有效围压、固结比、含砾量和颗粒破碎对砂砾土动剪切模量和阻尼比影响的规律已有较丰富的研究成果,但有关颗粒形状影响的研究鲜见报道。利用英国GDS公司的扭剪仪,对级配相同的圆砾砂砾土和角砾砂砾土进行动三轴对比试验,研究相对密度为4...有效围压、固结比、含砾量和颗粒破碎对砂砾土动剪切模量和阻尼比影响的规律已有较丰富的研究成果,但有关颗粒形状影响的研究鲜见报道。利用英国GDS公司的扭剪仪,对级配相同的圆砾砂砾土和角砾砂砾土进行动三轴对比试验,研究相对密度为45%,不同围压下颗粒形状对砂砾土动剪切模量和阻尼比的影响,发现:有效围压大于300 k Pa或剪应变幅值大于7×10-4时,圆砾砂砾土比角砾砂砾土具有更大的动剪切模量;对于最大动剪切模量,圆砾砂砾土和角砾砂砾土均存在砾石(粒径大于5 mm)含量P5的一个阀值P5cr,且角砾砂砾土的砾石含量阀值P5cr较圆砾砂砾土的大,当P5为阀值P5cr时,砂砾土的最大动剪切模量达到极大值;剪应变幅值大于2×10-4时,角砾砂砾土的阻尼比比圆砾砂砾土的大。展开更多
Experimental investigations of the dilatancy and particle breakage of gravelly material from the Zipingpu concrete-faced rock- fill dam, which was subjected to high-intensity seismic load during the 2008 Wenchuan eart...Experimental investigations of the dilatancy and particle breakage of gravelly material from the Zipingpu concrete-faced rock- fill dam, which was subjected to high-intensity seismic load during the 2008 Wenchuan earthquake, were conducted through a series of large-scale drained triaxial compression tests. A hyperbolic relation between the input plastic work and the degree of particle breakage was found for Zipingpu gravel, independent of the initial void ratio and confining pressures. The stress-dilatancy for Zipingpu gravel was analyzed and compared with data from two rounded alluvial and three angular quar- ried gravelly and rockfill materials in the literature. A nearly linear relationship between the dilatancy Dp and the stress ratio η was found at medium-to-large stress ratios before the peak stress ratio. The slope of the stress-dilatancy line before peak had slight dependence on the void ratio and confining pressure of the gravel. After peak, the stress-dilatancy relation shifts down compared with that before peak for the gravel specimen. The phase-transformation stress ratio decreased with increased con- fining pressure, with the exception of sub-rounded gravel with little particle breakage. A nearly linear relationship was found between the phase-transformation stress ratio Mf and the state parameter ψ for the Zipingpu gravel, regardless of the void ratio and confining pressure of the specimens.展开更多
The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM(Scanning Electron Microscopy)image analysis.The results show that the combinat...The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM(Scanning Electron Microscopy)image analysis.The results show that the combination of fly ash and water can fill the voids in cemented sand and gravel test blocks because of the presence of hydrated calcium silicate and other substances;thereby,the compactness and mechanical properties of these materials can be greatly improved.For every 10 kg/m^(3) increase in the amount of cementitious material,the density increases by about 2%,and the water content decreases by 0.2%.The amount of cementitious material used in the sand and gravel in these tests was 80-110 kg/m^(3),the water-binder ratio was 1-1.50.Moreover,the splitting tensile strength was 1/10 of the compressive strength,and the maximum strength was 7.42 MPa at 90 d.The optimal mix ratio has been found to be 50 kg of cement,60 kg of fly ash and 120 kg of water(C50F60W120).The related dry density was 2.6 g/cm^(3),the water content was 6%,and the water-binder ratio was 1.09.展开更多
Polyurethane foam adhesive(PFA)has been introduced as an alternative stabilizer in geotechnical applications because PFA can improve the engineering characteristics of soil by filling the pore space and generating adh...Polyurethane foam adhesive(PFA)has been introduced as an alternative stabilizer in geotechnical applications because PFA can improve the engineering characteristics of soil by filling the pore space and generating adhesive bonding among the particles.However,the dynamic properties of PFA-reinforced soils are not well understood.To analyze the dynamic characteristics of PFA-reinforced gravels,a series of cyclic triaxial tests were carried out to investigate the shear modulus and damping ratio of PFA-reinforced gravels,and to determine the corresponding effects of the PFA content,confining pressure,consolidation stress ratio and loading frequency.The results showed that the shear modulus increased,and the damping ratio decreased as the PFA content,confining pressure and consolidation stress ratio increased.In contrast,the effect of the loading frequency,which ranged from 0.05 to 1 Hz,was negligible.A modified hyperbolic empirical model can consider the effect of the PFA content on the maximum shear modulus and predict the relationship between the normalized shear modulus and the normalized shear strain was proposed.Moreover,the upper and lower bounds of the damping ratio were also proposed.展开更多
文摘有效围压、固结比、含砾量和颗粒破碎对砂砾土动剪切模量和阻尼比影响的规律已有较丰富的研究成果,但有关颗粒形状影响的研究鲜见报道。利用英国GDS公司的扭剪仪,对级配相同的圆砾砂砾土和角砾砂砾土进行动三轴对比试验,研究相对密度为45%,不同围压下颗粒形状对砂砾土动剪切模量和阻尼比的影响,发现:有效围压大于300 k Pa或剪应变幅值大于7×10-4时,圆砾砂砾土比角砾砂砾土具有更大的动剪切模量;对于最大动剪切模量,圆砾砂砾土和角砾砂砾土均存在砾石(粒径大于5 mm)含量P5的一个阀值P5cr,且角砾砂砾土的砾石含量阀值P5cr较圆砾砂砾土的大,当P5为阀值P5cr时,砂砾土的最大动剪切模量达到极大值;剪应变幅值大于2×10-4时,角砾砂砾土的阻尼比比圆砾砂砾土的大。
基金supported by the State Key Program of the National Natural Science Foundation of China(Grant No.51138001)the National Natural Science Foundation of China(Grant Nos.51279025+1 种基金91215301&51508071)the Program for New Century Excellent Talents in University(Grant No.NCET-12-0083)
文摘Experimental investigations of the dilatancy and particle breakage of gravelly material from the Zipingpu concrete-faced rock- fill dam, which was subjected to high-intensity seismic load during the 2008 Wenchuan earthquake, were conducted through a series of large-scale drained triaxial compression tests. A hyperbolic relation between the input plastic work and the degree of particle breakage was found for Zipingpu gravel, independent of the initial void ratio and confining pressures. The stress-dilatancy for Zipingpu gravel was analyzed and compared with data from two rounded alluvial and three angular quar- ried gravelly and rockfill materials in the literature. A nearly linear relationship between the dilatancy Dp and the stress ratio η was found at medium-to-large stress ratios before the peak stress ratio. The slope of the stress-dilatancy line before peak had slight dependence on the void ratio and confining pressure of the gravel. After peak, the stress-dilatancy relation shifts down compared with that before peak for the gravel specimen. The phase-transformation stress ratio decreased with increased con- fining pressure, with the exception of sub-rounded gravel with little particle breakage. A nearly linear relationship was found between the phase-transformation stress ratio Mf and the state parameter ψ for the Zipingpu gravel, regardless of the void ratio and confining pressure of the specimens.
基金supported by the Scientific Research Fund of Yunnan Provincial Department of Education(2022Y286)15th Student Science and Technology Innovation and Entrepreneurship Action Fund Project of Yunnan Agricultural University(2022ZKX098)+1 种基金the Yunnan University Professional Degree Graduate Student Practical Innovation Fund Project(Grant Number ZC-22222374)the Scientific Research Fund Project of Yunnan Education Department(Grant Numbers 2023J1974 and 2023J1976).
文摘The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM(Scanning Electron Microscopy)image analysis.The results show that the combination of fly ash and water can fill the voids in cemented sand and gravel test blocks because of the presence of hydrated calcium silicate and other substances;thereby,the compactness and mechanical properties of these materials can be greatly improved.For every 10 kg/m^(3) increase in the amount of cementitious material,the density increases by about 2%,and the water content decreases by 0.2%.The amount of cementitious material used in the sand and gravel in these tests was 80-110 kg/m^(3),the water-binder ratio was 1-1.50.Moreover,the splitting tensile strength was 1/10 of the compressive strength,and the maximum strength was 7.42 MPa at 90 d.The optimal mix ratio has been found to be 50 kg of cement,60 kg of fly ash and 120 kg of water(C50F60W120).The related dry density was 2.6 g/cm^(3),the water content was 6%,and the water-binder ratio was 1.09.
基金the National Natural Science Foundation of China(Grant Nos.51709139 and 51678094)。
文摘Polyurethane foam adhesive(PFA)has been introduced as an alternative stabilizer in geotechnical applications because PFA can improve the engineering characteristics of soil by filling the pore space and generating adhesive bonding among the particles.However,the dynamic properties of PFA-reinforced soils are not well understood.To analyze the dynamic characteristics of PFA-reinforced gravels,a series of cyclic triaxial tests were carried out to investigate the shear modulus and damping ratio of PFA-reinforced gravels,and to determine the corresponding effects of the PFA content,confining pressure,consolidation stress ratio and loading frequency.The results showed that the shear modulus increased,and the damping ratio decreased as the PFA content,confining pressure and consolidation stress ratio increased.In contrast,the effect of the loading frequency,which ranged from 0.05 to 1 Hz,was negligible.A modified hyperbolic empirical model can consider the effect of the PFA content on the maximum shear modulus and predict the relationship between the normalized shear modulus and the normalized shear strain was proposed.Moreover,the upper and lower bounds of the damping ratio were also proposed.
