Estimating the possibility of explosion in the method of destruction of secondary layers (case study of anomaly 12 of Se Chahoun mine)

Dissertation

To receive a master's degree

Mining Engineering - Rock Mechanics

Abstract

Today, blasting operations in hard rock masses are considered inevitable in many mining and construction projects, and in case Inaccuracy in its design can cause great loss of life and money to all construction or mining projects. When an explosion takes place in two different rock masses with the same explosion geometry and explosive energy, different degrees of fragmentation are observed in them. The reason is that rock masses have different inherent resistance to crushing by explosion. This property is called explosive ability. This characteristic is an inherent property of the stone, such as hardness, and many factors affect it. Explosiveness has a direct relationship with fragmentation and the results of fire. Many relationships have been presented to calculate the explosiveness, and their validation has been done with real fire data. If the real data is not available or the mine is in the initial design stage, indirect methods should be used to calculate the explosion capability. Shrinkage estimation methods are one of the most important indirect estimation methods of explosiveness. The two methods of Couse-Ram [1] and Soberk [2] are the most important methods for estimating crushing and also indirect estimation of explosiveness. Sehchahoun 12 mine is in the initial design stage, due to the lack of real explosive data, indirect methods were used to estimate the explosiveness and based on the mine's geotechnical information, the explosiveness was calculated. Finally, according to the modelling, the explosion capability was estimated between the values ??of 3.7 and 4.5 using the Latham classification method [3]. In order to create a gravity flow, the optimal fire pit diameter will be 25-40 mm according to the modeling. rtl;">1-1-Introduction

Today, blasting operation in hard rock mass is considered inevitable in many mining and construction projects, and in case of inaccuracy in its design, it can cause great loss of life and money to all construction or mining projects.

The result of a blasting operation depends on several parameters such as the mechanical properties of the rock mass (single compressive strength) axial and triaxial, shear strength, tensile strength and modulus of elasticity of the rock mass, etc.), dynamic characteristics of rock, the amount and type of discontinuities, characteristics of the blasting pattern (hole diameter, length of the hole, thickness of the rock load, row distance of the holes, height of planting, additional length of drilling, etc.), type of explosives, method of spending, order of blasting the holes, amount of delays, etc. It depends. At first, the concept of explosiveness should be explained. When an explosion takes place in two different rock masses with the same explosion geometry and explosive energy, different degrees of fragmentation are observed in them. The reason is that rock masses have different inherent resistance to crushing by explosion. This property is called explosive ability. This characteristic seems to be an inherent property of the stone, such as hardness, and many factors affect it. The parameters affecting the blasting ability are divided into three general groups (1) rock material characteristics (2) rock mass characteristics (3) design specifications.

Rock rock physical and geomechanical properties are among the most important effective parameters in the design of drilling and blasting patterns. These parameters can be placed in two groups; The first group includes properties of stone material such as strength, hardness, modulus of elasticity, stone density, etc. These parameters depend on the construction of the rock material, internal consistency and the composition and distribution of the minerals that make up the rock. The second group includes the structure of discontinuities, such as directionality, distance and continuity of discontinuities, etc.

Explosiveness has a direct relationship with crushing and the results of blasting, so with explosiveness, you can design blasting in mines and as a result, optimal crushing.Many relationships have been presented to calculate the explosiveness, which are based and validated using real fire data. If the actual fire data is not available or the mine is in the initial design stage, the relationships that indirectly calculate the explosion capability should be used. Among the most important of these relations, we can mention the Koz-Ram relations [1] and the Soberk relation [2].

1-2-Research Background

Various methods have been used to evaluate the explosiveness of rocks using rock engineering classification. Serious studies and researches were conducted on the presentation of the method since 1954. In this context, we can refer to Frankel's method [3] [1], the latter method has low accuracy due to the effect of controllable design parameters such as pit depth, pile height, pile diameter, etc. and not considering rock mass parameters. In 1954, Hino [4] proposed that the explosive ability (which he called the explosive factor) is equal to the ratio of compressive strength to tensile strength of the rock [1]. This method also has low accuracy due to the inclusion of few parameters and not taking into account the parameters related to the rock mass. After that, many studies were conducted by people such as Hinin and Dimak [5] in 1976, Ashby [6] in 1977 and Bourqueiz [7] in 1981 [1], which were not highly reliable due to the inclusion of few parameters of rock and rock mass characteristics. In 1982, Rakshiv [8] expressed explosiveness, fracture resistance against explosion as a function of rock density, longitudinal wave velocity, Poisson's coefficient, elastic modulus, compressive strength and tensile strength of rock mass, average unit of natural structure, and a coefficient representing the properties and degree of joint opening, and by influencing them, he completed the previous methods [1]. After that, the explosibility index was introduced by Lilly [9] in 1986, which is the most widely used method [2]. But this method is very general and has many disadvantages. To get rid of this problem, Lu and Latham[10] in 1998 introduced the explosibility index, which has more parameters than other methods and is more accurate[3]. In 2000, Jiang Han et al.[11] used the neural network method to classify the explosiveness of rock mass. This method is not trusted due to low accuracy [3]. In 2006, Momiwand found a new factor affecting the explosiveness of rocks, called the size of discontinuities opening, and proposed a new method called the rock crushing index [4]. Due to the use of sharp boundaries between the ranks of two adjacent classes, overlap in the boundaries of the presented classification classes, subjective uncertainty in the data that is close to the separation boundary of the two classes, and the large range of points of the classification classes presented in the method presented by Latham, as well as Momiwand, Dashtaki and Yar Ahmadi in 2005 presented a new classification based on BRMR in order to determine the explosiveness of rock masses and their crushing rate. In this classification, in addition to the factors mentioned in the RMR classification, the factors mentioned in the classification proposed by Low and Latham are included [5]. In 2010, Azimi and Asanlo presented a method based on the fuzzification of the method presented by Latham [6], which is not reliable due to the uncertainty of the fuzzy logic method. In a research project in 2014, while classifying the explosiveness of the central Iran block, they included the dynamic characteristics of the rock mass such as the velocity of the longitudinal wave in the calculation of the fragmentation caused by the explosion and the calculation of the specific cost.

Abstract

Today, blasting operation in hard rock mass is inevitable in many mining and civil projects and if not accurately designed, it can bring loss of life and property in all mining and civil projects. When the geometry of the rock mass and energy blasting explosives similar explosion takes place, different degrees of crushing on them can be seen. This is due to the inherent strength of the rock mass, which is different from those crushed by the explosion. This property is called Blastability Index. This property is a stone's inherent properties, such as hardness and many factors affect it. Blastability Index directly related to the results of the explosive blasting is crushing.