Determination of In-situ Stress by Observations of Rock Deformation in Underground Mine

Determination of In-situ Stress by Observations of Rock 

Deformation and Numerical Modeling on the Ramp down CGT, 

Gudang Handak Mine, PT. Aneka Tambang, UBPE Pongkor

 West Java, Indonesia

Patrick Marcell FANDY¹, Made Astawa RAI¹ and Budi SULISTIANTO¹

¹Faculty of Mining and Petroleum, Institute of Technology Bandung, Bandung 40191, Indonesia

ABSTRACT

The existence of excavation activities to create one or more openings underground in the rock mass, will result in changes in the stress distribution and will display the new stress conditions (induced stress) experienced by the rock mass around the hole opening. In many cases, this induced stress will exceed the strength of the rock mass and cause instability underground openings. Before the excavation is done, the rock mass in a state of equilibrium, but after the excavation is done, the equilibrium is disrupted and it can change the initial stress distribution.

Insitu stress measurement is relatively more difficult than the measurement of deformation in underground mine openings. Measurement of rock deformation in Ramp down openings conducted by measuring the relative displacement between two points or so called convergence measurement. Deformation result that occurs in Ramp down the basis for the estimates do major and minor principal stress is going on and the direction of the principal stresses. To find out how much stress is going around openings Ramp down, the deformation results that have been obtained will be used and made in the modeling. The software-based method of finite elemet (FEM) is a Phase2 2D will be used in this research. Model created should match the actual conditions. large displacement obtained to enlarge the openings Ramp down is +13.10 mm and minimize openings is -5.48 mm. While the relationship of the stress displacement measurements that have been modeled, the major principal stress obtained is equal to 2.375 MPa. For Minor principal stress is 0 MPa, the direction of stress acting on the openings Ramp down at 80⁰ or may be occurring at the opening stress Ramp down is uniaxial stress, this condition occurs due to ramp down is at shallow depth by the distance to the surface is 95 meters and near the river.

Keywords: Insitu Stress,Convergence monitoring, Cut-and-fill underground mine, Ramp down, , Numerical analysis