岩溶隧道侧部岩盘突水机制研究

Study on Mechanism of Batholite Water Inrush in Lateral Karst Tunnel

我国岩溶地区广泛分布,隧道建设穿越岩溶区域极易发生突水突泥灾害。为防止灾害的发生,采用隔水关键层原理对断层段岩盘突水力学机制进行了理论分析研究。就岩溶隧道断层段岩盘力学破坏机制探讨建立了溶腔位于隧道侧面条件下断层突水力学模型,推导了岩溶隧道断层段岩盘最小安全厚度计算公式,并结合工程实例对岩盘最小安全厚度的确定进行了讨论。对于压性断层,最小安全厚度计算依据以水压0.8 MPa为分界,小于0.8 MPa时应按抗弯强度分析,反之则应按抗剪强度分析,同时不能忽略零水压情况;对于张性断层,最小安全厚度计算需考虑侧方岩体上下部长度,较长部分更易被破坏,等长时下部易被破坏。确定岩盘最小安全厚度,综合考虑岩盘力学性质、溶腔水压及隧道半径等因素,对侧部岩溶隧道断层段设计施工提供了具体参考。

Karst region is widely distributed in China and water or mud inrush disaster easily happens when tunnel construction is going across the region. In order to prevent the disaster,the principle of water-resisting key strata is applied to analyse the fault batholite water bursting mechanical mechanism. The mechanical model of fault water inrush when cavities are in the side of tunnel is discussed and found based on the mechanical failure mechanism of batholite in faultage of Karst tunnel. The minimum safety thickness calculation formula of batholite in faultage of Karst tunnel is derived,and the determination of minimum safety thickness of the batholite is discussed combining with the engineering cases. The result shows that（ 1）for compressional fault,the calculation of minimum safety thickness is dependent on whether the hydraulic pressure is greater than 0. 8 MPa or not,when the hydraulic pressure is less than 0. 8 MPa,it should be analyzed based on bending strength,otherwise it should be analyzed based on shear strength,and the 0hydraulic pressure should not be ignored;（ 2） for tensional fault,the calculation of minimum safety thickness should be consider the lengths of the top and bottom part in lateral rock,the longer part is more likely to be destroyed or the bottom is more likely to be destroyed when equal. Batholite properties,hydraulic pressure ofcavity,radius of tunnel etc. should be considered comprehensively to provide reference to the design and construction of lateral karst tunnel fault segment after determining the minimum safety thickness of batholite.