| The long and complicated geological tectonic movement leads to the defects of cracks,joints and faults in the engineering rock mass.Under the influence of external loads,the cracks in the rock mass will continue to produce,expand and coalescence until the rock mass is destabilized.Therefore,it is of great theoretical value and engineering significance to study the expansion mode of cracks in rock mass and the characteristics of rock bridge coalescence and its strength change laws.In this paper,through primary and secondary cracks prefabricated containing in rock-like specimen under uniaxial compression test the influence of crack geometry size and spatial distribution on rock bridge coalescence model and the mechanical properties of rock mass destruction process is studied.The mechanical properties and energy release laws of crack rock-like destruction were further analyzed basing on RFPA2D software.Specific research contents and results are as follows:?1?Rock-like specimen containing primary and secondary cracks with different crack angles,crack length and rock bridge size are designed and prepared,there are 42 groups,total 126 specimen;The new crack types of prefabricated cracks in the destruction process of specimen under uniaxial compression are recorded and summarized by cameras,there are three types of wing crack,slant crack and co-plane crack;Four kinds of rock bridge coalescence mode are found according to the rock bridge coalescence path number and position,the influence of crack geometry size and spatial distribution on rock bridge coalescence mode are summarized.?2?Basing on the stress and strain datas collected by the test system,influence of the crack geometry size and spatial distribution on the mechanical behavior of specimen damage are studied according to the crack rock specimen stress drop,initial crack strength,peak strength.It come to the result that the primary crack controls crack propagation and rock bridge coalescence and secondary crack play a supporting role,the calculation formula of the influence coefficient of secondary crack is given according to the experimental results.?3?Through non-contact video measuring instrument,analyzing width variation of tip and central of crack and the change of shear slip on both sides of the crack,the crack open failure model and crack shear slip failure model are summarized.?4?Influence of angle of rock bridge and horizontal spacing of primary and secondary cracks on destruction process and energy release of specimen under uniaxial compression load.The rule that stress drop of stress-strain curve with specimen destruction process is positively correlated with simulated acoustic emission curve is gotten. |
PDF Full Text Request