Evolution mechanism of tunnel water and sand inrush considering water-rich sandy dolomite hazard-causing structures

Abstract

Water-rich sandy dolomite stratum is prone to water and sand inrush disasters during tunnel construction. It is of great significance to explore its hazard-causing structure and water inrush mechanism for disaster control. The physical and mechanical properties of dolomite samples are tested to reveal the difference between unsanded dolomite and sandy dolomite. Based on the advanced geological prediction and geological sketching, three types of water and sand inrush hazard-causing structures are identified. Furthermore, three types of water and sand inrush mechanisms under different hazard-causing structures are explored by using fluid–solid coupling model test. One is the progressive failure type of water and sand inrush caused by crack coalescence for the broken unsanded dolomite outburst prevention structure, another is the failure type in which the seepage failure of sandy dolomite strips promotes the crack coalescence of unsanded dolomite, and the other is seepage failure type for the overall sandy dolomite outburst prevention structure. Finally, fluid–solid coupling simulation is used to discuss the failure characteristics of outburst prevention structure with different factors. The results show that the critical sandy dolomite area ratio of the three types is 25 % and 75 %. The factors affecting the inrush disaster are ranked as follows: sandy dolomite area ratio > unsanded dolomite fragmentation degree > buried depth > water storage structure pore pressure > water storage structure size. The findings provide valuable reference for disaster control in water-rich sandy dolomite area.