深厚覆盖层结构面及软弱夹层诊断与定位——以金沙江下游乌东德水电站坝址为例

DIAGNOSING AND LOCATING OF DEEP OVERBURDEN STRUCTURAL PLANE AND WEAK INTERCALATED LAYERS TAKING WUDONGDE HYDROPOWER STATION DAM SITE AT DOWNSTREAM OF JINSHA RIVER FOR EXAMPLE

深厚覆盖层是一种特殊工程地基。其结构松散、岩性不连续、成因类型及岩土体结构组成复杂、物理力学性质呈非均质性分布。深厚覆盖层中的结构面、软弱夹层呈非连续性分布,给分层带来困难,是目前尚未解决的热点工程地质问题。结合乌东德水电站坝址深厚覆盖层分层进行实测试验,依据孔间电磁波Color-CT成像结果,揭示出深厚覆盖层内保存有完好的软弱夹层地质事件证据。以孔间Color-CT成像为研究对象,采用非线性计算岩土体吸收系数,将岩土体结构面进行阈值划分,把不同结构面区域标定出来,最终通过面积、位置参数、形状等特征划分出软弱夹层区域,定位出孔间剖面内软弱夹层个体数量和空间分布。

Deep overburden layer is a special engineering foundation. It is distributed non-uniformly in loose structure,lithologic discontinuity,genetic type and rock-soil structure,physico-mechanical properties. The structure plane in deep overburden and weak intercalated layers distribute discontinuously,which make it difficult to identify those layers. It is currently an unsolved hotspot problem of engineering geology. Field experiments to identify the deep overburden layers were implemented at Wudongde hydropower station. The geological evidence is revealed that the intact weak intercalated layers are preserved in the deep overburden layer based on cross-well electromagnetic wave Color-CT imaging findings. Through the study of cross-well Color-CT images,the threshold values are selected for separating the structure planes of rock and soil mass and the regions of different structure planes are calibrated,using the nonlinear calculation of the absorption coefficients of rock and soil mass. Finally,the weak intercalated layer regions are located based on the feature parameters of area,location and shape. The quantity and spatial distribution of the weak intercalated layers in the cross-section between holes are defined.