Dynamic centrifuge tests on isolation mechanism of tunnels subjected to seismic shaking

Simplified equivalent static methods for seismic analysis of shallow buried rectangular underground structures

Based on the equivalent mass-spring model and considering the coupling effect between creep soil and prestressed anchors, the dynamic calculation model of prestressed anchors with frame structure is established. The soil mass is expressed in the form of concentrated mass. The action of the frame structure on the soil is treated as a parallel coupling of a linear spring and a linear damper, and the free section of the anchor is treated as a linear spring. Considering the creep characteristics, the soil is regarded as a Generalized Kelvin body and the anchoring section of the anchor is regarded as an equivalent spring body, which are coupled in parallel. Considering the effect of slope height, the dynamic calculation model is solved and the seismic response is analyzed. Finally, an engineering example is used to verify the calculation method in this paper, and the results are compared with the shaking table test and numerical simulation. It shows that the calculation model proposed in this paper is safe and reasonable for the seismic design and analysis of the slope supported by prestressed anchors with frame structure.

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Seismic Response of Prestressed Anchors with Frame Structure

With the vigorous development of urban rail transit system, especially the construction of subway system, the safety of subway system draws more and more attention. The study of anti-seismic for underground structures has also become an important problem to be solved in the construction of Metro system. Based on the typical underground structure seismic damage phenomenon, this paper summarizes the seismic characteristics, research methods and design methods of underground structures to offer a guide for engineers.

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Overview of Anti-Seismic Researches of Underground Structures

By adopting dynamic time-history analysis method, the seismic analysis for the joint between intake tunnel and circumfluence groove is performed by FLAC3D. Aiming at the mechanical characteristics of this structure and rocky features, according to the design scheme, the analysis of seismic response is carried out, on the base of which envelopes of internal forces are given in this paper. The results show that change of the temperature has much influence on internal force in the same load effect combination. Temperature load also change the direction of internal force in some part. For the similar anti-seismic design, this paper has certain reference value and guiding sense.

Seismic Analysis of Nuclear Project for Joint between Intake Tunnel and Circumfluence Groove

This paper presents a closed-form solution for determining bending moments and axial loads for tunnels and shafts under earthquake load, while considering soil-structure interaction as a pseudostatic problem. The results are presented graphically in terms of nondimensional parameters, such that these curves can be used directly to aid in design-load calculations. The solutions are particularly useful for relatively rigid structures embedded in soft soils, or for tunnels/shafts with small segment lengths.

D K Shukla

Papers

Earthquake load analysis of tunnels and shafts