The Development Law Of Fold Structure And Its Control Function On Gas Occurrence In Xinjing Coalmine,Yangquan

This thesis systematically studied the development characteristics and laws of fold structures and expounded the formation and evolvement process of fold structures. Based on the underground coal wall observation, borehole logging analyzation and well logging interpretation, we analyzed the development characteristics of deformed coal and discussed the control effect of fold structures on deformed coal. Using mercury intrusion method, the pore structure characteristics of different types of deformed coal was studied to get the gas transport and storage characteristics. We analyzed the gas storage environment under the control of fold structures and obtained these main results and understanding about the control mechanism of fold structures to the gas occurrence:(1) Characterized by the folds with weak deformation, the folds with direction of NNE~NE, almost EW and almost NW. The NNE ~ NE folds controlled the main form of the mine. The superimposed folds models including vault, basin and saddle-shaped form. The fold association styles including en echelon, ladder, fastigiated, palisade, grid and fusiform. We found the mine folds is characterized by its regionalization, sub stage, orientation, consistent scale, symmetrical characteristic, and equidistant array. The mine folds were developed under the buckle folding effects. In the Indosinian, broad folds with smaller size and approximately EW direction were formed while the bigger folds of NNE~NE were developed in the Yanshanian period. And in the Himalaya period, the earlier fold structures were reformed and transformed into approximately NW folds with small scales.(2) Deformed coal were mainly the brittle series of structural coal with weak deformation. From the primary structure coal to the crumpled coal, the friction surface is more and more developed and the fractures are developing increasingly. At the same time, the stress function on the coal body also tends to be complicated. It is believed that the deformed coal is particularly developed in the related structural parts with complicated fold deformation or near the small faults, large-scaled joints, erosion zones, and that the deformed coal is more developed among the lower part of the coal seam than the upper part of the coal seam. Then the 6 control modes of fold structures on the deformed coal development are put forward. Then, we got that the development degree of the deformed coal is enhanced with the increase of the degree of fold deformation.(3) From the primary structure coal to the fragmented coal, as the deformation increased, the capacities of gas transport and storage enhanced. From the schistose coal to the crumpled coal, the capacity of gas transport firstly enhanced apparently and weakened later, with the capacity of gas storage increased apparently in this process. It is believed that the fold structure action plays an important controlling effect on the progress of gas transport and storage. The controlling mechanisms of fold actions on the gas storage were explained in the 5 aspects, such as the distribution difference of different types of deformed coal caused by different degree of fold deformation, the deformed coal with strong deformation formed in the superposed folding area, the formation of associated faults and associated joint caused by fold actions, and the different destruction of coal seam roof resulted from fold actions. And we put forward the new understanding that fold actions controlled the gas storage by controlling the development of the deformed coals and resulting in the different destruction of coal seam roofs.