Study On The Deformation Of Tectonically Deformed Coal Under Multi-stage Reaming Drilling Condition

Tectonically deformed coal is taken as the research object in this paper.Through the laboratory simulation test,theoretical analysis,numerical simulation and other methods,the damage characteristics of tectonically deformed coal under multi-stage reaming drilling conditions are studied.The basic mechanical properties of the constructed coal are studied by triaxial tests.The constitutive model of tectonically deformed coal damage under triaxial conditions is derived and the parameters of constitutive model are discussed.Similar materials are prepared.The self-made multi-stage reaming simulation drilling tool is used to study the deformation characteristics and deformation mechanism of surrounding rock in the coal seam under multi-stage reaming drilling conditions.The FLAC^3D numerical simulation software is used to analyze the surrounding rock displacement and stress distribution of the drilling.The main conclusions are as follows:?1?The stress-strain curve of tectonically deformed coal can be divided into five deformation stages:compaction deformation,elastic deformation,yield deformation,failure and residual deformation.The second compaction will cause the compact phase of the coal sample to become less and less noticeable.The increase in confining pressure is the main reason for the increase in tectonically deformed coal stiffness.The Poisson's ratio of the tectonically deformed coal is not fixed at a slightly larger than the Poisson's ratio of the general rock.?2?Based on the statistical theory,it is assumed that the strength of the tectonic coal micro-elements conforms to the Weibull distribution,and the statistical damage constitutive model of the tectonic coal is obtained.The model parameters are obtained and the physical meaning is determined.It is concluded that the increase in confining pressure will cause the structural coal to tend from the brittle characteristic to the plastic characteristic and the average strength increases.?3?The deformation characteristics of the surrounding rock of the drilling wall are obtained.After the first drilling,the 90° direction after the first reaming has the greatest influence,followed by the 0° direction and the 180° direction,followed by the45° direction and the 135° direction,followed by the 225° direction and the 315° direction,and the 90° direction has the smallest influence range.After the second drilling?first reaming?,the 270° direction has the greatest influence after the second drilling,followed by the 225° direction and the 315° direction,followed by the 45° direction and the 135° direction,followed by the 180° direction and the 0° direction,and the 90° direction has the smallest influence range.After the third drilling?second reaming?,the 270° direction has the greatest influence after the third drilling,followed by the 225° direction and the 315° direction,followed by the 45° direction and the135° direction,followed by the 180° direction and the 0° direction,and the 90° direction has the smallest influence range.The displacement distribution of the experimental simulation wis verified by numerical simulation,and the results prove to be in good agreement.?4?The deformation mechanism of surrounding rock under multi-stage reaming drilling conditions is proposed.The deformation of surrounding rock is the result of the combination of material properties,rock mass force,strain softening phenomenon and expansion of rock mass after compression.