AMW Mining & Allied Services was engaged by M/s PPK Granites Pvt Ltd to re-engineer the drilling and blasting operation at their stone quarry in Palakkad District, Kerala. The assignment combined blast design optimization, controlled blasting techniques and a site-calibrated vibration monitoring programme — with the objective of improving fragmentation and productivity while keeping ground vibration at nearby structures within statutory limits under DGMS (Tech)(S&T) Circular 7 of 1997.
A hard-rock quarry under pressure from both economics and proximity to habitation
A scientific, data-driven blast engineering workflow
Detailed joint mapping and discontinuity survey of the quarry faces; RQD assessment (70–85, "good" class); laboratory UCS testing of representative samples (120–180 MPa, ISRM "very strong" class); in-situ density 2.65–2.75 t/m³. The massive, moderately jointed charnockitic granite was assigned a Kuz-Ram rock factor A ≈ 13, confirming a hard-blasting rock mass requiring disciplined pattern design.
Pattern geometry was redesigned for 100 mm diameter holes on 8 m benches: burden B = 2.75 m (≈27.5 × hole diameter, within the 25–40 d rule), spacing S = 3.0 m (S/B ≈ 1.09), subdrill 0.9 m (≈0.3 B), stemming 2.8 m (≈28 × d) using drill cuttings. Staggered (triangular) pattern with stiffness ratio H/B ≈ 2.9 for controlled fragmentation and minimal backbreak.
B ≈ 25–40 d · S = 1.0–1.4 B · Subdrill ≈ 0.3 B · Stemming ≈ 20–30 dPresplitting along final pit limits (75 mm line holes at 0.6 m spacing, decoupled charges) to protect final slopes; cushion (buffer) blasting with reduced charge per hole adjacent to vibration-sensitive receptors; smooth-wall blasting at the working face to eliminate backbreak and toe problems.
NONEL dual-delay initiation with 25 ms inter-hole and 42 ms inter-row delays, tuned iteratively from fragmentation and vibration feedback. Maximum charge per delay was capped using the site-calibrated scaled-distance regression so that predicted PPV at the nearest structure remained below the statutory limit.
PPV = K · (R/√W)⁻ᵝ · SD = R/√W (m/√kg)Seismographs deployed at the nearest structures and at the quarry boundary for every production blast. Site-specific K and β constants were calibrated by regression (R² > 0.85) from the monitoring record. Peak particle velocity was evaluated against DGMS Circular 7 of 1997 frequency-based limits, and blast records were compiled into verifiable compliance reports.
Measured outcomes after pattern stabilization
Secondary blasting was eliminated entirely; loading and crushing cycles shortened with consistently finer, well-distributed fragmentation. Ground vibration at all monitored structures remained within statutory limits throughout, and no further complaints were recorded after the first month of the optimized pattern.
Standards and regulations applied
AMW Mining delivers scientifically engineered blast designs, controlled blasting and DGMS-compliant vibration monitoring for quarries and mines across India and the GCC.
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