Dynamic Response Characteristics Of Rectangular Cross Section Composite Pipe Gallery Under Gas Explosion Load

With the rapid development of urbanization in China,natural gas,as a kind of clean energy,has been widely used.In order to make the gas pipeline easy to repair and install,it is laid in the underground comprehensive pipe gallery.However,natural gas,as a kind of combustible gas,is very easy to cause an explosion accident when encountering open flame after leakage,which will endanger the normal use of urban roads and people’s life,health and property safety.Therefore,it is necessary to provide theoretical basis for the protection work and design of integrated pipe corridor through model test and numerical simulation.Methods outlined inthis paper,based on comprehensive underground pipeline corridor,using relevant knowledge of the similarity theory,the design of model test,the first was derived by calculating the similarity criterion,the model test need to obtain the dimensional parameters of the model test specimens,and then make the template,the casting pipe gallery model specimen,after molding,maintenance of comprehensive utility tunnel gas tank filling the gas,By means of detonating gas with electric detonator,the strain time history curve and failure pattern of the model specimen under the action of gas implosion were obtained,and then analyzed.Based on the finite element software ANSYS/LS-DYNA and the multi-material fluid-structure coupling algorithm,the blasting calculation model of pipe corridor was established.The measuring points on the inner wall of pipe corridor were taken.The impact dynamic response characteristics of pipe corridor under different gas concentrations(7.8%,9.5%,11.6%,12.3%)and different gas volumes(1/3,2/3,3/3)wereanalyzed.Comprehensive utility tunnel gas tank(1)of the outer wall and partition wall at the same height of measuring point peak stress were similar,roof and floor of the peak stress are smaller,the peak stress of the roof and floor than the outer wall and partition of peak stress decreases in the range of11% ～ 14%,the peak stress on the various sectors as distance initiation point increase peak stress reduced,That is,the peak stress of the measured point decreases by about 22%-25% with every increase of 200 mm.By comparing the peak stress at the same position of the inner and outer wall of the plate,it is found that the peak stress at the outer measuring point increases by about 30%～33%compared with that at the inner measuring point.(2)According to the failure form of the model specimen,it can be concluded that the gas tank in the integrated pipeline corridor has the most serious damage,and the corner connected to the outer wall of the gas tank is a weak place.Under the action of explosion impact load,the first longitudinal cracks appear at the corner of the axel,and the cracks are parallel to the longitudinal of the pipe corridor.The partition wall of the gas tank is connected with the upper and lower roof after the axils make the combination of the partition wall and the upper and lower roof more firm,and because of the large stress of the partition wall of the gas tank,so in the middle of the partition wall produces a clearly visible longitudinalcrack.(3)The numerical simulation results show that when the volume concentration of methane gas in the gas compartment is 9.5%,the peak stress of each plate in the gas compartment of the integrated pipeline corridor is the largest.When the gas concentration increases from 7.8% to 9.5%,the peak stress of the roof increases by 18.40%,the peak stress of the partition wall increases by 10.27%,and the peak stress of the floor increases by 31.97%.The peak stress of the outer wall increased by30.50%.When the gas concentration increases from 9.5% to 11.6%,the peak stress of the roof decreases by 15.54%,that of the partition wall decreases by 7.2%,that of the floor decreases by20.10% and that of the outer wall decreases by 16.26%.When the gas concentration increases from11.6% to 12.3%,the peak stress of the roof decreases by 19.78%,that of the partition wall decreases by 11.29%,thatof thefloordecreases by8.06%andthat of theouterwall decreases by 24.27%.(4)When the gas volume concentration is 9.5% and the gas volume is 1/3,the peak shear stress of the vertical reinforcement measurement point in the middle of the partition wall is 63.41 MPa,and when the gas volume is 2/3,the peak shear stress of the vertical reinforcement measurement point in the middle of the partition wall is 102.27 MPa,and the gas volume is 2/3.The peak shear stress of measuring point of vertical reinforcement in the middleof partition wall is 162.17 MPa.That is,when the gas volume increased from 1/3 to 2/3,the peak shear stress of the vertical reinforcement of the partition wall increased by 61.28%,and when the gas volume increased from 2/3 to 3/3,the peak shear stress of the vertical reinforcement of the partition wall increased by 58.67%.When the gas volume concentration is 9.5%,with the increase of the gas volume,the measuring points on the inner wall of the pipe corridor show that the peak stress on the partition wall increases in the form of a quadratic function.When the gas volume increases from 1/3 to 2/3,the peak stress on the measuring point of the vertical bar in the middle of the partition wall increases by 29.36%,and when the gas volumeincreases from 2/3 to3/3,Thepeak stress increased by 37.90%.