高地震烈度区粉土地基抗液化及隧道抗震研究

昆明东外环下穿隧道工程是昆明南火车站枢纽工程中的一个重大项目,在勘察过程中发现K2+100~K2+200隧段含两层粉土层,且其中一层紧靠隧道设计底板。由于该工程处于高地震烈度区,在地震作用下粉土极易发生液化,直接影响到上部隧道结构的稳定。针对该工程实例,利用FLAC~(3D)软件开展了高地震烈度区粉土地基抗液化及不同隧道衬砌混凝土强度等级与衬砌厚度等条件下的隧道抗震研究。计算结果表明,在设计地震动加速度为0.2 g的条件下,该工程粉土地基超孔压比约为0.2,粉土地基不会发生液化;随着衬砌厚度的增加,衬砌弯矩和剪力总体呈现增长趋势,而混凝土强度等级的变化对衬砌的受力影响很小。分析结果初步揭示了可液化土中隧道结构的抗震特性,可为设计所参考。

Anti Liquefaction of Silty Soil Foundation and Seismic Performance of Tunnel in High Earthquake Intensity Area

The under-crossing tunnel of east external ring of Kunming is one of the most important projects of the Kunming South Railway Station hub construction.Two layers of silty soil are found in K2 + 100 ～ K2 + 200 tunnel section and one of them lies closely under the tunnel floor.Since the project lies in a high seismic intensity area and the silty soil is easy to liquefied under the action of earthquake,it is important to study the anti liquefaction of silty soil foundation and the seismic performance of tunnel.The liquefaction and seismic performance under different concrete strength grade and different thickness of lining is studied using FLAC3D software.The results indicate that the silty soil foundation will not be liquefied under the designed seismic peak ground acceleration 0.2 g;the maximum bending moment and shear force of lining increase along with the increment of the concrete strength grade,however,the increment of lining thickness has little influence on the tunnel stresses.The analysis results preliminarily reveal the seismic performances of the tunnel structure in liquefied soil,which can be used for design reference.