Gas disasters are a major factor influencing safe production in mines: Gas extraction can reduce the gas content in coal seams, providing a guarantee of safer production. The parameters for gas extraction are the primary factors influencing the effectiveness thereof. Aiming at the creep properties of soft coal, a fluid‐solid coupling mathematical model considering creep properties of coal was established based on dynamic evolution equation for permeability considering the effects of matrix shrinkage and effective stress. Additionally, by utilizing COMSOL Multiphysics software, the gas extractions from a single borehole and multiple boreholes were calculated. Moreover, the parameters for gas extraction were optimized and applied and tested in field conditions. The result showed the reduction in gas pressure around the boreholes was larger than that from a single borehole when conducting gas extraction from multiple boreholes. The borehole spacing when extracting gas in coal seams by drilling multiple boreholes should be more than twice that of the effective drainage radius. The optimal borehole spacing ranged from 3.2 to 4.2 m for gas extraction lasting 180 d. Numerical simulation was carried out to ascertain the distribution of stress on coal around a roadway. The result revealed that the damage radius of the roadway was 11.8 m, and a reasonable hole‐sealing depth was 12 m. On condition that the borehole spacing during gas extraction from multiple boreholes was 4 m, the reasonable pre‐extraction time was 180 days taking the gas pressure being reduced to <0.74 MPa as a critical point. Furthermore, the gas content, the amount of extracted gas, etc, in a working face after the parameters for gas extraction were optimized were measured. The result suggested that the effect of gas extraction after optimizing parameters conformed to industry standards.
BackgroundSynchronous development of primary hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC) in different sites of the liver have rarely been reported before. The purpose of this study is to investigate the clinicopathological characteristics of synchronous double cancer of HCC and ICC.Case presentationA 56-year-old Chinese man without obvious liver cirrhosis was preoperation diagnosed with multiple HCC in segments VI (SVI) and VII (SVII) by the abdominal computed tomography (CT) and contrast-enhanced ultrasonography (CEUS). We performed hepatic resection of both segments. The tumors in SVI and SVII were pathologically diagnosed as ICC and HCC, respectively. Immunohistochemically, the HCC in SVII was positive for HepPar-1 and negative for CK19, while the ICC in SVI tumor was positive for CK19 and negative for HepPar-1. Interestingly, the immunohistochemical results also showed that the classic hepatic progenitor cell (HPCs) markers CD34 and CD117 were both positive of the two tumors. The patient still survived and at a 1-year follow-up did not show evidence of metastasis or new recurrent lesions. We speculate that the two masses may have originated from HPCs based on the findings of this patient.ConclusionsSynchronous development of HCC and ICC is very rare with unique clinical and pathological features. The correct preoperative diagnosis of double hepatic cancer of HCC and ICC is difficult. Hepatitis B virus (HBV) and hepatitis C virus (HCV) infection were both the independent risk factor to the development of double liver cancer. Hepatic resection is the preferred and most effective treatment choice. The prognosis of synchronous occurrence of double hepatic cancer was poorer than for either HCC or ICC, and the origin of it needs further study.
With mine mining depth increasing, the situation of mine gas control is more rigorous, and the existing single hydraulic fracturing method often cannot achieve the ideal effect. Based on the characteristics of high gas and low permeability coal seam, this paper designed different ways of hydraulic fracturing experiment to investigate the differences of gas extraction ability, and eventually optimize the hydraulic fracturing method. The experimental results show that repeated hydraulic fracturing and directional hydraulic fracturing methods are more suitable for increasing soft coal seam permeability than conventional hydraulic fracturing method, and the gas extraction ability of repeated hydraulic fracturing is better than directional hydraulic fracturing. After repeated hydraulic fracturing, the single-hole average pure volume of gas drainage has reached 10.224m³/d, which is 2.5 times as much as the conventional hydraulic fracturing; The extraction concentration is 63% -72%, with an average of 67.8%, which is 19.2% higher than the conventional hydraulic fracturing.
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