Spatial distribution of inter-layer shear zones at Gaobazhou dam site, Qingjiang River, China

Abstract

The spatial distribution of inter-layer shear zones is studied, based on the fully mapped inter-layer shear zones at the Gaobazhou dam site on the Qingjiang River in Hubei province, China. The field observations revealed that two types of inter-layer shear zone, under-developed and well-developed, are distributed differently. The former are associated with the incompetent rock layers, and the latter are controlled by the inter-bed folds and lithological properties of the strata. To represent their lithological properties geomechanically, data on strength by the Schmidt hammer test and thickness of each field-identified rock layer were collected to form strength sequences and thickness sequences. The adjacent rock layers of similar strength are then grouped, and two grouped sequences are combined into a single sequence, whose individual term is the strength weighted by the exponential function value of the centralized thickness (SCT). The rescaled range (R/S) analysis results of SCT (SCT-R/S), taking into account the presence of inter-bed folds, are in good agreement with R/S analysis results of the spacing sequence of the well-developed inter-layer shear zones. Thus the SCT-R/S model has the potential to predict their spatial distributions. (C) 2000 Elsevier Science B.V. All rights reserved. | The spatial distribution of inter-layer shear zones is studied, based on the fully mapped inter-layer shear zones at the Gaobazhou dam site on the Qingjiang River in Hubei province, China. The field observations revealed that two types of inter-layer shear zone, under-developed and well-developed, are distributed differently. The former are associated with the incompetent rock layers, and the latter are controlled by the inter-bed folds and lithological properties of the strata. To represent their lithological properties geomechanically, data on strength by the Schmidt hammer test and thickness of each field-identified rock layer were collected to form strength sequences and thickness sequences. The adjacent rock layers of similar strength are then grouped, and two grouped sequences are combined into a single sequence, whose individual term is the strength weighted by the exponential function value of the centralized thickness (SCT). The rescaled range (R/S) analysis results of SCT (SCT-R/S), taking into account the presence of inter-bed folds, are in good agreement with R/S analysis results of the spacing sequence of the well-developed inter-layer shear zones. Thus the SCT-R/S model has the potential to predict their spatial distributions.