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Discussion of “Smear Effects of Vertical Drains on Soft Bangkok Clay”

TitleDiscussion of “Smear Effects of Vertical Drains on Soft Bangkok Clay”
Publication TypeJournal Article
Year of Publication1993
JournalJournal of Geotechnical Engineering
Start Page181
Date Published01/1993

The authors have presented an interesting study demonstrating how the installation of vertical drains by full displacement can alter the flow characteristics of a soft clay. Like most field studies involving large-scale features, the results of back calculations from field observations presented by the authors provide a convincing but indirect assessment of soil behavior. Based on their observations, the authors infer that, as previously suggested by Hansbo (1987), the hydraulic conductivity of the clay near the drain is substantially altered by the wick installation and the horizontal hydraulic conductivity in the disturbed zone immediately adjacent to the drain approximates the original (undisturbed) vertical hydraulic conductivity. ApaOctober, 1991, Vol. 117, No. i0, by Dennes T. Bergado, Hiroshi Asakami, Marolo C. Alfaro, and A. S. Balasubramaniam (Paper 26216). 5Assoc. Prof., Dept. of Civ. Engrg., Univ. of Mass., Amherst, MA 01003. ~ Prof., Dept. of Civ. Engrg., Univ. of Mhss., Amherst, MA. 181 J. Geotech. Engrg., 1993, 119(1): 181-184 Downloaded from by University of Massachusetts, Amherst on 02/07/17. Copyright ASCE. For personal use only; all rights reserved. parently, this assumes a priori that the value of r k = kh/k v prior to drain installation is greater than 1. This appears to be confirmed by the authors' data shown in Fig. 1; however, it is unclear to the writers whether any of the test results presented in Fig. 1 were obtained from flexible wall hydraulic conductivity tests. This raises some interesting issues related to other initial flow conditions. In homogeneous, massive clay deposits wherein rk = 1.0, would this suggest that the horizontal hydraulic conductivity near the drain would be less than that of the undisturbed clay in the vertical direction? In the extreme case where r k < 1.0, how would one reasonably use the results of field tests to infer any reliable hydraulic response?