Indian Minerology

Rock failure theories:-  Rock failure can occur due to various factors and can be explained by several theories. Here are some of the commonly accepted theories of rock failure:- 1. Mohr-Coulomb Theory:- This theory is widely used to understand the failure of rocks under different stress conditions. It is based on the concept of shear strength and assumes that failure occurs when the shear stress exceeds the shear strength of the rock material. The Mohr-Coulomb theory considers the cohesive strength and frictional strength of rocks in determining failure.   2. Griffith Theory:-  This theory, also known as the linear elastic fracture mechanics theory, focuses on the failure of rocks due to the presence of pre-existing cracks or flaws. It suggests that failure occurs when the stress intensity factor at the tip of a crack exceeds a critical value. The theory considers the elastic properties of the rock material and the size and shape of the crack.   3. Hoek...

Rock Fragmentation Mechanisms Rock fragmentation by blasting is a process commonly used in mining, quarrying, and construction to break large rock masses into smaller, more manageable pieces. The main goal of blasting is to efficiently break the rock while minimizing damage to the surrounding environment. Several mechanisms contribute to rock fragmentation during blasting:   1. Shockwave Propagation:-    - The detonation of explosives generates a shockwave that travels through the rock mass at a high velocity.    - The shockwave creates stress waves that cause the rock to undergo compressive and tensile stresses.   2. Stress Waves:-    - The shockwave creates stress waves that generate tensile stresses in the rock.    - When these tensile stresses exceed the tensile strength of the rock, fractures and cracks begin to form.   3. Crack Initiation:-    - The tensile stresses caused by the shockwave lead ...

Slope Stability, Overburden Management Slope stability diagram  Slope stability and overburden management are important considerations in various fields, including geotechnical engineering, mining, construction, and environmental management. Let's discuss each of these topics in more detail: 1. Slope Stability: Slope stability refers to the ability of a slope or an embankment to resist failure or collapse. It is a critical aspect in engineering design, particularly in projects involving excavations, embankments, and natural slopes. Slope failures can result in landslides, rockfalls, or slope movements, which can cause property damage, loss of life, and environmental hazards. Factors Affecting Slope Stability: Geological and geotechnical properties of the soil or rock mass, including strength, permeability, and cohesion. Slope geometry, including slope angle, height, and shape. Surface and subsurface water conditions, such as rainfall, groundwater, and seepage. Climate and weatherin...

Sacrificial Support External to Strata:- This section relates largely to passive support placed in openings to prevent movement of the strata into the opening. It includes the oldest type of support, timber props and bars, and a whole variety of material placed in openings between roof and floor – timber chocks, roadside stone or pumped packs, cans, cementitious blocks or props, steel bars and legs, steel arches, etc. It could also include items such as steel straps or mesh, but these are generally used in conjunction with strata reinforcement and will be included in that section. Some of these, notably timber props, provide minimal resistance to roof movement and really only serve to prevent failed material from falling. Others are able to provide a fair degree of resistance but require a considerable amount of roof/floor movement before high resistance is obtained, and are very dependent on the installation standards applied. The use of this type of support is n...

Mine Design Relating to Mining Direction:- This relates mainly to horizontal stress fields. Stress fields are seldom equal in all directions and in a horizontal plane it is usual for there to be a highest stress direction, the  "major principal stress" , perpendicular to the lowest stress, the  "minor principal stress" . In general a roadway driven parallel to the direction of the major principal stress will be more stable than at any other angle, the worst direction being perpendicular to the major principal stress. It may be desirable to lay out the mine such that most of the headings, or at least the main headings are in the best direction and accept that cut-throughs may require heavy support or may be sacrificed at times. Alternatively it may be desirable to mine at an angle in between to get the best conditions possible in both directions. The effects of stress redistribution on gate roads at the ends of a longwall face and the possible use...

Mine Design Relating to Dimensions and Shape:- The aim of this aspect of strata control is to make the strata self supporting as far as possible, or if not, to minimize the extra support work required. With regard to opening size, this involves designing minimum practical widths for whatever operations are carried out and could involve modifying the design of equipment to fit into smaller openings. It is perhaps more common to install extra support to stabilize an opening that is suited to available equipment rather than design and manufacture equipment to suit the opening. It is likely that the economics of the latter alternative are seldom examined closely. Mining sequences can be designed to allow intersections to be mined across existing roadways and minimse breakaways which are always bigger excavations. Equipment still needs to be able to turn the corners however. Opening size is always going to be a compromise between a desire to minimise excavation and maxim...

STRATA CONTROL:- General:- The term "strata control" generally refers to controlling the strata to maintain stability around the mine openings underground where operations are or will be taking place. It does not cover such subjects as subsidence or strata remote from the workings. Strata control is the science (some would suggest art) of utilizing various techniques to prevent or control failure of the strata around mine openings at least for the period where access is required. For different locations in the mine this period may be for the life of the mine (which can be considered as permanent), such as the main mine accesses from the surface, or for a matter of less than an hour, such as a lift off a coal pillar with a continuous miner. The need for strata control may extend into a goaf area for a short distance, essentially to the goaf edge, however strata control within the goaf is generally of no interest. In order to analyse strata reactions, ...

Common Terms applied to Rock Mechanics in Geotechnical Engineering:- Rock mechanics is a field of engineering that involves interaction between geology, mathematics, physics, petroleum, mining, and civil engineering. There's a lack of standardization in rock mechanics terminology, so this beginner's guide is intended to help you get started with rock mechanics. What is Rock Mechanics? The terminology of rock mechanics is related to the response of rocks as well as rock masses toward the force fields of their respective physical environment. In other words, it is the theoretical as well as applied science of the mechanical characteristics of rock masses. Rock mechanics is a division of the broader topic, geomechanics, which is classified under geotechnical engineering; this subject deals with the mechanical reactions of all geological elements like soil, rock, etc. Overview Presently, there is no complete correlation between the ...

The role of the rock mechanics engineer in the mining industry:- The responsibilities of the rock mechanics engineer in the mining industry, and the available computer programs and their applications. Over the past decade (1963 – 1973), there has been a change of emphasis in the field of rock mechanics from a purely theoretical approach to the practical solution of problems which occur in the mining industry. However, without the theoretical and research work in the period before 1967, the rock mechanics engineer would not be in a position where he can plan the mining operations safely, particularly in deep-level, hard rock mines. Numerous papers have been published in recent years, describing in detail the computer programs and tools available to the rock mechanics engineer and their application to particular problems in the mining industry. It is not the purpose of this article to examine rock mechanics in detail, but to describe the organisation of rock...