侧压影响下圆形洞室岩爆双轴物理模拟试验研究

Biaxial physical simulation test of rock burst in circular tunnel under influence of lateral pressure

为研究侧压影响下圆形洞室岩爆机制,采用双轴加载装置对含孔洞红砂岩试样进行了物理模拟试验,期间采用高速相机观测了孔洞破坏全过程。研究结果表明:岩爆过程可划分为平静期、剥落期、屈曲期和岩爆期四个时期;洞壁垂直起裂应力和岩爆V型槽破坏深度均随侧压增大而呈线性增大趋势。侧压主要从两方面影响岩爆发生:一是影响洞室破坏机制,当侧压较低时,洞壁垂直方向起裂应力小、水平方向应力梯度小,以拉伸破坏机制为主,破坏范围小,而侧压较大时,洞壁浅部区域破坏机制与低侧压时类似,但洞壁深部区域由于水平应力增加,受力类似三轴压缩,以剪切破坏机制为主,破坏范围大;二是影响洞壁能量积聚释放特征,由于侧压增大,平静期持续时间增加,而破坏期持续时间减小,造成洞壁破坏时单位时间内能量释放率增加,岩爆发生更加剧烈。

In order to study the rockburst mechanism of circular tunnel under the influence of lateral pressure,the physical test of red sandstone samples with holes was carried out by means of biaxial loading device.The high-speed camera was used to record the whole process.The results show that the rockburst process can be divided into four periods:The quiet period,spalling period,buckling period and rockburst damage period.With the increase of lateral pressure,the vertical initiation stress of the borehole and the depth of the V-shaped notch increase linearly.Lateral pressure affects rockburst primarily from two aspects.Firstly,it affects the failure mechanism of caverns.The vertical crack initiation stress and the horizontal stress gradient of the borehole are low during low lateral pressure.The tensile failure mechanism is the main failure mechanism and the failure range is minimum.When the lateral pressure is large,the failure mechanism in the shallow part of the borehole is similar to the case with low lateral pressure.But the failure mechanism in the deep sections of the borehole is similar to the triaxial compression with the increase of horizontal stress.The main failure mechanism is shear failure mechanism and the failure range is high.Secondly,it affects the energy accumulation and release characteristics of the borehole.As the lateral pressure increases,the duration of the quiet period increases while the duration of the failure period decreases.As a result,the energy release rate per unit time increases and the rockburst occurs more violently.