Open-pit mining: Difference between revisions

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==Hydrology in mining==

Open-pit mines operating in an area with heavy groundwater features may eventually face hydrology-related problems. This includes heaving and bursting of the mine floor due to excessive uplift pressure. A groundwater control system must be installed to fix problems caused by hydrology. The formation of an appropriate open-pit slope design, changes throughout the life of a mine. It is based mainly on an ever-increasing understanding of the rock mass conditions, including groundwater and associated pressures that may be acting within the slopes. The reduction of groundwater related to pore pressures is a crucial aspect of determining whether or not a geotechnical engineering design for open-pit slopes is attainable. Groundwater control systems, which include dewatering and depressurization wells, may also have a large impact on local groundwater. Because of this, an optimization-based version of the control system is required to ensure that local and regional hydro-geological impacts are within acceptable ranges.<ref name=depressurization>{{Cite documentweb |url=https://www.imwa.info/docs/imwa_2008/IMWA2008_035_Leech.pdf|work=International Mine Water Association |last1=Leech |first1=Simon |last2=McGann |first2=Matthew |title=Open Pit Slope Depressurization using Horizontal Drains – a Case Study |date=2008}}</ref>

Open Pit depressurization is the process of removing tensions or pressure from different areas of a mine. Depressurization helps to make open-pit mines more stable and secure. By using an integrated mine slope depressurization program the likelihood that mine plans can be achieved, and at an acceptable level of risk increase drastically.<ref name=depressurization /><ref>{{Cite journal|author=Stephen P. White|author2=Ashley L. Creighton|author3=Paul F. Bixley|author4=Warwick M. Kissling|date=August 2004|title=Modeling the dewatering and depressurization of the Lihir open-pit gold mine, Papua New Guinea|journal=Geothermics|volume=33|issue=4|pages=443–456|doi=10.1016/j.geothermics.2003.09.011|bibcode=2004Geoth..33..443W }}</ref> Depressurization allows considerable expansions of a mine, and can extend the life of the mine by 10 to 15 years. One technique used in depressurization is annealing. Annealing is the slow heating and cooling of a metal, alloy or glass. This slow heating and cooling relieves the internal stress of surrounding areas. Annealing will increase a material's workability and durability, which overall increases open-pit mine safety.<ref>{{Cite journal|author=S. Mohan|author2=P.K. Sreejith|author3=S.K. Pramada |date=July 1, 2007|title=Optimization of Open-Pit Mine Depressurization System Using Simulated Annealing Technique|journal=Hydraulic Engineering|volume=133|issue=7}}</ref> When groundwater pressures cause problems in open-pit mines, horizontal drains are used to aid in accelerating the slope depressurization process. Which helps to prevent large scale slope failure in the mine. Horizontal drains are used to lower pore pressure by reducing groundwater head, which enhances slope stability.<ref name=depressurization />