Simulation Study on Rock Mechanical Properties Under Sleeve Alternating Fracturing Effect
In order to broaden the method of forced roof caving for hard roof and solve the problem of stress concentration in surrounding rock caused by hard roof,the mechanical mechanism of sleeve rock breaking is derived based on elastic mechanics.PFC3D numerical simulation software is used to analyze the rock fracture morphology and expansion force characteristics during sleeve fracturing process by changing the expansion path of the sleeve.The results show that increasing the drilling hole radius,increasing the number of sleeves,or reducing the spacing between drilling holes can all reduce the injection pressure required for rock cracking during the porous sleeve fracturing process;compared to synchronous fracturing,alternating fracturing prolongs the fracturing time,forms a more complex fracture network,and has a larger range of rock damage;alternating fracturing reduces the required expansion pressure during the fracturing process,exacerbates rock fatigue damage,presents a multi peak value distribution of acoustic emission signals,and increases the number of rock fractures;compared to synchronous fracturing,sleeve alternating fracturing generates a higher dissipated energy and dissipated energy proportion and causes greater degree of damage to the rock.
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