| Submarine metro tunnels are located in semi-infinite aquifers,and groundwater recharge is theoretically infinite,so groundwater is an important consideration.At the same time,because of the drilling and blasting method,the vibration effect caused by the blasting construction will damage the surrounding rock of the tunnel in the fluid-solid coupling effect.Once the water inrush disaster is induced under such harsh conditions,the consequences are unimaginable.In the fluid-solid coupling effect,when the tunnel passes through the fault fracture zone,it will aggravate the degree of surrounding rock fragmentation,further increase the possibility of tunnel instability and damage,and increase the risk of construction.This paper takes the Wawuzhuang Station-Guizhou Road Station section of Qingdao Metro Line 1 as the engineering support,and mainly takes the sea-crossing section of this section as the research object.Through theoretical analysis,numerical simulation and on-site monitoring,the vibration response and stability of blasting construction in the process of submarine tunnel construction are studied.At the same time,the pertinent stratum reinforcement design is proposed.The main research results are as follows:In this paper,the basic theories and equations of fluid-solid coupling effect,calculation of water inflow and strength criterion of submarine tunnels are studied,and the seepage enhancement mechanism of blasting vibration on surrounding rock of tunnels is analyzed.It lays a theoretical foundation for the later study of numerical simulation of tunnel construction in fluid-solid coupling effect.At the same time,the numerical model of permeability evolution of tunnel surrounding rock is established by FLAC3D software.The numerical simulation method is applied to derive the new calculation formula of tunnel water inflow.Based on the equivalent circle theory of submarine tunnel,the calculation formula of water inflow in line with the engineering environment is derived.The results of the new formula and the traditional theoretical formula are all in an order of magnitude,and the difference is small.Therefore,it is feasible to apply numerical simulation to the new formula for calculating the water inflow of submarine tunnels.During the construction of submarine tunnel,both seepage and blasting will increase the plastic zone of surrounding rock around the tunnel.Blasting vibration has greater influence on the development of plastic zone of surrounding rock around the tunnel than seepage.It is one of the main factors causing the plastic zone of submarine tunnel.Under the action of construction disturbance when a submarine tunnel crosses a fault fracture zone,due to the different physical and mechanical properties of different strata,different stress and strain fields,and different stress and strain variables,large deformation slip and shear failure can easily occur between the two strata in the contact area of different strata due to different deformation quantities of each stratum.Under the fluid-solid coupling effect,the pore water pressure around the tunnel decreases all the time,and the decreasing range is larger from the upper part of the tunnel to the lower part of the tunnel.The squeezing effect of blasting vibration makes the pore water pressure of surrounding rock around the tunnel rise rapidly in a short time,and then decrease slowly with the decrease and disappearance of blasting vibration after reaching the peak value.Blasting vibration effect makes the permeability and permeability coefficient of rock with poor lithology higher than that of rock with good lithology,and then changes the size of fluid flow vector after adding blasting vibration effect.Blasting vibration effect makes the deformation of surrounding rock increase sharply,and the deformation caused by blasting and seepage is larger than that caused by seepage only.During the construction of tunnel through fault fracture zone,the deformation value of monitoring points is obtained by numerical simulation.It is found that the deformation of surrounding rock around the tunnel is too large,the maximum deformation is 16.82mm,and many places exceed the allowable warning value(the vault settlement is ± 12mm,the clearance convergence is ±8mm).Therefore,effective reinforcement measures should be put forward for tunnel crossing bad geological section.The grouting reinforcement design aiming at tunnel crossing fault fractured zone is put forward.Comparing the simulated data with the measured data,it is found that the trend of displacement and surrounding rock pressure is the same.The difference between the simulated and measured values of surrounding rock deformation is not more than two times.The calculated values of surrounding rock pressure after convergence of numerical simulation are almost the same as the measured values,which proves the feasibility and accuracy of the numerical simulation method.After the grouting reinforcement design is adopted in the actual project,the maximum settlement value of the vault is-0.9mm and the maximum convergence value of the clearance is 2.6mm,which do not exceed the early warning value required by the code,and the rock deformation around the cave has been effectively controlled. |
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