Abstract
We took into account the adverse influence of the karst water seepage effect on the water-resistant rock mass of karst tunnel face. Based on the upper-bound theorem of limit analysis and the Hoek–Brown failure criterion, we obtained the calculation method of the critical safety thickness of the water-resistant rock mass. We carried out a feasibility analysis, an analysis of influencing factors and a comparative analysis with previous related research achievements of this method. The results showed that: (1) With the decrease of surrounding rock grade, the safety thickness of water-resistant rock mass gradually increased, and the safety thickness of surrounding rock at all grades remained within a reasonable range. (2) The safety thickness decreased as the compressive strength, the tensile strength and parameter A increased, and it increased as the karst water pressure, the tunnel excavation height, and parameter B increased. (3) The change trend of the safety thickness with the influencing factors was completely consistent under the two conditions of considering and without considering the seepage effect, and the safety thickness with considering the seepage force was greater than that without considering the seepage force. Taking the Yunwushan Tunnel of Yiwan railway as an example, the critical safety thickness of the water-resistant rock mass was calculated and the calculated value was in good coincidence with the safety thickness adopted in the actual project. The research results are of great significance to prevent the occurrence of high pressure filling karst geological disasters such as water inrush in tunnels.
Highlights
China has a vast territory, 70% of which are mountainous areas
On the basis of the upper-bound theorem of limit analysis and the Hoek-Brown failure criterion, we derived and obtained the expression of the critical safety thickness of the water-resistant rock mass of karst tunnel face considering the adverse influence of karst water seepage effect on the water-resistant rock mass
In order to verify the feasibility of the above method, we calculated the critical safety thickness of the water-resistant rock mass under I–V grade surrounding rock
Summary
China has a vast territory, 70% of which are mountainous areas. The geographical and geological conditions are very complex. Meng et al (2020) established models of water inrush in fault fracture zone and obtained the calculation formula of minimum safety thickness These achievements are mostly based on specific engineering cases, and each research direction has its own emphasis, different mechanical models, influencing factors, and judgment standards. On the basis of the upper-bound theorem of limit analysis and the Hoek-Brown failure criterion, we derived and obtained the expression of the critical safety thickness of the water-resistant rock mass of karst tunnel face considering the adverse influence of karst water seepage effect on the water-resistant rock mass. The research results are of great significance to prevent the occurrence of high pressure filling karst geological disasters such as water inrush in tunnels
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