Study On The Relationship Between Structure、Acoustic Characteristics And Mechanical Properties Of Sandstone In Shendong Mining Area

In this paper,Taking weakly cemented sandstone of Shendong mining area as the research object,by using polarizing microscope,scanning electron microscope,nuclear magnetic resonance system,RMT-150C mechanical testing machine,DS5-8B series full information of acoustic emission instrument for different types of sandstone mineral composition,morphology,pore characteristics,mechanical properties and acoustic emission characteristics of the a comprehensive and systematic research.The relationship between pore structure,acoustic characteristics and mechanical properties of different sandstone are mainly discussed,which lays the foundation for the related theoretical research of building sandstone mechanics constitutive model in Shendong Mining Area.The main conclusions are as follows:（1）The main components of sandstone are quartz and feldspar,in which the content of quartz is above 15%,the content of feldspar is more than 40%,and there is a small amount of mica;The pore diameter and size of sandstone basically obey normal distribution;The surface of siltstone is smooth and dense,while Small pores are distributed on the surface of fine-grained sandstone.the middle grained sandstone pore structure is developed,with cluster shape;The T₂ distribution of siltstone and fine-grained sandstone shows obvious double peak.Both of them are mainly micropores and small pores.The T₂ spectrum distribution of medium grain sandstone has both single peak and double peak.The distribution of large,medium and small pores are relatively homogenous compared with the first two kinds of sandstone.（2）The relationship between compressive strength and porosity of sandstone shows positive correlation,stress-strain curves is two kinds of damage model.However,The ductility stage is due to the cementation state formed by the mineral particles and cementation,which has a certain bearing capacity.The curve shows that the stress remains unchanged and the stress increases continuously;The main failure forms of sandstone are splitting and conical failure,The siltstone and medium grained sandstone are mainly split and cracked,and the fine grained sandstone has two types of failure modes,which are conical failure and main failure surface throughout the whole rock sample.（3）The cumulative ringing count、cumulative energy and stress change of sandstone are consistent.the cumulative ringing count increases with the enlargement of rock skeleton structure,but there is no obvious law of accumulative energy.In the stage of compaction,The maximum ringing count and acoustic emission energy of sandstone are negatively correlated with particle size;in the stage of elastic,siltstone and fine sandstone accumulative count and cumulative energy approximately show linear growth,sandstone curve is concave;at the yield stage,the AE activity is more active,the count of ringing and the energy of acoustic emission are roughly stepped up,and the internal damage of the specimen is further aggravated;At the stage of strain softening,the sudden increase of the ringing count and acoustic emission energy are more than 2.5times that of the origina,it can be considered as precursor of impending destruction.（4）The compressive strength of sandstone is negatively exponential with porosity and spectral area,and there are critical points on the curve.when the critical point is lower than the critical point,the degradation rate of mechanical properties is faster,and the critical porosity is positively correlated with particle diameter and pore diameter;there is a negative correlation between elastic modulus and porosity、spectral area.for porosity,siltstone and fine grained sandstone decrease exponentially,while middle granular sandstone is linear;however,the spectral area of the siltstone is reduced by power function,and the other two kinds of sandstone are consistent,and the correlation coefficient is lower than that of the compressive strength and the pore structure.There is no obvious relationship between Poisson’s ratio and porosity and spectral area,indicating that Poisson ratio is not highly sensitive to porosity change.