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Abstract 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.
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Received: 11 July 2012
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2013, Vol. 32 
