贵阳地铁车站基坑岩溶多道瞬态瑞雷波探测及工程验证

Application effect of multichannel transient Rayleigh wave probing technique in detection of Karst gaps in foundation pit of metro station in Guiyang

轨道交通建设是贵阳市"十二五"期间的重大工程项目,贵阳地处岩溶富水区,贵阳地铁工程施工中最具挑战和威胁的问题之一就是岩溶突水.贵阳地铁延安路站是地铁1号线与地铁2号线的换乘站.车站场地地层由浅表第四系覆盖层和下伏三叠系白云岩组成.基岩中溶蚀裂隙、沟槽、石芽、溶洞极其发育,导致基岩顶面凹凸起伏显著,岩体中岩溶空区充填物富水承压,严重威胁基坑开挖工程及周边环境的安全.为有效控制岩溶突水对工程的危害,我们尝试将瑞雷波探测方法引入贵阳地铁车站深基坑工程中,展开对基坑岩体岩溶带的探测定位,以期为基坑岩溶突水部位的判断和注浆止水方案制定提供依据.探测采用考虑道间时差相位的多道瞬态瑞雷波方法,对基坑开挖面以下岩体进行了探测.根据工程场地的具体条件,按一定的密度布置测线构成对车站基坑工程岩土体的瑞雷波观测系统,采用多道检波器排列覆盖测线,提取排列中各道检波器(测点)之间的瑞雷波相速度,考虑车站工程基坑岩土体性质与弹性波速的关系和特殊的工程地质条件,确定瑞雷波相速度分级,构建车站基坑岩土体瑞雷波相速度三维成像.瑞雷波相速度三维成像沿测线的铅垂剖面和不同深度(高程)的水平切片清楚地揭示了车站基坑岩体土体中岩溶带的规模和位置.工程开挖验证表明:考虑道间时差相位的多道瞬态瑞雷波探测方法对贵阳地铁车站基坑岩体中岩溶带的探测行之有效,探测解译结果直观形象,与工程开挖揭露的情况十分吻合,为基坑岩体突水部位判断以及工程止水方案制定提供了有效的技术支撑.

The construction of underground track communication is a significant project during the Twelfth Five-year Plan of Guiyang which is located in the water-abundant Karsrt area. One of the most challenging and threatening problems in the metro construction of Guiyang is karst water inrush. Yan’an road station of Guiyang metro is a transfer station of metro line 1 and metro line 2. The strata of the ground within the area of Yan’an Road Station consist of Quaternary systems of loose deposits and their underlying Triassic System of dissoluble rock masses. Karst gaps such as grykes and caves etc. are extremely developed in the underlying rock masses, which result in the extremely uneven top surfaces of the rock masses, and also form Karst gaps full of soft masses with abundant confined water in the rock masses, seriously threaten the safety of foundation excavation works and their surrounding environments.In order to control the dangers of Karst water inrush, we try to introduce Rayleigh wave probing method to the project of foundation pit of subway station in construction in Guiyang, and carry out Rayleigh wave detecting for the positions and scales of Karst belts in the bedrock masses of the foundation pit, so as to provide references for the judgment to water inrush positions and the scheme of water inrush control. The Multichannel Transient Rayleigh wave probing technique is used to detect the rock mass below the excavation surface. According to the engineering site specific conditions, using a certain density arrangement line form the Rayleigh wave observation system of the station foundation pit engineering rock mass and using multichannel detector array to cover line. Through extracting the phase speed of Rayleigh wave in which between each detector determined the phase velocity classification of Rayleigh wave which based on the relationship between rock and soil properties and elastic wave velocity in station foundation pit and special engineering geological conditions. The above data was used to construct 3-D Rayleigh wave phase Velocity image of bedrock mass in the foundation pit. And the image is displayed with a series vertical profiles and horizontal slices of Rayleigh wave phase Velocities that can clearly reflect special variation of elasticity of rock mass in the pit, and furthermore, the positions and scales of Karst gapts such as Karst grykes and Karst caves can be revealed.Later excavation of the pit Verifies that the Rayleigh wave probing method works for the detection of Karst belt in rock masses of the foundation pit of Yan’an Road metro station in Guiyang, and the results of Rayleigh wave probing is direct and vivid, and more important is that the results is in accordance with real situations revealed by the excavation, and has technically and effectively supported the judgment to water inrush positions and the scheme of water inrush control.