Measurement of local stress and estimation of regional stress associated with stability assessment of an open-pit rock slope

This paper discusses the concept of a new methodology for rock slope stability assessment. Then, results on rock stress measurement using the compact conical-ended borehole overcoring (CCBO) technique at Torigata limestone mine in Japan are presented. A procedure for back analysis of the regional strain and stress field with the 3-D finite element method, using the measured local stress, is suggested and demonstrated successfully in relation to Torigata limestone mine. Finally, to estimate the state of stress at the mine excavation level, 3-D finite element analyses were performed using boundary conditions from the analyzed regional strain and stress field. It is shown that the horizontal stress at the present excavation level is not reduced, and that the horizontal stress component cannot be disregarded in estimating the stability of rock slopes at this location, even though the mine is located near the top of a mountain. (C) 2000 Elsevier Science Ltd. All rights reserved.