Research On Stratum Spring Parameters And Stratum Boundary In Dynamic Calculation Of Underground Structure

With the continuous development of urban construction,people are making more and more use of underground space.Nowadays,many civil engineering projects of large dynamic machines choose to build the main engine room structure underground,so as to use the constraints of the foundation soil on the structure to reduce the vibration of the structure when the dynamic machine is running.However,the dynamic interaction between soil and structure is very complicated.How to simulate the action of soil on the structure during dynamic analysis has become a major difficulty in the design of the underground structure of the main engine room of such large-scale dynamic machines.There are two commonly used calculation methods for underground structures:load-structure method and stratum-structure method.The existing load-structure method lacks a unified method for the value of foundation spring parameters,and does not consider the change of spring parameters under dynamic loads;the existing stratum-structure method lacks theoretical basis when determining the position of the formation boundary,and the formation boundary The method of processing is not uniform.Based on this background,this paper proposes improvements to these two calculation methods,making it suitable for dynamic analysis of underground structures,and the calculation process is relatively simple and can be used in engineering practical.In this paper,these two methods are used to analyze the dynamics of the underground structure of a super gravity centrifuge.Chapter 1 introduces the main types and characteristics of underground structures,summarizes the research status of two calculation models and the theory of soil-structure dynamic interaction in underground structure design theory,and points out the research ideas and core content of this articleChapter 2 introduces the theory of dynamic interaction between foundation and structure.Taking the rigid circular foundation as an example,the analytical solution is used to express the effect of soil on the structure,and the relation between the effect of soil on the structure under the dynamic load and the load frequency is obtained.At the same time,by comparing the half-space system with the single-degree-of-freedom system,it is explained how the effect of soil on the structure is equivalent through the spring-damper.Chapter 3 proposes an improved load-structure method for the dynamic calculation of underground structures.When calculating the foundation spring parameters,this method first calculates the static stiffness of the spring,and then obtains the dynamic stiffness of the spring and the damping coefficient of the damper through the relationship between the spring parameters and the load frequency.By analyzing a simple example,it is proved that the method can successfully obtain the natural vibration characteristics and dynamic response of the structure.Chapter 4 proposes an improved stratum-structure method for the dynamic calculation of underground structures.In this method,the structure and the stratum are jointly modeled by finite element.The range of the finite field of the soil is 5 times the size of the structure,and a viscoelastic artificial boundary is set outside the layer to simulate the infinite field of the soil.Through the analysis of simple calculation examples,it is proved that the method can successfully obtain the dynamic response of the structure,and it is mutually verified with the calculation results in Chapter 3.Chapter 5 carries out dynamic analysis of the main gravity room structure of the super gravity high-speed centrifuge in the national major scientific and technological infrastructure project,super gravity centrifugal simulation and experimental device.The methods in Chapter 3 and Chapter 4 are used to calculate the structure of the main engine room respectively.The calculation results of the two methods are close,which proves the correctness of the calculation results.After analyzing the calculation results,it is proved that the response of the main engine room structure under simple harmonic load meets the requirements,but the natural frequency does not.Chapter 6 summarizes the full text research and points out that the research content of this article is insufficient.Suggestions are made on which areas can be studied in the future.