English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

is defined as one that dips at an angle greater than 45° (Cao and Gou, 2011), as shown in Figure 1. In contrast to coal seams with little or no (flat) dip angle, mining production from steeply dipping seams is inherently low and the cost is relatively high. These factors hinder extraction from such seams in developed countries, such as the USA. In developing countries, however, mining of steeply dipping coal seams is rapidly growing because of high reserves available in such configurations, such as in western China and the Jharia coalfield in India. In China, steeply dipping coal seams comprise 15–20% of total coal reserves. Underground mining of steep coal seams using current technologies presents significant safety risks: sliding movements cause instability in the working faces and the rock mass in and around such seams tends to be fragile due to impact of local geological structures such as faults and folds. Generally, fractures exist in the roof strata before mining; these fractures propagate and further coalesce with new fractures developed in the mining process, increasing the probability of roof collapse. Such roof failure can extend upwards as a consequence of the large inclination angle of the coal seam. To reduce deformation of the surrounding rock for ground control, backfill technology has been introduced in steep coal seam mining. In addition, backfill mining is also more environmentally friendly because less surface land is required to store mine tailings and dust or water contamination from surface storage of waste rock is reduced (Bian et al., 2012; Sui et al., 2015). Wang et al. (2011) numerically determined that pillar strength increases with the extent of roadway backfill, regardless of the cohesive or non-cohesive nature of the backfill, especially for pillars of large height-to-width ratio. However, Kostecki and Spearing (2015) numerically found that use of a cohesive fill can improve the pillar strength by 10–40% with fill extent of 25% and 75%, while noncohesive fill contributed little to pillar strength, indicating that the early bearing capacity of backfill should be considered in pillar design for weak roof conditions. Tesarik, Seymour, and Yanske (2009) investigated the long-term stability of a backfilled room-and-pillar test section in a metal mine (where the roof and floor strata usually consist of hard rocks) and found that backfill helps to maintain roof strata integrity and the pillar strength for longterm stability. All of these studies were, however, carried out in flat or gently inclined, rather than steep, strata. For steep coal seam mining, Kulakov (1995a, 1995b) argued that Ground control in mining steeply dipping coal seams by backfilling with waste rock