Influence Of Backfill Research Articles

The Influence of Backfill on the Driving Energy Intensity and Axial Load Resistance of Piles with Shaft Widenings: Modeling Research

This article is dedicated to addressing the current challenge of augmenting the load-bearingcapability of pile foundations. This predicament is most effectively addressed by employing piles with unconventional geometries along with atypical methodologies for installing these foundation piles. The primary objective of the research wasto examine the impact of various fill materials (including both soil and rigid substances) on the energy consumption during pile driving and the resistance to static loads by piles with multiple shaft expansions. The findings derived from model-based investigations demonstrate that the load-bearing capacity of piles with shaft expansions installed with bulk material filling surpassed that of conventional piles (prismatic and pyramidal) by a factor ranging from 1.5 to 4.6. Furthermore, the research outcomes also indicated greater energy consumption (1.14–1.66 times) and enhanced load-bearing capacity (1.15–1.68 times) for piles with shaft expansions driven with backfill in comparison to piles installed without backfill. It is noteworthy that the type of backfill material significantly influenced the energy consumption during pile driving and their stability under axial static loads. The correlation relationships can be applied to approximate projection of the energy-related and structural parameters of piles with shaft expansions embedded with the addition of bulk materials.

Experimental Investigation of Water-Inrush Risk Based on Permeability Evolution in Coal Mine and Backfill Prevention Discussion

Induced by coal mining, the fractures constantly occur in geologic strata until failure occurs, which provide channels for water flow. Therefore, it is essential to investigate the permeability evolution of rocks under load. Borehole sampling was conducted in a bedrock layer beneath an aquifer, and the permeability evolution of sandstone specimens under different confining pressures was tested in rock mechanics testing laboratories. The results indicated that the permeability gradually decreases with the increasing confining pressures, while the peak strength increases with the increase of confining pressures. The minimum and maximum permeabilities occurred in the sandstone specimens that were subjected to elastic deformation and strain-softening stages, respectively. The failure, and maximum permeability, of these sandstone specimens did not occur simultaneously. To prevent the flow channel being formed due to the development and failure of rock fractures, a method of backfill gob was proposed and also the influence of backfill on fracture development was discussed.

Influence of backfill on coal pillar strength and floor bearing capacity in weak floor conditions in the Illinois Basin

This paper discusses the current theoretical design equations associated with foundation design in the Illinois Basin, as well as the benefits of utilizing high density backfill in a numerical model, to improve pillar and floor stability. Based upon the results, Vesic’s bearing capacity solution for a two layered soil tends to underestimate the true bearing capacity of a foundation, especially at higher friction angles and when footings are placed in close proximity. Minimizing the distance between adjacent foundations has shown an improvement in the ultimate bearing capacity of a foundation; however, placing the foundations in too close proximity has shown the foundations may behave as a single foundation and undergo appreciable settlement. A 10–40% increase in pillar strength and ultimate bearing capacity can be expected when a cohesive fill is used between 25 and 75% fill of the mined height, respectively. The non-cohesive nature of the simulated backfill showed little influence on increased pillar strength, even at higher fill ratios. It was determined, that as the shearing resistance, tensile strength and stiffness of the backfill are reduced, increases in coal pillar strength is due more to the confinement aspect of an underground mine rather than the strength properties of the material itself. A methodology for analyzing the plastic flow characteristics of a coal pillar and a footing using FLAC3D has also been presented herein.

Influence of backfill on the capacity of masonry arch bridges

The influence of the presence of backfill on the load-carrying capacity of a masonry arch bridge can be considerable. The backfill is responsible for transmitting and distributing live loads from the road or rail surface through to the arch barrel and also for laterally stabilising the arch barrel as it sways under load. However, it can be difficult to separate these two distinct effects, and hence also difficult to ascertain whether existing assessment code recommendations are realistic. To address this, a series of experiments designed to separate these two effects have been performed. A total of 27 small-scale bridge tests were undertaken and the experimentally obtained peak loads then compared with results from limit analysis software of varying complexity. It was confirmed that passive restraint and live load distribution both contribute significantly to bridge-carrying capacity, and that, when failure involves a four-hinge failure mechanism, even comparatively simple limit analysis software can model the various effects remarkably well.