Study On Pseudo-static Seismic Analysis Method Of Underground Structures And Pushover Test

At present,with the accelerating of urbanization process and the increasing of population,a lot of extra large cities come into being all over the world,a large number of rural population gather into the limited central zone of the city.Many cities have fallen into the dilemma that the ground space is not enough,traffic congestion often happens on the ground,the shortage of ground transportation capacity forms the problem need to be solved urgently.The quick development of subway engineerings has greatly improved traffic congestion.The development of underground engineering has brought convenience to us,at the same time,its seismic safety becomes more and more important,because the construction and reconstruction of underground structure is difficult and costly,the damage of underground structure will lead to great economic loss and social impact.In the past,the seismic design method of ground structure is often used to underground structure,but the earthquake response and stress features of underground structure are different from ground structure,it’s not appropriate to design underground structure according to the seismic design method of ground structure.Therefore,it’s necessary to study on the seismic design method specially for underground structures.On the basis of predecessors’ research,this paper contrastively analyses the applicability of various existing simplified analytical method for seismic design of underground structure through numerical simulation and pseudo-static test,meanwhile,a new type of model box is used in pseudostatic test to measure the soil spring stiffness.Specific content as follows:1.Research statusThe research status and seismic damage data of underground structures are systematically analyzed,and then this paper introduces seven cross-section simplified analytical methods of underground structure,including their specific calculation steps,advantages and disadvantages.The seven simplified analytical methods are consist of seismic coefficient method,free field deformation method,flexibility coefficient method,response displacement method,response acceleration method,forced displacement method and pushover analysis method.2.Contrastive study of simplified analytical methodsThis paper selects three simplified analytical methods whose calculation models need to be accompanied by soil,the seismic analyses of underground structure were carried out by finite element software Abaqus,the results of dynamic time-history analysis were compared to verify the influence of model lateral distance on the calculation results.Contrastive studies between four simplified analytical methods whose calculation models without soil and three methods whose calculation models with soil are carried out under the condition of different soil hardness.3.Comparative analysis of model boxThis paper introduces the structural forms of the model box used in the existing seismic tests of underground structures,comparatively analyzes the advantages and disadvantages of various types of model box.According to the experimental requirements of this paper,the structural forms of three new model boxes are designed,the characteristics of the three new model boxes as well as their range of application are analyzed.4.Free field pseudo-static testBased on the newly developed pseudo-static model box,this paper introduces the large scale pseudo-static pushover test under the condition of free field.The attenuation law of soil strain is studied by analyzing the displacement of soil in the model box.The relationship between soil pressure and soil displacement in the middle of the soil is analyzed to study on the distribution of soil spring stiffness along depth.