Characterization of soil permeability in the former Lake Texcoco, Mexico

摘要

The geotechnical subsoil conditions of the former Lake Texcoco represent a complex sequence of highly compressible lacustrine clays interbedded with layers and seams of harder and more permeable materials. Although the mechanical properties of these deposits have been extensively studied in the past, the information about their hydraulic properties is scarce. Currently, a comprehensive characterization of the hydraulic conductivity of this site has become necessary because of the construction of the New Mexico International Airport (NAIM). The present study describes a systematic evaluation of the hydraulic conductivity in the former Lake Texcoco through three different in-situ methods (well permeameter, LEFRANC and piezocone dissipation test). The measurements, taken from 155 locations, show a high spatial variability, with ranges spanning more than two orders of magnitude. The results also reveal that the estimated permeabilities vary significantly among methods. These discrepancies reflect the scale dependency of the hydraulic conductivity in the area caused by soil heterogeneities. A comparison of the presented results with previous studies demonstrates that piezocone tests provide representative results for the clayey formations, while LEFRANC tests better estimate the hydraulic conductivity of the permeable strata. Besides, CPTu tests yield more consistent values of hydraulic conductivity, with smaller dispersion than well permeameter and LEFRANC tests.