Investigation Of Dynamic Response Of Connecting Passage Between Urban Underground Structures Under Blast Loading

With the development of underground infrastructure,the construction of underground structures has becoming more significant.The underground spaces are in demand for different uses.The connecting chamber between the large spaces and civil air defense projects are the key to make the underground spaces a functional whole.At the same time,the international terrorism is still exist and spreading and around the world that the relation of international are still in tension.Modern air strike has already developed into a precise way that the important large and medium-sized cities tend to be the preferred targets for attacks and the connecting projects are important at that time,particularly.The anti-explosion of various underground structures has become one of the topics that China needs to pay high attention and in-depth research.The research before is mainly based on simulation methods and generally the explosives were simplified as cubes.In reality,however,the explosives are cylindrical with an aspect ratio of 3:1.And in previous studies,the depth of invasion in the soil are often ignored without considering the explosive from the air.First,this paper applies theoretical methods to verify the simulation methods and parameters.Then,the dynamic response results of the lining structures of the underground tunnel are systematically studied when the columnar explosive penetrate into the soil and then exploded at a certain depth.The main research results are as follows:(1)The process and propagation law of explosion in free atmosphere and soil are analyzed and the existing theoretical formulas are simplified.Compared the results of theoretical calculation and numerical simulation,it is showed that the parameters and methods used in the study are reasonable.(2)Taking the underground connecting chamber in Wuhan as the background,the ANSYS/LS-DYNA finite element(FE)dynamic analysis program are used to analyze the response results and mechanical laws of the lining structure of the underground passage subjected to blasting loads.The depth of explosive in the earth is based on the standard of today's conventional weapons.In these way,the response of stress,strain,displacement,velocity,acceleration,etc.at various parts of the structure are obtained.The parameters of elements from the locations where are easier to get destroyed are discussed in detail.(3)In order to study the influence of different explosion equivalency,cross-section width of lining structure and depth of passage on the dynamic response of the structure subjected to blast loading,the FE numerical simulation method are used.Then,this paper has an intensive study on the influence of haunches which fewer has done.Through comparing the difference of response in the structure affected by the explosion with/without enhanced haunches,it is showed that the haunch can mainly make a control of the displacement of the roof.Further,the influence of the size of the haunch is discussed in detail.It is showed that the increase in the size of the haunch can improve the bearing capacity of the lining structure of the rectangular tunnel.However,the structural bearing capacity will be less affected when the size of haunch increases to a limited bound.