Search Results (3)

This study investigates the effectiveness of combining helical piles (HPs) with geogrid reinforcement compared to conventional piles in improving pullout performance in dense sand, addressing a key challenge in reinforced foundation design. A comprehensive experimental program was conducted to evaluate the pullout behavior of HPs embedded in Shahriyar sand reinforced with geogrid layers. The research focused on quantifying the effects of critical parameters—pile configuration, helix pitch, and geogrid placement depth—on ultimate pullout capacity and displacement response to better understand hybrid reinforcement mechanisms. Pullout tests were performed using a Zwick/Roell Z150 universal testing machine with automated data acquisition via TestXpert11 V3.2 software. The experimental program assessed the following influences: (1) pile configurations—plain, single-helix, and double-helix; (2) helix pitch ratios of 1.00, 1.54, and 1.92 (pitch-to-shaft diameter); and (3) geogrid placement depths of 7.69, 11.54, and 15.38 (depth-to-shaft diameter) on pullout behavior. Results demonstrate that geogrid reinforcement substantially enhances pullout resistance, with single-helix HPs achieving up to a 518% increase over plain piles. Pullout resistance is highly sensitive to geogrid spacing, with optimal performance at a non-dimensional distance of 0.47 from the pile–soil interface. Additionally, double-blade HPs with geogrid placed at 0.35 exhibit a 62% reduction in displacement ratio, underscoring the role of geogrid in improving pile stiffness and load-bearing capacity. These findings provide new insights into the synergistic effects of helical pile geometry and geogrid placement for designing efficient reinforced granular foundations. Full article

The use of pumpable emulsion explosives in the stopes of narrow-reef gold mines is an emerging practice. This is due to recent developments in the delivery and placement mechanisms of emulsion and gassing agents through portable charging units into small-diameter blastholes. With these developments, this paper outlines the performance of pumpable emulsion explosives in a non-trial basis at two underground gold mines in South Africa, where a combined 33 underground drilling and blasting outcomes were observed in two shafts, where three key performance indicators—namely face advance, powder factor, and fragmentation size distribution—were evaluated. The results indicated that the use of emulsion explosives can enhance the probability of achieving the target face advance, whereas the results of the powder factor are mixed. In one shaft, the actual powder factor of the observed blasts mostly exceeded the planned powder factor, whereas in the other shaft, the latter was largely achieved. Lastly, the results of the fragmentation size distribution analyses are inconclusive; that is, it cannot be conclusively pointed out whether the use of pumpable emulsion explosives can achieve a mean particle fragmentation range of 11.5 cm to 13.5 cm at Shafts A and B. Full article

In this study, an innovative approach to torque transmission mechanisms within the context of hub–shaft connections is introduced by exploring the viability of a transverse key configuration. Unlike traditional longitudinal key placements, the proposed method positions the key perpendicularly to the rotational axis, resembling a pin joint at the interface of the shaft and the hub. This research primarily aims to elucidate the maximum torque capacity of such a connection, juxtaposed against conventional methodologies. Employing a rigorous analytical framework, equations originally designed for pin connections are adapted to suit the unique geometric and loading conditions presented by the transverse key. This adaptation is essential in quantifying the resultant torque that the connection could sustain without failure. The study meticulously accounts for the variations in key dimensions and the inherent limitations posed by the method’s reliance on the end-face connection strategy. Comparative analyses underscore the manufacturing advantages of the proposed method, notably its reduced machinery requirements, by leveraging standard milling processes over more complex machining operations that are traditionally associated with keyway or keyseat creation. However, the findings also highlight the compromised torque transmission capability due to the reduced contact area, a significant consideration for designers. This research contributes to the broader discourse on mechanical connection innovations, offering a novel perspective on torque transmission solutions. It provides a foundation for future exploration into alternative key configurations, potentially revolutionizing hub–shaft connection designs in applications constrained by manufacturing capabilities or cost considerations. Full article