Hydraulic conductivity of Boom Clay in north-east Belgium

Hydraulic conductivities of Boom Clay measured through various testing techniques in the laboratory exhibit similar K values in the order of 10 m/s. In situ measurements obtained from various scales at the HADES underground research facility yield K values that are very similar to values measured in the laboratory on samples of a few centimetres. Spatial analysis of K values across the Boom Clay at the Mol site reveals a typical profile with a very homogenous 61-m thick central part (the Putte and Terhagen Members), which is also the least permeable part of the Boom Clay. The geometric mean of the vertical (Kv) and horizontal (Kh) hydraulic conductivities for the Putte and Terhagen Members at the Mol site are 1.7×10 and 4.4×10 m/s, respectively, with a vertical anisotropy Kh/Kv of about 2.5. Higher K values, but still low (10 to 10 m/s), are observed in the more silty zones above and below. A regional analysis of vertical K variability of the Boom Clay in the northeast of Belgium confirms this typical K profile of the Boom Clay based on test results from other four regional boreholes. Furthermore, an increase in overall Boom Clay vertical hydraulic conductivity from the east towards the west in north-east Belgium was observed.