We simulated hydraulic fracturing in different lithologic rocks in the horizontal drilling by using the true physical model experiment and large rock specimens, carried out the real-time dynamic monitoring with adding...We simulated hydraulic fracturing in different lithologic rocks in the horizontal drilling by using the true physical model experiment and large rock specimens, carried out the real-time dynamic monitoring with adding tracer and then did post-fracturing cutting and so on. Based on this monitoring results, we compared and assessed the factors affecting expansion in shale, shell limestone, and tight sandstone and the fracture expansion in these rocks. In shale, the reformed reservoir volume is the highest, fracture network is formed in the process of fracturing. In tight sandstone, the fracture surface boundaries are curved, and the fracture surface area accounts for 25–50% of the entire specimen. In shell limestone, the complexity of the fracture morphology is between shale and tight sandstone, but no fracture network is developed. Brittleness controls the fracture surface area. In highly brittle rocks, the fracture surface area is high. Fracture toughness mainly affects the initiation and propagation of cracks. A fracture network is formed only if bedding planes are present and are more weaker than their corresponding matrix. The horizontal in situ deviatoric stress affects the crack propagation direction, and different lithologies have different horizontal in situ deviatoric stress thresholds. Low f luid injection rate facilitates the formation of complex cracks, whereas high fluid injection rate favors the development of fractures. Fluid injection weakly controls the complexity of hydraulic fracturing in low-brittleness rocks, whereas lowviscosity fracturing fluids favor the formation of complex cracks owing to easy enter microcracks and micro-pore. Displacement has a greater impact on high brittle rocks than low brittle rocks.展开更多
To characterize the shape of sand particles for concrete,a new method is proposed based on digital image processing(known as the DIP method).By analyzing sand particles projection,the length,width and thickness of san...To characterize the shape of sand particles for concrete,a new method is proposed based on digital image processing(known as the DIP method).By analyzing sand particles projection,the length,width and thickness of sand were measured to characterize particle form.The area and perimeter were measured to characterize particle angularity.The results of the DIP method and Vernier caliper were compared to examine the accuracy of the DIP method.The sample size test was conducted to show the statistical significance of shape results measured by the DIP method.The practicality of the DIP method was verified by instance analysis.The results show that aspect ratios and roundness measured by the DIP method are equal to ones by the Vernier caliper.Results by DIP are dependent on the sand particle number,and at least 350 particles should be measured to represent the overall shape property of sand.The results show that the DIP method is able to distinguish the differences in the shape of sand particles.It achieves the direct measurement of sand particle thickness,and the characterization results of sand aspect ratios and roundness are accurate,statistically significant and practical.Therefore,the DIP method is suitable for sand particle shape characterization.展开更多
In order to expand the engineering application of recycle aggregate mortars (RAM) with aggregates from demolished concretes, the models for the properties of RAM and the replacement rate of these recycled fine aggre...In order to expand the engineering application of recycle aggregate mortars (RAM) with aggregates from demolished concretes, the models for the properties of RAM and the replacement rate of these recycled fine aggregates were proposed. First, different kinds of mathematical models for the basic properties (compressive strength, water retention rate, and consistency loss) of RAM with two kinds of admixtures, thickening powders (TP) and self-made powdery admixtures (SSCT) designed for RAM, and the replacement rates were established, while the average relative errors and relative standard errors of these models were calculated. Additionally, the models and their error analyses for the curves of drying shrinkage and curing time of RAM + SSCT at different replacement rates were put forward. The results show that polynomial functions should be used to calculate the basic properties of RAM + TP and RAM + SSCT at different replacement rates. In addition, polynonfial functions are the most optimal models for the sharp shrinkage sections in the curves of drying shrinkage-curing time of RAM + SSCT, while exponential functions should be used as the models for the slow shrinkage sections and steady shrinkage sections.展开更多
The axial bearing capacity of prefabricated composite walls composed of inner and outer concrete wythes,expandable polystyrene(EPS)boards and steel sleeve connectors is investigated.An experimental study on the axial ...The axial bearing capacity of prefabricated composite walls composed of inner and outer concrete wythes,expandable polystyrene(EPS)boards and steel sleeve connectors is investigated.An experimental study on the axial bearing capacity of four prefabricated composite walls after fire treatment is carried out.Two of the prefabricated composite walls are normal-temperature specimens,and the others are treated with fire.The damage modes and crack development are observed,and the axial bearing capacity,lateral deformation of the specimens,and the concrete and reinforcing bar strain are tested.The results show that the ultimate bearing capacity of specimens after a fire is less than that of normal-temperature specimens;when the insulation board thicknesses are 40 mm and 60 mm,the decrease amplitudes are 20.8%and 16.8%,respectively.The maximum lateral deformation of specimens after a fire is greater than that of normal-temperature specimens,and under the same level of load,the lateral deformation increases as the insulation board thickness increases.Moreover,the strain values of the concrete and reinforcing bars of specimens after a fire are greater than those of normal-temperature specimens,and the strain values increase as the thickness of insulation board increases.展开更多
The damping properties were improved by preparing Al matrix composites reinforced with glass cenospheres through the pressure infiltration method.Transmission electron microscopy and scanning electron microscopy were ...The damping properties were improved by preparing Al matrix composites reinforced with glass cenospheres through the pressure infiltration method.Transmission electron microscopy and scanning electron microscopy were employed to characterize the microstructure of the composites.The low-frequency damping properties were examined by using a dynamic mechanical thermal analyzer,aiming at exploring the changing trend of damping capacity with strain,temperature,and frequency.The findings demonstrated that the damping value rose as temperature and strain increased,with a maximum value of 0.15.Additionally,the damping value decreased when the frequency increased.Dislocation damping under strain and interfacial damping under temperature served as the two primary damping mechanisms.The increase in the density of dislocation strong pinning points following heat treatment reduced the damping value,which was attributed to the heat treatment enhancement of the interfacial bonding force of the composites.展开更多
基金supported by the National Key Research and Development Program Funding Project(2018YFC1504903)the National Natural Science Foundation of China(Nos.51574218,51678171,51608139,U1704243,and 51709113)+2 种基金Guangdong Science and Technology Department(No.2015B020238014)Guangzhou Science Technology and Innovation Commission(No.201604016021)High-level Talent Research Launch Project(No.950318066)
文摘We simulated hydraulic fracturing in different lithologic rocks in the horizontal drilling by using the true physical model experiment and large rock specimens, carried out the real-time dynamic monitoring with adding tracer and then did post-fracturing cutting and so on. Based on this monitoring results, we compared and assessed the factors affecting expansion in shale, shell limestone, and tight sandstone and the fracture expansion in these rocks. In shale, the reformed reservoir volume is the highest, fracture network is formed in the process of fracturing. In tight sandstone, the fracture surface boundaries are curved, and the fracture surface area accounts for 25–50% of the entire specimen. In shell limestone, the complexity of the fracture morphology is between shale and tight sandstone, but no fracture network is developed. Brittleness controls the fracture surface area. In highly brittle rocks, the fracture surface area is high. Fracture toughness mainly affects the initiation and propagation of cracks. A fracture network is formed only if bedding planes are present and are more weaker than their corresponding matrix. The horizontal in situ deviatoric stress affects the crack propagation direction, and different lithologies have different horizontal in situ deviatoric stress thresholds. Low f luid injection rate facilitates the formation of complex cracks, whereas high fluid injection rate favors the development of fractures. Fluid injection weakly controls the complexity of hydraulic fracturing in low-brittleness rocks, whereas lowviscosity fracturing fluids favor the formation of complex cracks owing to easy enter microcracks and micro-pore. Displacement has a greater impact on high brittle rocks than low brittle rocks.
基金The National Key Research and Development Program of China(No.2017YFB0310100)the National Natural Science Foundation of China(No.51978318)。
文摘To characterize the shape of sand particles for concrete,a new method is proposed based on digital image processing(known as the DIP method).By analyzing sand particles projection,the length,width and thickness of sand were measured to characterize particle form.The area and perimeter were measured to characterize particle angularity.The results of the DIP method and Vernier caliper were compared to examine the accuracy of the DIP method.The sample size test was conducted to show the statistical significance of shape results measured by the DIP method.The practicality of the DIP method was verified by instance analysis.The results show that aspect ratios and roundness measured by the DIP method are equal to ones by the Vernier caliper.Results by DIP are dependent on the sand particle number,and at least 350 particles should be measured to represent the overall shape property of sand.The results show that the DIP method is able to distinguish the differences in the shape of sand particles.It achieves the direct measurement of sand particle thickness,and the characterization results of sand aspect ratios and roundness are accurate,statistically significant and practical.Therefore,the DIP method is suitable for sand particle shape characterization.
基金The National Key Research and Development Program of China(No.2017YFC0703100)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX18_0081)
文摘In order to expand the engineering application of recycle aggregate mortars (RAM) with aggregates from demolished concretes, the models for the properties of RAM and the replacement rate of these recycled fine aggregates were proposed. First, different kinds of mathematical models for the basic properties (compressive strength, water retention rate, and consistency loss) of RAM with two kinds of admixtures, thickening powders (TP) and self-made powdery admixtures (SSCT) designed for RAM, and the replacement rates were established, while the average relative errors and relative standard errors of these models were calculated. Additionally, the models and their error analyses for the curves of drying shrinkage and curing time of RAM + SSCT at different replacement rates were put forward. The results show that polynomial functions should be used to calculate the basic properties of RAM + TP and RAM + SSCT at different replacement rates. In addition, polynonfial functions are the most optimal models for the sharp shrinkage sections in the curves of drying shrinkage-curing time of RAM + SSCT, while exponential functions should be used as the models for the slow shrinkage sections and steady shrinkage sections.
基金The National Key Research and Development Program of China(No.2016YFC0701703)the Natural Science Foundation of Higher Education Institutions of Jiangsu Province(No.2016TM045J)the Scientific Innovation Research of Graduate Students in Jiangsu Province(No.KYLX_0151)
文摘The axial bearing capacity of prefabricated composite walls composed of inner and outer concrete wythes,expandable polystyrene(EPS)boards and steel sleeve connectors is investigated.An experimental study on the axial bearing capacity of four prefabricated composite walls after fire treatment is carried out.Two of the prefabricated composite walls are normal-temperature specimens,and the others are treated with fire.The damage modes and crack development are observed,and the axial bearing capacity,lateral deformation of the specimens,and the concrete and reinforcing bar strain are tested.The results show that the ultimate bearing capacity of specimens after a fire is less than that of normal-temperature specimens;when the insulation board thicknesses are 40 mm and 60 mm,the decrease amplitudes are 20.8%and 16.8%,respectively.The maximum lateral deformation of specimens after a fire is greater than that of normal-temperature specimens,and under the same level of load,the lateral deformation increases as the insulation board thickness increases.Moreover,the strain values of the concrete and reinforcing bars of specimens after a fire are greater than those of normal-temperature specimens,and the strain values increase as the thickness of insulation board increases.
基金financially supported by the National Key Research and Development Program of China(No.2022YFE0121400)the National Natural Science Foundation of China(Nos.52071117,52111530297,51601047)+1 种基金the Heilongjiang Provincial Science Fund for Distinguished Young Scholars,China(No.JQ2021E002)the Guangdong Basic and Applied Basic Research Foundation,China(No.2022B1515120016)。
文摘The damping properties were improved by preparing Al matrix composites reinforced with glass cenospheres through the pressure infiltration method.Transmission electron microscopy and scanning electron microscopy were employed to characterize the microstructure of the composites.The low-frequency damping properties were examined by using a dynamic mechanical thermal analyzer,aiming at exploring the changing trend of damping capacity with strain,temperature,and frequency.The findings demonstrated that the damping value rose as temperature and strain increased,with a maximum value of 0.15.Additionally,the damping value decreased when the frequency increased.Dislocation damping under strain and interfacial damping under temperature served as the two primary damping mechanisms.The increase in the density of dislocation strong pinning points following heat treatment reduced the damping value,which was attributed to the heat treatment enhancement of the interfacial bonding force of the composites.