Research On Dynamic Model And Influence Of Model Parameters On Seismic Response Of Underground Structure

With the increasing popularity of underground and underground shopping malls,the design of underground structures has become increasingly important.In multi-seismic countries such as China,the seismic design of underground structures is particularly important.At present,there are many methods for seismic design of underground structures,but few are widely used in practical projects.This paper mainly studies the influence of the interaction between soil and structure.Using the Winkel model,the influence of these factors on the spring constant of the foundation is studied,and finally the influence of the nonlinear foundation spring on the vibration is extended.This thesis is consisted of three parts.In the first part,the method of dimension analysis was used to determine foundation spring coefficient,Several parameters,including the diameter of the structure,the depth of burial,the type of structure,the fixing method,the embedment method,the viscous coefficient of the foundation soil,the seismic frequency and so on,are taken into account.The derivation combined theoretical derivation,experimental fitting and verification,and provide a new method for rational determination of foundation coefficient.In this part,the influence of the seismic frequency,the structure depth and size on soil spring coefficient is discussed in detail.The study showed that with the increase of seismic frequency,the strain rate effect of soil spring increases which leads to the increase of the stiffness.As the size of the structure increases,the influence domain of the structure on the surrounding soil increases.Under the same pressure,the stiffness of the soil spring gradually decreases with increase of structure size.As the depth increases,according to Terzaghi’s theory of "arching in ideal soil",the overlying soil stress increases with the increase of the buried depth.And finally,it tends to be a fixed value.This pressure is calculated as the self-weight stress,and the relationship between the ground coefficient and the buried depth is obtained.The ground coefficient increases with the buried depth of the structure.And finally,it tends to be a fixed value.In the second part,the ground coefficient is used for the calculation of the seismic response of underground structure.Using structural dynamics,the maximum displacement and natural frequency of the rigid body structure are obtained.Compared with the linear elastic soil,the structural displacement increases and the natural frequency decreases when considering the viscous behavior of the soil.First,the vibration frequency is no longer a fixed value,it is related to the external frequency and other factors.Furthermore,the structural resonance is weakened,the displacement amplitude decreases,and the resonance has a hysteresis.It provides references for practical engineering design,and is significant for the seismic safety of underground structures.The third part of the thesis discusses the influence of soil nonlinearity on the vibration of underground structures.Compared with the linear foundation,the nonlinearity of the soil and the seismic frequency have a remarkable influence on the natural vibration frequency and maximum displacement of the underground structure.When considering the nonlinearity of the soil,the vibration displacement of the structure increase and the natural frequency of the structure decrease.