Study on burst risk assessment of coal seam in folded area based on pre-mining stress back analysis

In order to scientifically evaluate the impact risk of steeply inclined extra-thick coal seam in folded area and provide theoretical guidance for the prevention and control of rock burst, a numerical model including folds is established in this paper based on the prevention and control of rock burst in south mining area of Wudong Coal Mine. With the help of multiple linear regression and CASRock engineering software, the back analysis of ground stress field of steeply-inclined extra-thick coal seam in folded area of Wudong Mine is carried out. Taking B1+2 coal seam as the research object, the stress data in coal seam, roof and floor are extracted, the stress-cover depth variation curve is plotted, the distribution characteristics of pre-mining stress field are explored, and the risk assessment index related to pre-mining stress is determined. According to the back analysis data of in-situ stress and previous research results, the evaluation indexes of burst risk are determined from the aspects of geological factors and mining conditions. The static weights of 7 geological factors and 5 mining conditions are obtained by Analytic Hierarchy Process. By substituting the static weight into the dynamic weight calculation formula and combining with the traditional comprehensive index method, the risk assessment of B1+2 panel at +500 m level in the south area of Wudong Mine is carried out. According to the rockburst risk classification table, the burst risk of this panel is medium, which is consistent with the conclusion of the geological report, and the rationality of the method was verified. This method is used to estimate the burst risk of coal seam with different depths. Control group is chosen, using the traditional comprehensive risk index method to evaluate the burst of the same area, the results show that the method to obtain the risk ratings were higher than the traditional methods, approach of this paper highlights the risk factors in the evaluation index, overcoming the other indicators evaluation error caused by the interference factors

A reactive oxygen species–related signature to predict prognosis and aid immunotherapy in clear cell renal cell carcinoma

BackgroundClear cell renal cell carcinoma (ccRCC) is a malignant disease containing tumor-infiltrating lymphocytes. Reactive oxygen species (ROS) are present in the tumor microenvironment and are strongly associated with cancer development. Nevertheless, the role of ROS-related genes in ccRCC remains unclear.MethodsWe describe the expression patterns of ROS-related genes in ccRCC from The Cancer Genome Atlas and their alterations in genetics and transcription. An ROS-related gene signature was constructed and verified in three datasets and immunohistochemical staining (IHC) analysis. The immune characteristics of the two risk groups divided by the signature were clarified. The sensitivity to immunotherapy and targeted therapy was investigated.ResultsOur signature was constructed on the basis of glutamate-cysteine ligase modifier subunit (GCLM), interaction protein for cytohesin exchange factors 1 (ICEF1), methionine sulfoxide reductase A (MsrA), and strawberry notch homolog 2 (SBNO2) genes. More importantly, protein expression levels of GCLM, MsrA, and SBNO2 were detected by IHC in our own ccRCC samples. The high-risk group of patients with ccRCC suffered lower overall survival rates. As an independent predictor of prognosis, our signature exhibited a strong association with clinicopathological features. An accurate nomogram for improving the clinical applicability of our signature was constructed. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses showed that the signature was closely related to immune response, immune activation, and immune pathways. The comprehensive results revealed that the high-risk group was associated with high infiltration of regulatory T cells and CD8+ T cells and more benefited from targeted therapy. In addition, immunotherapy had better therapeutic effects in the high-risk group.ConclusionOur signature paved the way for assessing prognosis and developing more effective strategies of immunotherapy and targeted therapy in ccRCC

The Mechanism and Application of Deep-Hole Precracking Blasting on Rockburst Prevention

The mechanism of preventing rockburst through deep-hole precracking blasting was studied based on experimental test, numerical simulation, and field testing. The study results indicate that the deep-hole precracking could change the bursting proneness and stress state of coal-rock mass, thereby preventing the occurrence of rockburst. The bursting proneness of the whole composite structure could be weakened by the deep-hole precracking blasting. The change of stress state in the process of precracking blasting is achieved in two ways: (1) artificially break the roof apart, thus weakening the continuity of the roof strata, effectively inducing the roof caving while reducing its impact strength; and (2) the dynamic shattering and air pressure generated by the blasting can structurally change the properties of the coal-rock mass by mitigating the high stress generation and high elastic energy accumulation, thus breaking the conditions of energy transfer and rock burst occurrence

5-alpha Reductase inhibitors and risk of male breast cancer: a systematic review and meta-analysis

Abstract Objective: To assess the relationship between 5α-reductase inhibitors (5ARIs) and the risk of male breast cancer (MBC). Material and Methods: We systematically searched Medline via PubMed, Embase and the Cochrane Library Central Register up to May 2017 to identify published articles related to 5ARIs and the risk of MBC. Results: Summary effect estimates were calculated by a random-effect model, and tests for multivariable-unadjusted pooled risk ratios (RR) and heterogeneity, as well as the sensitivity analyses were conducted to assess publication bias. All four studies were conducted in a quality assessment according to the Newcastle Ottawa Scale system. The strength of association between 5ARIs and the prevalence of MBC was evaluated by using summarized unadjusted pooled RR with a 95% confidence interval [CI]. Four studies involving 595.776 participants, mean age range from 60 to 73.2 years old, were included in a meta-analysis, which produced a summary unadjusted RR of the risk of MBC for the treatment of 5ARIs of 1.16 (95% CI 0.85-1.58, P=0.36) and the multivariable-adjusted RR is 1.03, (95% CI 0.75-1.41, p=0.86). There was no heterogeneity among included studies (I2=0%, P=0.49). Estimates of total effects were generally consistent with the sensitivity. Conclusion: We did not observe a positive association between the use of 5ARIs and MBC. The small number of breast cancer cases exposed to 5ARIs and the lack of an association in our study suggest that the development of breast cancer should not influence the prescribing of 5ARIs therapy

Investigation of Pressure Relief Borehole Effects Using In Situ Testing Based on Distributed Optical Fibre Sensing Technology

Borehole pressure relief method is one of the most effective ways of rock burst prevention in coal mines. The measured results of borehole pressure relief at no. 8939 longwall face in Xinzhouyao coal mine, China, are presented here. The analyses identify the pressure relief magnitudes in coal mass around the boreholes with different diameters, spacing, and drilling time. This research has established that the best pressure relief of the rib coal can be achieved by using φ108 mm borehole with 0.7 m interval after 288 hours. The strain relief is acceptable after 288–360 hours of drilling, while the best result is achieved after 432 hours. It is also the first time to monitor the borehole pressure relief in a coal mine on-site using Brillouin optical time domain reflectometer (BOTDR) distributed fibre-optic sensing. The method implemented in this research provides new ways to improve stress relief design and minimize the rock burst occurrence for mine practitioners

Dorsal penile nerve block versus eutectic mixture of local anesthetics cream for pain relief in infants during circumcision: A meta-analysis.

OBJECTIVE:To compare dorsal penile nerve block (DPNB) and eutectic mixture of local anesthetics (EMLA) cream for pain relief in infants during circumcision. METHODS:We systematically searched Medline via PubMed, Embase, CNKI and the Cochrane Library Center Register to identify randomized controlled trials up to March 2018. Effect estimates were performed in random effect models. Mean neonate infant pain scale (NIPS) scores, incidence of hematoma, edema and erythema, mean heart rate were conducted to assessed the effect of analgesia. We found that the EMLA had significantly higher pain scores compared to DPNB (SMD = 3.72, 95% CI 1.27-6.17, P = 0.003). In DPNB group, the incidence of hematoma was significantly higher than EMLA group, OR = 0.03, 95% CI 0.00-0.24, P = 0.001. The analysis did not show any significant differences in mean heart rate and the risk of edema and erythema between EMLA and DPNB group (SMD = 21.71, 95% CI = -0.88-44.30, P = 0.06 & OR = 0.40, 95% CI 0.15-1.07, P = 0.07 & OR = 7.33, 95% CI 0.84-64.07, P = 0.07). CONCLUSION:Based on the pooled results from the included studies, we found that DPNB was significantly more effective in pain relief as indicated by mean NIPS score than EMLA in infants during circumcision. However, use of DPNB significantly increased the risk of hematoma

How to realize safe-efficient-intelligent mining of rock burst coal seam

How to realize safe and efficient intelligent mining of rock burst coal seam is an important industrial technical problem. This paper systematically analyzes the distribution characteristics, mining status and development trend of rock burst mine in China, and deeply analyzes the main mining problems faced by rock burst mine. From the aspects of regional ground stress monitoring and inversion, mine development layout optimization, coal pillar size optimization, combined depressurization up and down well, displacement and filling mining, separated layer grouting, etc., the development status of rock burst mine life cycle prevention and control technology is described. In view of the difficult problem of roadway rock burst prevention and control, the collaborative intelligent adaptive anti-impact support technology and equipment for all roadways with rock burst are developed. The energy absorption anti-impact hydraulic support is used to achieve the effect of strong support for roadway surrounding rock under normal condition and rapid displacement and energy absorption during the impact process. Based on intelligent migration device of support, monitoring and warning system of support and intelligent design method of all roadway collaborative adaptive anti-impact support, the prevention and control system of intelligent energy absorption support of roadway under rock burst is constructed. This paper analyzes the anti-shock principle of the intelligent mining system of coal face, proposes to predict and warn the location and probability of rock burst by monitoring and analyzing the mining stress of surrounding rock and the fracture structure of overlying rock, based on 3D geological model and big data algorithm, etc., and carry out intelligent linkage control on the supporting posture and supporting force of hydraulic support and the cutting speed of shearer through the intelligent mining system. Realize the intelligent mining of coal face and the intelligent prevention and control of rock burst. From the aspects of intelligent monitoring of stope stress and overburden structure, construction of rock burst disaster database, classification prediction and early warning of rock burst disaster, this paper analyzes the research and development focus of intelligent rock burst prevention and control technology, and puts forward the composition and overall structure of mine rock burst monitoring and early warning system. From the aspects of top-level design, key technology, intelligent and accurate crisis relief and effect evaluation, the technical path and research and development direction of realizing safe and efficient intelligent mining of coal seam with rock burst in China are put forward

Research on the Control of Mining Instability and Disaster in Crisscross Roadways

In order to solve the disaster caused by the instability of spatial crisscross roadways under the action of leading abutment pressure in the coal mine face, combined with a specific engineering example, the methods of theoretical analysis, numerical simulation and field measurement are adopted to simulate and analyze the stress mutual disturbance intensity and influence range of spatial crisscross roadways. The evolution law of the plastic zone in spatial crisscross roadways under the influence of mining is explored, and the key to mining instability control is made clear. The roof of the return air roadway, the shoulder angle of the two sides and the coal wall are the key parts of surrounding rock stability control. On this basis, the cooperative control scheme of changing the roadway section shape (straight wall semicircular arch), supporting (anchor cable and “U” section steel) and modifying (grouting) is put forward. Through the field measurement, within the influence range of the return air roadway, the displacement deformation of the top and bottom is less than 200 mm, which achieves the goal of roadway safety and stability. Furthermore, based on the theory of “butterfly plastic zone”, the mechanical mechanism of the overall instability of the spatial crisscross roadway is revealed; that is, during the advance of the working face, the advance mining stress is superimposed with the surrounding rock stress of the crisscross roadway, and the peak value of the partial stress of the surrounding rock mass of the crisscross roadway is increased. The expansion of the plastic zone is intensified, and beyond 7 m from the crisscross position, the shoulder angle of the two sides and the leading plastic zone of the coal wall of the working face are connected with each other, which leads to the overall failure and instability of the surrounding rock between the roadways at the intersection

Preliminary Discussion on Comprehensive Research Method for Rock Burst in Coal Mine Based on Newton’s Second Law

Rock burst is one of the major dynamic disasters that directly threaten production safety in coal mines. According to the current research, the occurrence of rock burst can be described by the generalized Newton’s second law with three elements which are research object, force condition, and motion state. These three elements refer to the coal and rock mass in the mining area, concentrated static and dynamic loads, and dynamic instability of surrounding rock, respectively. On this basis, a comprehensive rock burst research method involving the three elements of Newton’s second law was proposed, which especially focuses on the investigation into geological conditions of mining areas. The research procedure of this method specifically includes the detailed exploration of engineering geological bodies, the classification and stability evaluation of surrounding rock, the measurement and inversion of in situ stress, the evolution analysis of mining-induced stress field, energy field, and fracture field, the study of multiscale failure mechanism of coal and rock mass, the establishment of theoretical failure model of coal and rock mass, the real-time monitoring and warning in potentially dangerous areas, and the reasonable prevention and control in key risk zones. As a preliminary discussion, the significant research progress in each aspect mentioned above has been reviewed and the feasible research directions of rock burst are presented in this paper