Title: Improvement of soft Bangkok clay using vertical geotextile band drains compared with granular piles
Abstract: For the first time, improvement of the soft Bangkok clay by accelerated consolidation has been studied by constructing two full-scale, instrumented, test embankments. In one, consolidation was accelerated by vertical band drains and in the other, by granular piles. The embankment on granular piles, initially 2·4 m high, was later raised to a height of 4 m after 345 days, to impose the same level of applied stress as the other embankment on vertical band drains. The actual settlements and pore pressure build-up have been constantly monitored for both embankments since their construction in 1985. Relative comparison with previous embankment performance on umimproved ground demonstrated the effectiveness of the vertical drains to accelerate the consolidation process and increase the shear strength of the soft clay. The installation of vertical band drains at 1·5 m spacing on a triangular pattern, resulted in achieving 90% consolidation after 430 days using 4 m high embankment preloading. In contrast, the embankment on granular piles indicated reduction in settlements by as much as 20–40%. The results suggested that the granular piles seemed to reinforce the soft clay rather than draining it, increasing the bearing capacity up to four times and increasing the slope stability safety factor by up to 25%. Comparison of actual and predicted values using different methods of settlement predictions are presented. It was found that for the embankment on vertical drains, best agreement between the observed and predicted settlments were obtained using the Asaoka method adopting back-analyzed parameters. The Skempton & Bjerrum method yielded good agreement with the observed data except at the initial stages of loading, where overestimation of settlement could be seen. In addition, underestimation of settlements resulted using the one-dimensional method. Settlement reduction due to the presence of granular piles were calculated using the equilibrium (Aboshi et al.; Barksdale) and finite element (Balaam et al.) methods. The equilibrium method resulted in overestimation of settlements while Balaam's finite element formulation yielded good agreement with the observed data.
Publication Year: 1990
Publication Date: 1990-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 42
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