Stability analysis of the overturning collapse of the north wall of Chogharat mine due to dynamic loads resulting from the explosion

Number of pages: 168 File Format: word File Code: 32611
Year: 2014 University Degree: Master's degree Category: Mining Engineering
  • Part of the Content
  • Contents & Resources
  • Summary of Stability analysis of the overturning collapse of the north wall of Chogharat mine due to dynamic loads resulting from the explosion

    Dissertation

    To receive a master's degree

    Rock Mechanics Engineering

    Introduction

    Excavations made in rocks, according to their purpose It has different dimensions and varies from small dimensions to dimensions comparable to huge concrete structures. Surface excavations can be used as a space for extracting mines, creating buildings, and supporting and overflowing dams, factories, power plants, as well as pipelines, canals, and railways.

    When designing slopes in rock, as a general rule, one should always look for potential ruptures that are controlled by unfavorable structural conditions. Common modes of collapse in rock slopes are planar collapse, spherical collapse, overturning collapse, and circular collapse. If the fall is in soil or stones with a high number of joints and low spacing, the shape after the fall is generally curved or so-called spoon. In rocks with a greater distance, depending on the location of the main seams, the falls generally operate in three modes: wedge, plate, and overturn [1]. The dominant fall in the north wall of Chagharat mine is of the overturning type, and this type of fall is due to the presence of many unknown parameters in the analysis and high variability of behavior, and no significant progress has been made in their analysis. In this chapter, overturning collapse and its characteristics are discussed.

    1-2- Overturning collapse

    Overturning collapse is one of the dangerous instabilities in rock slopes. From the point of view of the mechanism, the main overturning falls are classified into three classes: bending, block and block-bending. If the rock mass has steep discontinuities in the opposite direction of the sloping surface and parallel to this surface, it acts like stone columns that are placed on top of each other and will have the potential of overturning.

    When stone columns are formed by a series of discontinuities with a slope towards the inside of the surface and there is another group of seams close to or perpendicular to the previous discontinuity that cuts the height of the columns, the prone area It will be a type of overturning collapse called block overturning. The small columns at the bottom of the slope are pushed forward by the load applied to them from the larger columns at the top, and this sliding at the bottom of the slope allows the overturning to continue towards the wing. A drop base generally includes a surface that increases in height as it approaches the top. Geometric conditions in this type of collapse can be seen in columnar sandstones and basalts where orthogonal columns are well formed [1].

    (images are available in the original file)

     

    When continuous columns of rock created by steep discontinuities break due to bending and bend forward, a type of overturning is called overturning. A bend is defined. The usual geometric conditions of this collapse can be seen in the narrow layering of slates and shales. The base plate of the collapse in this type of overturning is not well recognizable. Downslope sliding, drilling and erosion allow the overturning process to begin and continue into the rock mass.

    (Images are available in the main file)

    Block-bent overturning is another type of collapse and overturning, and consists of columns that are apparently continuous but are divided into separate blocks by a few cross seams, Fig. has taken In this case, the collapse is due to the displacement that occurs on the cross joints, and therefore, the tensile crack that existed in the bending type will be less effective. This type of overturning is more common in nature[1].

    (Images are available in the main file)

     

    [1]

    Many researchers have studied this type of instability. Müller [1] 1968 was the first person to study the overturning of natural blocks near the famous Lake Wyonet [2]. Ashby [3] 1971 presented a simple criterion to calculate this overturning loss.He was the first person to propose the name of Toppling overturning for this instability. According to Goodman and Berry [4] 1967, overturning is classified into two main and secondary types. The main types include block overturning, bending and block-bending. In this case, the columns fall due to their weight. In the secondary overturning class, the external force causes the columns to fall. This classification is highly accepted among researchers, and many people, such as Aidan and Wiley [5] 1980 and Aidan Wakamato [6] 1991, based on it, investigated the overturning collapse. Goodman and Barry presented a step-by-step analysis method for block overturning, which later charts and computer codes were designed [1]. Goodman and Barry introduced the following equation in their study as a necessary criterion for determining the overturning potential: Abstract

    Rock slopes should be applied to static loads. and dynamic loads. Drilling and blasting method is commonly used in open pit mining. During blasting, the additional load induced by blasting may result in loss of rock slope. In order to ensure the stability of the rock slope design and fire control, explosion speed is important to determine the safety factor. In this paper we study the dynamic response such as speed, acceleration, displacement or stress rock slope under blast in the north wall of Choghart Mine. In this paper, using the discrete element method (in the software UDEC) and the geomechanical properties and parameters of Choghart north wall, dynamic stability analysis is discussed.

  • Contents & References of Stability analysis of the overturning collapse of the north wall of Chogharat mine due to dynamic loads resulting from the explosion

    List:

    Chapter One

    overturning spillage and its analysis methods

    1-1- Introduction. 2

    1-2- overturning fall. 3

    1-3- Methods of analyzing the stability of rock slopes against overturning collapse 6

    1-3-1- Limit balance method in overturning collapse 7

    1-3-2- Experimental models. 20

    1-3-3- Numerical models. 25

    Chapter Two

    Explosion and its effect on the stability of rock slopes

    2-1- Introduction. 28

    2-2- Theory of explosion 29

    2-3- Pressure caused by the explosion of explosives 33

    2-3-1- Qualitative description of shock waves. 36

    2-3-2- How to form a shock wave. 37 2-3-3- Reciprocal equation of shock wave attenuation - weakening of the shock wave after release 38 2-4- Different relations of pit pressure measurement and explosion pressure. 40

    2-4-1- Empirical and semi-empirical relationships. 40

    2-4-2- Theoretical and laboratory methods. 40

    2-4-3- TPL and its concepts. 43

      2-4-4- Using the load triangle 49

    2-5- Waves caused by the explosion 50

    2-5-1- Waveform. 51

    2-5-2- Empirical relationship to determine the maximum speed of particles. 52

    2-6- Picking up the wave resulting from the explosion 53

    2-6-1- Different parts of the seismograph device and how to record the earthquake 56

    2-6-2- Explosion recording devices 58

    Chapter 3

    Analysis of the stability of rock slopes

    3-1- Introduction. 65

    3-2- Methods of static analysis of slope stability. 65

    3-2-1- Experimental methods. 65

    3-2-2- Probability method. 66

    3-2-3- Limit balance methods. 72

    3-2-4- Numerical methods. 74

    3-3- Methods of dynamic analysis of rock slopes. 76

    3-3-1- Experimental methods. 76

    3-3-2- Physical model method. 78

    3-3-3- Newmark method. 78

    3-3-4- Pseudo-static analysis. 83

    3-3-5- Numerical methods. 85

    Chapter IV

    Static analysis of the north wall of Chogharat mine

    4-1- Introduction. 94

    4-2- Location and geology of the region. 94

    4-2-1- Tectonics of the region. 96

    4-3- Static analysis. 97

    Chapter Five

    Dynamic analysis of the north wall of Chogharat mine due to the loading resulting from the explosion

    5-1- Introduction. 105

    5-2- Dynamic properties of stone. 105

    5-3- The general process of dynamic analysis in Yodek. 106

    5-3-1- Ensuring the fulfillment of model conditions necessary for wave passage. 106

    5-3-2- Determining proper mechanical damping. 111

    5-3-3- Application of dynamic load and boundary conditions. 111

    5-4- Explosion pressure 113

    5-5- Calculation of explosive pulse. 114

    5-6- control of dynamic responses. 117

    5-7- The results of dynamic analysis. 117

    Chapter Six

    Conclusion and suggestions

    6-1- Conclusion. 134

    6-2- Suggestions. 135

    Resources. 137

    Source:

    [1] Hoek, E. & Bray, JW. (1981). Rock slope engineering (3 ed.). London: Institution Mining and Metallurgy.

    [2] Andreas Goricki and Richard E. Goodman. Failure Modes of Rock Slopes Demonstrated with Base Friction and Simple Numerical Models. (2003).

    [3] Abbas Majdi, Mehdi Amini. Analysis of geo-structural defects in flexural topping failure. (2010).

    [4] Abbas Majdi and Mehdi Amini. Flexural Toppling Failure in Rock Slopes: From Theory to Applications. (2011).

    [5] Zhang, Z. Y. Chen, and X. G. Wang. (n.d.). Centrifuge Modeling of Rock Slopes Susceptible to Block Toppling. [6] Pritchard, Savigny. Numerical modeling of toppling. (1990).

    [7] Duncan C Wyllie, Christopher W Mah. rock Slope Engineering Based on the third edition by E Hoek and J Bray." (n.d.).

    [8] C.H. Liua, M.B.Jaksab, A.G.Meyersc. Improved analytical solution for toppling stability analysis of rock slopes. International Journal of Rock Mechanics&Mining Sciences (2008).

    [9] D. P. Adhikary, A. V. Dyskin, R. J. Jewell, and D. P. Stewart. A Study of the Flexural Failure of Rock Slopes. Rock Mech. (10) Luc Scholtes, Modeling progressive failure inModeling progressive failure in fractured rock masses using a3D discrete element method. International Journal of Rock Mechanics&Mining Sciences (2011).

    [11] P.M. Maurenbrecher Dr. H.R.G.K. Hack. Toppling Mechanism: solving the problem of alignment of slope and discontinuities. (n.d.).

    [12] Mehdi Amini, Abbas Majdi, Mohammad Amin Veshadi. Stability Analysis of Rock Slopes Against Block-Flexure Toppling Failure. (2012).

    [13] Singh, P. Controlled Blasting (Pre-splitting) at an Open-pit Mine in India. Rock Fragmentation by Blasting (pp. 481-489). London: Taylor & Francis Group. (2010).

    [14] Wyllie, D., & Mah, C. Rock Slope Engineering. Taylor & Francis(2005).

    [15] Shi, X., & Chen, S. Delay time optimization in blasting operations for mitigating the vibration-effects on final pit walls' stability. Soil Dynamics and Earthquake Engineering, 31, 1154–1158. (2011).

    [16] Ma, G. Study on the Numerical Investigation on Breakage behavior of reinforced concrete by Blasting demolition. Journal of the Japan explosive society, 59(2), 49-56. (1998).

    [17] Fourney, W. Gas Well Stimulation Studies. In Rock fracture mechanics. R.H.P. , Verlag: Springer. (1983).

    [18] Brinkman, J. Separating Shock and Gas Expansion Breakage Mechanisms. On Rock Fragmentation by Blasting. Keystone, Colorado. (1987).

    [19] Cook, M. Theory and new developments in explosives for blasting. Sixth Annual Drilling and Blasting Symposium, (pp. 31-44). (1956).

    [20] Wilson, J., & Moxon, N. The Development of a Low Shock Energy Ammonium Nitrate Based Explosive. in Proceedings Explosives in Mining Workshop. . AuslMM, Melbourne. (1988).

    [21] Kurokawa, K., Hashimoto, K., & Tabuchi, M. Experimental Study on the Effects of Explosive Performance on Rock Fracture. Rock Fragmentation by Blasting. Balkema Rotterdam(1993).

    [22] Heynrich, J. The Dynamics of Explosion and Its Use. New York: Elsevier Scientific Publishing Company. (1979).

    [23] Liu, Q., & Katsabanis, P. A Theoretical Approach to the Stress Waves around a Borehole and Their Effect on Rock Crushing. Rock Fragmentation by Blasting. Balkema Rotterdam. (1993).

    [24] Hartman, H. Introductory Mining Engineering. ( 1978).

    [25] Sharpe, J. The Propagation of Elastic Waves by Pressure Explosives. Geophysics, 144-154. (1942).

    [26] Mortazavi, A., & Katsabanis, P. Modeling the Influence of the Joint Orientation and Continuity on the Process of the Rock Breakage by Blasting. International Journal for Blasting and Fragmentation, 33(4). (2001).

    [27] Company, A. Explosives and Rock Blasting. p. 662. (1987).

    [28] Pijush, P., & Bibhu, M. A Study on the Usage of Sawdust in ANFO. Proceedings of the Seventh International Symposium on Rock Fragmentation by Blasting. (2002).

    [29] Sanchidrian, J., & Patino, A. Numerical Modeling of Detonating Cords in Uncoupled Holes. Rock Fragmentation by Blasting. . (2002).

    [30] Liu, Q. Estimation of Dynamic Pressure around a Fully Blasthole in Rock. Rock Fragmentation by Blasting. (2002).

    [31] Hustrulid, W., & Johnson, J. A Gas Pressure-Based Drift Round Blast Design Methodology. 5th International Conference & Exhibition on Mass Mining, (pp. 657-669). Schunesson, Nordlund. (2008).

    [32] SINGH, V., & SINGH, D. Controlled blasting in an open-pit mine for improved slope stability. Geotechnical and Geological Engineering, 13, 51-57. (1995).

    [33] Duvall, W. Strain-wave Shapes in Rock near Explosion. Geophysics, 18, 310-326(1953).

    [34] Hino, K. Fragmentation of Rock through Blasting. Journal of the industrial explosive society, 17(1), 2-11. (1956).

    [35] Simha, K. Wave Patterns in Tailored Pulse Loading. Rock Fragmentation by Blasting. Balkema Rotterdam. (1993).

    [36] Kim, D. Development of a new center-cut method: SAV-cut (Stage Advance V-cut). Underground Space – the 4th Dimension of Metropolises.

Stability analysis of the overturning collapse of the north wall of Chogharat mine due to dynamic loads resulting from the explosion