IN-SITU STRESS DETERMINATION ON DEEP MILL LEVEL ZONE’S (DMLZ) ROCK MASS BY MEANS HYDRAULIC FRACTURING METHOD

• Main Author: Nur Fahrudin, Sahrul
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/48673
• Institution: Institut Teknologi Bandung

Determination of in-situ stress is necessary to determine the state of stress in the rock mass. The actual stress state can differ greatly from the theoretically calculated stress state. Theoretical calculations can only provide estimates of the magnitude of existing stress intensity, while in-situ stress measurements can provide important parameters regarding the orientation and magnitude of stresses in rock masses that are underground. These parameters will be used as input in the modeling and analysis of building construction in rock masses such as tunnels or underground mine openings. With this in-situ stress parameter input, it is expected that the results obtained from modeling and analysis will be closer to the truth or in accordance with the actual situation. One of the tests used to determine the in-situ stress value of a rock mass is the Hydraulic Fracturing Test. PT Freeport Indonesia in particular for the Deep Mill Level Zone (DMLZ) mining area has implemented this method. The application itself aims to precondition the rock mass so that block caving mining can run fluently and reduce the level of seismic that occurs. From the data of the hydraulic fracturing process carried out by PTFI in order to recondition the rock mass of Deep Mill Level Zone (DMLZ) it can also be used to determine in-situ stresses with several assumptions made, such as using secondary data. For example, frack no-76 with frack position at a depth of 74,5 m, the magnitude of the vertical and horizontal stresses in this frack are 41,619 MPa and 26,200 MPa. The ratio of the two in-situ stress (?H / ?V) is 0,633.