热-力作用下隧道岩爆温度效应的物理模型试验

Physical model tests on thermo-mechanical effects in rockbursts around tunnels

随着西部大开发战略的深入实施,重大工程建设中遇到越来越多的高地温和高地应力隧道。为了研究这类隧道工程在高地温和高地应力耦合作用下发生岩爆的特性,通过一系列技术研发,在二维地质力学模拟试验加载系统上成功进行热–力作用下隧道岩爆温度效应的物理模型试验。在研制具有岩爆倾向的硬脆性岩爆相似材料基础上,自主开发大型物理模型温度场加载系统和隧道开挖装置,考虑20℃,40℃,60℃,80℃四种温度和侧压力系数为2的高地应力作用,共开展4个模型试验。试验研究结果表明,在20℃~80℃温度范围,温度增大提高了材料的硬脆性,围岩能积聚更高弹性应变能,温度应力引起的洞壁切向应力以及应力差增大,为岩爆创造了更有利的条件。模型温度越高,围岩破坏前变形越小,模型破裂过程中释放的能量越大,破裂源越多;随着温度增高,围岩脆性破坏更强烈且更突然,渐进过程越不明显,岩爆剥落弹射的块径更大。因此,在热力耦合作用下隧道岩爆表现出在一定温度范围内随着温度增大而更加强烈的规律。

With the large-scale developments in west China,the high geothermal and high geostress conditions have been encountered in growing number of tunnels.To study the thermo-mechanical characteristics of rock bursts occurred around tunnels with coupled high geothermal-geostress processes,the physical model with two-dimensional geomechanical loading system was developed.Based on the researches concerning the rockbursts prone similar materials,a tunneling excavation equipment and a thermal-stress loading system was also developed in this study.Four model tests,corresponding to four temperatures fields（20 ℃,40 ℃,60 ℃,80 ℃） under high geostress and with the lateral pressure coefficient of 2.0,were carried out to obtain the strains,acoustic emission features and deformation failure characteristics of surrounding rocks.The results show that during the range of 20 ℃–80 ℃,the degree of brittleness of and the accumulated elastic strain energy in surrounding rock increase with the rising of the temperature.The tangential stress and stress difference in tunnel wall increases,which creates more favorable conditions for rock burst.The higher the temperature,the smaller the deformation of surrounding rock before failure,and the bigger the released energy,the more fracture sources.Besides,the higher the temperature,the brittle failure of surrounding rock is more intense and occurs more suddenly,and the gradual process of rockburst is less seen,the block sizes of spalling rock and burst ejection are bigger.Hence,it can be concluded that the rockbursts take place more intensely with the increase of temperature（geothermal） under the coupled thermo-mechanical processes in a certain range of temperatures.