A practical tool for the preliminary estimation of stability of underground quarries excavated in jointed chalk layers of north france

Abstract

The presence of huge surfaces in North France under-lied by unexploited quarries constitutes a risk of damage on both people and constructions. In this paper, a stability analysis of quarries, excavated in jointed chalk substratum of North France by the method of rooms and pillars, is presented. Using geometric data collected from site: width of the pillar W, height of the pillar H, span between pillars L, and the inclination of joints θ, a parametric numerical stability study is conducted. Factors of safety Fs (num) are numerically computed using a classical shear strength reduction technique. A correlated regression technique between Fs (num) at one hand and W, H, L, and θ at the other hand, is integrated for the development of extrapolated formulae factor of safety Fs (ex) . These proposed formulae designate a practical tool for the rapid preliminary estimation of the stability state of jointed chalk quarries having known only few geometric data. © 2018 Taylor & Francis Group, London, UK.