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Using an industrial CT scanning system, we observed the characteristics of micro-fracture Generation and expansion in coal under different gas pressure conditions, providing a new basis for revealing the factors controlling the gas flow output of coal seams. The results of the test analysis showed that: under the action of non-adsorbed gas, the growth rate of fracture volume and fracture area percentage decreases gradually as the pore pressure increases and the sprouting and expansion of microfractures inside coal becomes more obvious. Fracture expansion equation under the influence of pore pressure is satisfied; microfracture extension is mainly controlled by stress concentration effect and coal matrix shrinkage effect. Under the action of adsorptive gas, with the extension of adsorption time, generation and expansion in coal of micro fissures become more and more significant until the expansion equilibrium; the growth rate of fissure volume and fissure area percentage then gradually becomes smaller, in line with the fissure expansion equation under the influence of adsorption time; the fracture extension is mainly affected by stress concentration effect, coal matrix shrinkage effect, erosion effect and deterioration mechanism. The larger the adsorption pressure the longer the adsorption equilibrium time required for the coal; the micro fissure expansion equilibrium time is longer than the gas adsorption equilibrium time, and the fissure expansion has obvious hysteresis.

Objective To clarify the efficacy and safety of magnetic resonance IVIM imaging in guiding target delineation and dose escalation of concurrent radiochemotherapy on locally advanced NSCLC. Methods From September 2014 to March 2018, 60 patients with inoperable locally advanced NSCLC were randomly divided into the experimental group and the control group. In the experimental group, 4DCT combined with IVIM imaging was used to guide the delineation of the target area of SIB-IMRT and dose escalation during radiotherapy. In the control group, 4DCT simulation was used to delineate the target area of SIB-IMRT. The clinical efficacy and safety between the two groups were compared, and the correlation between IVIM parameters and chemoradiotherapy efficacy was analyzed. Results Compared with the control group, the overall response rate was higher (86.7% vs. 60%, P=0.020) and the incidence of grade 3/4 radiation pneumonia was lower (20% vs. 46.7%, P=0.028) in the experimental group. The change of D value during treatment was related to the overall response rate of patients (P < 0.05). The more the D value increased, the longer PFS of patients was(P=0.006). Conclusion IVIM imaging guide could significantly increase the overall response rate of locally advanced NSCLC to concurrent chemoradiotherapy and reduce the incidence of grade 3/4 radiation pneumonia. The change of IVIM imaging parameter D value during radiotherapy is expected to be a predictor of chemoradiotherapy efficacy.

o determine the reasonable spacing of holes for gas drainage, an experimental study was conducted on the effective influence radius of drilling hole through the pressure drop method based on the actual condition of coal seams. The coal seam that contains gas is regarded as elastic-plastic dual media. The governing equation of gas transport is established by analyzing the different flow forms of gas in the pore and fissure systems as well as by considering the mass exchange capacity in the pore-fissure system. The equation is embedded into COMSOL Multiphysics (COMSOL) software to simulate the gas drainage effect further by drilling along a coal seam under a 3-D space. Upon confirming the effective radius and drainage influence radius of a single pore, the holes for gas drainage can be reasonably spaced along the coal seam by analyzing the change features of coal permeability around the borehole and the functional mechanism of the superimposed effect of drainage, namely, 2r≤L≤R. The study results can reliably guide practical gas drainage theoretically and can also effectively lower the cost of gas drainage as well as ensure the safe production in mines.

Based on the reasonable consideration of the role of the second main stress in D-P criterion, the distribution of stress and deformation with the method of finite difference was simulated. And the stress relief angles along incline and strike according to the rules of stress and deformation were obtained. Then the protective area resulted from exploiting the lower protective coal seam were acquired. The results show that the stress relief angles along incline are 75.5 and 77.7 degrees, the ones along strike are 78.4 and 83.5 degrees in the sense of protection when the advancing distance is 300m. But the real effective protective area is much smaller. The largest degree of stress relief locates in the protected coal seam corresponding to the upper and middle of the working face. According the simulation results and the water inrush coefficient method of effective water-resisting seam, the water inrush risk area of lower protective coal seam was divided, and the feasibility of exploiting protective coal seam was analysed and judged. Research results are of certain guidance and reference significance in the layout of mining and gas extraction for the similar coal mines.