This paper presents results from a series of stress-controlled undrained cyclic triaxial tests on the undisturbed marine silty clay,silt,and fine sand soils obtained from the Bohai Sea,China.Emphasis is placed on the ...This paper presents results from a series of stress-controlled undrained cyclic triaxial tests on the undisturbed marine silty clay,silt,and fine sand soils obtained from the Bohai Sea,China.Emphasis is placed on the major factors for predominating the dynamic shear modulus(G)and damping ratio(λ)in the shear strain amplitude(γ_(a))from 10^(-5) to 10^(-2),involving depth,sedimentary facies types,and water content of marine soils.The empirical equations of the small-strain shear modulus(G_(max))and damping ratio(λ_(min))using a single-variable of depth H are established for the three marine soils.A remarkable finding is that the curves of shear modulus reduction(G/G_(max))and the damping ratio(λ)with increasing γ_(a) of the three marine soils can be simply determined through a set of explicit expressions with the two variables of depth H and water content W.This finding is validated by independent experimental data from the literature.At the similar depths,the G value of the marine soils of terrestrial facies is the largest,followed b_(y) the neritic facies,and the G value of the marine soils of abyssal facies is the smallest.The sedimentary facies types of the marine soils have slight effect on theλvalue.Another significant finding is that the shear modulus reduction curves plotted against the γ_(a) of the three marine soils at the similar depths are significantly below those of the corresponding terrigenous soils,while the damping curves plotted against γ_(a) are just the opposite.The results presented in this paper serve as a worthful reference for the evaluation of seabed seismic site effects in the Bohai Sea due to lack of experimental data.展开更多
Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping chara...Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping characteristic, rubbers can be used as either soil alternative or mixed with soil to reduce vibration when seismic loads are of great concern. Therefore, the objective of this work was to evaluate the dynamic properties of such mixtures prior to practical applications. To this reason, torsional resonant column and dynamic triaxial experiments were carried out and the effect of the important parameters like rubber content and ratio of mean grain size of rubber solids versus soil solids(D50,r/D50,s) on dynamic response of mixtures in a range of low to high shearing strain amplitude from about 4×10-4% to 2.7% were investigated. Considering engineering applications, specimens were prepared almost at the maximum dry density and optimum moisture content to model a mixture layer above the ground water table and in low precipitation region. The results show that tire inclusion significantly reduces the shear modulus and increases the damping ratio of the mixtures. Also decrease in D50,r/D50,s causes the mixture to exhibit more rubber-like behavior. Finally, normalized shear modulus versus shearing strain amplitude curve was proposed for engineering practice.展开更多
The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculat...The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculation. The test results indicate that the power function is a suitable form for describing the relationship between the ratio of the maximum dynamic shear modulus due to anisotropic and isotropic consolidations and the increment of the consolidation ratio. When compared to sand, the increment of the maximum dynamic shear modulus for undisturbed soil due to anisotropic consolidation is much larger. Using a one-dimensional equivalent linearization method, the earthquake influence factor and the characteristic period of the surface acceleration are calculated for two soil layers subjected to several typical earthquake waves. The calculated results show that the difference in nonlinear properties due to different consolidation ratios is generally not very notable, but the degree of its influence on the surface acceleration spectrum is remarkable for the occurrence of strong earthquakes. When compared to isotropic consolidation, the consideration of actual anisotropic consolidation causes the characteristic period to decrease and the earthquake influence factor to increase.展开更多
The dynamic shear modulus (DSM) is the most basic soil parameter in earthquake or other dynamic loading conditions and can be obtained through testing in the field or in the laboratory. The effect of consolidation rat...The dynamic shear modulus (DSM) is the most basic soil parameter in earthquake or other dynamic loading conditions and can be obtained through testing in the field or in the laboratory. The effect of consolidation ratios on the maximum DSM for two types of sand is investigated by using resonant column tests. And, an increment formula to obtain the maximum DSM for cases of consolidation ratio κc>1 is presented. The results indicate that the maximum DSM rises rapidly when κc is near 1 and then slows down, which means that the power function of the consolidation ratio increment κc-1 can be used to describe the variation of the maximum DSM due to κc>1. The results also indicate that the increase in the maximum DSM due to κc>1 is significantly larger than that predicted by Hardin and Black's formula.展开更多
Under repeated freezing and thawing in deep seasonal frozen regions, the stability and strength of the soil are imposed in the form of large uneven settlement, instability and strength reduction, which affect the norm...Under repeated freezing and thawing in deep seasonal frozen regions, the stability and strength of the soil are imposed in the form of large uneven settlement, instability and strength reduction, which affect the normal operation of railway lines. This study is to obtain the influencing rules of freeze-thaw on the dynamic properties （dynamic strain, confining pressure and compactness） of silty sand. Based on an amount of inner tests, the dynamic modulus and damping ratio properties of silty soil subjected to repeated freeze-thaw cycles were deeply researched and analyzed. The results are as follows： At the same dynamic strain, the relationship of dynamic stress and freeze-thaw cycles presents negative cor- relation, and the relationship of dynamic stress, confining pressure and compactness present positive correlation. The dynamic modulus double decreases while the damping ratio double increases with incremental increase in dynamic strain. The dynamic modulus sharply decreases while the damping ratio increases with incremental increase in freeze-thaw cycles, and then the changes level off after six freeze-thaw cycles. The dynamic modulus increases while the damping ratio decreases as the confining pressure and compactness increase at the same strain level.展开更多
The dynamic shear modulus ratio and damping ratio of sandy gravel are important parameters for the seismic response analysis of valley geomorphic sites,which have an important impact on the determination of design gro...The dynamic shear modulus ratio and damping ratio of sandy gravel are important parameters for the seismic response analysis of valley geomorphic sites,which have an important impact on the determination of design ground motion parameters. In this paper,the dynamic triaxial test of sandy gravels has been performed based on the project of the Shangluo Seismic Microzonation. Combined with the other results of sandy gravel,the recommended results of slightly dense,medium dense and dense sandy gravel were obtained. By building the typical site model,the influence of the dynamic shear modulus ratio and the damping ratio uncertainty on the seismic response of the site is studied. The results show that the uncertainty of the average of the dynamic shear modulus ratio and the damping ratio ± 1 times the standard deviation has little effect on the peak acceleration of the sandy gravel site,and the rationality of the grouping and statistical results is explained. Under different probability levels,the change in the shear modulus ratio and damping ratio leads to a significant difference in the high frequency response spectrum.The response spectrum of 0. 04-0. 1s ranges from about 20%,but it has little effect on the long period spectrum of more than 1. 0s. The study of dynamic shear modulus ratio and damping ratio of sandy gravel has the ability to improve the reliability of the designing ground motion parameters.展开更多
The behavior of shear modulus in solid-liquid mixing phase has been discussed and analyzed. The result was concluded that shear modulus went to zero as the melting mass ratio attained a critical value. The percolation...The behavior of shear modulus in solid-liquid mixing phase has been discussed and analyzed. The result was concluded that shear modulus went to zero as the melting mass ratio attained a critical value. The percolation theory model we pro-posed showed that this value was about 0.68742. The melting-induced destabilizing factor of material proposed by us can represent phenomenologically the change of shear modulus in melting process.展开更多
基金National Natural Science Foundation of China under Grant Nos.51978334 and 51978335。
文摘This paper presents results from a series of stress-controlled undrained cyclic triaxial tests on the undisturbed marine silty clay,silt,and fine sand soils obtained from the Bohai Sea,China.Emphasis is placed on the major factors for predominating the dynamic shear modulus(G)and damping ratio(λ)in the shear strain amplitude(γ_(a))from 10^(-5) to 10^(-2),involving depth,sedimentary facies types,and water content of marine soils.The empirical equations of the small-strain shear modulus(G_(max))and damping ratio(λ_(min))using a single-variable of depth H are established for the three marine soils.A remarkable finding is that the curves of shear modulus reduction(G/G_(max))and the damping ratio(λ)with increasing γ_(a) of the three marine soils can be simply determined through a set of explicit expressions with the two variables of depth H and water content W.This finding is validated by independent experimental data from the literature.At the similar depths,the G value of the marine soils of terrestrial facies is the largest,followed b_(y) the neritic facies,and the G value of the marine soils of abyssal facies is the smallest.The sedimentary facies types of the marine soils have slight effect on theλvalue.Another significant finding is that the shear modulus reduction curves plotted against the γ_(a) of the three marine soils at the similar depths are significantly below those of the corresponding terrigenous soils,while the damping curves plotted against γ_(a) are just the opposite.The results presented in this paper serve as a worthful reference for the evaluation of seabed seismic site effects in the Bohai Sea due to lack of experimental data.
文摘Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping characteristic, rubbers can be used as either soil alternative or mixed with soil to reduce vibration when seismic loads are of great concern. Therefore, the objective of this work was to evaluate the dynamic properties of such mixtures prior to practical applications. To this reason, torsional resonant column and dynamic triaxial experiments were carried out and the effect of the important parameters like rubber content and ratio of mean grain size of rubber solids versus soil solids(D50,r/D50,s) on dynamic response of mixtures in a range of low to high shearing strain amplitude from about 4×10-4% to 2.7% were investigated. Considering engineering applications, specimens were prepared almost at the maximum dry density and optimum moisture content to model a mixture layer above the ground water table and in low precipitation region. The results show that tire inclusion significantly reduces the shear modulus and increases the damping ratio of the mixtures. Also decrease in D50,r/D50,s causes the mixture to exhibit more rubber-like behavior. Finally, normalized shear modulus versus shearing strain amplitude curve was proposed for engineering practice.
基金National Natural Science Foundation of China under Grant No.51108163Natural Science Foundation of Heilongjiang Province under Grant No.E201104
文摘The dynamic shear modulus for three types of undisturbed soil under different consolidation ratios is presented by using the resonant column test method. Its effects on surface ground motion is illustrated by calculation. The test results indicate that the power function is a suitable form for describing the relationship between the ratio of the maximum dynamic shear modulus due to anisotropic and isotropic consolidations and the increment of the consolidation ratio. When compared to sand, the increment of the maximum dynamic shear modulus for undisturbed soil due to anisotropic consolidation is much larger. Using a one-dimensional equivalent linearization method, the earthquake influence factor and the characteristic period of the surface acceleration are calculated for two soil layers subjected to several typical earthquake waves. The calculated results show that the difference in nonlinear properties due to different consolidation ratios is generally not very notable, but the degree of its influence on the surface acceleration spectrum is remarkable for the occurrence of strong earthquakes. When compared to isotropic consolidation, the consideration of actual anisotropic consolidation causes the characteristic period to decrease and the earthquake influence factor to increase.
基金The Science and Technology Ministration of China and the Earthquake Science Foundation of China (Grand No. 102033)
文摘The dynamic shear modulus (DSM) is the most basic soil parameter in earthquake or other dynamic loading conditions and can be obtained through testing in the field or in the laboratory. The effect of consolidation ratios on the maximum DSM for two types of sand is investigated by using resonant column tests. And, an increment formula to obtain the maximum DSM for cases of consolidation ratio κc>1 is presented. The results indicate that the maximum DSM rises rapidly when κc is near 1 and then slows down, which means that the power function of the consolidation ratio increment κc-1 can be used to describe the variation of the maximum DSM due to κc>1. The results also indicate that the increase in the maximum DSM due to κc>1 is significantly larger than that predicted by Hardin and Black's formula.
基金funded by the National Key Basic Research Development Plan of China (Grant No. 2012CB026104)the National Natural Science Foundation (NSFC) of China (Grant Nos.51208320 and 51171281)
文摘Under repeated freezing and thawing in deep seasonal frozen regions, the stability and strength of the soil are imposed in the form of large uneven settlement, instability and strength reduction, which affect the normal operation of railway lines. This study is to obtain the influencing rules of freeze-thaw on the dynamic properties （dynamic strain, confining pressure and compactness） of silty sand. Based on an amount of inner tests, the dynamic modulus and damping ratio properties of silty soil subjected to repeated freeze-thaw cycles were deeply researched and analyzed. The results are as follows： At the same dynamic strain, the relationship of dynamic stress and freeze-thaw cycles presents negative cor- relation, and the relationship of dynamic stress, confining pressure and compactness present positive correlation. The dynamic modulus double decreases while the damping ratio double increases with incremental increase in dynamic strain. The dynamic modulus sharply decreases while the damping ratio increases with incremental increase in freeze-thaw cycles, and then the changes level off after six freeze-thaw cycles. The dynamic modulus increases while the damping ratio decreases as the confining pressure and compactness increase at the same strain level.
基金sponsored by the Earthquake Disaster Prevention and ReductionProgram for the 12th “Five-year Plan” of Shaanxi Province(SCZC2012-TP-905/1)
文摘The dynamic shear modulus ratio and damping ratio of sandy gravel are important parameters for the seismic response analysis of valley geomorphic sites,which have an important impact on the determination of design ground motion parameters. In this paper,the dynamic triaxial test of sandy gravels has been performed based on the project of the Shangluo Seismic Microzonation. Combined with the other results of sandy gravel,the recommended results of slightly dense,medium dense and dense sandy gravel were obtained. By building the typical site model,the influence of the dynamic shear modulus ratio and the damping ratio uncertainty on the seismic response of the site is studied. The results show that the uncertainty of the average of the dynamic shear modulus ratio and the damping ratio ± 1 times the standard deviation has little effect on the peak acceleration of the sandy gravel site,and the rationality of the grouping and statistical results is explained. Under different probability levels,the change in the shear modulus ratio and damping ratio leads to a significant difference in the high frequency response spectrum.The response spectrum of 0. 04-0. 1s ranges from about 20%,but it has little effect on the long period spectrum of more than 1. 0s. The study of dynamic shear modulus ratio and damping ratio of sandy gravel has the ability to improve the reliability of the designing ground motion parameters.
文摘The behavior of shear modulus in solid-liquid mixing phase has been discussed and analyzed. The result was concluded that shear modulus went to zero as the melting mass ratio attained a critical value. The percolation theory model we pro-posed showed that this value was about 0.68742. The melting-induced destabilizing factor of material proposed by us can represent phenomenologically the change of shear modulus in melting process.
