Use of CPT and other direct push methods for (hydro-) stratigraphic aquifer characterization--a field study

Every environmental site investigation aims at delineating near-surface (hydro-) stratigraphic units and their characterization. To determine the type and hydraulic properties of sedimentary deposits, direct push (DP) sensor probes and tools are promising methods and are therefore frequently applied to measure high-resolution vertical profiles of soil properties. Given the variety of these tools, the objective of this paper is to compare selected DP tools for the (hydro-) stratigraphic subsurface characterization in a heterogeneous unconsolidated sedimentary aquifer. An overview of current DP applications is given and selected DP tools were tested for reproducibility, as well as their ability to reflect soil variability and to estimate hydraulic conductivity, K. Although resolution differences exist, all of the applied methods captured the main aquifer structure. Correlations of the DP-based K estimates or proxies with DP slug tests (DPST) show that it is possible to describe the aquifer hydraulic structure on less than a metre scale by combining DPST data and continuous DP measurements. Although correlations are site-specific and appropriate DP tools must be chosen, DP is a reliable and efficient alternative for characterizing even strongly heterogeneous sites with complex sedimentary architectures. Key words: direct push, aquifer characterization, hydraulic profiling, cone penetration testing. Les etudes environnementales de sites servent a identifier et caracteriser les unites (hydro-) stratigraphiques pres de la surface. Afin de determiner le type de depots sedimentaires et leurs proprietes hydrauliques, les sondes et outils de poussee directe (PD) font partie des methodes prometteuses, et ainsi sont frequemment appliques pour mesurer a haute resolution les profils verticaux des proprietes des sols. Comme ces outils sont nombreux et varies, l'objectif de cet article est de comparer certains de ces outils de PD pour la caracterisation (hydro-) stratigraphique sous la surface dans un aquifere sedimentaire heterogene et non consolide. Un sommaire des applications courantes de PD est presente, et certains outils ont ete testes pour evaluer leur reproductibilite ainsi que leur capacite a identifier la variabilite des sols et a estimer la conductivite hydraulique, K. Meme si les methodes appliquees different dans leur resolution, elles ont toutes reussi a evaluer la structure de l' aquifere principal. Des correlations entre les estimations de K basees sur la PD ou obtenues indirectement avec des essais de cone en PD (ECPD) demontrent qu'il est possible de decrire la structure hydraulique d'un aquifere a une echelle inferieure au metre en combinant les donnees d' ECPD et les mesures en continu de PD. Malgre que les correlations soient specifiques a un site donne et que les outils de PD appropries doivent etre choisis, la PD est une alternative efficace et fiable pour caracteriser les sites tres heterogenes ayant des architectures sedimentaires complexes. Mots-cles : poussee directe, caracterisation d'aquifere, profilage hydraulique, essai de penetration du cone. [Traduit par la Redaction]
Introduction Environmental site investigations require high-resolution information about lithology and hydraulic properties of the subsurface. Knowledge of the spatial distribution of hydraulic conductivity (K) is the prerequisite for understanding flow [...]