国际岩石力学学会(International Society for Rock Mechanics——ISRM)在1995年提出一种新型的岩石断裂韧度试样——人字型切槽巴西圆盘试样(cracked chevron notched Brazilian disc —— CCNBD)。但是,该试样的重要力学参数即无量纲...国际岩石力学学会(International Society for Rock Mechanics——ISRM)在1995年提出一种新型的岩石断裂韧度试样——人字型切槽巴西圆盘试样(cracked chevron notched Brazilian disc —— CCNBD)。但是,该试样的重要力学参数即无量纲应力强度因子的标定尚有问题。针对此关键问题进行深入的研究,获得了该试样新的更准确的标定值。采用大型商业有限元软件ANSYS,引入了ANSYS子模型法和局部裂纹子模型法进行三维应力强度因子的计算。结果表明,子模型方法具有很高的精度和适用性。在计算了CCNBD试样的无量纲应力强度因子以后,还综合比较了前人相关的一些结果,从理论分析的角度证明了所得结果是合理可靠的。展开更多
There is no doubt that an understanding of brittle rock fracturing is a key element in the solution of many engineering problems that involve rock structures.Some rock structures such as bridge and dam abutments and f...There is no doubt that an understanding of brittle rock fracturing is a key element in the solution of many engineering problems that involve rock structures.Some rock structures such as bridge and dam abutments and foundations,and tunnel walls,undergo both static and cyclic loading caused by drilling and blasting,and vehicle-induced vibrations.This type of loading often causes rock to fail at a lower than its static strength due to the effect of rock fatigue.A series of laboratory diametrical compression tests was performed on Brisbane tuff disc specimens to investigate their mode-I fracture toughness response to static and cyclic loading,as a function of the applied load.Both the static and cyclic loading tests were carried out on CCNBD(cracked chevron notched Brazilian disc)rock specimens.In the tests described herein,the reduction in fracture toughness under dynamic cyclic loading was found to be up to 48%of the static fracture toughness.Contrary to the static tests,the cyclic tests produced much more crushed material in front of the tip of the chevron notched crack.展开更多
The mode-I fracture toughness is of great significance for evaluating the fracturing ability of shale reservoirs.In this study,the mode-I fracture toughness of the shale in the Lower Silurian Longmaxi Formation,Southe...The mode-I fracture toughness is of great significance for evaluating the fracturing ability of shale reservoirs.In this study,the mode-I fracture toughness of the shale in the Lower Silurian Longmaxi Formation,Southern Sichuan Basin was determined with the Cracked Chevron Notched Brazilian Disc(CCNBD).Based on the experimental data,the relationships among the mode-I fracture toughness,the density,the acoustic time and the clay mineral content were analyzed.The shale samples for fracture toughness test from cores were commonly limited,the investigation of fracture toughness using well logs was necessary.Therefore,a prediction model was proposed by correlating the fracture toughness with well logs responses.The results indicate that the fracture toughness of shale samples is from 0.4744 MPa$m1/2 to 1.0607 MPa$m1/2 with an average of 0.7817 MPa$m1/2,indicating that the anisotropy of fracture toughness of the Longmaxi Formation shale.The clay mineral content and the density have a positive effect on the fracture toughness,whereas the acoustic time plays a negative role on the fracture toughness.The clay mineral content has an important effect on the relationships among fracture toughness,acoustic time and density.The prediction model can provide continuous data of mode-I fracture toughness along the wellbore for field hydraulic fracturing operation,and it has certain guiding significance in the exploration and development of oil and gas reservoirs.展开更多
文摘国际岩石力学学会(International Society for Rock Mechanics——ISRM)在1995年提出一种新型的岩石断裂韧度试样——人字型切槽巴西圆盘试样(cracked chevron notched Brazilian disc —— CCNBD)。但是,该试样的重要力学参数即无量纲应力强度因子的标定尚有问题。针对此关键问题进行深入的研究,获得了该试样新的更准确的标定值。采用大型商业有限元软件ANSYS,引入了ANSYS子模型法和局部裂纹子模型法进行三维应力强度因子的计算。结果表明,子模型方法具有很高的精度和适用性。在计算了CCNBD试样的无量纲应力强度因子以后,还综合比较了前人相关的一些结果,从理论分析的角度证明了所得结果是合理可靠的。
文摘There is no doubt that an understanding of brittle rock fracturing is a key element in the solution of many engineering problems that involve rock structures.Some rock structures such as bridge and dam abutments and foundations,and tunnel walls,undergo both static and cyclic loading caused by drilling and blasting,and vehicle-induced vibrations.This type of loading often causes rock to fail at a lower than its static strength due to the effect of rock fatigue.A series of laboratory diametrical compression tests was performed on Brisbane tuff disc specimens to investigate their mode-I fracture toughness response to static and cyclic loading,as a function of the applied load.Both the static and cyclic loading tests were carried out on CCNBD(cracked chevron notched Brazilian disc)rock specimens.In the tests described herein,the reduction in fracture toughness under dynamic cyclic loading was found to be up to 48%of the static fracture toughness.Contrary to the static tests,the cyclic tests produced much more crushed material in front of the tip of the chevron notched crack.
基金by the National Science and Technology Major Project(Grant No.2019A-3307)the National Natural Science Foundation of China(Grant No.41872167)。
文摘The mode-I fracture toughness is of great significance for evaluating the fracturing ability of shale reservoirs.In this study,the mode-I fracture toughness of the shale in the Lower Silurian Longmaxi Formation,Southern Sichuan Basin was determined with the Cracked Chevron Notched Brazilian Disc(CCNBD).Based on the experimental data,the relationships among the mode-I fracture toughness,the density,the acoustic time and the clay mineral content were analyzed.The shale samples for fracture toughness test from cores were commonly limited,the investigation of fracture toughness using well logs was necessary.Therefore,a prediction model was proposed by correlating the fracture toughness with well logs responses.The results indicate that the fracture toughness of shale samples is from 0.4744 MPa$m1/2 to 1.0607 MPa$m1/2 with an average of 0.7817 MPa$m1/2,indicating that the anisotropy of fracture toughness of the Longmaxi Formation shale.The clay mineral content and the density have a positive effect on the fracture toughness,whereas the acoustic time plays a negative role on the fracture toughness.The clay mineral content has an important effect on the relationships among fracture toughness,acoustic time and density.The prediction model can provide continuous data of mode-I fracture toughness along the wellbore for field hydraulic fracturing operation,and it has certain guiding significance in the exploration and development of oil and gas reservoirs.
