A Review of Instability Mechanisms and Control Technologies for Gas Drainage Boreholes in Soft Coal Seams in China

In China, soft coal seams make up over 50% of all coal seams. The instability and failure of boreholes in soft coal seams are key factors that result in an average gas drainage rate of less than 30% in China, which has become a "bottleneck" for safe and efficient coal mining. Based on 247 articles from the Web of Science Core Collection database (up to April 30, 2025), this review uses a CiteSpace bibliometric analysis to categorize the research into three distinct temporal stages: the exploration stage (2007-2012), the rapid development stage (2013-2019), and the refined research stage (2020-present). Additionally, it conducts an in-depth analysis of five categories comprising nine key influencing factors for borehole stability. In the field of instability prevention and control, the technical processes and their advantages and disadvantages during the borehole construction period and the service period are comprehensively evaluated. Specifically, during the construction period, three types of chemical grouting reinforcement methods and eight types of drilling technologies are covered. During the service period, the review focuses on three types of borehole instability control technologies, including screen pipe physical support, porous material backfilling, and intelligent monitoring. Finally, five critical current bottlenecks are identified, and six development directions are proposed.