Estimating the possibility of explosion in iron ore mines of central Iran block with emphasis on the velocity of longitudinal waves

Dissertation for Master's Degree in Rock Mechanics

Abstract

Explosion ability of rock mass is a very important feature in explosive designs in mines and construction activities, which is closely related to rock mass system, environmental conditions and blasting system. Among the factors affecting the explosiveness, there are controllable ones, and there are some that are uncontrollable, and perhaps these parameters have the greatest effect on the explosiveness. These parameters are related to the rock mass system. Among the factors affecting the explosiveness are the dynamic characteristics of the rock mass, such as the speed of elastic waves. Due to the multiplicity and complexity of the factors affecting the explosiveness, each of the researchers have only investigated the effect of one or a limited number of these parameters on the explosiveness, but by summarizing the studies, it was found that despite the huge effect of the speed of the waves on the explosiveness, not much research has been done on it. The main goal of this thesis is to investigate the possibility of replacing the velocity of longitudinal waves with geomechanical parameters of the rock mass and to present a relationship for predicting the amount of crushing after explosion using SPSS statistical analysis software, and then to investigate and compare the correlation coefficient of the relationships obtained with the data mining method of artificial neural network and neuro solution software. Another goal is to provide a classification to determine the explosiveness in iron ore mines of central Iran, which was done using the rock engineering system, which will be explained in detail below.

Keywords: Explosiveness, rock mass system, dynamic parameters, classification of explosibility

A well-designed fire operation is an operation that leads to the production of crushed stone whose dimensions and granulation distribution are in accordance with the dimensions and distribution of granulation that can be loaded and loaded by existing equipment and can be crushed by a stone crushing plant, and there is no need to crush the stone again. Since the amount of crushing caused by blasting has an important effect on the process of other mining operations such as loading, carrying, crushing and grinding, conducting studies to optimize crushing is very important because in addition to having a direct effect on the cost of extracting and processing mineral matter, it is also effective on the safety of this operation and the control of throwing rocks and walls [1][2][3]. It has been done to develop quantitative and systematic parameters effective on this ability of stone. The studies conducted in this field, which have sometimes led to the presentation of relationships, are not able to express the characteristics of the flammability of the rock mass, and a comprehensive classification system has not yet been provided to predict this rock mass capability. The efforts made in this field are not widely applicable in fire operations. Because in order to operationalize these classification systems, it is necessary to examine a series of characteristics of the rock mass, which take a lot of time to estimate. While in the mining industry, production time and speed are very important, and this design requires a rock mass classification system that can quickly describe the characteristics of the rock mass in relation to its flammability. On the other hand, it has the ability to create a relationship with the design parameters and explosives.

The importance of such a rock mass classification system is its applicability in mining projects for the optimal design of the explosive plan to achieve the desired size distribution of the particles resulting from the explosion with minimal explosives. If such classification of rock mass is achieved, in addition to reducing the cost of producing desired mineral materials, the cost of loading, transportation, crushing and processing of mineral material can be reduced to a great extent, and as a result, the economic viability of the mine is greatly increased. (Figure 1-2) and the result is the crushing of the rock mass to the dimensions and with the required granulation distribution.

Since there are many features that affect the explosiveness and the result of fire, in their research, researchers have examined some of them depending on the weight of the impact and inferred their effect through relationships.

Some of these scientists expressed the explosiveness with a simple index, some with a classification with multiple parameters, and others They have found their relationship using smart methods. In this chapter, all the past views and researches that have been done on the explosiveness of the rock mass are examined

rock mass system

parameters related to the nature of the rock mass include the physical and mechanical characteristics of virgin rock and discontinuities, the rules governing their resistance and behavior, and environmental conditions such as stresses, dynamic loads, and hydro system, which are different parameters Controllable effective on the explosion is called. The properties of virgin stone include compressive and tensile strength, volumetric weight, shear strength, hardness, elasticity, deformation, durability and grain size. These characteristics are related to the texture of the stone, the internal links, the composition and distribution of the minerals that make up the stone. The properties of discontinuities can also include orientation, spacing, continuity, openness, roughness, properties of filler materials. pointed out Figure (1-3) shows some characteristics of the rock mass affecting the explosiveness.

The characteristics of the rock mass are the most important and complex factors that affect it in blasting operations, and therefore should be taken into consideration when starting mining in open-pit mines or in construction projects, as well as during planning and design. [2]

Apart from the static parameters affecting the explosiveness, there are other factors that have a significant effect on the degree of fragmentation, explosiveness and the negative effects of the explosion, which are called dynamic parameters affecting the explosiveness. These parameters include the waves produced by the explosion and propagated in the rocks. The strength, speed and propagation of these waves are among the important factors that determine the explosiveness, therefore, in this study, we tried to briefly mention the waves resulting from the explosion, the laws governing the waves, how they are created and harvested. The explosion geometry is called the explosion system. The parameters of this system are usually controllable and can be changed to achieve the optimal explosion, therefore, whenever we talk about the design of explosions and fires, the intention is to change these parameters based on the uncontrollable parameters of the rock mass and the conditions of the explosion until the result of the explosion is desired.

Explosive substance is a chemical compound or a mechanical mixture that decomposes due to spark, impact, heat or flame in a short period of time and produces a very large amount of gas and heat. These materials store energy and are ready for military and engineering purposes. Explosives exist in solid, liquid or mixed solid and liquid form. In an explosion, most of the constituents of the explosive change their state and while creating a shock wave, they mostly turn into gas, and in these interactions, a large amount of heat is produced, which causes the expansion of gases and puts pressure on the wall of the surrounding environment.

Abstract

The blastability of rock mass is one of the most important features of the rock mass in blasting designs in the mines and construction activities which has a close relationship with the system of the rock mass, environmental situations and blasting systems. Among the effective factors on the blastability, some of the factors had been controllable and there are still some uncontrollable factors and in addition, they have the most effect on the blastability on these parameters. These parameters are related to the rock mass system.  Among the effective factors on the blastability, there are dynamical features of rock mass including the speed of elastic waves.