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2 2024

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A field-scale investigation into the strategic location of air decks for improved blasting performance

100%

Saqib S. , Qureshi M. U. , Rashid H. M. A. , Ali D. , Rasool A. M.

Archives of Mining Sciences

2024

tom Vol. 69, no. 3

391--407

Airdeck blasting is a promising technique for improved blast efficiency, reducing explosive consumption, and enhancing fragmentation. Nevertheless, it lacks widespread adoption due to design guideline gaps and differing opinions on air deck placement. This study offers technical guidance based on field experiments to optimise air deck blasting. Full-scale blast experiments were conducted at four distinct limestone benches to evaluate the efficacy of air deck implementation. At Bench-1, experiments were performed using conventional blasting (with full-column charge) and air decks at three strategic air deck positions (i.e., top, mid, and bottom) within blast holes at a selected quarry site. For Benches 2 and 3, comparative fragmentation analyses were conducted between conventional blasts and those utilising air decks positioned in the middle of the explosive column. Furthermore, the impact of multiple mid-air decks within explosive columns was also evaluated at Bench-4. A comparison of blast fragmentation results revealed that fragments obtained through the air decking technique surpassed those from the full-column charge, regardless of air deck placement. Among the tested air deck positions, the single air deck positioned at the middle of the explosive column yielded superior fragmentation results than other locations. In addition, this technique showed a reduction in explosive charge, back break, and toe-related issues.

Development of Wetting-Drying Curves from Elastic Wave Velocities Using a Novel Triaxial Test Apparatus

86%

Irfan M. , Rasool A. M. , Aziz M. , Ali U. , Niazi F. , Uchimura T.

Studia Geotechnica et Mechanica

2024

tom Vol. 46, nr 2

111--124

The relationship between the soil water characteristic curve (SWCC) and the mechanical behavior of unsaturated soil is imperative and has been well investigated. However, the correlation between elastic wave velocity along the wetting and drying paths of SWCC is largely unknown due to the nonavailability of a standard experimental setup for such a purpose. An ordinary triaxial apparatus has been modified for laboratory assessment of SWCCs under different Ko stresses, along with the measurement of shear and compression wave velocities in due course. The main aim of the study is to draw SWCC, wave velocity characteristic curve (WVCC), and a Poisson’s ratio characteristic curve (PRCC) and to establish the phenomenon that these curves possess hysteresis. The Poisson’s ratio was obtained indirectly by measuring Vp and Vs. Three soil samples with relative densities of 85%, 56%, and 39% were prepared and placed in a modified triaxial test apparatus under wetting and drying cycles. The test results showed that the newly developed apparatus is accurately capable of measuring SWCC. Owing to the similarity in the shape of wave velocity and Poisson’s ratio, response to SWCC, WVCC, and PRCC are drawn. The phenomenon of stress history and the effective stress of the soil affected the behavior during wetting and drying paths.