Research And Improvement Of Practical Analysis Method For Seismic Resistance Of Underground Structures

This dissertation systematically researches and analyzes the practical analysis method of earthquake seismic of underground structures through theoretical analysis and numerical simulation,and improves the method.The main contents and conclusions are as follows:(1)The formula for calculating the inertial acceleration of onedimensional soil layer using free field displacement is given,and a displacement-based response acceleration method is proposed.The new method is compared with the response acceleration method recommended by the existing code.The variation law of inertial acceleration calculated by different response acceleration method is studied with site type,site shear wave velocity and ground motion intensity.The result preliminarily proves that the displacement-based response acceleration method has good calculation accuracy and wider adaptability.(2)By analyzing the one-dimensional seismic response characteristics of soil under the incident P-wave and S-wave,a unified mechanical model for the analysis of soil seismic response under the combined action of horizontal and vertical ground motions and gravity is proposed.The calculation accuracy and applicability of the unified mechanical model are verified by comparison with the traditional model;the comparison with the extended model shows that the unified mechanical model has higher calculation accuracy than that of the traditional model when considering geometric nonlinearity.(3)The dynamic time history analysis of the typical single-span,doublespan and three-span underground structures under the combined action of horizontal and vertical earthquakes was carried out to obtain the response characteristics of the underground structures under the combined action of horizontal and vertical earthquakes.The most unfavorable deformation state and the corresponding moment of the structural response under the combined action of the earthquake is determined.(4)The integrated response displacement method with the combined action of horizontal and vertical earthquakes is proposed.Through the comparative analysis of the integrated response displacement method and the dynamic time history method under the conditions of different ground motions,different medium stiffnesses and different structural stiffnesses,it is verified that the new method has good performance,good computational accuracy and good adaptability.(5)The influence of the artificial boundary distance of the integral response displacement of the traditional shallow buried underground structure was analyzed,and the influence law of the far-field medium outside the artificial boundary was obtained.An integral response displacement method considering the influence of far-field medium is proposed.Through the comparative analysis of this method and the traditional integral response displacement method of shallow buried underground structures under the conditions of different ground motions and different artificial boundary distance,it is verified that the method has high calculation accuracy and efficiency.Through theoretical derivation,the artificial boundary condition of infinite-domain static problem analysis-elastic artificial boundary is obtained,and the infinite-domain elastic artificial boundary is used in the finite element model of deep underground structure,and the integral response displacement method of seismic analysis of deep underground structure is proposed.Through the comparative analysis with the traditional integral response displacement method,it is proved that the proposed integral response displacement method has higher accuracy and computational efficiency when used for seismic analysis of deep underground structures.