Locating neutral surface of fold and its application in Laohe syncline in Liupanshui area

The paper supposed that the rock formations of bending flowage fold is heterogeneous board agglutinated by many isotropic thin layers.Based on elastic thin plate theory, we have studied the questions about locating neutral surface of fold when the rock formation of fold is under pure buckling only, and obtained the location formula of neutral surface of fold with main parameters of modulus of elasticity, Poisson's ratio, and thickness of each rock formation.Combined with Laohe syncline of Liupanshui coalfield in Guizhou province, the neutral surface of Laohe syncline was located in the fine sandstone of coal seam 9^# floor of Longtan Formation, as far as 966m from the bottom of Maokou Formation.The nearer the distance of coal seam to neutral surface was, the less the fold structure influence on gas occurrence was, resulting in less difference between the gas content of coal seam near neutral surface and that of wing of syncline.Our research results have certain steering effects on coal bed methane exploitation and preventing coal and gas outburst.