Non-monotonic piezocone dissipation curves of backfills in a soil-bentonite slurry trench cutoff wall

• Published in: Journal of Zhejiang University. A. Science 2018-04, Vol.19 (4), p.277-288
• Main Authors: Li, Yu-chao, Tong, Xing, Chen, Yun, Ke, Han, Chen, Yun-min, Wen, Yi-duo, Pan, Qian
• Format: Article
• Language: English
• Subjects: Backfill; Bentonite; Civil Engineering; Classical and Continuum Physics; Consolidation; Dissipation; Empirical analysis; Engineering; Hydraulic properties; Industrial Chemistry/Chemical Engineering; Mechanical Engineering; Penetration; Pore pressure; Pressure; Slurries; Slurry trenches; Soils; Test procedures
• ISSN: 1673-565X; 1862-1775
• DOI: 10.1631/jzus.A1700097

Pore pressure dissipation during piezocone testing provides a unique tool for estimating the hydraulic properties of in-situ backfills in soil-bentonite (SB) slurry trench cutoff walls. Six tests were performed in an SB slurry trench cutoff wall located in Jiangsu Province, China. The pore pressure dissipation curves obtained are non-monotonic, which, as far as the authors are aware, is reported for the first time in SB cutoff walls. The non-monotonic dissipation curves are attributed to the redistribution of excess pore pressures between the base soil clods and the rest of the backfill around the cone. Four existing interpretation methods are adopted to analyze the measured non-monotonic piezocone dissipation curves. The horizontal coefficients of consolidation ( c h ) of the backfills obtained by three methods are close to each other and in agreement with the results of fixed-ring consolidometer tests, while the other method gives a high overestimate. The hydraulic conductivities ( k h ) of the backfills are also estimated by four methods, three based on dissipation test results and one based on piezocone penetration data. k h estimated by consolidation theory are close to the results of flexible wall permeameter tests. Two empirical expressions for dissipation tests give relatively low k h , but the method based on penetration gives k h much larger than the laboratory test results.