Hydraulic Conductivity Assessment of Slurry Wall Using Piezocone Test

Abstract

Cone‐penetration tests (CPTs) with pore pressure (u) measurement or piezocone tests (CPTUs) are carried out inside a cutoff wall for polluted‐ground‐water containment. The backfilling material for the cutoff wall is a typical cement‐bentonite (CB) self‐hardening slurry whose composition is 76.8% water, 19.2% blast furnace cement, and 4% sodium bentonite. A tentative framework for interpretation of CPTUs in terms of hydraulic conductivity (k) is developed. In particular, a continuous assessment of hydraulic conductivity along a vertical profile is attempted by combining the piezocone penetration parameters [i.e. total point resistance (qr), pore‐pressure increment (Δu), and sleeve friction (fs)]. The obtained k results are comparable with results from CPTU dissipation tests, in‐situ borehole infiltration tests, and laboratory tests performed on the same CB mixture. The test results indicate that the CPTUs are a promising tool for in‐situ quality control of cutoff walls in terms of evaluating the actual hydraulic conductivity of the completed cutoff wall and, to some extent, of detecting and locating hydraulic defects that, in many cases, are the main causes of poor in‐situ performance.