| When a tunnel passes through a mountain area,it often encounters large-scale geological disasters such as water inrush and mud inrush due to complex geological conditions and other factors.Tunnel water inrush,with its characteristics of high incidence,sudden occurrence and great harm,seriously restricts the development of underground engineering construction in Karst areas: water inrush disasters often accompany immeasurable losses,tunnel flooding,damage of mechanism and equipment,forced interruption of construction,or irreversible consequences such as soil erosion,water resources balance damage,and even endanger life safety.With the perfection and perfection of the legal system of ecological protection,the implementation of the responsibility of ecological governance,the intensification of punishment for ecological damage and the establishment of public participation in the mechanism of ecological protection,more attention has been paid to the engineering treatment of geological hazards in tunnel construction,especially in mountain tunnels.Taking the engineering cases of water inrush and mud inrush disasters in the construction of several tunnels in China as the research object,this paper analyzed the structure type,catastrophic mode and catastrophic mechanism of water inrush(mud)disasters in the construction of mountain tunnels by means of engineering case investigation,numerical simulation and theoretical analysis,and then obtained the minimum safety of water and mudstone(soil)pan through mechanical derivation and numerical simulation comparative study.Prediction method of full thickness,comprehensive advance prediction method of tunnel water inrush(mud)disaster and specific prevention and control measures of tunnel water inrush and mud inrush disaster caused by typical disaster-causing structure are studied in combination with the treatment method of water inrush disaster in case.The main research results are as follows:(1)Statistical analysis of water(mud)inrush disasters occurred in long tunnels of different areas and lines was carried out.The types of disastrous structures caused by different water and mud inrush disasters were obtained,and the formation conditions and mechanism of various disastrous structures were analyzed.(2)Disaster-causing model of water(mud)inrush disaster in Mountain Tunnel Several representative major water inrush events in karst tunnels are selected toinvestigate their disaster-causing process and mechanism in detail.Based on these,the water inrush models of each event are generalized.The water inrush models are compared and analyzed,and two kinds of water inrush(mud)disaster-causing models are divided based on the spatial relationship between the disaster-causing structure and the tunnel and the time of the water inrush and mud inrush disasters.The disaster-causing model based on the relationship between the disaster-causing structure and the spatial location of the tunnel can be divided into intersecting and separating type,top-lying type,side-lying type,bottom-lying type and through type.The disaster-causing model based on the occurrence time of water and mud inrush can also be divided into instant water inrush,delayed water inrush and intermittent water inrush.(3)Firstly,based on the strength theory,the water-proof and mudstone(soil)plate of the disaster-causing structure located at the top,side and bottom of the tunnel is simplified to a two-end fixed-supported beam model,and the water-proof and mudstone(soil)plate of the disaster-causing structure developed in front of the face of the tunnel is simplified to a circular plate model with surrounding fixed support.Using the elastic theory,based on the bending,shear or tensile strength criteria of the beam and slab.Establish the prediction method of minimum safe thickness of water-proof and mudstone(soil)pan,simplify the top and bottom outburst-proof layer to two-end fixed-supported beam model,simplify the front and side outburst-proof layer to four-side fixed-supported plate model,and establish the calculation formula of safe thickness of outburst-proof layer based on cusp catastrophe model.(4)The water pressure of surrounding rock and karst cavern of common grade in the practice of cross-combination project forms different calculation conditions.Based on this,the numerical model test of water inrush hidden danger tunnel is established,and the mechanical response of tunnel construction under the condition of step excavation and step support is studied considering the fluid-solid coupling effect.The model and rock(soil)under the condition of different surrounding rock grade and karst water pressure in the process of tunnel excavation are put forward and analyzed.Based on the evolution law of displacement field,the minimum safe thickness of rock(soil)plate under different surrounding rock levels and combined conditions of water pressure in karst caverns is proposed.Through regression and fitting analysis of the results,the formula for calculating the minimum safe thickness of rock(soil)plate of water inrush tunnel under different surrounding rock conditions is established.(5)Comparing the advantages and disadvantages of several tunnel advanceprediction methods,such as geological analysis method,TSP method,geological radar method,transient survey method and advance drilling method,analyzing the geological and hydrological conditions of the tunnel site area,adopting a combination of various prediction methods,establishing a comprehensive advance geological prediction process for tunnel water inrush(mud)and illustrating its actual engineering through the case of Chuntianmen tunnel.Application.Combining with the engineering cases of Chunmen Tunnel and Yunwushan Tunnel,the disaster-causing structure types,catastrophic models and the prediction of minimum safety thickness of water-proof and mudstone(soil)pan studied in the previous paper,the paper puts forward the specific prevention and control measures for water-inrush(mud)disasters under typical disaster-causing structure conditions.The main innovations of this paper are:(1)Combining the disaster-causing characteristics of typical water-inrush(mud)disaster-causing structures in tunnel construction with common disaster control measures,this paper puts forward specific engineering treatment measures for water-inrush and mud-inrush disasters under typical disaster-causing structures,and verifies the practicability of the measures through engineering examples.(2)Based on the strength theory,the formula for calculating the minimum safe thickness of water-proof and mudstone(soil)tray is derived.The formula for predicting the minimum safe thickness of water-proof and mudstone(soil)tray is obtained by numerical simulation test.The theoretical deduction and numerical simulation formulas are verified by the case of water inrush disaster in practical engineering,and the rationality of the predicted results is proved. |
PDF Full Text Request