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In order to study the influence of cement content, comprehensive water-cement ratio, formation characteristics and other factors on the performance of equal thickness soil-cement cut-off curtain in coal mine, the principle analysis of equal thickness soil-cement curtain, the influencing factors of curtain performance analysis, the test and performance test of equal thickness soil-cement curtain were carried out, the key influencing factors were determined, the parameters of soil-cement of equal thickness in composite strata were obtained, and the field demonstration application was carried out. The results show that: the main factors affecting the performance of equal thickness soil-cement curtain were rock (soil) body properties, groundwater characteristics, cement cementitious materials, mixing process and curing conditions. Rock (soil) body properties and cement content were the direct factors affecting wall quality; water-cement ratio and curing period were the key factors to ensure wall quality. The ground layer had higher strength and better grain gradation, so the strength of soil-cement of equal thickness was higher and the permeability coefficient was smaller. According to the influencing factors, the cement content of the demonstration project was determined to be 25%, the comprehensive water-cement ratio was 1.2:1, and the formation was composite formation material. The treatment results of the complex formation leakage section of the gentle slope inclined shaft in Luotuoshan Coal Mine showed that the three-step construction process was used to construct the outer water cutting curtain wall of the inclined shaft with good quality. The 28 d compressive strength of the field samples was 5.3—31.8 MPa, and the permeability coefficient was 0.005×10−7—0.2403×10−7 cm/s. Wellbore water inflow decreased from 16.8 m3/h to about 1.6 m3/h, which was reduced by about 90.5% compared with before treatment.

The loose layers and shallow weathered bedrock in western China are rich in water, and the inclined shaft crossing the water-rich loose layer is prone to leak at the wellbore construction joints, concrete joints and wall cracks. Leakage will lead to the deterioration of underground working environment, lower working efficiency, increase the burden and cost of underground drainage, and affect the safety of coal mine production. In order to solve the above problems, this paper analyses the characteristics of water seepage in slanting coal mine shafts from the perspective of protecting groundwater resources and safe operation of shafts, and the existing management measures such as drainage, post-wall grouting, rotary pile spraying and curtain grouting. And the principle and structure of soil-cement curtain with equal thickness of water leakage level in inclined shaft, the basis of parameter selection and the method of curtain construction were studied. The effects of formation conditions, comprehensive moisture content, cement content and other factors on the performance of cement curtain were analyzed. The field test application of water leakage control of inclined shaft was carried out in test mining area. The research results shows that the water leakage of inclined shaft in coal mine mostly occurs in the bottom plate, waist wall and the joint of both, and the water inflow was tens of m3/h～ hundreds of m3/h, and some even had water gushing and carrying sand, endangering the safety of the shaft. The equal-thickness soil-cemented curtain forms an equal-thickness wall with uniform thickness, few joints and high water interception rate in the outer stratum of the slanting coal mine shaft through three steps: lateral cutting, retraction cutting and mixing, and slurry mixing to form a wall. It effectively blocks the the hydraulic connection between the inclined shaft, the outside loose layer and the weathered bedrock. The strength of the cement curtain of equal thickness is positively correlated with the cement admixture, and the permeability coefficient is negatively correlated with the cement admixture. The performance of the cement curtain of clay stratum is weaker than that of loess and fine sand stratum. The in-situ core sample of the curtain at the demonstration application site has a compressive strength of 8.62MPa and a permeability coefficient of 2.69×10−8 cm/s. The water influx in the borehole is reduced from 16.8 m3/h to about 1.6 m3/h, which is 90.5% less than before the treatment, and achieved good application results. This method can solve the seepage problem of inlcined shaft in loose layer in western China, ensure the safe operation of the well shaft, and protect the groundwater resources.

ObjectiveA high level of vascular endothelial growth factor (VEGF) has been implicated in brain arteriovenous malformation (bAVM) bleeding and rupture. However, direct evidence is missing. In this study the authors used a mouse bAVM model to test the hypothesis that elevation of focal VEGF levels in bAVMs exacerbates the severity of bAVM hemorrhage.MethodsBrain AVMs were induced in adult mice in which activin receptor-like kinase 1 (Alk1, a gene that causes AVM) gene exons 4-6 were floxed by intrabasal ganglia injection of an adenoviral vector expressing Cre recombinase to induce Alk1 mutation and an adeno-associated viral vector expressing human VEGF (AAV-VEGF) to induce angiogenesis. Two doses of AAV-VEGF (5 × 109 [high] or 2 × 109 [low]) viral genomes were used. In addition, the common carotid artery and external jugular vein were anastomosed in a group of mice treated with low-dose AAV-VEGF 6 weeks after the model induction to induce cerebral venous hypertension (VH), because VH increases the VEGF level in the brain. Brain samples were collected 8 weeks after the model induction. Hemorrhages in the bAVM lesions were quantified on brain sections stained with Prussian blue, which detects iron deposition. VEGF levels were quantified in bAVM tissue by enzyme-linked immunosorbent assay.ResultsCompared to mice injected with a low dose of AAV-VEGF, the mice injected with a high dose had higher levels of VEGF (p = 0.003) and larger Prussian blue-positive areas in the bAVM lesion at 8 or 9 weeks after model induction (p = 0.002). VH increased bAVM hemorrhage in the low-dose AAV-VEGF group. The overall mortality in the high-dose AAV-VEGF group was 26.7%, whereas no mouse died in the low-dose AAV-VEGF group without VH. In contrast, VH caused a mortality of 50% in the low-dose AAV-VEGF group.ConclusionsUsing mouse bAVM models, the authors provided direct evidence that elevation of the VEGF level increases bAVM hemorrhage and mouse mortality.