地下立交分岔式隧道三维地震波动反应特性分析

Bifurcated tunnel emerges as a new type of tunnel structure in recent years and it is characteristic of large-span tunnel, multi arch tunnel and the small spacing tunnel. These characteristics make its structure more complex and its stress conversion more variable. Based on the finite element software MSC.Marc, a 3D structure-soil interaction model was developed for bifurcated tunnel in this paper: continuous arc parts, which is the weakest of this tunnel, were studied and analysis focused on its horizontal displacement, stress and characteristics of acceleration response along the length, the width and the height. These were indicated that 1) The height is the primary factor of acceleration response of tunnel structure for the same cross section of continuous arc parts; 2) The spatiality is apparent for the displacement response of tunnel structure in which one-way cumulative permanent deformation will happen under the seismic motion; 3) The stress response is relatively big for continuous arc parts whose connections between walls and bottom are weak for seismic motion; The tensile and compressive stress are concentrated in middle walls, while the peak value of shear stress appears in connection walls; 4) The stress concentration appears for the transition sections between different structures of big-span tunnel, continuous-arch tunnel and the small-span tunnel, and the acceleration and displacement response experience abrupt change. Much more attention shall be paid on these weak sections during seismic design and more seismic capacity should be considered.