**1. Introduction**

The degree of roof collapse after coal mining is related to the strength and structure of the overlying rock [1–3]. Overlying rocks with stronger rock strength and more complete structure are not easy to collapse. Therefore, the cantilever beam structure is formed at the edge of the goaf, leading to the phenomenon of strong strata behaviors in the roadway and working face [4,5]. The key stratum breakage block size and form determine the drastic degree of manifestation of strata behaviors [6,7]. Strong strata behaviors' manifestation is often accompanied by severe deformation of the roadway [8,9], wall caving [10], rock bursts [11], and other disasters [12,13].

In the traditional practice of prevention and control of the manifestation of strong strata behaviors, disasters such as roof collapse and coal wall caving are often prevented passively by optimizing support parameters [14,15]. However, passive support cannot effectively prevent hazards, such as large deformation of the roadway and comprehensive cutting of the roof of the mining goaf [16]. These strong strata behaviors' manifestation is caused by the rapid release of enormous potential energy stored in the rock layers during the crushing of high-strength and large overhanging overlying rocks [17,18]. Therefore, it is necessary to adopt the method of "active elimination" to reduce the potential energy stored in rock strata [19]. Hydraulic fracturing has been promoted for its effectiveness in dealing with various dynamic hazards [20,21]. Nguyen et al. [22] provide methods for hydraulic fracturing modeling, such as grid generation, execution time, convergence, and numerical integration problems, and indicate that Newton–Cotes orthogonality must be used for cohesive interface elements of secondary flow, at least for the proposed problems. Wu et al. [23] investigated the effect law of primary laminar orientation and horizontal stress difference magnitude on hydraulic fracture initiation pressure, extension pattern,

**Citation:** Li, C.; Xin, D.; Liu, Y.; Chen, T. A Case Study on Strong Strata Behaviors Mechanism of Mining Reserved Roadway and Its Prevention Techniques. *Processes* **2023**, *11*, 1341. https://doi.org/ 10.3390/pr11051341

Academic Editors: Feng Du, Aitao Zhou and Bo Li

Received: 21 February 2023 Revised: 23 April 2023 Accepted: 25 April 2023 Published: 26 April 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

hydraulic pressure–time curve, and fracture volume by large true triaxial directional hydraulic fracture test with a high-energy industrial CT scan. Cheng et al. [24] studied the propagation process of multi-well fractures through physical model experiments, simulated the dynamic fracture initiation and propagation process of cross-hole fractures during directional hydraulic fracturing, and analyzed the evolution law of pore elastic stress and pore pressure between multiple wells.

At present, the technology to solve the strata behaviors after coal mining in the Shendong Mining Area is more inclined to carry out strong support in the working face and roadway, and there is no precedent to use hydraulic fracturing technology to weaken the key layer of overlying rock in strong mining face [25,26]. Therefore, it is crucial to study the prevention and control principles of hydraulic fracture based on the analysis of the mechanism and dominance of strong strata behaviors' manifestation. In this paper, we take panel 42107 of the Buertai Coal Mine as the engineering background. Based on the theoretical analysis, the prevention and control principles and technical solutions of hydraulic fracturing technology were studied. The practical application is remarkable.
