硬脆性岩石的工程力学性质关注度越来越高。本项目针对锦屏二级水电站大理岩展开了系统的力学试验研究，获得了该岩石在0MPa、5MPa、10 MPa和15 MPa围压下的抗压强度以及对应的分级加载抗压强度；除力学试验以外，项目组还对常规试验和分级加载试验的岩样进行了CT扫描试验，获得其CT数分布规律，并根据其规律特征获得硬脆性岩石在不同加载条件下的损伤规律；最后，结合硬脆性岩石时效性强度理论对岩石的强度演化规律进行了工程验证，获得了锦屏水电站引水隧洞围岩的强度演化特征。本项目获得的主要结论有：（1）锦屏二级水电站大理岩的分级加载强度大致会在150h内降至原有强度的80%；（2）基于CT数、岩样应力状态以及分形维数三个因素获得岩石材料的损伤变量表达式；（3）数值分析显示围岩的损伤区在开挖卸荷后初始发展较为缓慢，随着时间推移近似呈现线性增加的趋势，最后又逐渐趋于稳定，与现场监测数据互相印证。本项目所开展的研究能够对工程中出现的硬脆性岩石强度弱化问题进行科学的指导，具有现实的工程意义。