Experimental research on water inrush in tunnel construction

With the rapid development of underground construction, a large number of tunnels will be built at the positions where unprecedentedly complex geological conditions exist. It results in more and more tunnel water inrush accidents. Study on water inrush becomes more and more important. The water inrush in tunnel construction is the results of water-rock coupling interaction. The surrounding rock stress state changes continuously in tunnel excavation, so recording the data of stress, displacement and water pressure in the whole process is essential to the research of the tunnel water inrush mechanism. By the physical simulation experiment of water inrush in tunnel excavation, the change laws of stress, displacement and water pressure were analyzed: The displacement increased gradually at the beginning, but sharply increased when excavation reached the water-bearing structure; the stress concentrated in the early period and released later; the water pressure increased sharply firstly and stabilized afterward with slow but continuous decrease. The whole water inrush process can be divided into two periods: accumulating period and instability period. The accumulating period was characterized by the stable development with elastic potential energy and rock damage accumulating continuously, while the instability period performed state's sudden changing. Based on the analysis above, actual engineering cases and cusp catastrophe theory, the criteria of water inrush were established and verified with the experimental data.