On the use of CPTs in stratigraphy: recent observations and some illustrative cases

Abstract

1. Introduction During 2008 and 2010 the National Institute for Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS) organized two comprehensive field test campaigns (Wouters & Schiltz, 2013) situated in the NE of Flanders. The subject of these field campaigns was a hydrogeological safety study for a disposal facility for low radioactive waste storage. This investigation area is situated in the NE of the Flanders region in Belgium, at the Dessel nuclear site and a surrounding safety area on the territory of the Dessel–Geel–Kasterlee communities (Fig. 1). This field test campaign consisted in seven cored and logged boreholes and of about 200 CPTs (depth up to 35 m) in a regular grid of ~1 km² over an area of ~60 km² in the Dessel–Geel–Kasterlee area. This area is situated in a geological setting where, under a thin (1–4 m) cover of Quaternary sediments, Miocene sandy sediments outcrop (Fig. 1). In some preliminary minor field campaigns one of the cored boreholes revealed the presence of a ~10 m thick clayey layer on a stratigraphic level that was supposed to be sandy. Obviously the primary objective of the large number of CPTs was determining the presence and extension of this aquitard. It turned out that these data were also valuable in the discussion of the complex detail stratigraphy of the area. Therefore CPT data have been integrated in the unravelling of the local stratigraphy as presented in Vandenberghe et al. (2020, this volume). More information on the CP