Search Results (96)

Under deep, high-intensity mining conditions, a high mineral pressure develops at the working face, which can easily cause floor heave deformation of the roadway. In this paper, with the geological conditions of Buertai coal mine as the background, through on-site monitoring and numerical simulation, the mechanism of strong dynamic pressure roadway floor heave is clarified and a cooperative control method for roadway floor heave deformation is proposed. The main conclusions are as follows: (1) The overall strength of the floor of this strong dynamic pressure roadway is low, which can easily cause roadway floor heave, and on-site multivariate monitoring of the mine pressure is carried out, which clarifies the evolution law of the mine pressure of the mining roadway and along-the-airway roadway. (2) Combined with FLAC3D numerical simulation software, we analyze the influence of coal seam depth and floor lithology on the stability of the roadway floor and find that both have a significant influence on the stability of the roadway. Under the condition of high-intensity mining, the floor will deteriorate gradually, forming a wide range of floor heave areas. (3) Based on the deformation and damage mechanism of the roadway floor, a synergistic control method of “roof cutting and pressure relief + floor anchor injection” is proposed and various technical parameters are designed. An optimized design scheme is designed for the control of floor heave in Buertai coal mine. Full article

In the Karaganda coal basin, deteriorating geomechanical conditions have been observed, including seam disturbances, diminished strength of argillite–aleurolite strata, water ingress, and pronounced floor heave, all of which markedly increase the labor intensity of maintaining developmental headings. The maintenance and operation of these entries for a reference coal yield of 1000 t necessitate 72–75 man-shifts, of which 90–95% are expended on mitigating ground pressure effects and restoring support integrity. Conventional heave control measures—such as relief drifts, slotting, drainage, secondary blasting, and the application of concrete or rock–bolt systems—deliver either transient efficacy or incur prohibitive labor and material expenditures while lacking unified methodologies for predictive forecasting and support parameter design. This study therefore advocates for an integrated framework that synergizes geomechanical characterization, deformation prognosis, and the tailored selection of reinforcement schemes (incorporating both sidewall and floor-anchoring systems with directed preloading), calibrated to seam depth, geometry, and lithological properties. Employing deformation state assessments to optimize reinforcement layouts for floor stabilization in coal mine workings is projected to curtail repair volumes by 30–40% whilst significantly enhancing operational safety, efficiency, and the punctuality of face preparation. Full article

Background/Objectives: Vibration foam rolling (VFR) has emerged as a popular intervention in sports and rehabilitation settings to enhance recovery and flexibility. This systematic review aimed to evaluate the effects of VFR on pain, fatigue, and range of motion (ROM) in individuals experiencing exercise-induced muscle fatigue and to assess its clinical applicability. Methods: A systematic literature search was conducted across five databases: PubMed, Cochrane Library, Embase, Web of Science, and CINAHL. Studies were included if they involved participants with muscle fatigue, applied VFR as an intervention, and measured outcomes related to pain, fatigue, or ROM. Methodological quality was assessed using the Joanna Briggs Institute critical appraisal tools. Results: Eight studies published between 2019 and 2024 met the inclusion criteria. VFR showed beneficial effects in reducing delayed onset muscle soreness, improving pressure pain threshold, and lowering subjective fatigue. Several studies also reported increased ROM in specific joints, including the hip and knee. However, findings across studies were inconsistent, particularly in physiological markers such as muscle oxygen saturation and blood flow parameters, where statistically significant differences were not always observed. Conclusions: VFR may offer potential benefits for pain relief, fatigue recovery, and ROM improvement in fatigued individuals. Nonetheless, its effects remain difficult to isolate from those of mechanical pressure and friction associated with foam rolling. Future studies with standardized intervention protocols and long-term follow-up are needed to clarify the independent role of vibration in recovery outcomes. Full article

To address the issue of rockburst in deep return airways caused by thick, hard sandstone roofs in the Hulusu Coal Mine, this study proposes a deep borehole pressure relief technique based on hydraulic fracturing. The goal is to proactively weaken the hard roof structure and effectively mitigate rockburst hazards. The research integrates numerical modeling, theoretical analytics, and field application to systematically delve into the unstable mechanism of deep hard rock and determine the crack propagation patterns and optimal borehole parameters. Engineering validation was carried out at the 21,103 mining face. Results indicate that when the borehole inclination is 45°, the spacing is 15 m, the diameter is 65 mm, the borehole depth is 24 m over the coal pillar (CP) and 30 m on the operating face, the pressure relief effect is optimal. This configuration effectively forms a pressure relief zone in the roof, significantly reduces surrounding rock stress concentration, and enhances structural stability. Field monitoring shows that the roof energy is released stably through crack propagation, effectively reducing the risk of rockburst. The proposed technique provides theoretical and engineering support for rockburst prevention in deep hard rock mining conditions. Full article

The characterization of the mechanical parameters of rock mass is a basic problem in the field of rock mechanics, and it is also an important basis for surrounding rock classification, stability analysis, and support design in underground engineering. Based on the engineering background of pressure relief drilling in Guotun Coal Mine, this paper carries out an engineering test while drilling. The numerical simulation method is used to explore the influence of different lithology rocks, different control conditions, and different confining pressure conditions on the parameters while drilling and to study the variation in drilling time, drilling depth, drilling rate, and revolution speed. The results show that under the same control conditions, the drilling rate of coal, mudstone, sandy mudstone, and siltstone are in the order of coal > mudstone > sandy mudstone > siltstone. For similar rock specimens, when the thrust is fixed, the drilling rate increases with the increase in the revolution speed, and when the revolution speed is fixed, the drilling rate increases with the increase in the thrust. When the rock specimen is in different confining pressure states, the drilling rate decreases with the increase in confining pressure, and the torque increases with the increase in confining pressure. This study provides a scientific basis for the realization of in situ rapid and effective measurement technology for the rock mechanical parameters of coal and rock mass, which is helpful for improving the measurement accuracy and efficiency and promoting the safe and efficient mining of coal mines. Full article

The COVID-19 pandemic raised global concerns about the shortage of ventilators and revealed the challenges of rapidly scaling up production to meet emergency needs. In response, numerous teams worldwide attempted to develop emergency and simple mechanical ventilators. Among these, the CoroVent ventilator was developed to meet the urgent need for ventilatory support in the Czech Republic. The aim of this study was to describe the innovative and simple design of the CoroVent emergency ventilator, evaluate its compliance with international safety and performance standards, verify its reliability under simulated clinical conditions, and demonstrate its suitability for use in crisis scenarios. CoroVent was designed with a focus on the clinical needs of patients with COVID-19 respiratory failure and to ensure safe ventilation while maintaining a simplified design. It features volume-controlled, pressure-limited mandatory ventilation and supports key adjustable parameters such as tidal volume, respiratory rate, inspiratory-to-expiratory time ratio, inspired oxygen fraction, and positive end-expiratory pressure (PEEP). The ventilator incorporates robust safety mechanisms, including alarms and a safety relief valve, to protect against excessive airway pressures. Results confirmed the ability to maintain consistent tidal volumes, stable PEEP, and precise pressure limitation over extended periods of use. The results showed that CoroVent met the essential international standards for accuracy, including those set by the UK Medicines and Healthcare products Regulatory Agency, U.S. Food and Drug Administration, and ISO 80601-2-12. Although production of these ventilators was stopped in 2021 as the Czech Republic managed the crisis and shortage of ventilators, the results validate their reliability as emergency ventilators and indicate their potential to support critical care needs in crisis situations. Full article

Based on considering the stress state distribution and potential failure surface of the specimen during uniaxial compression, the drilling parameters (layout, spacing, position) are set. Thoroughly understanding the influence of different drilling parameters on the pressure relief effect is conducive to reducing the occurrence of coal mine rock burst accidents. Through laboratory tests and numerical simulation tests under different drilling parameters, the influence laws of mechanical parameters, failure characteristics, AE characteristic parameters and energy evolution of specimens under different drilling parameters were studied. The pressure relief effect under different drilling parameters was evaluated by using the pressure relief effect evaluation index (X), and the best combination of drilling parameters was obtained. The results show the following: (1) Compared with the intact specimen, the peak strength of the drilling specimen is significantly reduced, and the drilling layout has the greatest influence on the mechanical properties, followed by the drilling spacing and drilling position. (2) Different drilling layouts will form different weak-strength surfaces in the specimen, and lead the expansion and penetration of cracks, resulting in different failure modes of the specimen. The stress distribution inside the specimen will affect the stress concentration around the borehole, finally affect the damage degree of the specimen. (3) Drilling can not only effectively reduce the energy accumulation capacity, but also enhance the degree of energy dissipation. The AE ringing counts and energy of the triangular-drilling specimens are the least. The AE ringing counts and energy decrease first and then increase with the increase in drilling spacing, and are the smallest at three times the drilling diameter. The AE ringing counts and energy increase gradually with the upward movement of the drilling position. (4) The optimal combination of drilling parameters was obtained by the test, and it was triangular-layout drilling, drilling spacing three times the diameter, and the drilling position in the middle of the specimen, and the value of the pressure relief effect evaluation index (X) was 65.41. The research results can provide some reference for the selection and optimization of drilling pressure relief parameters in rock burst mines. Full article

To address the risk of annular pressure relief channel blockage caused by solid deposition in the B and C annulus of deepwater wells, solid deposition tests were conducted on deepwater drilling fluid systems. The test results provided the solid settling heights of different drilling fluid systems and the post-settling solid seepage characteristics. Based on the parameters of solid seepage characteristics and considering the impact of solid deposition in annular fluids, a predictive analysis method for annular pressure buildup under seepage conditions was established, and case studies were performed. The results indicate that the settling height showed the following trend: oil-based drilling fluid > EZFLOW drilling fluid > HEM drilling fluid. In contrast, the post-settling solid permeability exhibited the opposite trend, EZFLOW drilling fluid > HEM drilling fluid > oil-based drilling fluid, with the maximum permeability reaching 2216 mD. Under the condition of solid deposition in annular fluids, as the viscosity of annular fluids decreases and the formation permeability and open-hole section length increase, the viscous forces of fluid flow decrease, and the seepage contact area with the formation increase, leading to an increase in annular fluid seepage flow. Reducing the viscosity of drilling fluids and increasing the open-hole section length of the cementing can enhance the pressure release capability of the B and C annulus in deepwater wells. However, due to the influence of solid deposition, the seepage flow rate is significantly lower than the pressure reduction rate under non-solid deposition conditions, and there is a risk of pressure relief failure after solid settlement. Full article

The elastic valve plate and guide flow disc are key components that influence parameters such as opening and pressure difference of pilot-relief valve, which are also the core components enabling continuous damping adjustment in valve-controlled continuously variable dampers. Based on deformation characteristics of elastic valve plate and various structural types of guide flow disc, this paper reveals the impact of structural types of guide flow disc and design parameters of elastic valve plate on the performance of pilot-relief valve and obtains the relationship curves between opening pressure, pressure difference and opening of relief valve versus structural types and the angle, width and the number of arc plates of elastic valve plate. It shows that the pressure difference of the relief valve reaches maximum with min angle, max width, most arc plates and irregular-shaped type, and the opening reaches maximum with max angle, min width, fewest plates and round hole type. By adjusting structural types of guide flow disc and design parameters of elastic valve plate, the pressure difference and opening of the relief valve can be precisely controlled, providing theoretical support for the precise design of pilot-relief valve and the optimization of damping characteristics. Full article

Roof cutting by dense drilling is one of the main methods of gob-side entry retaining. Taking the 203 working face of the Ruineng Coal Mine as the engineering background, a mechanical model is established to clarify the roof breaking mechanism. Numerical simulation is conducted to analyze the roof cutting effects of different parameters, and reasonable roof cutting parameters are identified. The results show that: ① The increase in roof cutting height is beneficial to roof cutting, but excessive height will cause stress concentration of the ‘key structure’ on the side of the coal pillar. ② It is difficult to cut off the roof when the roof cutting angle is too small, and the cantilever length of the roof increases when the roof cutting angle is too large. ③ The larger the borehole spacing, the smaller the plastic penetration rate between boreholes. The optimal parameters of roof cutting are determined as follows: roof cutting height 8 m; roof cutting angle 15°; aperture size 48 mm; hole spacing at 200 mm. The deformation of the resulting roadway is controllable, indicating that the key parameter determination method is effective. Full article

With the gradual depletion of global oil and gas resources, accurate prediction of anomaly formation pressure caused by pressure relief from other sources has become increasingly crucial in oil and gas exploration and development. The anomaly formation pressure caused by pressure relief affects the well’s stability and significantly impacts the safety and economy of drilling operations. However, traditional methods for predicting anomaly formation pressure, such as Bowers’ method, may not accurately identify the complex relationship between parameters and pore pressure. In contrast, the BP neural network (BPNN) can learn the complex relationship between input and output from data, which has a significant advantage in accurately identifying anomaly formation pressures caused by pressure relief from other sources. This study proposes a neural network-based method for accurately predicting anomaly formation pressure caused by pressure relief from other sources. The high quality of input data is ensured through meticulous preprocessing related to anomaly formation pressure caused by pressure relief from other sources, including data cleaning, standardization, and correlation analysis. Subsequently, model training was conducted to fully utilize its powerful nonlinear fitting ability and capture the complex changes in formation pressure caused by anomaly pressure relief from other sources. This method collects and organizes the parameters of the formation, including Gamma-ray (Gr), Delta-T (Dt), wave velocity (V_p), and Resistivity (R10), to train a BPNN model for predicting pressure relief type anomaly formations. The trained model has a Bayesian regularized backpropagation function, and the average absolute percentage error (AAPE) and correlation coefficient (R) of predicting pore pressure in well A are 4.22% and 0.875, respectively. To verify the proposed model’s effectiveness, it was applied to a blind dataset of adjacent B wells and successfully predicted pore pressure with AAPE of 5.44% and R of 0.864. We compare and analyze the formation pore pressure predicted by the traditional Bowers model and support vector machine (SVM) model. The prediction results of the BPNN model have more minor errors and are closer to the actual pressure coefficient. This study demonstrates the accuracy of the proposed model in predicting pressure relief type anomaly formation pressure using drilling data. Full article

In view of the high-level, thick, and hard roof in a mine in Shaanxi, it is difficult for existing technology to solve the problem of frequent rock bursts, which are caused by the direct weakening of the whole underground layer. In this paper, a technology for preventing rock bursts using the long-distance drilling and blasting of a thick and hard roof in a high drilling field is proposed. The authors used theoretical analyses, numerical simulations, and other research methods to analyze the mechanisms of pressure relief and load reduction achieved by this technology, determined its layout parameters and layers, and carried out engineering practices in 2412 working faces in a mine in Shaanxi. The results show that the long-distance drilling and blasting technology can achieve the aim of unloading the pressure drop load by arranging a high-level drilling field to achieve the whole-layer presplitting of the thick and hard roof above the working face. According to the orthogonal test method, when using long-distance drilling and blasting under the condition of a high-level roof, the choice of the blasting layer is the biggest factor affecting the change in overburden subsidence. Using the identification basis of the main control disaster causing the layer of overburden, it was determined that 52~67 m above the coal seam of the 2412 working faces was the blasting layer. According to the periodic weighting interval of the working face and the development radius of the fractures in the blasting surrounding rock, the blast hole spacing was determined to be 30 m. After long-distance drilling and blasting, the frequency and energy of micro seismic events were reduced, the entry deformation was reduced compared with the common roof deep-hole blasting technology, and the pressure relief effect of the long-distance drilling and blasting technology was better. These research conclusions can provide theoretical support for the prevention and control of rock bursts during mining production under similar conditions by reducing the load and the unloading pressure on thick and hard roof layers that are difficult to unload from the source. Full article

Liquid carbon dioxide (L-CO₂) phase transition blasting technology, known for its high efficiency, environmental friendliness, and controllable energy output, has been widely applied in mine safety fields such as coal roadway pressure relief and coal seam permeability enhancement. However, the synergistic control mechanism between L-CO₂ blasting loads and in situ stress conditions on coal seam fracturing and permeability enhancement remains unclear. This study systematically investigates the key process parameters of L-CO₂ phase transition blasting in deep coal seams using response surface methodology and numerical simulation. First, three commonly used L-CO₂ blasting tubes with the overpressure of 150 MPa, 210 MPa, and 270 MPa were selected, and the corresponding material parameters and state equations were established. A dynamic mechanical constitutive model for a typical low-permeability, high-gas coal seam was then developed. A numerical model of L-CO₂ phase transition blasting, considering fluid–solid coupling effects, was then constructed. Multiple experiments were designed based on response surface methodology to evaluate the effects of blasting pressure, in situ stress, and stress difference on L-CO₂ fracturing performance. The results indicate that the overpressures of the three simulated blasting loads were 156 MPa, 215 MPa, and 279 MPa, respectively, and the load model closely matches the actual phase blasting load. L-CO₂ blasting creates a plastic deformation zone and a pulverized zone around the borehole within 500 μs to 800 μs after detonation, with a tensile fracture zone appearing at 2000 μs. By analyzing radial and tangential stresses at different distances from the explosion center, the mechanical mechanisms of fracture formation in different blast zones were revealed. Under the in situ stress conditions of this study, the number of primary fractures generated by the explosion ranged from 0 to 12, the size of the pulverized zone varied from 1170 cm² to 2875 cm², and the total fracture length ranged from 44.4 cm to 1730.2 cm. In cases of unequal stress, the stresses display axial symmetry, and the differential stress drives the fractures to expand along the direction of the maximum principal stress. This caused the aspect ratio of the external ellipse of the explosion fracture zone to range between 1.00 and 1.72. The study establishes and validates a response model for the effects of blasting load, in situ stress, and stress difference on fracturing performance. A single-factor analysis reveals that the blasting load positively impacts fracture generation, while in situ stress and differential stress have negative effects. The three-factor interaction model shows that as the in situ stress and stress difference increase, their inhibitory effects become stronger, while the enhancement effect of the blasting load continues to grow. This research provides a theoretical basis for blasting design and fracture propagation prediction using L-CO₂ phase transition blasting in the coal seam under varying in situ stress conditions, offering valuable data support for optimizing the process of L-CO₂ phase transition fracturing technology. Full article

Background: CPAP has been shown to be particularly beneficial in the management of acute cardiogenic pulmonary edema by reducing both preload and afterload, thus decreasing the work of breathing and improving oxygenation. Methods: This study was a prospective observational study, conducted in the period from 2022 to 2024, assessing the effectiveness and safety of prehospital CPAP therapy use in patients with acute cardiogenic pulmonary edema, administered alongside standard care. Results: In this study, 50 patients with acute cardiogenic pulmonary edema were treated by physician-led emergency teams in the Canton of Sarajevo. CPAP significantly improved clinical parameters across all time points. Systolic blood pressure decreased from 151.0 ± 41.0 mmHg at initial contact to 138.4 ± 32.0 mmHg before transportation and further to 130.2 ± 28.5 mmHg upon hospital admission (p < 0.001). Diastolic pressure dropped from 85.6 ± 17.2 mmHg to 81.1 ± 15.2 mmHg before transportation (p = 0.018), with a slight further decrease to 80.2 ± 13.9 mmHg (p = 0.083). Heart rate fell from 114 ± 26.4 bpm to 111.3 ± 24.9 bpm before transportation (p = 0.003) and finally to 99.5 ± 18.2 bpm before hospital admission (p < 0.001). Respiratory rate decreased from 31.0 ± 10.2 to 28.0 ± 10.5 breaths/min (p = 0.002) and further to 22.6 ± 7.3 breaths/min (p < 0.001). End-tidal CO₂ levels increased from 28.0 mmHg (23.5; 33.5) to 30.0 mmHg before transportation (p < 0.001), and to 35.0 mmHg (32.0; 37.5) before hospital admission (p < 0.001). Oxygen saturation improved from 79.0% (72.0; 81.0) to 84.0% before transportation (p < 0.001) and reached 94.0% (91.0; 98.2) before hospital admission (p < 0.001). VAS scores for dyspnea significantly dropped from 8.0 (6.0; 8.2) at initial contact to 6.0 (4.0; 8.0) before transportation (p < 0.001) and further to 4.0 (3.0; 5.0) before hospital admission (p < 0.001), indicating substantial symptom relief. ECG findings remained stable throughout the intervention. Conclusions: Prehospital CPAP therapy significantly improved clinical outcomes in cardiogenic pulmonary edema, including reductions in blood pressure, heart rate, respiratory rate, and enhanced oxygenation and symptom relief. These findings support its broader use in emergency care, even during short transport times. Full article

In order to optimize the pressure relief gas extraction process for the 1504 working face in East 2 of Dalong Coal Mine based on its mining and gas conditions, a physical model of pressure relief gas extraction in the airspace using two preliminary extraction processes—a high-level oblique borehole and a directional long borehole—was established using COMSOL 6.2 software. The changes in the gas extraction effect of high-level oblique boreholes were analyzed through a simulation of the advancement of the working face, and the reasons for the low utilization rate of the high-level oblique boreholes were outlined. The effects of the horizontal distance of the directional long boreholes from the side of the air return lane, the borehole spacing, and the negative pressure of the boreholes on the gas extraction effect were analyzed, and the gas extraction process of the directional long boreholes was optimized and applied in the field. The results showed that the directional long borehole gas extraction process had a better extraction effect, a higher borehole utilization rate, and superior cost savings, and was thus was the preferred process. Additionally, the optimal parameters were a 30 m horizontal distance of the boreholes from the side of the air return lane, a 30 m spacing between the boreholes, and a 20 kPa negative extraction pressure. Full article