深埋隧洞让压支护结构的锚固机理探究

Research on Anchorage Mechanism of Yielding Support in the Deep-buried Tunnel

为研究层状岩性下深埋隧洞让压支护结构对围岩分区破裂的影响及其锚固机理,文章开展了高应力条件下深埋隧洞三维相似物理模型试验。选取3∶3和4∶3两种配比的相似材料分层铺设夯实,对4种支护结构形式(刚性衬砌支护、刚性衬砌+让压锚杆支护、柔性衬砌支护和柔性衬砌+让压锚杆支护)进行对比研究。应力试验结果表明,采用刚性衬砌与柔性衬砌支护时,隧洞拱顶、拱肩和侧墙应力均出现波峰与波谷的波浪变化,围岩依然存在分区破裂趋势。而刚性衬砌+让压锚杆组合支护下应力波浪变化趋势减弱,表明支护结构抑制了围岩分区破裂趋势。让压锚杆应变监测结果表明,刚性衬砌和柔性衬砌拱顶位置,让压锚杆均出现了拉压应变交替变化规律,而柔性衬砌支护时隧洞拱肩与侧墙位置让压锚杆只出现拉应变现象。刚性衬砌+让压锚杆的新型让压组合支护结构对抑制深埋隧洞围岩分区破裂有重要意义。

To investigate the effect of yielding support structure on zonal fracturing of surrounding rock and its anchorage mechanism in the deep-buried tunnel in stratified stratum, a three-dimensional similar material physical model test of the deep-buried tunnel under high geo-stress was carried out. A contrast study on the four kinds of support structures(rigid lining, rigid lining + yielding anchor bolt, flexible lining and flexible lining + yielding anchor bolt) was taken by laying and tamping the similar materials with proportions of 3∶3 and 4∶3 respectively. The stress test results show that peak stress and trough stress both occur at tunnel crown, spandrel and sidewall in conditions of rigid lining and flexible lining, and it has a tendency of zonal fracturing for the surrounding rock, while the tendency of wave-shape stress variation is declining in condition of rigid lining + yielding anchor bolt, which shows the support structure restrains the tendency of zonal fracturing of rock mass. The strain monitoring results of yielding anchor bolt show that tensile strain and compression strain occur alternatively for the yielding anchor bolt at tunnel crown in conditions of rigid lining and flexible lining, while only tensile strain occurs for the yielding anchor bolt at spandrel and sidewall in condition of flexible lining. The combination support of rigid lining + yielding anchor bolt is significant for restraining zonal fracturing of surrounding rock of the deep-buried tunnel.