TY - JOUR
T1 - Discontinuity geometry characterization in a tunnel close to the proposed permanent shiplock area of the Three Gorges dam site in China
AU - Kulatilake, P. H.S.W.
AU - Chen, J.
AU - Teng, J.
AU - Shufang, X.
AU - Pan, G.
N1 - Funding Information:
Acknowledgemenis-The Chinese Natural Science Foundation and the Yangtze Water Resources Commission provided partial financial support for this study. Rayner Dean, Roberto Gig&, Bibhuti Panda and Jeong-Gi Urn performed some of the calculations for this study by running available computer programs.
PY - 1996
Y1 - 1996
N2 - Discontinuity data from a 400m tunnel located close to the proposed shiplock area were investigated to characterize the discontinuity geometry of the rock mass around the tunnel. Traces of 39 major discontinuities (faults and dykes) were found on the tunnel exposures. Over 2000 minor discontinuity (joint) trace data available showed that the rock mass can be separated into about five statistically homogeneous regions. Three to four joint sets were found to exist in each of these regions. Available theoretical probability distributions were found to be insufficient to represent the statistical distribution of orientation of joint clusters. For about 94% of the joint sets, the gamma distribution was found to be the best probability distribution for representing a joint size distribution. Exponential and gamma distributions were the best probability distributions for representing joint spacing distributions for the joint data studied here. Censored joint trace data showed a significant effect of the trace length biases on the estimated mean trace length. This indicated that the 2m wide exposures which were used for collecting the joint trace data may not be sufficient to produce reliable estimates for joint size parameters for the shiplock area. Different estimates were obtained based on wall data and roof data for the joint size and 3-D intensity parameters. The following may have contributed to this result: (a) the effect of different finite sample sizes used; (b) the effect of sampling biases; and (c) the effect of modelling uncertainties on the estimated parameters. To obtain better estimates, it is suggested to collect joint data for several exposures which are at least 4-5m wide and have different orientations. When such data become available for the Three Gorges region, it is suggested to perform validation studies to check the applicability of the models, in addition to performing the joint geometry modelling.
AB - Discontinuity data from a 400m tunnel located close to the proposed shiplock area were investigated to characterize the discontinuity geometry of the rock mass around the tunnel. Traces of 39 major discontinuities (faults and dykes) were found on the tunnel exposures. Over 2000 minor discontinuity (joint) trace data available showed that the rock mass can be separated into about five statistically homogeneous regions. Three to four joint sets were found to exist in each of these regions. Available theoretical probability distributions were found to be insufficient to represent the statistical distribution of orientation of joint clusters. For about 94% of the joint sets, the gamma distribution was found to be the best probability distribution for representing a joint size distribution. Exponential and gamma distributions were the best probability distributions for representing joint spacing distributions for the joint data studied here. Censored joint trace data showed a significant effect of the trace length biases on the estimated mean trace length. This indicated that the 2m wide exposures which were used for collecting the joint trace data may not be sufficient to produce reliable estimates for joint size parameters for the shiplock area. Different estimates were obtained based on wall data and roof data for the joint size and 3-D intensity parameters. The following may have contributed to this result: (a) the effect of different finite sample sizes used; (b) the effect of sampling biases; and (c) the effect of modelling uncertainties on the estimated parameters. To obtain better estimates, it is suggested to collect joint data for several exposures which are at least 4-5m wide and have different orientations. When such data become available for the Three Gorges region, it is suggested to perform validation studies to check the applicability of the models, in addition to performing the joint geometry modelling.
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U2 - 10.1016/0148-9062(95)00060-7
DO - 10.1016/0148-9062(95)00060-7
M3 - Article
AN - SCOPUS:0030126518
SN - 0148-9062
VL - 33
SP - 255
EP - 277
JO - International Journal of Rock Mechanics and Mining Sciences and Geomechanics
JF - International Journal of Rock Mechanics and Mining Sciences and Geomechanics
IS - 3
ER -