Time dependent behaviour of Class II rocks under the confining pressure

对5个岩石试样进行了三轴压缩试验，采用恒应变率法对一类岩石进行加载，采用应力反馈法对二类岩石进行加载。结果表明：强度随加载速率增大而增大，高加载速率下破坏后区域的应力-应变曲线与低加载速率下的应力-应变曲线相封闭；通过反复的卸载-加载循环，研究了岩石试样在破坏后区域的卸载顺应性。发现柔度逆随卸载周期开始时的应力呈线性减小。根据试验结果，提出了一个简单的模型，可以解释加载速率和破坏后区域柔度变化的影响，该模型也可以定性地解释恒应变（松弛）和恒应力（蠕变）下的行为，但存在一些不完整的问题，如不能解释应变硬化现象。将该模型应用于矿井地下巷道随时间变化特性的模拟。在计算中，采用有限元方法，参数根据岩样试验结果进行假设。并将计算结果与秋田地区两个矿井的实测结果进行了比较。本研究考虑的巷道为u形巷道，采用锚杆或钢拱组支护。岩壁内收敛和扩展的计算结果至少在定性上与实测值有较好的吻合，可以说该模型具有较好的应用潜力。然而，为了定量讨论，更准确地估计岩体的压力和强度可能是不可避免的。

Triaxial compression tests were performed upon 5 sample rocks to investigate the effect of loading rate by constant-strain-rate method for a Class I rock and stress- feedback method for the other Class II rocks. Results show that strength increases with loading rate, and that stress-strain curve in the post-failure region at a higher loading rate encloses those at lower rates. Also, the unloading compliance of rock specimen in the post-failure region was investigated by repeated unloading-loading cycles. It is found that the inverse of comliance decreases linearly with stress at which the unloading cycle starts.Based on the test results a simple model which explains the effect of loading rate and the compliance change in the post-failure region was proposed, the model can also explain behaviours under constant strain (relaxation) and constant stress (creep) qualitatively, though it has some incompletenesses such as the inability of explaining strain hardning phenomenon.The model was applied to simulate the time-dependent behaviour of underground roadway in mine. In the calculation, FEM techinique was used with paeameters assumed on the basis of test results of sample rock. The calculated results are compared with those of field measurement conducted at two nines located in Akita. The roadways considered in this study are U-shaped and supported by rock bolts or steel arch sets. The calculated results of convergence and extension in the rock wall indicate a fairly good coincidence at least in qualitative means, with measured ones, It can be said that the model showed a good potential for application purpose. However, for quantitative discussion, more accurate estimation of rock pressure and strength of rock mass may be inevitable.