The Dynamic Differentiation Characteristics And Mechanisms Of Stress-sensitive Elements And Minerals In Tectonically Deformed Coals

Tectonically deformed coals(TDCs)are selected as the key research objects,and the systematical research is performed around the core scientific issue 'the dynamic differentiation characteristics and mechanisms of elements and minerals in TDCs'.The inner connection and response to stress-strain of dynamic metamorphism of organic matter and deformation,displacement or metamorphism of minerals are thoroughly investigated,and the stress-senstivity and migration-variation mechanism of elements in TDCs are furtherly revealed,which could support the prediction of coal and gas outburst with new idea and method.The main conclusions are summarized as following.(1)Stress-strain environments of diverse types of TDCs are revealed,the brittle deformed coals are commonly formed in extrusion,extension or shear stress environments with high strain rates,the brittle-ductile deformed coals are commonly formed in shear stress environment,and the ductile deformed coals are commonly formed in extrusion or shear stress environments with low strain rates.The mechanism of coal brittle and ductile deformation was investigated from a microscopic perspective,compared with brittle deformation,ductile deformation could facilitate the relaxation of coal molecules and liberation of small free molecules through the transformation of mechanical energy into strain energy,which could enhance the plasticity of coal and promote the ductile deformation.Results of high temperature and high pressure experiments show that the transformation condition of low rank bituminous in Suxian coal mine is 100~200?C and 100~150MPa.(2)The evolutionary route and mechanism of TDC molecules is revealed based on the composite model of coal molecules.Evolution of TDC molecules mainly includes relaxation and rearrangement process,in brittle deformed coals,the non-covalent bonds are preferentially disrupted under the influence of tectonic stress,and the relaxation of cross-link molecular networks took the leading position,in brittle-ductile and ductile deformed coals,the rearrangement of molecules is significantly enhanced,which is mainly ascribed to the dynamic metamorphism promotion of shear stress and the transformed strain energy that is more conductive to coal molecular evolution.(3)The deformation,displacement and metamorphism of minerals in TDCs are summarized.With the increasing coal deformation intensity,particle size and psephicity of minerals are decreased and increased,respectively,under the influence of mechanical crushing and grinding,and under the influence of compression-shear stress,morphologies of minerals are altered and minerals could locally move along the friction surfaces.Besides,the material substitution in TDCs was enhanced by tectonic stress(especially near the fault plane),which could lead to the mechanical mixing of minerals in coals.As the representative of stress-sensitive minerals in TDCs,physical and chemical properties of clay minerals are both altered under the influence of tectonic stress.Furthermore,the adsorption capacity of clay minerals to elements is significantly modified by tectonic stress.(4)The dynamic differentiation mechanism of elements forming organic matters and elements with organic affinity are revealed.Dynamic metamorphism of TDC molecular structures could not only lead to the concentration variation of elements forming organic matters,but also result in the regular variation of occurrence state of elements without affecting the concentration.Besides,the stress degradation of functional groups as the important adsorption sites of element with organic affinity could directly lead to the migration and deficit of those elements.(5)The dynamic differentiation of elements with inorganic affinity is closely related to the stress-induced mixing,local dynamic migration and dynamic metamorphism of minerals.The stress-induced mixing affects the migration of elements through controlling the development of cleat minerals.The local dynamic migration could lead to the migration of minerals through the rheology of coal,which could make the related elements migrated and accumulated.The dynamic metamorphism of minerals could also affect the dissipation and accumulation of elements.(6)Stress-sensitive elements in TDCs are filtrated,which could be divided into accumulated and dissipative types.Pore structural characteristics of TDCs are consistent with the distribution of accumulated or dissipative types of stress-sensitive elements.Thus,the migration and accumulation of stress-sensitive elements could be the indicator of the distribution of TDC,which could provide the prediction of coal and gas outburst with new idea and method.There are 211 figures,32 tables,and 390 references in this paper.