Water-inrush mechanism from the head-on working face roof in a Jurassic coal seam in the Ordos Basin.

When Chinese coal mines are mining Carboniferous Permian coal seams, the mechanism of water inrush from the roof of the working face usually conforms to the "Upper Three Zones" or "Upper Four Zones" theory. The water inrush passageway is water-conducting fracture zone, and the water inrush position is located in the goaf. However, when mining Jurassic coal seams in Chinese coal mines, the location of water inrush often appears at the head-on working face, above the coal mining machine. Due to the support of the fully mechanized mining support, the roof rock layer cannot collapse and therefore cannot form water-conducting fracture zone. Therefore, the water inrush mechanism cannot be explained by the above two theories. This paper is guided by the Practical Mine Pressure Control Theory, and based on the explanation of the motion forms of bending (pulling) failure movement and shearing (cutting) failure movement, and combined with on-site examples, it is revealed that the passageways leading to from the head-on working face roof in a Jurassic coal seam in the Ordos Basin are splitting zones type, fracture line type and structural fracture type, respectively. Taking the changes in water inflow during the mining process of the 3301 and 3302 working faces in Zhujiamao Coal Mine as examples, this paper reveals the mechanism of water inrush from the head-on working face roof caused by splitting zones type, and proves the existence of this passageway through on-site 3D high-density electrical detection and tracing experiments. Taking two catastrophic water inrush accidents that occurred head-on in the 1309 working face of Guojiahe Coal Industry Co., Ltd. as examples, the water inrush mechanism of the fracture line type and the water inrush mechanism of the structural fracture type were respectively revealed. Based on mechanism of water inrush from head-on roof of working face and the analysis of the on-site water inrush process, a method for distinguishing the type of water inrush passageway from the front roof of the working face is proposed. The results indicate that the Jurassic coal seam mining in the Ordos Basin is prone to shearing (cutting) failure movement, resulting in the frequent formation of the three types of water inrush passageways mentioned above.

Preventing water-inrush from floor in coal working face with paste-like backfill technology.

In the view of the situation where great economic loss often occurs during mining deep coal seams in Feicheng coal field due to water inrush from the floor Ordovician limestone aquifer, the floor "lower four-zone" theory was used as a guide. 81006 working face of Caozhuang Coalmine in Feicheng coal field was taken as the research background, and paste filling technology was proposed to inhibit or reduce the damaged floor depth caused by mine ground pressure in order to prevent water inrush from the floor Ordovician limestone aquifer. Glue material, coal gangue powder, and fly ash were selected as filling material, and a ground filling system, including a material production system, storage material system, power supply and water supply system, automatic control and measurement system, monitoring and control communications system, emergency response system, and underground filling system, including pipe conveyor system and working face blocking grout loss system, were established to achieve effective filling goaf. Field stress monitoring and floor damaged depth measurement showed that when reaching a steady state after a period of time, paste filling working face not only restored to the original stress state but also significantly reduced the floor's damaged depth caused by mine ground pressure. This verifies that working face with paste-like backfill technology is a very effective measure to prevent water-inrush from the floor.

Finite Element Analysis and Comparative Study of 4 Kinds of Internal Fixation Systems for Anterior Cervical Discectomy and Fusion in Children.

Background: Spinal injury in children usually occurs in the cervical spine region. Anterior fixation of the lower cervical spine has been applied in treating pediatric cervical spine injury and disease due to its stable and firm mechanical properties. This study performed finite element analysis and comparison of four different anterior cervical internal fixation systems for children to explore more standard methods of anterior cervical internal fixation in children and seek more effective and safe treatment for children's cervical spine diseases. Methods: A finite element model of 6-year-old children with lower cervical spine C4/5 discectomy was established, and the self-designed lower cervical spine anterior locking internal fixation system ACBLP and the children's anterior cervical internal fixation system ACOP, ACVLP, and ACSLP plate screws were fixed and loaded on the model. 27.42 N·m torque load was applied to each internal fixation model under six working conditions of anteflexion, backward flexion, left flexion, right flexion, left rotation, and right rotation, to simulate the movement of the cervical spine. The activity and stress distribution cloud diagram of each finite element model was obtained to explore the optimal method of anterior cervical fixation in children. Results: In the four internal fixation models of ACOP, ACVLP, ACSLP, and ACBLP, the mobility of the C4/5 segment showed a decreasing relationship, and the mobility of adjacent segments increased significantly. In the Mises stress cloud diagram of the cervical spine of the four models, the vertebral body and accessories of the ACBLP model born the least stress, followed by ACSLP. The steel plate and screws in the ACVLP internal fixation model were the most stressed. The stress of the internal fixation system (plate/screw) in all models increased in the order of ACBLP, ACSLP, ACVLP, and ACOP. Conclusions: ACBLP internal fixation system had obvious advantages in anterior internal fixation of the lower cervical spine in children, C4/5 had the smallest degree of movement, relative displacement was minimal, and the stress on the centrum and pedicle was the least, while the stress on the plate screw was relatively the smallest.

Anatomical Study on the Safety of Anterior Cervical Craniovertebral Fusion with Clival Screw Placement in Children Aged 1-6 Years.

OBJECTIVE: This study aimed to investigate the safety of clival screw placement in children aged 1-6 years. METHODS: The cranial computed tomography data of 92 children aged 1-6 years were divided into three groups, according to age, for three-dimensional reconstruction. Three clival screw placement points were defined: (1) median point A at the middle and upper third of the tripartite distance from the spheno-occipital synchondrosis to the base of the skull; (2, 3) critical points B and C on the horizontal line with point A, where the screw placement passage was parallel to the sagittal plane. Parameters such as the passage length and angle were measured for horizontal, vertical facial, and extreme screw placement. RESULTS: The length parameters of the clival screw placement increased with age, and the screw passage length was the shortest for the vertical facial type in each age group. There were significant differences in all three groups between the length of screw placement in the vertical bone surface, the length of screw placement in the horizontal direction, and the length of screw placement on the limit at points A, B, and C (P < 0.05); the length of screw placement on the vertical bone surface was the shortest. There was no significant difference between the horizontal screw length at point A and the extreme screw length (P > 0.05). The difference between the horizontal screw length and the extreme screw length in the groups aged 1-2 years and 5-6 years was statistically significant (P < 0.05), and the horizontal screw length was longer. CONCLUSION: The cranial slope of children aged 1-6 years has the morphological basis for the placement of 3.5 mm screws, and each placement point has a safe angle range for screw placement.

Gray Evaluation of Water Inrush Risk in Deep Mining Floor.

With the increase of the mining intensity of coal resources in China, the geological conditions of minefields have become more and more complex. The mining conditions of high pressure and high stress bring great challenges to the safe mining of coal resources. To accurately evaluate the risk of water inrush from the broken floor under high pressure and high stress, a gray evaluation model coupling the work breakdown structure (WBS), the risk-based supervision (RBS) theory, ordered binary comparison quantization method, and the center-point triangular whitenization weight function was proposed in this paper. Taking the No. 21 coal seam of Shanxi Formation in Guhanshan minefield as an example, studying the distribution characteristics of high pressure and high stress and the water inrush mechanism from the broken floor during No. 21 coal seam mining and analyzing the hydrochemical characteristics of the main water inrush aquifers below the No. 21 coal seam floor, this paper determined five main factors, including fault fractal dimensions, aquifer pressure, water-richness, destroyed floor depth, and effective aquiclude thickness. First, the work breakdown structure (WBS), the risk-based supervision (RBS) theory, and the ordered binary comparison quantization method were used to calculate the weight vectors of each index. Then, the center-point triangular whitenization weight function based on the work breakdown structure (WBS), the risk-based supervision (RBS) theory, and the ordered binary comparison quantization method were constructed to evaluate the water inrush risk from the broken floor under high pressure and high stress. Finally, the risk of water inrush from the broken floor during No. 21 coal seam mining in Guhanshan minefield was predicted using the gray evolution trend, which effectively reflects the risk characteristics of water inrush from the coal seam floor under high pressure and high stress. The results show that the evaluation and prediction results are consistent with the actual situation in Guhanshan minefield, which indicates that the model is suitable for evaluating and predicting the risk of water inrush from the broken floor under high pressure and high stress.

Evaluation of Groundwater Resources and Exploitation Potential: A Case from Weifang City of Shandong Province in China.

With the rapid growth of population and economy, the demand for groundwater resources is also increasing, leading to the exploitation of groundwater in some areas far greater than the recharge, which easily causes a series of environmental geological problems such as groundwater drawdown, water quality deterioration, surface subsidence, and so on. Taking Shouguang water resource in Weifang City, Shandong Province, China, as an example, the water-bearing formation in the study area can be divided into three types: pore water-bearing formation of unconsolidated sediments, karst fissure water-bearing formation of carbonate rock, and bedrock fissure water-bearing formation. According to the pumping test results, the groundwater-richness zones in the study area were delineated first. On this basis, by analyzing the dynamic changes of groundwater, the study area was divided into 40 blocks, and the natural recharge of groundwater in each block was calculated by the analogy method of the infiltration coefficient of precipitation. Then, combined with the actual situation of the study area, the allowable withdrawal of groundwater resources, mainly including pore water-bearing formation of unconsolidated sediments, karst fissure water-bearing formation of carbonate rock, and bedrock fissure water-bearing formation, was calculated using the safe yield modulus method, the improved method of the uniform arrangement of wells, and temporary storage capacity, respectively. Through the calculation, it can be concluded that the total allowable withdrawal of shallow groundwater resources in Shouguang city is 6292.5783 × 104 m3/a, that of middle and deep layer groundwater resources is 2574.92 × 104 m3/a, that of karst fissure water in carbonate rock is 1767.92 × 104 m3/a, and that of bedrock fissure water is 307.89 × 104 m3/a. The results show that within the study area, karst fissure water in carbonate rock and bedrock fissure water have immense exploitation potential.

Integrin CD11b mediates locus coeruleus noradrenergic neurodegeneration in a mouse Parkinson's disease model.

BACKGROUND: The loss of locus coeruleus noradrenergic (LC/NE) neurons in the brainstem is reported in multiple neurodegenerative disorders, including Parkinson's disease (PD). However, the mechanisms remain unclear. Strong evidence suggested that microglia-mediated neuroinflammation contributes to neurodegeneration in PD. We recently recognized integrin CD11b, the α-chain of macrophage antigen complex-1 (Mac-1, also called CR3), as a key regulator for microglial activation. However, whether CD11b is involved in LC/NE neurodegeneration in PD remains to be investigated. METHODS: LC/NE neurodegeneration and microglial activation were compared between wild type (WT) and CD11b KO mice after treated with paraquat and maneb, two pesticides that widely used to create PD model. The role of NLRP3 inflammasome in CD11b-mediated microglial dysfunction and LC/NE neurodegeneration was further explored. LC/NE neurodegeneration, microglial phenotype, and NLRP3 inflammasome activation were determined by using Western blot, immunohistochemistry, and RT-PCR technologies. RESULTS: Paraquat and maneb co-exposure elevated the expressions of CD11b in the brainstem of mice, and CD11b knockout significantly reduced LC/NE neurodegeneration induced by paraquat and maneb. Mitigated microglial activation and gene expressions of proinflammatory cytokines were also observed in paraquat and maneb-treated CD11b-/- mice. Mechanistically, CD11b-mediated NLRP3 inflammasome activation contributes to paraquat and maneb-induced LC/NE neurodegeneration. Compared with WT controls, CD11b deficiency reduced paraquat and maneb-induced NLRP3 expression, caspase-1 activation, and interleukin-1ß production in mice. Furthermore, inhibition of NLRP3 inflammasome by glybenclamide, a sulfonylurea inhibitor of NLRP3 inflammasome, was found to be able to suppress microglial proinflammatory activation and nuclear factor-κB activation induced by paraquat and maneb. Moreover, reduced reactive oxygen species production, NADPH oxidase, and inducible nitric oxide synthase expressions as well as 4-hydroxynonenal and malondialdehyde levels were detected in combined glybenclamide and paraquat and maneb-treated mice compared with paraquat and maneb alone group. Finally, we found that glybenclamide treatment ameliorated LC/NE neurodegeneration and α-synuclein aggregation in paraquat and maneb-treated mice. CONCLUSION: Our findings suggested that CD11b mediates LC/NE neurodegeneration through NLRP3 inflammation-dependent microglial proinflammatory activation in a two pesticide-induced mouse PD model, providing a novel insight into the immune pathogenesis of LC/NE neuronal damage in related disorders.