基于岩溶演化模型的隧道突水危险性评价

Risk Evaluation of Water Inrush in Karst Tunnel Based on Karst Evolution Model

岩溶隧道是否发生涌突水,主要取决于洞身岩溶发育程度和岩溶系统结构类型,而这与岩溶系统的演化过程密切相关。岩溶系统的发育演化始于具有侵蚀性的水对可溶性岩体中裂隙的溶蚀扩展。基于此,本研究耦合了渗流模型和溶蚀扩展模型,并结合鸡公岭隧道区水文地质背景资料,建立了隧道区岩溶系统岩溶演化模拟模型,模拟再现了隧道区岩溶含水介质的发育情况。结果显示:随着岩溶系统的发育演化,整个系统中裂隙不断被溶蚀扩展,差异性溶蚀越来越显著,岩溶含水介质的非均质性越来越强;同时随着埋深的增加,岩溶发育程度及非均质性越来越弱;浅部和深部裂隙的平均溶蚀扩展率相差近1 500倍;鸡公岭隧道洞身标高处岩溶发育微弱,裂隙溶蚀扩展较小,仍为裂隙岩体,其等效渗透系数为0.51m/d,岩溶突水概率极低,隧道发生涌水时的涌水量为127.9m3/d,对隧道施工影响较小。

The occurrence of water burst and water inrush in karst tunnel mainly depends on the develop- ment degree of karst cave and the structure type of karst system, which is closely related to the evolution of karst system. The evolution of karst system begin with the dissolution widening of cracks in rock mass by aggressive water. This study introduces the establishment of the karst evolution simulation model cou- pled with seepage model and dissolution widening model based on the regional hydrogeological conditions. The evolution simulation model is used to reconstruct the changes of water-bearing medium during the evo- iution process of Jigongling karst system. The result shows that, with the karst system＇s evolution, the fissures are widened progressively by dissolution with obvious differential dissolution and the heterogeneity of karst aquifer becomes more and more obvious. However, karst development extent and heterogeneity level become milder with the increase of depth. The average widening rate of fissures in the shallow system is almost 1500 times higher than that in the deep system. At the portal elevation of Jigongling tunnel, the karst development extent is mild, with the smaller dissolution widening fractures. The tunnel surrounding rocks are still a fractured rock mass with the permeability coefficient 0. 51 m/d. The water inflow of 127.9 ma/d when water burst accident happened is considered to be quite a small amount to exert effects on the tunnel construction.