Abstract
In this paper, the crack initiation characteristics of compression-shear plane crack with hydraulic pressure were studied by using theoretical analysis and experimental verification methods. The formula derivation process of stress intensity factor of crack tip and open-type crack initiation angle and initiation strength was expounded in detail. Cement mortar specimens prefabricated with open-type crack were made for biaxial compression test. The results show that the mode I stress intensity factor is inversely proportional to the dip angle of pre-exciting crack, water pressure and crack width. The fracture toughness is most easily achieved when the dip angle of pre-exciting crack is 60°. The mode II stress intensity factor is symmetrically distributed with the dip angle and independent of the water pressure and crack width. For open-type crack, the crack initiation angle decreases with the increase of the dip angle of pre-exciting crack, water pressure and crack width; the crack initiation strength is inversely proportional to the water pressure and proportional to the lateral pressure. The research results can provide ideas for the study of crack initiation under the coupling of ground stress and osmotic pressure in tunnel engineering.
Highlights
IntroductionZhao Y L et al [4] [5] have studied the crack initiation law of frictional crack under seepage pressure
The results show that the mode I stress intensity factor is inversely proportional to the dip angle of pre-exciting crack, water pressure and crack width
The analytical solution of stress intensity factor and crack initiation angle was calculated by substituting the experimental parameters into the above derivation formulas
Summary
Zhao Y L et al [4] [5] have studied the crack initiation law of frictional crack under seepage pressure They developed a damage fracture mechanics model of rock cracks under jointed action of compressive-shear stress field and seepage field. XB LI et al [6] studied the mechanical model of fracture and damage and the evolution equation of stress intensity factor at crack tip under the action of compression-shear field and seepage field, and proposed the crack initiation criterion by using the stress intensity factor. It can be seen that the initiation and expansion of compression-shear mode I cracks depend on the normal stress of two vertical directions, the radius of curvature of crack tip and the circumference angle. The seepage water pressure p has a promotion effect on the initiation and expansion of compression-shear fracture
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