Shear-sliding mode(mode Ⅱ)fracture of rocks is a vital failure form in deep underground engineering.To gain deep insight into the anisotropic shear fracture behaviors of a typical shale under high normal stress condi...Shear-sliding mode(mode Ⅱ)fracture of rocks is a vital failure form in deep underground engineering.To gain deep insight into the anisotropic shear fracture behaviors of a typical shale under high normal stress conditions,a series of direct shear tests were conducted on double-notched specimens in three typical bedding orientations(i.e.,the arrester,divider,short-transverse orientations)and under five normal stresses.The modeⅡfracture toughness(K_(Ⅱc))is found to exhibit a significant 3D anisotropy.The maximum K_(Ⅱc)is obtained in the divider orientation,followed by those in the arrester and short-transverse orientations.In contrast,the 3D anisotropy in the critical modeⅡenergy release rate(G_(Ⅱc))is not as significant as that in K_(Ⅱc),and G_(Ⅱc)in the arrester orientation is quite close to that in the divider orientation.The anisotropy in the prepeak input energy accumulated during shearing is found to be exactly consistent with that in G_(Ⅱc),which has not been noted before.Furthermore,the anisotropies in the modeⅡfracture resistances will,unexpectedly,not be weakened by the high normal stress.Owing to the layered structures,tensile cracks are involved during the modeⅡfracture process,resulting in the formation of rough fracture surfaces.展开更多
Previous strategies for controlling the surface morphologies of polyvinyl alcohol(PVA)-based hydrogels,including freeze-drying and electrospinning,require a posttreatment process,which can affect the final textures an...Previous strategies for controlling the surface morphologies of polyvinyl alcohol(PVA)-based hydrogels,including freeze-drying and electrospinning,require a posttreatment process,which can affect the final textures and properties of the hydrogels.Of particular interest,it is almost impossible to control the surface morphology during the formation of PVA hydrogels using these approaches.The strategy reported in this study used the novel vortex fluidic device(VFD)technology,which for the first time provided an opportunity for one-step fabrication of PVA hydrogel films.PVA hydrogels with different surface morphologies could be readily fabricated using a VFD.By also reducing the crosslinking agent concentration,a self-healing gel with enhanced fracture stress(60%greater than that of traditionally made hydrogel)was achieved.Interestingly,the associated selfhealing property remained unchanged during the 260-s mechanical testing performed with the strain rate of 5%s-1.The VFD can effectively tune the surface morphologies of the PVA-based hydrogels and their associated properties,particularly the self-healing property.展开更多
基金Project(12172240)supported by the National Natural Science Foundation of ChinaProject(2021YFH0030)supported by the Science&Technology Department of Sichuan Province,China。
文摘Shear-sliding mode(mode Ⅱ)fracture of rocks is a vital failure form in deep underground engineering.To gain deep insight into the anisotropic shear fracture behaviors of a typical shale under high normal stress conditions,a series of direct shear tests were conducted on double-notched specimens in three typical bedding orientations(i.e.,the arrester,divider,short-transverse orientations)and under five normal stresses.The modeⅡfracture toughness(K_(Ⅱc))is found to exhibit a significant 3D anisotropy.The maximum K_(Ⅱc)is obtained in the divider orientation,followed by those in the arrester and short-transverse orientations.In contrast,the 3D anisotropy in the critical modeⅡenergy release rate(G_(Ⅱc))is not as significant as that in K_(Ⅱc),and G_(Ⅱc)in the arrester orientation is quite close to that in the divider orientation.The anisotropy in the prepeak input energy accumulated during shearing is found to be exactly consistent with that in G_(Ⅱc),which has not been noted before.Furthermore,the anisotropies in the modeⅡfracture resistances will,unexpectedly,not be weakened by the high normal stress.Owing to the layered structures,tensile cracks are involved during the modeⅡfracture process,resulting in the formation of rough fracture surfaces.
基金International Research Grant(International Laboratory for Health Technologies)of South Australia for supportRaston CL is grateful for support from the Australian Research CouncilMa Y is grateful for the support from the National Natural Science Foundation of China(51679183)。
文摘Previous strategies for controlling the surface morphologies of polyvinyl alcohol(PVA)-based hydrogels,including freeze-drying and electrospinning,require a posttreatment process,which can affect the final textures and properties of the hydrogels.Of particular interest,it is almost impossible to control the surface morphology during the formation of PVA hydrogels using these approaches.The strategy reported in this study used the novel vortex fluidic device(VFD)technology,which for the first time provided an opportunity for one-step fabrication of PVA hydrogel films.PVA hydrogels with different surface morphologies could be readily fabricated using a VFD.By also reducing the crosslinking agent concentration,a self-healing gel with enhanced fracture stress(60%greater than that of traditionally made hydrogel)was achieved.Interestingly,the associated selfhealing property remained unchanged during the 260-s mechanical testing performed with the strain rate of 5%s-1.The VFD can effectively tune the surface morphologies of the PVA-based hydrogels and their associated properties,particularly the self-healing property.
