The fracture toughness of rocks is a critical fracturing parameter in geo-energy exploitation playing a significant role in fracture mechanics and hydraulic fracturing.The edge-notched disk bending(ENDB)specimens are ...The fracture toughness of rocks is a critical fracturing parameter in geo-energy exploitation playing a significant role in fracture mechanics and hydraulic fracturing.The edge-notched disk bending(ENDB)specimens are employed to measure the entire range of mixed-modeⅠ/Ⅲfracture toughness of Longmaxi shale.To theoretically interpret the fracture mechanisms,this research first introduces the detailed derivations of three established fracture criteria.By distinguishing the volumetric and distortional strain energy densities,an improved three-dimensional mean strain energy density(MSED)criterion is proposed.As the critical volumetric to distortional MSED ratio decreases,the transition from tensiondominated fracture to shear-dominated fracture is observed.Our results indicate that both peak load and applied energy increase significantly with the transition from pure mode I(i.e.,tension)to pure modeⅢ(i.e.,torsion or tearing)since mode-Ⅲcracking happens in a twisted manner and mode-Ⅰcracking occurs in a coplanar manner.The macroscopic fracture signatures are consistent with those of triaxial hydraulic fracturing.The average ratio of pure mode-Ⅲfracture toughness to pure mode-Ⅰfracture toughness is 0.68,indicating that the obtained mode-Ⅲfracture resistance for a tensionbased loading system is apparent rather than true.Compared to the three mainstream fracture criteria,the present fracture criterion exhibits greater competitiveness and can successfully evaluate and predict mixed-modeⅠ/Ⅲfracture toughness of distinct materials and loading methods.展开更多
Objective:To exploit- the effects of gentiana scabra bage on the expression of hepatic collagen proteins in Paragonimus skrjabini rats with liver fibrosis.Methods:Immunohistochemical technique was used to observe the ...Objective:To exploit- the effects of gentiana scabra bage on the expression of hepatic collagen proteins in Paragonimus skrjabini rats with liver fibrosis.Methods:Immunohistochemical technique was used to observe the changes of content of hepatic type Ⅰ,Ⅲ collagen proteins in Paragonimus skrjabini rats with Liver fibrosis before and after the gentiana scabra bage treatmeat.Results:Comparing with the model group,changes of hepatic tvpe Ⅰ and type Ⅲ collagen proteins in gentiana scabra bage treated group were significantly weakened.Conclusions:Gentiana scabra bage treatment can reduce the content of hepatic type Ⅲ and type Ⅰ collagen protein significantly in Paragonimus skrjabini rats with liver fibrosis,thereby,playing the role against hepatic fibrosis.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.52364004,52264006,and 52164001).
文摘The fracture toughness of rocks is a critical fracturing parameter in geo-energy exploitation playing a significant role in fracture mechanics and hydraulic fracturing.The edge-notched disk bending(ENDB)specimens are employed to measure the entire range of mixed-modeⅠ/Ⅲfracture toughness of Longmaxi shale.To theoretically interpret the fracture mechanisms,this research first introduces the detailed derivations of three established fracture criteria.By distinguishing the volumetric and distortional strain energy densities,an improved three-dimensional mean strain energy density(MSED)criterion is proposed.As the critical volumetric to distortional MSED ratio decreases,the transition from tensiondominated fracture to shear-dominated fracture is observed.Our results indicate that both peak load and applied energy increase significantly with the transition from pure mode I(i.e.,tension)to pure modeⅢ(i.e.,torsion or tearing)since mode-Ⅲcracking happens in a twisted manner and mode-Ⅰcracking occurs in a coplanar manner.The macroscopic fracture signatures are consistent with those of triaxial hydraulic fracturing.The average ratio of pure mode-Ⅲfracture toughness to pure mode-Ⅰfracture toughness is 0.68,indicating that the obtained mode-Ⅲfracture resistance for a tensionbased loading system is apparent rather than true.Compared to the three mainstream fracture criteria,the present fracture criterion exhibits greater competitiveness and can successfully evaluate and predict mixed-modeⅠ/Ⅲfracture toughness of distinct materials and loading methods.
基金supported by National Natural Science Foundation of China(No.81360252:81360128)Natural Science Foundation of Yunnan Province(No.2012FB025)
文摘Objective:To exploit- the effects of gentiana scabra bage on the expression of hepatic collagen proteins in Paragonimus skrjabini rats with liver fibrosis.Methods:Immunohistochemical technique was used to observe the changes of content of hepatic type Ⅰ,Ⅲ collagen proteins in Paragonimus skrjabini rats with Liver fibrosis before and after the gentiana scabra bage treatmeat.Results:Comparing with the model group,changes of hepatic tvpe Ⅰ and type Ⅲ collagen proteins in gentiana scabra bage treated group were significantly weakened.Conclusions:Gentiana scabra bage treatment can reduce the content of hepatic type Ⅲ and type Ⅰ collagen protein significantly in Paragonimus skrjabini rats with liver fibrosis,thereby,playing the role against hepatic fibrosis.
