OVER BREAK ANALYSIS OF ROCK MASS IN SMOOTH PPT[1 main].pptx

mining engineering

1. OVER BREAK ANALYSIS OF ROCK MASS IN SMOOTH BLASTING A project Submitted In Fulfilment of the Requirements for the degree of Bachelor of Technology In Mining Engineering By Aniket Gupta , Soumyadip Biswas, Srinjoy Chatterjee, Surjit Kumar Kewat , Gour Mudi , Ritik Raj Under the guidance of Mr. Himadri sekhar Mahata Department of Mining Engineering , Kazi Nazrul University, Asansol

2. Table of Contents Introduction Blasting Technique Smooth Blasting Overbreak Literature Review Methodology Graphical Representation Conclusion

3. Introduction This project provides an introduction to over break analysis of smooth blasting . Due to blasting some negative effects are often encountered under the blasting loads, such as blast-induced damage ,vibration, stability of slope , under break and over break. The task of quality evaluation of smooth blasting is highly challenging which is focused on the overbreak or underbreak evaluation, rock damage, and ground vibration assessment, as well as the blasting control.

4. Types of controlled blasting Controlled Blasting Line Drilling Cushion Blasting Smooth Blasting Pre-splitting Blasting

5. Blasting Technique

6. What is smooth blasting? Smooth blasting, is a controlled blasting technique used in mining operations to create smooth, stable final walls and minimize overbreak to the surrounding rock. Smooth blasting is typically used in opencast mining operations & tunneling operation , to achieve precise control over the blast and ensure the stability and integrity of the excavation walls.

7. Purpose of smooth blasting 1. Create a smooth, stable wall. 2. Minimize overbreak (damage to surrounding rock). 3. Control rock fragmentation. 4. Enhance safety by preventing rock falls and slope failures. 5. Improve operational efficiency by facilitating easier loading and hauling of fragmented rock .

8. What is over break? This occurs when the actual excavation extends beyond the intended boundaries. The quality of the contour (excavation line) may be characterized by overbreak/underbreak as well as contour roughness. Over-break also increases muck pile volume resulting in more mucking time.

9. Purpose of controlling over break? Safety: Overbreak refers to the unintended fragmentation and removal of rock beyond the planned excavation limits. Optimal Fragmentation: Smooth blasting techniques are designed to achieve precise fragmentation of rock according to engineering specifications. Cost Efficiency: Effective control of overbreak contributes to overall cost efficiency by reducing the need for additional excavation, transportation, and disposal of excess material .

10. Limitations of smooth blasting (From Literature Review ) 1. Geological conditions 2. Depth and height of blasting 3. Complexity of blast design 4. Higher costs

11. Limitations of smooth blasting 5. Requires specialized expertise 6. Limited applicability

12. Influencing parameters of smooth blasting Insitu stress & re-distribution control Influence of face length Influence of burden Influence of spacing Influence of delay timing Influence of depth of hole Influence of explosive Damage scale, Extensional stress Charge concentration Charging explosive Rock mass charge Detonating velocity Timing sequence control

13. Methodology

14. How Burden , Spacing , and linear charge concentration effects smooth blasting ? T he relationship between face Burden and face spacing and linear explosive quantity directly affects the overall blasting scenario. B urden in smooth blasting is a critical parameter . S = S f × d 2 …………. (1) B = B f × S … ………… (2) Q = Q f × d 2 …………. (3) Where, Qf = Explosive charge factor, Q = Explosive charge, (Kg/meter) D= Diameter of the hole in meters S = Spacing between perimeter holes in meters Sf = Spacing factor B = Burden for perimeter holes in meters Bf = Burden factor. * Reference (Influence of rock mass quality in controlled basting ,Paul singh )

15. How Burden , Spacing , and linear charge concentration effects smooth blasting ? (Conditions) * Reference (Influence of rock mass quality in controlled basting ,Paul singh )

16. Influence of delay timing in smooth blasting . Delay timing between holes in a row and between rows play an important role in generating cracks in both front burden rock and back-wall of in-situ rock mass. [TBH = Targeted Bore Hole ] TBH: Δt ≈ (H /C)……….. (3) In the formula, Δt represents borehole initiation delay time; H is space between the PBH and the TBH; C represents the velocity of stress wave. ( Referance :A study of smooth wall blasting fracture mechanisms using the Timing Sequence Control Method , Xing ping li )

17. Stress wave S tress concentration effect : T he effect of rock mass material properties on wave velocity, the longitudinal wave velocity C p and the transverse wave velocity C s in the rock mass can be calculated from the following equation : C p = [E(1 – ν )/ (1 + ν ) (1 – 2ν )] ½ …………. (4) C s =[ G / ρ ] ½ ……………( 5) where E represents the modulus of elasticity of rock mass, v represents Poisson’s ratio of rock mass, and ρ represents the rock density . ( Referance :A study of smooth wall blasting fracture mechanisms using the Timing Sequence Control Method , Xing ping li )

18. Q - System The Q system determines the rock mass quality as a function of six geological parameters: Rock quality designation (RQD), number of joint sets (Jn), joint roughness number (Jr), joint alteration number (Ja), water reduction factor ( Jw ), and stress reduction factor (SRF). A value is measured or assigned for each parameter, and the rock mass quality Q is obtained from the following equation: Q = (RQD/ J n )×(J r / J a ) × (J W /SRF) ……. (6) The other parameters were selected using the Barton classification.

19. Over Break vs Q - factor Reference : Causes, impact and control of overbreak in underground excavations S. Paul Singh a,*, Peter Xavier b a School of Engineering, Laurentian University, Sudbury, Ont., Canada P3E 2C6

20. Influence of detonation velocity in Smooth Blasting The VoD is selected based on these factors to achieve the desired balance between : fragmentation quality, displacement and environmental impact. Monitoring and analyzing the VoD during trial blasts can provide valuable data to optimize future blasting operations..

21. Influence of detonation velocity in Smooth Blasting Reference : Causes, impact and control of overbreak in underground excavations S. Paul Singh a,*, Peter Xavier b a School of Engineering, Laurentian University, Sudbury, Ont., Canada P3E 2C6

22. Influence of detonation velocity in Smooth Blasting The powder factor is the ratio of the explosive weight and the volume of rock blasted. Generally, higher powder factor will produce overbreak and lower powder factor may produce may produce overbreak or underbreak. But from the blast damage point of view, the perimeter powder factor is more critical than the overall powder factor. Reference : Causes, impact and control of overbreak in underground excavations S. Paul Singh a,*, Peter Xavier b a School of Engineering, Laurentian University, Sudbury, Ont., Canada P3E 2C6

23. Over Break Analysis Analysis of the measurements reveal a relationship between PPF and log Q, and between overbreak, a significant result can achieved . Overbreak(%) = -0.12 + 15.07×PPF- 2.55×log(Q) ….. (7) ( Referance :overbreak and underbreak in underground openings Part 2: and implications , J B IBARRA )

24. Over Break Analysis Overbreak(%) = -0.12 + 15.07×PPF- 2.55×log(Q) ….. (7) Or , Overbreak(%) = - 0.12 + 15.07 × - × (RMR - 44) Where , = Explosive factor d = Diameter of blast hole Δ t = Dealy timing = Density E = Elastic Modulus .  

25. Assumptions From the above equation we get that RMR, elastic modulus, poision ratio, density are same for a specific site so we assume the values of these parameters are constant. and the drilling practice of a site is always same so we assume that the diameter of the all holes are constant. For a specific site or field the variables

26. BURDEN vs OVER BREAK Here the variable parameter is BURDEN . So , the plotting is described

27. OVER BREAK vs DELAY TIME Here the variable parameter is delay time . So , the plotting is described

28. Conclusion From the above study we have make a simple correlation in between all parameters of smooth blasting and also represent that by graphical representation. Our approach is to minimises the overbreak by changing the values of delay time and burden that's why we make some graphical representation with by the help of theoretical studies to verify this theoretical analysis we should implement it into the field or get some field data. Due to some unavoidable reasons we can't collect any data. We are trying our best to get the data and fulfilment of our project

29. Thank You