HR: 1340h
AN: MR33A-0141    [Abstracts]
TI: Induced seismicity in a salt mine environment evaluated by a coupled continuum-discrete modelling.
AU: * Mercerat, E
EM: dmercerat@yahoo.com
AF: LAEGO, Ecole des Mines de Nancy, Nancy, 54000 France
AU: Souley, M
EM: mountaka.souley@ineris.fr
AF: INERIS, Ecole des Mines de Nancy, Nancy, 54000 France
AU: Driad, L
EM: lynda.driad@ineris.fr
AF: INERIS, Ecole des Mines de Nancy, Nancy, 54000 France
AU: Bernard, P
EM: bernard@ipgp.jussieu.fr
AF: Dept. Sismologie IPGP, 4 Place Jussieu, Paris, 75005 France
AB: Within the framework of a research project launched to assess the feasibility of seismic monitoring of underground growing cavities, this specific work focus on two main complementary axis: the validation of seismic monitoring techniques in salt mine environments, and the numerical modelling of deformation and failure mechanisms with their associated acoustic emissions, the induced microseismicity. The underground cavity under monitoring is located at Cerville (Lorraine, France) within a salt layer 180 m deep and it presents a rather regular cylindrical shape of 100 m diameter. Typically, the overburden is characterized by the presence of two competent layers with elasto-brittle behaviour and located 50 m above the salt layer. When the salt exploitation restarts, the cavity will progressively grow causing irreversible damage of the upper layers until its final collapse at a time scale of the order of one year. Numerical modelling of such a complex process requires a large scale model which takes into account both the growing cavity within the salt layer and the mechanical behaviour of the overburden where high deformation and fracturing is expected. To keep the elasto-brittle behaviour of the competent layers where most seismic damage is expected, we use the PFC code (Itasca Cons). To approach the other layers (mainly composed of marls and salt) which present more ductile and/or viscoplastic behaviour, a continuum approach based on the FLAC code (Itasca Cons) is employed. Numerous calibration process were needed to estimate the microproperties used in PFC to reproduce the macroscopic behaviour from laboratory tests performed on samples extracted from the competent layers. As long as the size of the PFC inclusion representing the brittle material is much higher than the core sample sizes, the scale effect of microproperties is examined. The next stage is to perform calculations on the basis of previous macroscopic and microproperties calibration results, and compare them with the observed microseismicity in the rock mass.
DE: 5102 Acoustic properties
DE: 5104 Fracture and flow
DE: 5112 Microstructure
DE: 7219 Seismic monitoring and test-ban treaty verification
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005