循环加卸载条件下不同层理倾角磷块岩损伤特性研究OA

In order to reveal the damage evolution law of sedimentary phosphorite under the coupling action of bedding dip angle and cyclic loading and unloading,standard specimens with 0°,30°,60° and 90° bedding dip angles were prepared,and uniaxial step-by-step cyclic loading and unloading tests were carried out.Combined with RFPA2D numerical simulation,the regulation mechanism of bedding dip angle on stress-strain characteristics,hysteretic evolu-tion,modulus response and damage variables of phosphorite was explored.The results show that the synergistic effect of bedding structure and cyclic load makes the axial strain hysteresis loop of phosphate rock present the evolution process of'loose-dense-loose again'.With the increase of the number of cycles,the loading elastic modulus increa-ses as a whole,the unloading elastic modulus decreases slowly,and the damage variable accumulates monotonously in the form of'decreasing growth rate'.The peak strength shows a typical'V'shape with the increase of bedding dip angle,and the strength of 60° inclination specimen is the lowest.The RFPA2D numerical simulation confirms the con-trol effect of bedding dip angle on the failure mode of phosphate rock from the mesoscopic level,and is consistent with the macroscopic test results.The research results can provide theoretical support for the stability evaluation,support optimization and rockburst prevention and control of layered surrounding rock in deep phosphate rock.