PRELIMINARY-RESULTS OF A STUDY ON THE RESPONSES OF SEDIMENTARY-ROCKS TO SHAFT EXCAVATION

A shaft with a diameter of 6 m and a depth of 150 m was excavated in s edimentary rocks. An in situ study was carried out to identify the siz e and rock properties of the zone disturbed by the excavation and to e stimate the applicability of existing methods for measuring and modell ing such a zone. The study detected displacements and changes in the p roperties of the rock within about 1 m of the shaft wall. Numerical an alysis using a model of continuous rock mass can simulate some feature s of disturbance due to excavation, although slight discrepancies exis t between the measured and analysed results. The excavation disturbanc e detected in this study is probably due to fracturing, the redistribu tion of stress and undersaturation. However, the relationships between the disturbance due to excavation and these processes have not been q uantified. The existing methods for measurements and numerical analysi s can provide important information on the disturbance due to excavati on but need to be improved to understand disturbance due to excavation further.