257 1. Introduction Extra-thick coal seams (generally thicker than 8 m) are widely distributed in major coalproducing countries and constitute an important resource base for high-capacity and highefficiency underground mining. In China, extra-thick coal seams account for more than 45% of total coal reserves and are concentrated in large-scale modern mining districts in western regions (National Bureau of Statistics of China, 2025). Efficient exploitation of these seams is therefore critical to long-term energy security and sustainable coal mine development. Fully mechanized longwall mining with large mining height has been widely recognized as an effective approach for extra-thick coal seams due to its advantages in production efficiency, coal quality control, and recovery rate (Wang et al., 2015). Over the past two decades, continuous progress has been achieved worldwide, and the maximum practical mining height has been gradually increased from approximately 6 m to about 8–9 m (Xu et al., 2022; Yang., 2017; Yang., 2019). However, further increasing the mining height beyond this range has long been regarded as technically prohibitive. The reasons include the rapid escalation of ground pressure intensity, severe instability of ultra-high coal walls, extreme loading demands on hydraulic shields, and the lack of reliable equipment capable of operating under such conditions. As a result, extra-thick coal seams with thicknesses around 10 m have traditionally been mined using layered mining or top-coal caving methods. These methods suffer from inherent limitations such as low recovery rate, high gangue content, complex production organization, and increased safety risks, particularly in hard and thick roof conditions. These shortcomings have increasingly constrained the development of high-capacity modern mines. To overcome these limitations, China initiated a major engineering effort to explore the feasibility of fully mechanized longwall mining with a single-pass cutting height of 10 m. Centered on the Caojiatan Coal Mine, this project targeted the world’s first application of 10-m fully mechanized longwall mining in an extra-thick coal seam. The core objective was to break the long-standing mining-height limit by addressing surrounding-rock control, key equipment reliability, and system-level coordination under extreme conditions. In this paper, we present a concise overview of the geological challenges, key enabling technologies, system integration, and field performance of the world’s first 10-m fully mechanized longwall mining operation. The successful implementation of this project establishes a new upper limit for longwall mining height and represents a significant breakthrough for extra-thick coal seam development. 2. Geological Conditions and Engineering Challenges 2.1 Geological Conditions of the 10-m Longwall Face The world’s first 10-m fully mechanized longwall mining operation was implemented at the working face 122104 of the Caojiatan Coal Mine, located in the Yushen mining district,
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