Study On The Prediction Method Of Water Inflow In Subsea Tunnel And Its Impact Analysis Of Blasting Vibration

With the development of national economy and technology,the demand of national strategy and city development,the construction of undersea tunnel is in full swing,which not only shortens the journey effectively,but also greatly relieves the traffic pressure.The significance is self-evident.The subsea tunnel is usually excavated by drilling and blasting method,and the influence of blasting vibration is inevitable.However,at present,the influence law of blasting damage and the permeability enhancement mechanism are not clear,which is extremely disadvantageous to accurately predict the water inflow of subsea tunnel.Therefore,it is easy to lead to inadequate preventive measures and unreasonable measures.This paper,the water inflow of the subsea tunnel under the influence of blasting vibration was predicted and analyzed by means of laboratory test,theoretical analysis,field test and numerical simulation,and a comprehensive identification and prediction system for water inflow of subsea tunnel under the influence of blasting vibration was established in the Qingdao Metro Line 1 undersea tunnel,this provides theoretical basis and technical support for the problem of the water inflow of subsea tunnel.(1)Based on the actual boundary conditions of subsea tunnel and the shortage of existing research,analysis methods of seepage field and water inflow of subsea tunnel based on superposition principle was put forward,including the calculation model of double water inflow points and simplified calculation model of single water inflow point calculation model.The equivalent calculation formula for multi level rock mass was given.The research method was analyzed and verified in combination with the actual engineering situation,the optimum overburden thickness of undersea tunnel in this section was given.The influence of the depth of tunnel,the radius of the tunnel and the depth of the sea water on the water inflow of the subsea tunnel were analyzed,and the results were compared with the prediction results of common experience and analytical methods,such as the Custer formula,Kobayashi Yoshizheng formula,Huangfu Ming formula and Oshima Yoshi formula,and so on.(2)The mechanical and deformation characteristics of surrounding rock were analyzed and the constitutive model of surrounding rock was established by uniaxial compression test,tensile strength test and three axis compression test before excavation.Based on the theoretical analysis,the evolution model of permeability characteristics in the process of damage and failure of surrounding rock was established,and the evolution law of permeability characteristics was analyzed.The FLAC3D software was used to simulate the rock three axis compression test process and the permeability evolution model was embedded in the software to analyze the evolutional law of permeability,which verified the rationality and accuracy of the study,and laid foundation for the later study.(3)In this chapter a theoretical calculation method of seepage field and water inflow were presented,and on the basis of this,the relationship curve between the water inflow of the forward probes and the permeability of surrounding rock were established according to the design scheme of the forward probes in the subsea tunnel.The initial permeability coefficient of surrounding rock was determined by the field test data.The accuracy and rationality of the theoretical research were verified by numerical simulation.The initial permeability coefficient is the initial value of permeability coefficient before blasting vibration.(4)Based on the constitutive model of surrounding rock,the evolution model of permeability characteristics and the initial permeability coefficient of surrounding rock,the FLAC3D software was used to simulate the real blasting process of the subsea tunnel,to determine the distribution law of permeability coefficient of the surrounding rock under the influence of blasting vibration,and to obtain the water inflow of the subsea tunnel under the influence of blasting vibration.The results were compared with the water inflow of the subsea tunnel by permeability coefficient of exploration,initial permeability coefficient and the field measurement.It showed that the water inflow of the subsea tunnel under the influence of blasting vibration was closer to the reality,and was more reasonable.Furthermore,the influence of the different hole spacing and the different blasting pulse peak on the permeability enhancement effect and water inflow of the subsea tunnel was analyzed.The research results have a great guiding significance for practical projects.