Field scale hydraulic conductivity and compressibility of organic clays

Abstract

This paper uses the results of an extensive subsurface investigation performed along the Inner Harbor Navigational Canal in New Orleans, Louisiana to identify the scale effect of soil hydraulic conductivity (K) and compressibility (mv) for geotechnical and geoenvironmental analyses. The magnitude and variability of soil hydraulic conductivity and compressibility parameters were obtained from laboratory 1-D consolidation and permeameter tests, CPTu dissipation tests, field piezometer slug tests, and multiple well pump tests. The geometric means of horizontal hydraulic conductivity (Kh) measured by the laboratory permeameter, slug, and field pump tests are 2.5×10−7, 1.6×10−6, and 1.3×10−5cm/s, respectively. This represents a scale effect of about 50 times when increasing the sample volume tested from the laboratory to field scale. The uncertainty in vertical hydraulic conductivity (Kv), Kh, and mv values was determined using a coefficient of variation, which ranges from 0.34 to 0.73. While Kh is scale dependent, a comparison of mv evaluated from field pump and 1-D consolidation tests indicates that sample volume does not significantly impact measured values of mv, which signifies that laboratory consolidation tests can be used to predict field scale compressibility.