针对大倾角坚硬顶板采煤工作面中的缓倾斜煤层区段,基于有限差分和动力学模拟方法,建立了坚硬顶板非预爆破和预爆破2种方案下煤层回采的数值计算模型。对2种方案下围岩应力、位移、塑性区的演化规律进行了对比分析,获得了围岩在爆破扰动下的力学响应规律。结果表明:先顶板预爆破再回采方案可有效降低巷道围岩的应力集中程度,卸压释能,减小巷道变形量,便于支护控制,并且围岩塑性区范围增大,更有利于滞后工作面坚硬顶板及时垮落。所得结论对坚硬顶板动力灾害防治具有重要意义。

Faults encountered during coal mining can compromise the continuity and integrity of the overburden, resulting in considerable differences in the stress, displacement, and failure fields of the rocks surrounding the fault zone. When a working face is located adjacent to a fault, the fault-disturbed overburden becomes activated and unstable along the fault plane, which could lead to mining disasters. The fault-adjacent overburden morphology during mining was analyzed using a physical model. A mechanical model of the stability of the fault-disturbed overburden was constructed. The criteria for determining the sliding failure of the overburden during mining were defined, from which the critical coal pillar width required to maintain the overburden stability was determined. The results indicate that an inverted trapezoidal block forms in the overburden due to the combined effects of mining and faulting. The morphology of this block is influenced by the coal pillar width, the height of the fractured zone, and the dip angles of fault and coal seam. The block is prone to sliding or rotational failure along the fault plane during mining. As the coal seam and fault dip angles increase, the critical coal pillar width for maintaining overburden stability decreases. Conversely, increasing coal seam thickness increases the critical coal pillar width. The critical width of coal pillar was determined to be 176 m, which was verified through field observations performed in the #3307 working face.

Aiming at the problem of strong mining pressure in the near shallow buried and super-large mining height face, and considering the first 108 working faces in Jinjitan Coal Mine as the engineering background, the movement pattern and pressure distribution characteristics of the overlying rock layer on the 8.2 m fully mechanized mining face were analyzed from the perspective of theoretical analysis, field monitoring data, and numerical simulation. The results of the spatial structure mechanics model and FLAC3D numerical model of the mining face with a super-large mining height established in this study, which indicated that the mining operation of the mining face with a super-large mining height experienced rock dynamic load pressure and large-small periodic pressure phenomena. The fracture of the lower keystone beam leads to a small pressure cycle, and a large pressure cycle occurs when both the upper and lower keystone beams are fractured. Generally, the step distance during the size cycle is about twice the normal cycle. The site monitoring data shows that the initial incoming pressure step is 102 m and the periodic incoming pressure step is about 28.7 m, which is consistent with the theoretical value. When the working surface advances slowly, the dynamic load factor is smaller, and the incoming pressure step and duration are shorter, and vice versa. The research results are of important reference significance for mine pressure law and disaster prevention in similar conditions. © 2023, Springer-Verlag GmbH Germany, part of Springer Nature.

断层破坏覆岩地层的整体性，影响岩土体的强度特性和变形性质，导致开采沉陷规律更为复杂。为研究不同覆岩地层与正断层共同影响下煤层开采地表沉陷规律，构建不同覆岩地层正断层下盘煤层开采覆岩运动与地表变形的理论模型，数值模拟分析不同覆岩地层正断层下盘煤层开采地表下沉规律与特征，结合实例进行了对比分析。结果表明：地表移动变形范围与松散层厚度密切相关，随松散层厚度的增加，相较于无断层一侧，地表下沉盆地在断层一侧的移动变形范围先减小后扩大再减小，最终与无断层一侧相同；厚基岩地质条件下，随松散层厚度增加，地表产生裂缝的位置由断层露头先向采空区偏移后向断层上盘偏移；厚松散层地质条件下，松散层吸收了断层诱发的非连续变形，随松散层厚度增加，地表由偏态下沉盆地逐渐变为对称的下沉盆地。

The occurrence of disasters in deep mining engineering has been confirmed to be closely related to the external dynamic disturbances and geological discontinuities. Thus, a combined finite-element method was employed to simulate the failure process of an underground cavern, which provided insights into the failure mechanism of deep hard rock affected by factors such as the dynamic stress-wave amplitudes, disturbance direction, and dip angles of the structural plane. The crack-propagation process, stress-field distribution, displacement, velocity of failed rock, and failure zone around the circular cavern were analyzed to identify the dynamic response and failure properties of the underground structures. The simulation results indicate that the dynamic disturbance direction had less influence on the dynamic response for the constant in situ stress state, while the failure intensity and damage range around the cavern always exhibited a monotonically increasing trend with an increase in the dynamic load. The crack distribution around the circular cavern exhibited an asymmetric pattern, possibly owing to the stress-wave reflection behavior and attenuation effect along the propagation route. Geological discontinuities significantly affected the stability of nearby caverns subjected to dynamic disturbances, during which the failure intensity exhibited the pattern of an initial increase followed by a decrease with an increase in the dip angle of the structural plane. Additionally, the dynamic disturbance direction led to variations in the crack distribution for specific structural planes and stress states. These results indicate that the failure behavior should be the integrated response of the excavation unloading effect, geological conditions, and external dynamic disturbances. © 2022, The Author(s).

Surrounding rock control and support stability in the process of coal seam mining in ultra-large height mining face are the key to normal mine operation. In this study, the roof movement and deformation of an ultra-large height mining face are analyzed, and the working resistance of the ultra-large height mining face is obtained by introducing the equivalent immediate roof. By analyzing the coal wall spalling, the multiple positions of the spalling and the required support force of the support are obtained. At the same time, ultra-large height supports are more prone to instability problems. In this study, the stability of the ultra-large height supports was analyzed by establishing a mechanical model. The results show that: 1. The overturning limit angle of support has a hyperbolic relationship with the center of gravity. 2. Under the condition of ultra-large height, the increase in the base width of the bracket significantly improves the stability of the supports. 3. The sliding limit angle of support is positively correlated with the support load and the friction coefficient between the support and the floor. The above conclusions can provide guidance on the selection of supports and the adoption of measures to enhance the stability of the supports during use under ultra-large height conditions. The working resistance of the ultra-large height supports in the 108 mining face of the Jinjitan Coal Mine was monitored. The monitoring results show that: The average resistance of the supports is 22.6 MPa. The selected supports can meet the stability requirements of the working face support. The frequency of mining resistance in 0 similar to 5 MPa accounts for 28.38%, which indicates that some supports are insufficient for the initial support force during the moving process. Furthermore, the stability of the supports can be enhanced by adjusting the moving process. This study provides a reference for the selection of supports in ultra-large height mining faces and proposes measures to enhance the stability of the supports, which provides guidance for the safe mining of coal in ultra-large height mining faces.

Analyzing the characteristics of the chemical composition of coal mine water and discussing its formation process can provide baseline information for the prevention and control of water hazards. In this study, 152 mine water samples from 8 coal mines in the Xishan mining area (XSMA) were sampled, and their chemical characteristics and formation mechanism were analyzed comprehensively using standard hydrochemical and statistical methods. The results show that the main cations in the mine water are Na+ and Ca2+, and the dominant anions are SO42- and HCO3-. The mine water of Xiqu coal mine showed the highest concentrations of Ca2+, Mg2+, and SO42- ions, and the Guandi coal mine showed the highest Na+ content, but both mines showed relatively low Cl- concentration. Ca2+ and Mg2+ were significantly positively correlated with SO42-, while pH was significantly negatively correlated with Ca2+ and SO42-. The 152 samples were divided into 6 categories (G1-G6) through cluster analysis. Specifically, the hydrochemical type of G1 is HCO3-Na, G2 and G3 are mainly SO4 center dot Cl-Na, G4 is mainly HCO3-Ca center dot Mg, G5 is mainly SO4 center dot Cl-Ca center dot Mg type, and G6 is mainly SO4 center dot Cl-Ca center dot Mg and SO4 center dot Cl-Na. Through principal component analysis, three principal components were obtained, representing the oxidation of pyrite and the dissolution of carbonate and sulfate minerals, the weathering and alternating cation adsorption of silicate rocks, and the effects of rock salt dissolution and evaporative concentration. The ion proportion coefficient and principal component analysis showed that the mine water from the XSMA is mainly affected by rock (silicate and carbonate rock) weathering, mineral (gypsum) dissolution, cation exchange, and pyrite oxidation. The results are of great significance to the identification of mine water-inrush sources and the prevention and control of water disasters in the XSMA.

为探究远场低频地震波对冲击地压的作用机理，采用结构动力学理论，从共振角度研究了地震波对煤岩体稳定性的影响，解释了远场震源导致冲击地压的原因。研究表明：受采动影响，远场低频地震波也会对煤岩体造成累积损伤破坏，降低其强度；越靠近巷道表面，煤岩越破碎，其固有频率越低，越易与地震波发生共振效应，造成煤岩体进一步破坏；建立了地震波对煤岩体冲击扰动失稳破坏的响应机制模型，发现扰动能量越大，参与冲击地压的煤岩体越多，释放能量越大，破坏范围也较大；扰动能量越小，参与冲击地压的煤岩体较少，释放能量越小，破坏范围也较小；冲击地压演化过程中微震波形的主频降低，幅值呈线性递增；临近冲击失稳时，煤岩破裂从小尺寸串级过渡到大尺寸串级，波形的相似度及关联性也越来越大，Hilbert瞬时能量能够更明确体现地震波的累积损伤作用，研究成果有助于深刻认识远场地震波扰动诱冲机理。

To understand the hydrochemical characteristics and circulation pattern of groundwater in coastal coal mining areas, we analyzed 81 water samples from different water bodies in the Liangjia coal mine (LCM) area using multivariate statistical analysis and hydrochemical methods. The Quaternary groundwater (QW), accumulated water (AW) in the subsidence area, and mine water (MW) in the LCM all exhibit weakly alkaline to slightly saline water chemistry. The dominant cations and anions in the water are sodium (Na+) and chloride (Cl-), reflecting the influence of seawater intrusion. Some ions in QW, AW, and MW exhibited significant annual variations, but Na+ and Cl- concentrations increased with time. The water samples were divided into four categories through cluster analysis: C1 and C2 (bedrock water samples), C3 (water samples prominently affected by seawater intrusion), and C4 (QW and AW in the surface subsidence area). According to the Piper diagram, QW and AW in the surface subsidence area mainly correspond to the Na-Cl type, whereas the MW mainly consists of Na-Cl and Na-HCO3 types. Factor analysis revealed four main factors: seawater recharge, HCO3-rich bedrock water, alkaline water, and Quaternary groundwater (QW) with eigenvalues of 4.18, 2.44, 1.22, and 1.19 respectively, which explained 81.98% of the original data information. The comprehensive results of hydrochemical analysis and mathematical statistics indicated that the recharge sources of MW in LCM include seawater, QW, AW, HCO3-rich bedrock water, and mixed water. Based on regional hydrogeological conditions, a preliminary groundwater circulation model of the coastal coal mining area was constructed. Groundwater generally flows into the Bohai Sea from southeast to northwest, and coal mining has changed the original local groundwater runoff patterns and intensified seawater intrusion.