Water Inrush Mechanism And Process Control Method Of Fractured Rock Mass Induced By Blasting Power

Tunnel plays a key role in supporting the implementation of China's "transportation power" strategy and "One Belt And One Road" initiative.In the next 10 years,tens of thousands of kilometers of tunnels will be built,which will increase in scale and difficulty.Due to the widespread occurrence of groundwater and its storage structures,such as karst caves and faults,water gushing disasters occur frequently in tunnel construction,which seriously restricts the safe construction and efficient construction of tunnels.In view of the basic theoretical problems and major technical challenges faced by the safe construction of tunnels,it is difficult to actively prevent and control water inrush disasters due to the lack of scientific understanding of the mechanism of water inrush under blasting disturbance and the lack of effective control methods of disaster process.Around blasting dynamic induced fractured rock mass failure mechanism of water inrush and process control,this study by adopting the combination of theory and simulation experiment research methods,puts forward the method of physical simulation and numerical experiments of rock blasting,blasting dynamic disturbance is established under the water rock mass failure criterion of water inrush and outburst prevention minimum safe thickness calculation method,system analysis of water inrush disaster evolution process,The control mechanism of water burst process considering blasting disturbance was established and the following results were obtained.(1)Based on the principle of high pressure pulse cracking and blasting impact theory of rock mass,the correlation relationship between explosive mass and non-explosive excitation energy was established,and the method of quantitative simulation of blasting force by high pressure pulse cracking was proposed,which solved the problem that blasting force could not be accurately simulated in the past.Based on the discrete element particle dynamic contact expansive load method and dynamic stiffness calculation method,the blasting sinusoidal stress wave loading method was introduced,and the calculation process was dynamically updated by superposition principle.A three-dimensional blasting simulation method for fractured rock mass was established.A two-dimensional pipe domain model is used to apply constant water pressure to the prefabricated cracks,which is coupled with the explosion load to simulate the expansion of water-bearing cracks under the impact of explosion.According to different initial water pressure and blast load conditions,the failure process of fractured rock mass under single and cyclic blasting was simulated,and the deformation and failure law of fractured rock mass under blasting dynamical and hydraulic pressure was revealed.(2)Based on the blasting dynamic physical simulation test method,a dynamic damage performance test system for water-bearing crack was developed,which was composed of blasting dynamic simulation and testing device,hydraulic pressure loading and monitoring device in the crack,and monitoring device for internal crack damage and external crack expansion,and realized the quantitative characterization of dynamic damage test for water-bearing crack.For large scale rock specimens with different blasting intensity,initial hydraulic pressure,confining pressure and blasting distance,several groups of blasting dynamic damage tests were carried out for water-bearing cracks and dry cracks,and the phenomenon of water-pressure rise and strain oscillation in water-bearing cracks induced by blasting was found.Under the same initial water pressure,the increase of water pressure increases logarithmically with the increase of blasting intensity,while the increase of dynamic strain amplitude is S-shaped.Under the same blasting intensity,the amplitude of water pressure increases S-shaped with the increase of initial water pressure,while the amplitude of dynamic strain increases exponentially.With the increase of blasting distance,both the amplitude of water pressure and the amplitude of dynamic strain decrease inversely.With the increase of confining pressure,both the internal pressure rise and the dynamic strain amplitude increase exponentially.(3)For the square specimen with finite boundary,when the water pressure in the crack is low,only a single large equivalent blasting can cause the new crack at the blast center to connect to the water-bearing crack immediately.When the water pressure in the fissure is high,a single large equivalent blasting will lead to the instantaneous connection between the explosion-generated fissure and the prefabricated fissure and extend to the boundary.The internal rise of water pressure in fissure induced by blasting impact leads to the change of effective stress in fractured rock mass,further influences the stress distribution of rock mass,promotes the initiation,propagation and connection of water-bearing cracks,and influences the propagation mode of water-bearing cracks.(4)Based on the analysis of meso-failure characteristics of fractured rock mass,a coupled stress-seepage model reflecting the local progressive failure induced by the heterogeneity in rock mass was established.Based on the dynamic expansion model of water-bearing fissure,the dynamic stress intensity factors of pressure-shear and tension-shear under the action of blasting and water pressure were calculated,the criterion of water inrush by dynamic failure of fractured rock mass in tunnel was established,and the safety guidance method for tunnel construction based on safety factor was put forward.Based on the new understanding of blasting dynamic simulation test of fractured rock mass,the scientific subdivisions of tunnel outburst prevention structure failure are proposed:excavation failure zone,seepage failure zone and stratified crack failure zone,and the mechanical mechanism of progressive failure of fractured rock mass is revealed.(5)The excavation failure zone is affected by blasting disturbance,unloading and accumulation of original damage.The rock mass disturbance coefficient is dynamically corrected by calculating the strength reduction coefficient obtained from the rate of rock mass wave velocity reduction,and the thickness calculation method of excavation failure zone considering the dynamic disturbance of cyclic blasting is established.When the explosion stress wave propagates to the boundary of the disaster source such as the water-filled karst cave in front,the rock mass facing the void will produce tensile failure,which results in the obvious bedding fracture failure zone of the adjacent anti-outburst rock mass.Considering the reflection effect of the explosion stress wave,the calculation method of the thickness of the fracture failure zone under the effect of blasting disturbance and water pressure is established.In the middle of the outburst prevention rock mass is the seepage failure zone,and the plastic failure zone appears under the influence of the strong seepage of the water-rich stratified fracture zone.Based on the seepage differential equation and the equilibrium differential equation,the calculation method of the seepage failure zone under the water pressure transfer in stratified fracture zone is established.The blasting dynamic disturbance is effectively considered in the above zoning,and the minimum safe thickness of tunnel anti-outburst is determined by superposition calculation,which solves the problems that the blasting influence is not fully considered in the previous zoning and the calculation value is conservative,and plays an important guiding role in the construction safety of similar tunnels.(6)Based on the geological information identification and risk dynamic assessment information of tunnel engineering,a four-stage construction dynamic decision-making model is proposed:geological basis identification?water-inburst probability assessment?water-inburst performance analysis?hazard magnitude evaluation by integrating the performance evaluation of anti-outburst structure and multi-information fusion monitoring based on fiber laser microseismic.The main controlling factors of water inrush were obtained by using the comprehensive weight determination method.Based on the D-S evidence theory fusion analysis,the multi-index construction decision model and decision standard were constructed.In view of the relationship between different disaster sources and the future tunnel excavation contour range,a process regulation model for the performance of the anti-outburst structure was established to realize the process analysis and scientific decision-making of the major water inrush disaster.