Next Article in Journal
Numerical Simulation of Bottom-Water Coning Suppression by Artificial Barriers and Water Drainage
Previous Article in Journal
Graphene-Based Metal–Organic Frameworks for Advanced Wastewater Treatment: A Review of Synthesis, Characterization, and Micropollutant Removal
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Processes
Volume 14
Issue 1
10.3390/pr14010118
processes-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Comprehensive Evaluation of Directional Hydraulic Fracturing for Roof Pressure Relief and Disaster Prevention Based on Integrated Multi-Parameter Monitoring

by
Shuwei Hu
1,
Hualei Zhang
2 and
Cun Zhang
3,*
1
Inner Mongolia Yitai Coal Co., Ltd., Ordos 017000, China
2
School of Mining Engineering, Anhui University of Science & Technology, Huainan 232001, China
3
School of Energy and Mining Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China
*
Author to whom correspondence should be addressed.
Processes 2026, 14(1), 118; https://doi.org/10.3390/pr14010118 (registering DOI)
Submission received: 2 December 2025 / Revised: 21 December 2025 / Accepted: 24 December 2025 / Published: 29 December 2025
(This article belongs to the Topic Advances in Coal Mine Disaster Prevention Technology)
Browse Figures
Versions Notes

Abstract

With the increasing depth of coal mining, thick-hard overlying strata (THOS) often induce dynamic disasters such as rockbursts, posing significant threats to mine safety. This study focuses on the application of directional hydraulic fracturing roof pressure relief technology (HFRPRT) as a key disaster prevention technology in the Hongqinghe Coal Mine’s 3-1302 longwall face. An integrated monitoring system combining microseismic (MS) and acoustic emission (AE) data was established to quantitatively evaluate the fracturing process through multi-indicator analysis, including support pressure response, energy distribution, and surface subsidence. The results demonstrate that HFRPRT effectively weakened THOS integrity, reducing periodic weighting intervals by 25% and peak pressure intensity by 21.95%. Daily AE energy and event count increased by 154% and 636%, respectively, indicating enhanced microfracture propagation. MS events shifted to lower-energy patterns, with second-order events predominating (59.16%), highlighting the technology’s role in mitigating elastic energy accumulation and dynamic hazards. This research provides a theoretical foundation for optimizing hydraulic fracturing parameters in similar geotechnical conditions, advancing coal mine disaster prevention strategies.

1. Introduction

With the progressive exploitation of coal resources at increasing depths, intensive mining operations under thick-hard overlying strata (THOS) conditions have led to significantly exacerbated strata pressure behavior [1,2,3,4]. The THOS tend to develop extensive cantilevered structures under mining-induced stresses, resulting in abnormal stress concentration and elastic energy accumulation in the surrounding rock mass. This phenomenon ultimately induces severe roadway convergence, sudden roof collapse, and even rockbursts and other dynamic failures, posing substantial threats to longwall face (LWF) safety and productivity [5,6,7]. To solve this engineering challenge, hydraulic fracturing roof pressure relief technology (HFRPRT) has been extensively implemented in underground engineering applications, including mining and geotechnical projects, owing to its superior controllability, extensive influence range, and minimal environmental footprint. Successful field applications have demonstrated their effectiveness in multiple domains such as strata control in LWF, surrounding rock stabilization in roadways subjected to high-stress and intensive mining conditions, and rockburst prevention and mitigation [8,9,10]. By generating controlled directional fracture networks, HFRPRT effectively reduces rock mass continuity and modifies stress redistribution patterns within overlying strata (OLS). This technology exhibits superior performance in specific engineering applications, particularly in coal seam roof preconditioning and enhanced methane drainage operations.
The fundamental principle of hydraulic fracturing (HF) lies in the precise regulation of fracture initiation and propagation mechanisms, enabling targeted directional segmentation of stratified rock formations [1]. Extensive scholarly investigations have been systematically conducted on theoretical modeling of fracture propagation mechanics, laboratory-scale physical simulation experiments, integrated surface-downhole monitoring systems, and comprehensive evaluation of fracturing performance metrics. A computational model of four-edge-clamped thin plates was developed, establishing quantitative correlations between periodic weighting characteristics and fracture network geometries under mining-induced stresses [11]. Through physical similarity modeling of THOS fracture behavior, Li et al. [12] demonstrated that THOS rupture generates substantial energy release. Extensive experimental investigations have been conducted to elucidate key aspects of the process, such as the fundamental mechanisms governing fracture network propagation, and critical controlling factors, including in situ stress anisotropy, fracturing fluid rheology, and pre-existing fracture characteristics. These studies have systematically revealed the evolutionary patterns of HF propagation and OLS failure modes under varying geological and engineering conditions [13,14,15,16]. The advancement of microstructural characterization techniques has led to the widespread adoption of AE monitoring and CT scanning for investigating the formation mechanisms of 3D fracture networks [17,18,19]. Building upon this foundation, numerous scholars have investigated the spatial distribution and structural optimization of HF in naturally fractured rock masses, thereby elucidating the key factors governing the development of complex fracture networks [20,21,22].
Laboratory mechanical tests for HF often require the construction of scaled physical models, a process that is both time-consuming and subject to pronounced scale effects. Consequently, numerical simulations that can more faithfully reproduce in situ geological conditions have gradually emerged as a vital tool for advancing HF research. The ELFEN finite–discrete element code was employed to investigate the influence of injection-induced pore pressure on the distribution of mining-induced stresses in the LWF [23]. Considering the coupled fluid flow-stress-damage mechanisms involved in the HF of THOS, the RFPA2D-Flow simulation platform was employed to investigate the comparative effects of slotted directional HF and conventional non-directional HF [24]. A tailored implementation approach for coupling HF with pressure-relief mining was proposed, designed to match the formation scale based on DEM. Furthermore, the necessity, optimization strategies, and scalability considerations for up-scaled simulations of HF in hard roof strata were elucidated to facilitate effective pressure-relief mining [25]. At present, HFRPRT is widely used in the field of pressure relief in hard roofs. HF was carried out in the coal mine roadways targeting THOS, effectively interrupting the stress transfer pathways within the THOS above the coal pillars. The high stress originating from the surrounding rock of the roadway was redistributed, thereby reducing the intensity of the mining-induced stress field [26,27,28]. Some scholars systematically investigated the influence of different fracture types and parameters (including fracture length, orientation, and spacing) on the mechanical properties and failure behavior of coal–rock masses with artificial fractures by integrating physical experiments, numerical simulations, and theoretical analyses. The findings were successfully applied in field applications, resulting in a significant reduction in roadway deformation [29,30,31]. A numerical simulation model for HF was developed to determine the optimal hydraulic scheme. The application of HFRPRT can effectively reduce the working resistance of hydraulic supports [32]. The activity patterns of microseismic events (MSE) in the front and rear roof during HF and LWF recovery, as well as associated mining weighting behavior, were analyzed to quantitatively evaluate the pressure-relief effects of HF in roadways [33]. Kang et al. [34,35] conducted an investigation into the theories and processes of initial forced roof caving in HFRPRT. Their findings indicate that this technique effectively reduces roof pressure, mitigates the impacts of vertical stress, and diminishes the overall integrity of the roof strata. Moreover, it has been successfully applied in engineering practice.
Overall, the application of HF remains limited by complex geological conditions and dynamic mining-induced stresses. Existing studies still exhibit significant shortcomings in the multi-dimensional evaluation of fracturing effectiveness. Conventional monitoring methods are often restricted to localized stress field measurements or the analysis of isolated mining weighting parameters, making it difficult to comprehensively elucidate the evolution of overburden rock fracturing under HF or the underlying mechanisms for mitigating dynamic hazards. This issue is especially acute under deep THOS conditions, where the optimization of HF technology to weaken the OLS structure remains a critical and urgent technical challenge. To address these gaps, this study takes the 3-1302 LWF at Hongqinghe Coal Mine as its engineering context. Directional long-borehole HFRPRT was investigated, and an integrated underground-surface multi-parameter evaluation system was established. This system incorporates support pressure response (SPR), energy distribution, and spatiotemporal evolution characteristics of MSE, as well as surface subsidence (SFS) laws. The effectiveness of HF was evaluated in a comprehensive and multi-dimensional manner, and the evolutionary behavior of THOS in response to fracturing was systematically analyzed. The outcomes of this research provide a scientific basis for advancing the theoretical framework of HFRPRT and for systematically evaluating fracturing performance.

2. Geological Setting and Mining Conditions

2.1. Layout of 3-1302 Longwall Face

Hongqinghe Coal Mine is situated in Ejin Horo Banner, Inner Mongolia, China. The primary mined seam is the 3-1 coal layer. The 3-1302 LWF has a width of 300 m and a strike advance length of 3549 m, with a coal seam dip angle ranging from 1° to 5°. The seam thickness varies between 5.50 and 7.70 m, with an average thickness of 6.6 m, and a burial depth is 762 m. The withdrawal roadway is oriented toward the southeast of the LWF, while the auxiliary haulage gateway is adjacent to the 301 goaf, with solid coal prevailing in other surrounding areas. The planar layout of the LWF is shown in Figure 1.

2.2. Engineering Geological Condition

According to the drilling results, within a 30 m range above the roof of the 3-1 coal seam, the OLS are primarily composed of siltstone and fine-grained sandstone. THOS consists predominantly of fine sandstone and medium sandstone. The 3-1302 LWF has advanced approximately 200 m. In this section, the immediate roof consists sequentially of fine-grained sandstone, mudstone, and medium conglomerate. At 30~34 m above the coal seam lies a 36.23 m thick coarse-grained sandstone layer. At 70 m above the seam, a 10.95 m-thick medium-grained sandstone. At higher roof stratigraphic levels above the seam, a 38.09 m-thick coarse-grained sandstone is present, as shown in Figure 2.

3. Directional Long Borehole Hydraulic Fracturing Roof Pressure Relief Scheme

3.1. Hydraulic Fracturing Pressure Relief Mechanism

The failure and collapse of the OLS directly led to controlling the occurrence of mining weighting in the LWF. Due to the substantial thickness and high strength of THOS, they exert a dominant influence on the failure mechanisms of the OLS and the corresponding manifestation of mining weighting throughout the LWF mining process. Owing to their load-bearing characteristics, THOS form a cantilever beam structure with a hanging roof after the LWF has advanced a certain distance. When the critical breaking span is reached, the THOS and the overlying strata collapse synchronously, leading to a pronounced manifestation of mining-induced weighting in the LWF [28,36]. To effectively mitigate mining-induced weighting in the LWF, targeted HF of the THOS ahead of the LWF is required to artificially disrupt the integrity of the roof strata. This intervention increases the caving angle of the LWF, reduces the hanging roof distance, diminishes stress concentration at the LWF boundaries, and attenuates the peak values of both the advanced and lateral residual abutment pressures.

3.2. Hydraulic Fracturing Pressure Relief Strata Selection

To prevent the development of extensive hanging roof structures within the THOS above the 3-1302 LWF, and to ensure that these strata cave on time during mining, it is necessary to adequately fracture and weaken the roof rock mass overlying the LWF. Combined with the occurrence of OLS and key strata theory [37], the thick and hard coarse-grained sandstone located 34~70 m away from the coal seam has been identified as the target layer. Three HF heights were designed for the upper part of the target layer, located 50 m, 55 m, and 68 m above the coal seam.

3.3. Hydraulic Fracturing Roof Pressure Relief Design

The design of directional long-borehole HF for roof pressure relief involves several key elements, including borehole layout, equipment selection, pumping rate, fracturing interval, and fracturing duration [28,33]. In this study, a self-developed BYW-type hydraulic fracturing pump unit, specifically designed for underground coal mine applications, was utilized. This system is powered by a 450 kW explosion-proof motor and is equipped with a BY610Z hydraulic transmission, ensuring stable and efficient energy delivery during the fracturing process. Power is transmitted through a ball-cage synchronous universal coupling and reduced by a side-mounted gearbox to drive the pump, delivering a discharge flow rate of approximately 1.0 m3/min. The designed fracturing zone extends about 700 m ahead of the starting cut. Based on the selected fracturing horizons, the LWF layout, and engineering experience, three drilling sites were established within the LWF and #1 drainage tunnel, comprising a total of eight boreholes. Drilling Site-1 was located directly within the drainage tunnel and targeted the middle-to-high roof strata within 0–350 m ahead of the open-off cut. Drilling Site-2 and Drilling Site-3 were positioned in the driving chamber on the mining side of the roadway, primarily targeting the middle-to-high roof strata within 350–700 m ahead of the starting cut. The specific boreholes are shown in Figure 3 and Figure 4. The total drilling footage for this project is approximately 5200 m, of which about 4200 m is designated for HF. The open-hole diameter of the horizontal section is 120 mm. The detailed design parameters of the directional boreholes are summarized in Table 1.
A pullback staged hydraulic fracturing process was employed. The stage spacing was set at 30 m, and water was used as the fracturing fluid. By monitoring water pressure and flow rate in real time, the fracture water pressure can be identified as the value displayed right before the first drop occurs. During the fracturing process, adjacent boreholes and water inflow conditions in the surrounding roof strata were continuously monitored. The fracturing duration was generally no less than 30 min, with the specific time determined by borehole water pressure retention. As a principle, fracturing was continued for an additional 10 min once the pressure ceased to increase. The fracturing tool assembly comprised the following components in sequence: guide plug + check valve + packer 1 + two sections of water-conducting drill pipe + constant-pressure restrictor + two sections of water-conducting drill pipe + packer 2 + safety sub + water-conducting drill pipe extending to the borehole collar. The detailed configuration is illustrated in Figure 5.

4. Monitoring Methods

4.1. The Overview of the 3-1802 LWF

To evaluate the stress-relief effect of HFRPRT on the roof strata of the 3-1302 LWF, this study compares and analyzes the manifestations of mining pressure, fracture development, and SFS with those from surface observations in the 3-1802 LWF. Both the 3-1802 and 3-1302 LWF mine the 3-1 coal seam of the Yan’an Formation. The 3-1802 LWF has a strike length of 2775 m and a dip width of 280 m, with a coal seam dip angle ranging from 1° to 7°. The seam exhibits an average thickness of 5.91 m and an average burial depth of approximately 650 m. Based on borehole data, the OLS conditions of the two LWF were generally similar. And the 3-1802 LWF did not undergo roof fracturing. Through this comparative analysis, a quantitative evaluation of the HF roof pressure relief effect was achieved.

4.2. The Layout of the Monitoring System

Based on the chain transmission characteristics of mining-induced disturbance in coal seams, this study employs LWF pressure, OLS fracture development, and SFS as quantitative indicators. In this framework, mining pressure at the LWF serves as the monitoring source, OLS fractures act as a conductive pathway, and SFS represents the outcome of macroscopic disturbances. A three-dimensional chain monitoring system was established by integrating measurements of LWF support pressure, AE, MS, and SFS, as illustrated in Figure 6. The specific monitoring plan is as follows:
The working resistance of hydraulic supports monitoring: A total of 149 hydraulic supports are installed in the 3-1302 LWF of Hongqinghe Coal Mine, among which 15 are equipped with CDW-60R-type support pressure recorders. The KJ24 Coal Mine Roof Pressure Monitoring System is employed to collect data, and its analysis software provides real-time information on the current working resistance, initial support force, maximum working resistance, and end-of-cycle resistance of the fully mechanized mining supports, along with their operational status.
AE monitoring: In this study, the ARES-5E AE monitoring system was employed (as shown in Figure 6). Four AE monitoring sensors (D9–D11) were installed along the 3-1302 LWF, with a monitoring period of 192 days. The sensors’ layout is illustrated in Figure 6b, where solid red circles indicate the positions of the AE sensors. The probes were advanced alternately in synchronization with the progression of the LWF.
MS monitoring: Based on the monitoring range and accuracy of the ARAMIS-M/E system (as shown in Figure 7), a total of 11 probes were deployed along the 3-1302 LWF. Two probes were positioned near the rubber transport channel, five near the auxiliary transport channel, and four near the main transport channel. The MS sensor number is T, and the MS geophone number is S. The layout is illustrated in Figure 7b. MS monitoring was conducted over a period of 192 days to track the activity of roof strata within the mining zone of the LWF.
SFS observation: Regular SFS observation has been conducted on the 3-1802 and 3-1302 LWF since the start of backfilling. Observation points were arranged along both the strike and dip directions of the LWF. The spacing between measurement points along the strike of the 3-1802 LWF is approximately 40 m, while for the 3-1302 LWF it is approximately 25 m. The detailed layout is shown in Figure 8a,b.

5. Results and Discussion

5.1. Hydraulic Fracturing Construction Record Curve

Water pressure is a key parameter in HF, which directly influences the fracturing effectiveness [38]. An intermittent recording method was employed to monitor the pressure gauge and flow meter readings during construction. Figure 9 shows a typical pressure-flow-time variation curve during borehole construction. The pressure–flow–time variation trends of the boreholes were generally consistent, and the cyclic fracturing process can be divided into three stages: initial pressurization, fracture propagation and pressure-holding, and pressure release. As water was injected, the pressure increased to 10~20 MPa, entering the fracture propagation and pressure-holding stage. With prolonged pressure maintenance, fractures within the fracturing interval began to develop, causing a decrease in water pressure. However, continued injection rapidly filled the newly created fracture space with high-pressure water, resulting in a subsequent rise in injection pressure and producing a rapid fluctuation phenomenon during the fracture propagation stage. This indicates the progressive propagation of fractures within the THOS. When the water pressure dropped to approximately 10 MPa without further increase, the fracturing process was considered to have terminated.

5.2. Evolution Characteristics of Working Resistance of Hydraulic Supports in LWF

To quantitatively assess the influence of long-hole fracturing on the roof pressure of the 3-1302 LWF roof, a comparative analysis was conducted using pressure monitoring results of the 3-1802 LWF. As illustrated in Figure 10, the 3-1802 LWF exhibits extensive pressure distribution across the entire face, characterized by prolonged loading durations and irregular pressure step intervals during mining. During periodic weighting, the average step distance is approximately 16 m. The affected range of incoming pressure extends to about 20 m, with a peak intensity of approximately 41 MPa. As shown in Figure 10b, the 3-1302 LWF demonstrates a more uniform and dispersed pressure distribution across the face. The weighting step intervals are evenly distributed during mining. The initial weighting occurs when the LWF advances about 81 m, during which support pressure at positions #30–#40 and #60–#70 increases, with an average working resistance of about 35.81 MPa. During periodic weighting, the step distance is approximately 12 m, about 25% shorter than that of the 3-1802 LWF. The influence range of the periodic weighting is roughly 15 m, representing a 25% reduction compared with the 3-1802 LWF. The peak pressure intensity is around 32 MPa, which is approximately 21.95% lower than that of the 3-1802 LWF.
The monitoring results show that the support pressure distribution in the 3-1302 LWF reflects fracture development throughout the entire roof under the influence of long-hole HF. Consequently, the integrity of the OLS structure is significantly weakened. This indicates that roof fracturing effectively transforms the OLS above the LWF from a rigid structure into a more flexible one, thereby altering how its self-weight stress is transferred and distributed, thereby reducing the static load borne by the working face. After fracturing, the periodic weighting step distance becomes shorter and more uniform. With the increase in the number of weighting cycles, the average pressure intensity decreases, and small-scale cycles dominate, which markedly reduces the magnitude of instantaneous dynamic loads during roof breakage, which is relatively consistent with the research results of the reference [36]. Since rockbursts and mining tremors are dynamic loads, the application of long-hole fracturing provides an effective means to weaken the loading environment and substantially lower the risk of such dynamic hazards.

5.3. AE Monitoring Results Analysis

The daily variations in AE energy and frequency monitored by four probes in the two roadways of the 3-1802 LWF are shown in Figure 11. During an advancing distance of 706 m, the maximum daily AE energy and frequency recorded by the probes were as follows: probe #1 detected 0~3.80 × 106 J and 0~1783 events; probe #2 detected 0~4.80 × 105 J and 0~1611 events, probe #7 detected 0~2.02 × 107 J and 0~9581 events, and probe #8 detected 0~9.47 × 105 J and 0~971 events. Notably, during the periods corresponding to initial roof weighting single-goaf stage influence and double-goaf stage influence, both the daily AE energy and frequency exhibited marked increases. These results indicate that the evolution of AE energy and frequency is closely related to the intensity of roof breakage and movement in the LWF, suggesting that AE monitoring can effectively characterize the dynamic activity of the roof strata.
The daily variations in AE energy and frequency monitored by four probes in the two roadways of the 3-1302 LWF are presented in Figure 12. During an advancing distance of 706 m, the maximum daily AE energy and frequency recorded were as follows: probe #9 detected 0~5.14 × 107 J and 0~70,562 events; probe #10 AE detected 0~1.40 × 107 J and 0~27,991 events; probe #11 detected 0~2.24 × 106 J and 0~12,361 events, probe #12 detected 0~1.73 × 106 J and 0~3589 events. Notably, probes #9 and #10, located in the auxiliary transportation roadway adjacent to the 3-1301 goaf, recorded significantly higher AE energy and frequency compared with probes #11 and #12 installed in the belt transportation roadway. This indicates that OLS in the vicinity of the 3-1301 goaf experienced more frequent breakage and movement during mining.
In summary, the maximum daily AE energy and frequency at the 3-1802 LWF reached 2.02 × 107 J and 9581 events respectively, whereas at the3-1302 LWF they increased to 5.14 × 107 J and 70,562 events. Relative to the 3-1802 LWF, the AE daily energy and frequency at the 3-1302 LWF rose by 154% and 636% following the application of long-hole HF and roof pressure relief. These results indicate that HF promotes the generation of micro-fractures within the THOS, thereby weakening the integrity of the OLS. Consequently, stress concentration and energy accumulation in the roof are reduced, effectively alleviating the severity of dynamic ground pressure manifestations.

5.4. MS Monitoring Results Analysis

5.4.1. Comparative Analysis of the Number of MSE

To analyze the weakening effect of long-hole fracturing on the OLS of the 3-1302 LWF roof, the number and energy levels of MSE within a 706 m mining range were compared with 3-1802 LWF and 3-1302 LWF, as shown in Figure 13 and Table 2. During the mining process of the 3-1802 LWF without implementing long-hole HF, relatively fewer MSE were recorded, amounting to only 28.62% of those detected in the 3-1302 LWF. This indicates the dominant controlling effect of HF in bearing overburden load and guiding overall fracture and caving behavior. HF induced extensive fracture development events, effectively weakening the roof strata. In the 3-1802 LWF, MSE with magnitude class 2 accounted for the largest proportion (38.81%), followed by first-order level events (approximately 35.54%). Events above magnitude class 5 constituted only 0.15%, indicating that surrounding rock activities in the 3-1802 panel were dominated by low-energy microseismicity (second-order level events and below). In contrast, following the application of longhole HF in the 3-1302 LWF, second-order level events represented the majority (59.16%), with first-order level events comprising about 18.73%. Events above fourth-order level accounted for only 0.46%, demonstrating that moderate-energy second-order level events became predominant after fracturing treatment. This shift can be attributed to the release of accumulated elastic energy and sufficient internal crack propagation induced by HF. As a result, the rock deformation caused by the combined mining-induced and self-weight stresses could no longer accumulate significant elastic energy, leading to a mitigated risk of high-energy seismic events [39].

5.4.2. Evolution Characteristics of Roof Cracks Based on MS Daily Energy and Frequency

The variations in daily MS energy, daily MS frequency, linear-meter MS energy, and linear-meter MS frequency at comparable mining distances for 3-1802 and 3-1302 LWFs are presented in Figure 14. As shown, all four parameters fluctuate repeatedly during the advancement process in both LWFs, exhibiting broadly similar trends. These fluctuations are directly related to the periodic fracturing behavior of the OLS above the LWF. When large-scale roof failure occurs, substantial energy is released, leading to an increase in daily energy and linear-meter MS energy. Conversely, during intervals of roof stability, these parameters decrease correspondingly.
Compared with the 3-1802 LWF, the 3-1302 LWF has undergone pressure relief treatment on the THOS, enabling timely breakage and collapse of the roof during mining. Before the initial weighting stage, roof-breaking movements were more frequent, resulting in relatively high MS energy and frequency. This indicates that the roof was sufficiently pre-cracked, allowing fracture energy to be released in advance, thereby avoiding the formation of large-area hanging roofs. Consequently, the release of MS energy during the period weighting at the 3-1302 LWF was significantly reduced, and both MS energy and frequency exhibited a declining trend. In contrast, at the 3-1802 LWF, where no fracturing was performed, the initial weighting stage was accompanied by increased MS energy and frequency. This suggests that intensive roof fracturing during the initial weighting stage is unfavorable for effective roof control.
After the initial pressure on the LWF, the THOS undergoes periodic collapse, leading to fluctuations in MSE energy and frequency. As the LWF gradually enters the influence range of the single-goaf stage, the 3-1802 LWF exhibits an increasing trend in MS energy and frequency, reflecting frequent roof breakage. In contrast, the 3-1302 LWF, which underwent long-hole fracturing, shows a decreasing trend in MS daily energy and linear meter energy. Quantitatively, the daily frequency of MSE decreased by approximately 20%, while the frequency of linear-meter MSE decreased by about 70%. This indicates that the energy generated by roof-breaking was released in advance, and subsequent roof-breaking intensity was significantly weakened. Such behavior is favorable for mitigating the severity of mining pressure manifestations during the single-goaf stage period.
After the LWF enters the single-side square stage, the mining space expands further, leading to enhanced OLS movement and a corresponding increase in microseismic energy and frequency. When entering the double-goaf stage influence range, the MS daily energy and linear-meter energy of the 3-1302 LWF reached their maximum values since the onset of mining, indicating intense roof-breaking and substantial energy releases. This behavior is closely linked to the deep burial depth of the 3-1302 LWF and the presence of THOS in higher roof layers. The enlargement of the extraction space promotes delayed fracturing of these thicker and harder strata, resulting in significant energy release. By comparison, the 3-1802 LWF showed a more consistent increase in MS energy during this stage, whereas in the 3-1302 LWF, only localized points exhibited notable energy surges. Overall, during the double-goaf stage period, the MS energy of the 3-1302 LWF did not increase markedly, while its MS frequency exhibited only a slight rise, demonstrating that long-hole fracturing effectively weakened large-scale roof instability despite the presence of deep and hard strata.

5.4.3. The Spatial Distribution Pattern of MS Activity Under the Influence of HF

To visually compare the distribution ranges of MSE in 3-1302 LWF and 3-1802 LWF, spatial distribution maps of MSE were plotted, as shown in Figure 15. From Figure 15a, it can be observed that the density of MSE in the roof of 3-1802 LWF is relatively low, dominated mainly by second-order level events and third-order level events. Influenced by the adjacent goaf of 3-1801 LWF, MSE are primarily concentrated near the goaf side and mostly occur ahead of the LWF. In contrast, Figure 15c reveals that 3-1302 LWF exhibits a higher density of MSE, most of which involve energy levels below 1000 J. Among these, events around 1000 J are mainly distributed asymmetrically within the goaf area. This pattern is primarily attributed to the application of longhole HF in the THOS, which weakened the rock mass. As a result, the strata fractured and caved on time during mining, leading predominantly to low-energy MSE.
As shown in Figure 15b, MSE in 3-1802 LWF are largely confined within a range of approximately 70 m above the coal seam, indicating limited vertical propagation. This is because during mining, only lower rock layers underwent significant fracture, while the mid-to-upper thick-hard strata experienced minimal fracturing, effective stress transfer, and limited energy release, owing to their high load-bearing capacity. Under the influence of mining-induced and self-weight stresses, the roof strata underwent bending deformation and accumulated elastic energy. When local stress exceeded the strength limit, sudden rupture occurred, releasing substantial energy and significantly affecting ground pressure manifestations [39]. In comparison, Figure 15d indicates that MSE in 3-1302 LWF extended up to 300 m above the coal seam, with a high density of events near the fractured zone. Although the fracture density decreased with increasing height, the overall vertical development of MSE was more extensive compared to the unfractured roof in Figure 15b. The enhanced propagation of MS activity facilitated the timely fracturing of higher THOS. This process allowed the release of high stress and elastic energy stored within these strata, mitigating the dynamic loading effects caused by large-scale hanging and sudden ruptures of THOS. Consequently, the weighting intensity during mining was effectively reduced.

5.5. Evolution Characteristics of SFS

Based on the monitoring results, a comparative analysis of the SFS evolution during the advancement of 3-1802 LWF and 3-1302 LWF was conducted, as shown in Figure 16. As illustrated in Figure 16a, when 3-1802 LWF advanced to approximately 700 m, the maximum surface subsidence reached 2028 mm, corresponding to a subsidence factor of about 0.36. In contrast, Figure 16b shows that under the same advance distance, 3-1302 LWF exhibited a maximum surface subsidence of 1411 mm, with a subsidence factor of approximately 0.22. The maximum surface subsidence in 3-1302 LWF was only 69.58% of that in 3-1802 LWF, which is relatively consistent with the research results of the reference [40]. This reduction can be attributed to the weakening effect of HF on the OLS, which resulted in more gradual and controlled fracturing rather than instantaneous large-scale failure. Meanwhile, timely collapse of rock layers can effectively fill the goaf and suppress the development of subsidence space in overlying rock layers.
In addition, the surface subsidence curves in 3-1802 LWF have a large jump at position of 300 m at 512 m advance, while those in 3-1302 LWF vary relatively even or smooth. This is attributed to the load-bearing effect of the THOS, which possesses high strength and exhibits delayed caving. During the advance of the LWF, elastic energy accumulates extensively. Upon reaching its breaking interval, the energy is released instantaneously, leading to severe fracturing of the overlying strata and consequently causing intense surface subsidence. HF can induce the earlier caving of THOS, allowing the pressure arch to develop promptly and propagate deeper into the surrounding rock mass. The load-bearing capacity of the pressure arch led to delayed fracturing of the THOS. As a consequence, during the subcritical mining stage, SFS was significantly mitigated.

6. Conclusions

This study conducted a comprehensive field investigation into directional long borehole hydraulic fracturing for roof pressure relief at the Hongqinghe Coal Mine’s 3-1302 longwall face. By implementing an integrated surface-underground microseismic monitoring network and a multi-parameter analysis framework, the pressure-relief effects were quantitatively evaluated. The principal conclusions are as follows:
(1)
Establishment of a Multi-Dimensional Evaluation System: A three-dimensional chain monitoring system was successfully established, integrating support pressure response, spatiotemporal evolution of microseismic events, and surface subsidence laws. This system enables a comprehensive and quantitative assessment of the HFRPRT effectiveness, moving beyond single-parameter evaluations to provide a holistic view of the roof behavior after fracturing.
(2)
Significant Weakening of Thick-Hard Overlying Strata and Alleviation of Dynamic Pressure: The application of directional hydraulic fracturing successfully induced large-scale weakening of the THOS. This intervention transformed the overburden stress transfer mechanism from a rigid, large-scale cantilever structure to a more flexible, segmented one. Consequently, the periodic weighting interval at the 3-1302 LWF was reduced to approximately 12 m (a 25% reduction compared to the non-fractured 3-1802 LWF), the influencing range of weighting was shortened to about 15 m (25% reduction), and the peak weighting intensity was lowered to around 32 MPa (21.95% reduction). This confirms that HFRPRT effectively mitigates the intensity of mining-induced dynamic pressure.
(3)
Promotion of Micro-Fracturing and Prevention of Energy Accumulation: The analysis of Acoustic Emission (AE) and Microseismic (MS) data provides critical insights into the fracturing mechanism. Following HFRPRT, the daily AE energy and event count increased dramatically by 154% and 636%, respectively. This signifies that hydraulic fracturing actively promoted the propagation of internal micro-fractures within the THOS before large-scale mining-induced stresses occurred. The MS monitoring further revealed a shift in the energy distribution pattern, with lower-energy second-order level events becoming predominant (59.16%), while the proportion of high-energy events (above fourth-order) was minimal (0.46%). This indicates a transition from catastrophic, high-energy releases to frequent, low-energy ruptures, substantially reducing the risk of dynamic hazards like rockbursts.
(4)
Alteration of Overburden Failure Patterns and Mitigation of Surface Subsidence: The spatial distribution of MSE demonstrated that the fracturing treatment significantly enhanced the vertical extent of rock failure, with events propagating up to 300 m above the coal seam. This ensured the timely caving of higher-level THOS, facilitating the release of high elastic energy in a controlled manner. As a result, the load-bearing capacity of the pressure arch was altered, leading to a more gradual overburden failure process. This was directly evidenced by the mitigation of surface subsidence, where the maximum SFS at the 3-1302 LWF was only 69.58% of that observed at the 3-1802 LWF for the same advance distance.
In summary, this research verifies that directional long borehole HFRPRT is a highly effective technology for preventing dynamic disasters in mining conditions under THOS. The proposed integrated monitoring and multi-indicator evaluation methodology offers a robust framework for optimizing fracturing design parameters and quantitatively assessing their efficacy in similar geotechnical settings, thereby contributing significantly to the advancement of coal mine safety and disaster prevention technologies.

Author Contributions

Methodology, S.H.; Validation, H.Z.; Resources, H.Z.; Data curation, S.H. and H.Z.; Writing—original draft, S.H.; Writing—review and editing, C.Z.; Supervision, C.Z.; Funding acquisition, C.Z. All authors have read and agreed to the published version of the manuscript.

Funding

National Natural Science Foundation of China, 52474161; Postdoctoral Research Foundation of China, 2025T180509; Science and Technology Innovation Fund of China Coal Technology and Engineering Group Mining Research Institute, KCYJY-2023-MS-05.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

Author Shuwei Hu was employed by the Inner Mongolia Yitai Coal Co., Ltd. Inner Mongolia. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. Deng, Q.; Zhao, F.; Li, H.; Yin, J.; Zhang, T.; Wei, J. Technology and practice of the roof-caving of hydraulic fracturing in a fully mechanized caving face. Therm. Sci. 2021, 25, 2117–2126. [Google Scholar] [CrossRef]
  2. Ren, Z.; Zhang, C.; Wang, Y.; Yang, S.; Li, Q. Collaborative movement characteristics of overlying rock and loose layer based on block–particle discrete-element simulation method. Int. J. Coal Sci. Technol. 2025, 12, 17. [Google Scholar] [CrossRef]
  3. Jiang, Y.; Pan, Y.; Jiang, F.; Dou, L.; Ju, Y. State of the art review on mechanism and prevention of coal bumps in China. J. China Coal Soc. 2014, 39, 205–213. [Google Scholar] [CrossRef]
  4. Dou, L.; He, J.; Cao, A.Y.; Gong, S.Y.; Cai, W. Rock burst prevention methods based on theory of dynamic and static combined load induced in coal mine. J. China Coal Soc. 2015, 40, 1469–1476. [Google Scholar] [CrossRef]
  5. Li, X.; Chen, S.; Li, Z.; Wang, E. Rockburst mechanism in coal rock with structural surface and the microseismic (MS) and electromagnetic radiation (EMR) response. Eng. Fail. Anal. 2021, 124, 105396. [Google Scholar] [CrossRef]
  6. Li, X.; Wang, E.; Li, Z.; Liu, Z.; Song, D.; Qiu, L. Rock burst monitoring by integrated microseismic and electromagnetic radiation methods. Rock Mech. Rock Eng. 2016, 49, 4393–4406. [Google Scholar] [CrossRef]
  7. Lu, Y.; Han, L.; Wu, K.; Lu, L.; Tian, W.; Cui, Z. Characteristics of stress sources and comprehensive control strategies for surrounding rocks of gob-side driving entry in extra thick coal seam. J. China Univ. Min. Technol. 2024, 52, 238–249. [Google Scholar] [CrossRef]
  8. Huang, X.; Zhang, C.; Ren, Z. Parameter determination and effect evaluation of gob-side entry retaining by directional roof cutting and pressure releasing. Eng. Fail. Anal. 2024, 156, 107847. [Google Scholar] [CrossRef]
  9. Zhang, F.; Wang, X.; Bai, J.; Wu, B.; Wang, G.; Li, J.; Chen, D. Study on hydraulic fracture propagation in hard roof under abutment pressure. Rock Mech. Rock Eng. 2022, 55, 6321–6338. [Google Scholar] [CrossRef]
  10. Sun, R.; Xia, Y.; Gao, J. Study on anti-impact effect of hydraulic fracturing for long holes in medium and high thick hard roof. Saf. Coal Mines 2023, 54, 69–77. [Google Scholar] [CrossRef]
  11. Xu, C.; Yuan, L.; Cheng, Y.; Wang, K.; Zhou, A.; Shu, L. Square-form structure failure model of mining-affected hard rock strata: Theoretical derivation, application and verification. Environ. Earth Sci. 2016, 75, 1180. [Google Scholar] [CrossRef]
  12. Li, N.; Wang, E.; Ge, M.; Liu, J. The fracture mechanism and acoustic emission analysis of hard roof: A physical modeling study. Arab. J. Geosci. 2015, 8, 1895–1902. [Google Scholar] [CrossRef]
  13. Ma, G.; Zhang, F.; Liu, X.; Feng, D.; Zhang, P. Experimental study of impact of crustal stress on fracture pressure and hydraulic fracture. Rock Soil Mech. 2016, 37, 216–222. [Google Scholar] [CrossRef]
  14. Ren, Q.; Zhang, C.; Wu, G.; Zhang, H.; Gao, S.; Sun, Z. Hydraulic fracture initiation and propagation in deep coalbed methane reservoirs considering weak plane: CT scan testing. Gas Sci. Eng. 2024, 125, 205286. [Google Scholar] [CrossRef]
  15. Zhang, C.; Wang, X.; Han, P.; Zhang, T.; Zhang, L.; Wang, F. Acoustic emission and splitting surface roughness of sandstone in a Brazilian splitting test under the influence of water saturation. Eng. Geol. 2024, 329, 107369. [Google Scholar] [CrossRef]
  16. Cordero, J.A.R.; Sanchez, E.C.M.; Roehl, D.; Pereira, L.C. Hydro-mechanical modeling of hydraulic fracture propagation and its interactions with frictional natural fractures. Comput. Geo Tech. 2019, 111, 290–300. [Google Scholar] [CrossRef]
  17. Makoto, N.; Chen, Y.; Nishihara, K.; Yamamoto, K.; Yano, S.; Watanabe, S.; Morishige, Y.; Kawakata, H.; Akai, T.; Kurosawa, I.; et al. Monitoring hydraulically-induced fractures in the laboratory using acoustic emissions and the fluorescent method. Int. J. Rock Mech. Min. Sci. 2018, 104, 53–63. [Google Scholar] [CrossRef]
  18. Wu, C.; Gong, F.; Luo, Y. A new quantitative method to identify the crack damage stress of rock using AE detection parameters. Bull. Eng. Geol. Environ. 2021, 80, 519–531. [Google Scholar] [CrossRef]
  19. Li, Z.; Jia, C.; Yang, C.; Zeng, Y.; Guo, Y.; Heng, S.; Wang, L.; Hou, Z. Propagation of hydraulic fissures and bedding planes in hydraulic fracturing of shale. Chin. J. Rock Mech. Eng. 2015, 34, 12–20. [Google Scholar] [CrossRef]
  20. Wang, H. Hydraulic fracture propagation in naturally fractured reservoirs: Complex fracture or fracture networks. J. Nat. Gas Sci. Eng. 2019, 68, 102911. [Google Scholar] [CrossRef]
  21. Zhao, S.; Zhang, G.; Chai, H.; Su, Z.; Liu, Y.; Zhang, X. Mechanism of rockburst prevention for directional hydraulic fracturing in deep-hole roof and effect test with multi-parameter. J. Min. Saf. Eng. 2019, 36, 1247–1255. [Google Scholar] [CrossRef]
  22. Guo, T.; Zhang, S.; Qu, Z.; Zhou, T.; Xiao, Y.; Gao, J. Experimental study of hydraulic fracturing for shale by stimulated reservoir volume. Fuel 2014, 128, 373–380. [Google Scholar] [CrossRef]
  23. Gao, F. Influence of hydraulic fracturing of strong roof on mining-induced stress-insight from numerical simulation. J. Min. Strat. Control Eng. 2021, 3, 023032. [Google Scholar] [CrossRef]
  24. Ren, X.; Zhou, L.; Li, H.; Lu, Y. A three-dimensional numerical investigation of the propagation path of a two-cluster fracture system in horizontal wells. J. Pet. Sci. Eng. 2019, 173, 1222–1235. [Google Scholar] [CrossRef]
  25. Zhang, H.; Zhou, C.; He, J.; Yang, Q.; Ye, Z.; Zhang, S.; Rui, X.; Zhan, Y.; Ren, B. A coupled simulation method of hydraulic fracturing for relieving mining pressure under hard roof based on DEM method. J. China Soc. 2025, 50, 39–49. [Google Scholar] [CrossRef]
  26. Wu, Y.; Kang, H. Pressure relief mechanism and experiment of directional hydraulic fracturing in reused coal pillar roadway. J. China Coal Soc. 2017, 42, 1130–1137. [Google Scholar] [CrossRef]
  27. Feng, Y.; Kang, H. Hydraulic fracturing initiation and propagation and propagation. Chin. J. Rock Mech. Eng. 2013, 32, 3169–3179. [Google Scholar]
  28. Huang, X.; Zhang, C.; Wang, Y.; He, J. Failure analysis of flexible formwork concrete wall in gob-side entry and its control measures with roof cutting technology. J. Geophys. Eng. 2025, 22, 909–923. [Google Scholar] [CrossRef]
  29. Liu, J.; Wu, N.; Si, G.; Zhao, M. Experimental study on mechanical properties and failure behaviour of the pre-cracked coal-rock combination. Bull. Eng. Geol. Environ. 2021, 80, 2307–2321. [Google Scholar] [CrossRef]
  30. Li, Y.; Liu, J.; Yu, Q. Patterns of influence of parallel rock fractures on the mechanical properties of the rock–coal combined body. Sustainability 2022, 14, 13555. [Google Scholar] [CrossRef]
  31. Liu, C.; Liu, J. Principle and application of stress transfer of weak structure body in coal-rock mass cracking. J. Min. Saf. Eng. 2022, 39, 359–369. [Google Scholar] [CrossRef]
  32. Zhang, B.; Song, W.; Wang, Y.; Li, Z.; Huang, H.; Lin, Z.; Yao, B. Design and field evaluation of hydraulic fracturing bore holes for terminal mining faces. Sci. Rep. 2024, 14, 21933. [Google Scholar] [CrossRef] [PubMed]
  33. Shi, Y.; Wang, Z.; Cheng, L.; Xu, S. Application and effectiveness evaluation of hydraulic fracturing for roadway pressure relief in coal mines. Chin. J. Rock Mech. Eng. 2025, 44, 459–471. [Google Scholar] [CrossRef]
  34. Kang, H.; Jiang, P.; Yang, J.; Wang, Z.; Yang, H.; Liu, Q.; Wu, Y.; Li, W.; Gao, F.; Jiang, Z.; et al. Roadway soft coal control technology by means of grouting bolts with high pressure-shotcreting in synergy in more than 1000 m deep coal mines. J. China Coal Soc. 2021, 46, 747–762. [Google Scholar] [CrossRef]
  35. Kang, H.; Feng, Y. Hydraulic fracturing technology and its applications in strata control in underground coal mines. Coal Sci. Technol. 2017, 45, 1–9. [Google Scholar] [CrossRef]
  36. Yu, B.; Duan, H.F. Study of roof control by hydraulic fracturing in full-mechanized caving mining with high strength in extra-thick coal layer. Chin. J. Rock Mech. Eng. 2014, 33, 778–785. [Google Scholar] [CrossRef]
  37. Ju, J.; Xu, J. Surface stepped subsidence related to top-coal caving longwall mining of extremely thick coal seam under shallow cover. Int. J. Rock Mech. Min. Sci. 2015, 78, 27–35. [Google Scholar] [CrossRef]
  38. Pan, C.; Zuo, Y.; Song, X.; Wen, P.; Han, Y. Effect of Man-Made Weak Plane on Hydraulic Fracturing of Hard and Stable Roof. Chin. J. Undergr. Space Eng. 2016, 12, 783–788. [Google Scholar] [CrossRef]
  39. Zhao, Y.; He, P.; Zhang, Y.; Wang, C. A new criterion for a toughness-dominated hydraulic fracture crossing a natural frictional interface. Rock Mech. Rock Eng. 2019, 52, 2617–2629. [Google Scholar] [CrossRef]
  40. Zhang, Y.; Xiao, J.; Li, J.; Li, Y. Research on low-damage mining method and mechanism of overlying thick and hard rock strata structure regulation. J. Min. Strat. Control Eng. 2024, 6, 34–46. [Google Scholar] [CrossRef]
Processes 14 00118 g001
Figure 1. Layout of the 3-1302 LWF.
Figure 1. Layout of the 3-1302 LWF.
Processes 14 00118 g001
Processes 14 00118 g002
Figure 2. Borehole Columnar Section.
Figure 2. Borehole Columnar Section.
Processes 14 00118 g002
Processes 14 00118 g003
Figure 3. Fracturing Drilling Site and Borehole Layout Plan.
Figure 3. Fracturing Drilling Site and Borehole Layout Plan.
Processes 14 00118 g003
Processes 14 00118 g004
Figure 4. Fracturing Drilling Site and Borehole Layout Sectional View.
Figure 4. Fracturing Drilling Site and Borehole Layout Sectional View.
Processes 14 00118 g004
Processes 14 00118 g005
Figure 5. Staged Fracturing Tool Assembly Schematic.
Figure 5. Staged Fracturing Tool Assembly Schematic.
Processes 14 00118 g005
Processes 14 00118 g006
Figure 6. AE monitoring system (a) Structural diagram of the ARES-5/E AE monitoring system, (b) Layout of AE Monitoring Network for 3-1302 LWF.
Figure 6. AE monitoring system (a) Structural diagram of the ARES-5/E AE monitoring system, (b) Layout of AE Monitoring Network for 3-1302 LWF.
Processes 14 00118 g006
Processes 14 00118 g007
Figure 7. MS monitoring system: (a) Flowchart of the ARAMIS M/E MS monitoring system, (b) Layout of MS monitoring network for 3-1302 LWF.
Figure 7. MS monitoring system: (a) Flowchart of the ARAMIS M/E MS monitoring system, (b) Layout of MS monitoring network for 3-1302 LWF.
Processes 14 00118 g007
Processes 14 00118 g008
Figure 8. Layout of SFS Monitoring (a) Layout of SFS Monitoring Points for LWF 3-1802, (b) Layout of SFS Monitoring Points for 3-1302 LWF.
Figure 8. Layout of SFS Monitoring (a) Layout of SFS Monitoring Points for LWF 3-1802, (b) Layout of SFS Monitoring Points for 3-1302 LWF.
Processes 14 00118 g008
Processes 14 00118 g009
Figure 9. Evolution Curves of Borehole Water Pressure and Flow Rate over Time (a) Drill hole number #1, (b) Drill hole number #2, (c) Drill hole number #3, (d) Drill hole number #4.
Figure 9. Evolution Curves of Borehole Water Pressure and Flow Rate over Time (a) Drill hole number #1, (b) Drill hole number #2, (c) Drill hole number #3, (d) Drill hole number #4.
Processes 14 00118 g009
Processes 14 00118 g010
Figure 10. Cloud Map of Pressure Monitoring Results for LWF Support (a) 3-1802 LWF, (b) 3-1302 LWF.
Figure 10. Cloud Map of Pressure Monitoring Results for LWF Support (a) 3-1802 LWF, (b) 3-1302 LWF.
Processes 14 00118 g010
Processes 14 00118 g011
Figure 11. Changes in Daily Energy and Frequency of AE at LWF 3-1802 (a) #1 Probe, (b) #2 Probe, (c) #7 Probe, (d) #8 Probe.
Figure 11. Changes in Daily Energy and Frequency of AE at LWF 3-1802 (a) #1 Probe, (b) #2 Probe, (c) #7 Probe, (d) #8 Probe.
Processes 14 00118 g011
Processes 14 00118 g012
Figure 12. Changes in Daily Energy and Frequency of AE at LWF 3-1302 (a) #9 Probe, (b) #10 Probe, (c) #11 Probe, (d) #12 Probe.
Figure 12. Changes in Daily Energy and Frequency of AE at LWF 3-1302 (a) #9 Probe, (b) #10 Probe, (c) #11 Probe, (d) #12 Probe.
Processes 14 00118 g012
Processes 14 00118 g013
Figure 13. Energy level distribution of MSE (a) 3-1802 LWF, (b) 3-1302 LWF.
Figure 13. Energy level distribution of MSE (a) 3-1802 LWF, (b) 3-1302 LWF.
Processes 14 00118 g013
Processes 14 00118 g014
Figure 14. MS daily energy and frequency (a) Daily energy variation in MSE, (b) Daily frequency variation in MSE, (c) Energy variation in linear meter MSE, (d) Variation in MSE frequency in linear meters.
Figure 14. MS daily energy and frequency (a) Daily energy variation in MSE, (b) Daily frequency variation in MSE, (c) Energy variation in linear meter MSE, (d) Variation in MSE frequency in linear meters.
Processes 14 00118 g014
Processes 14 00118 g015
Figure 15. Spatial distribution of MSE (a) Plan view of LWF 3-1802, (b) Sectional view of LWF 3-1802, (c) Plan view of LWF 3-1302, (d) Sectional view of LWF 3-1302.
Figure 15. Spatial distribution of MSE (a) Plan view of LWF 3-1802, (b) Sectional view of LWF 3-1802, (c) Plan view of LWF 3-1302, (d) Sectional view of LWF 3-1302.
Processes 14 00118 g015
Processes 14 00118 g016
Figure 16. SFS Curve: (a) Evolution patterns of SFS in LWF 3-1802, (b) Evolution patterns of SFS in LWF 3-1302.
Figure 16. SFS Curve: (a) Evolution patterns of SFS in LWF 3-1802, (b) Evolution patterns of SFS in LWF 3-1302.
Processes 14 00118 g016
Table 1. Roof Strike Long Borehole Design Parameters.
Table 1. Roof Strike Long Borehole Design Parameters.
Drill Hole NumberDesign Length (m)Horizontal Distance 3-1302 Auxiliary Transportation Channel Production Assistance (m)Final Hole Height (m)Turning Length (m)Horizontal Hole Length (m)Fracturing Section Length (m)Number of Segments
#1680566828040048016
#26501195023042051017
#36501795520045051017
#46802426828040048016
#5620566818044054018
#66501195023042057019
#76501795523042057019
#86202426818044054018
Table 2. Comparison of MSE in LWF 3-1802 and 3-1302.
Table 2. Comparison of MSE in LWF 3-1802 and 3-1302.
Coal FaceMonitoring ItemsTotal<10 J101 J102 J103 J104 J105 J106 J
3-1802Number of MSE/each131492467510243020
Proportion of MSE/7%35.54%38.81%18.49%00.15%0
3-1302Number of MSE/each459123286027167512183
Proportion of MSE/5.05%18.73%59.16%16.36%0.46%0.17%0.07%
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Hu, S.; Zhang, H.; Zhang, C. Comprehensive Evaluation of Directional Hydraulic Fracturing for Roof Pressure Relief and Disaster Prevention Based on Integrated Multi-Parameter Monitoring. Processes 2026, 14, 118. https://doi.org/10.3390/pr14010118

AMA Style

Hu S, Zhang H, Zhang C. Comprehensive Evaluation of Directional Hydraulic Fracturing for Roof Pressure Relief and Disaster Prevention Based on Integrated Multi-Parameter Monitoring. Processes. 2026; 14(1):118. https://doi.org/10.3390/pr14010118

Chicago/Turabian Style

Hu, Shuwei, Hualei Zhang, and Cun Zhang. 2026. "Comprehensive Evaluation of Directional Hydraulic Fracturing for Roof Pressure Relief and Disaster Prevention Based on Integrated Multi-Parameter Monitoring" Processes 14, no. 1: 118. https://doi.org/10.3390/pr14010118

APA Style

Hu, S., Zhang, H., & Zhang, C. (2026). Comprehensive Evaluation of Directional Hydraulic Fracturing for Roof Pressure Relief and Disaster Prevention Based on Integrated Multi-Parameter Monitoring. Processes, 14(1), 118. https://doi.org/10.3390/pr14010118

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop