多年冻土场地路基地震加速度反应谱特性研究

多年冻土场地路基及与之相关土工构筑物的抗震己成为以往研究不足、而目前道路建设中又必须尽快解决的重要工程问题之一。以在建的青藏铁路工程的抗震设计与地震加固为应用背景，基于若干种较为典型的冻土场地路基工况，采用非水平场地土体(土工结构物)地震反应分析的二维动力有限元法，分别输入E1 Centro波及天津波，开展多年冻土场地路基地震加速度反应谱的研究工作。研究表明，在高频E1 Centro波和低频天津波输入下，无论冻土层存在与否，路基地震加速度反应谱均主要表现为高频脉冲型，反映了路基的地震冲击型破坏作用；当输入高频E1 Centro波时，在中、低频段，含冻土层路基的地震加速度反应谱较不含冻土层路基的地震加速度反应谱大；而在低频天津波输入下，冻土层存在与否，对路基地震加速度反应谱的影响较小。与不同的场地地形条件相比，输入地震波频率的不同，对冻土路基地震加速度反应的影响更大，尤其是当存在融沉盆时更加剧了路基的地震加速度反应。

STUDY ON RESPONSE SPECTRUM CHARACTERISTICS OF EARTHQUAKE ACCELERATION FOR ROADBED ON PERMAFROST SITE

At present,the aseismic problem of roadbed and other relevant earth structure on permafrost site has become a key problem that is not studied sufficiently in the past and needs to be solved urgently. Based on several typical cases of roadbeds of Qinghai-Tibet Railway Project,the response spectrum characteristics of earthquake acceleration for roadbed on permafrost site are studied by using two-dimensional dynamic FEM. The high-frequency El Centro wave and low-frequency Tianjin wave are input as an excitation. The result indicates that whether there is frozen layer,earthquake acceleration response spectrum is mostly the type of high frequency impulse,and the soil failure is bump type. In the mid and low frequency stage,the values of earthquake acceleration response spectrum for roadbed with frozen soil are larger than that without frozen soil when input is El Centro wave. But for Tianjin wave,there is no significant difference. Compared to different topography conditions,the frequence of input earthquake wave has great influence on earthquake acceleration response spectrum of roadbed. Especially,the existence of thawed basin ground enhances the effect of earthquake acceleration response for roadbed.