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Experimental Study on Damping Ratio Characteristics of Loose Silty Fine Sand at Different Saturations
YU Song, XU Meng-bing, FENG Zhi-guo, ZHANG Jun-jie, ZHANG Guo-chao, WANG Yong
Journal of Changjiang River Scientific Research Institute ›› 2025, Vol. 42 ›› Issue (11) : 103-110.
PDF(6521 KB)
PDF(6521 KB)
Experimental Study on Damping Ratio Characteristics of Loose Silty Fine Sand at Different Saturations
[Objective] Current research on the damping ratio evolution of silty fine sand under varying saturation conditions remains relatively limited, and in particular, systematic investigations revealing the mechanisms by which saturation variations influence damping ratios within the framework of unsaturated soil mechanics are still insufficient. To address this gap, typical loose silty fine sand from the Hangzhou Bay area is selected as the research subject. Utilizing a self-improved unsaturated soil resonant column testing system, the damping ratio evolution characteristics and underlying mechanisms along the desaturation path are thoroughly investigated. The findings aim to provide a scientific basis for analyzing dynamic properties and engineering applications of unsaturated soils. [Methods] An improved unsaturated soil resonant column apparatus was employed to conduct small-strain dynamic property tests under controlled drainage paths and saturation conditions. Test specimens were initially prepared with varying saturation levels and stress states. A stepwise desaturation process under constant net stress conditions was then applied to establish a series of samples with different saturation states. Subsequently, shear modulus and damping ratio measurements were performed across varying saturation levels and net stress conditions via resonant column loading. By integrating theoretical analyses of soil-water characteristic curves (SWCC) and pore water distribution states, distinct stages of damping ratio evolution were identified, and damping mechanisms induced by saturation variations were elucidated. [Results] The experimental results indicated that: (1) under identical saturation conditions, the damping ratio of silty fine sand gradually decreased with increasing net stress. (2) During saturation evolution, the damping ratio exhibited distinct stage-wise variations: when the soil approached full saturation, the damping ratio remained relatively stable. As saturation declined, the damping ratio rapidly attenuated and reached a minimum near the optimal saturation Sropt. Further saturation reduction led to a slight rebound in the damping ratio. (3) Based on the SWCC and pore water morphology evolution, the saturation-dependent damping ratio variations were categorized into three stages: boundary effect stage, transition stage, and residual saturation stage. [Conclusion] This study elucidates the damping ratio evolution mechanism of loose silty fine sand along desaturation paths. It demonstrates that the damping ratio is influenced not only by net stress but also closely associated with pore water distribution states, and that its minimum damping ratio occurs at the optimal saturation Sropt. The results reveal that saturation-dependent damping ratio changes can be categorized into three stages, each corresponding to distinct pore water morphology evolution processes. By employing the improved unsaturated soil resonant column, the complete damping ratio evolution process with saturation variation is observed. The principle of minimum damping ratio under “optimal saturation” control is proposed, and the three-stage evolution mechanism is revealed through SWCC analysis. These findings provide a foundation for refining unsaturated soil dynamic models and enhancing the scientific rigor of related engineering designs.
silty fine sand / damping ratio / resonant column / dynamic characteristics test / saturation / net stress
| [1] |
An experimental study aimed at providing insights into the cyclic deformation behavior of saturated marine silt under principal rotation, as induced by wave loading, is presented. Using the GDS hollow cylinder apparatus, a series of undrained tests are performed and the specimens at identical initial states are subjected to combined axial–torsional cyclic loading that imposes different levels of stress rotation. The cumulative generalized shear strain γg is used to describe the deformation of the silt under complex stress paths. The test results show that the cumulative generalized shear strain is significantly dependent on the cyclic stress ratio (CSR) and cyclic loading amplitude ratio δ. The cumulative generalized shear strain increases with the increase in CSR and decreases with the increase in δ. The development trend of γg can be well predicted through the correct Monismith model in the non-liquefaction silt, with a low error that is generally less than 10%.
|
| [2] |
|
| [3] |
崔凯, 荆祥. 地震荷载作用下粗颗粒含量对川西混合土动剪切模量和阻尼比的影响[J]. 中国公路学报, 2019, 32(12): 123-131.
为分析川西地区混合土地震荷载作用下的动力特性，针对该地区保留全部粒径的天然混合土，对3组土分别采用筛分法剔除60，20，10，5 mm粒径颗粒，制备粗颗粒含量不同的天然混合土土样，利用DJSZ-150粗粒土动、静两用三轴试验机进行大型动三轴试验，采用Hardin-Drnevich双曲线模型（H-D模型）拟合动应力-应变关系曲线，获得G<sub>d</sub>/G<sub>max</sub>-γ和λ-γ曲线变化规律，分析不同围压和粗颗粒含量对川西混合土动剪切模量G<sub>d</sub>和阻尼比λ的影响作用。结果表明：混合土动剪切模量G<sub>d</sub>、阻尼比λ均随围压及大于5 mm的粗颗粒含量的增大而增大，原因是随着围压增大，粗细颗粒的接触增多，土体结构更加紧实，提高了颗粒壁隙间的动摩擦力，增大了能量传递时的耗损，导致动剪切模量与阻尼比随之增大；当粗颗粒含量小于40%时，细颗粒构成土骨架，粗颗粒的接触被细颗粒阻隔，导致其对动剪切模量及阻尼作用贡献不大，此时动剪切模量和阻尼比随粗颗粒含量增加而增加的速度较慢，当粗颗粒含量为40%~60%时，混合土中粗颗粒骨架形成，且细颗粒有效填充了粗颗粒间的孔隙，粗颗粒在土中起主导作用，此时动剪切模量与阻尼比随着粗颗粒含量的增加而快速增加，当粗颗粒含量大于60%时，粗颗粒的增加无法进一步增强其骨架效应，而此时细颗粒间的胶结作用随粗颗粒的增多导致细颗粒的相应减少而减弱，动剪切模量和阻尼比随粗颗粒含量增加而增加的趋势不明显。
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To analyze the dynamic characteristics of mixed soil under seismic loading in the Western Sichuan area, in view of the natural mixed soils retaining all particle sizes in this area, we screened out three groups of soils (with particle sizes of 60, 20, 10, and 5 mm), and then prepared natural mixed soils with different coarse particle content. Large-scale dynamic triaxial tests were carried out using a DJSZ-150 dynamic and static dual-purpose triaxial testing machine for coarse-grained soils. Moreover, a Hardin-Drnevich hyperbolic model (H-D model) was used to fit the dynamic stress-strain relationship curve, and the variation rules of the <i>G</i><sub>d</sub>/<i>G</i><sub>max</sub>-γ and <i>λ-γ</i> curves were obtained. The effects of different confining pressures and coarse particle content on the dynamic shear modulus (<i>G</i><sub>d</sub>) and damping ratio (<i>λ</i>) of the mixed soils were analyzed. The results demonstrate that <i>G</i><sub>d</sub> and <i>λ</i> increase with increasing confining pressure and in soils with a content of coarse particles greater than 5 mm. This is because the contact between coarse and fine particles increases with increasing confining pressure, the structure of the soil is more compact, the dynamic friction force between particle gaps is increased, and the loss of energy transfer is increased. When the coarse particle content is less than 40%, fine particles constitute the soil skeleton and they block the contact of the coarse particles, which makes little contribution to <i>G</i><sub>d</sub> and <i>λ</i>. At this time, <i>G</i><sub>d</sub> and <i>λ</i> increase slowly with increasing coarse particle content. When the coarse particle content is 40%-60%, a skeleton of coarse particles is formed in the mixed soil and fine particles effectively fill the voids between the coarse particles. Here, coarse particles play a dominant role in the soil. At this time, <i>G</i><sub>d</sub> and <i>λ</i> increase rapidly with increasing coarse particle content. When the coarse particle content is more than 60%, the increase in coarse particles cannot further enhance the skeleton effect, whereas the cementation between fine particles decreases with increasing coarse particle content. Further, the increasing trend of <i>G</i><sub>d</sub> and <i>λ</i> with increasing coarse particle content is not obvious.
|
| [4] |
贺林. 振动频率和成样方法对饱和中砂动力特性的影响[D]. 大连: 大连理工大学, 2009.
(
|
| [5] |
尹松, 张先伟, 孔令伟, 等. 海洋沉积土动剪切模量与阻尼比的试验研究[J]. 岩土力学, 2015, 36(增刊1):459-464.
(
|
| [6] |
The small-strain stiffness of soil is significant in the accurate prediction of the deformation caused by interactions between foundation soil and structures. Considering the whole range of small strain (10−6~10−3), a bending element-resonant column (BE-RC) combined test system was developed to conduct continuous tests on the shear modulus of unsaturated soil. Under the dehydration path, it was used to investigate the small-strain shear modulus of unsaturated silty-fine sand in Hangzhou Bay, China. The results show that the shear modulus under different net stresses and matrix suctions appeared to non-linearly decay with the increase in strain until stable values were reached at a large strain. At the beginning from the saturated state, the Gmax value increased slowly with decreasing saturation and reached its maximum value at the optimum saturation (Sr)opt; then, it rapidly decayed to the level in the saturated, once the saturation degree decreased to a level lower than (Sr)opt. Additionally, an improved prediction model was proposed for the Gmax of unsaturated sand, considering different saturations. Based on the mesoscopic evolution of internal pore water morphology and the variation in intergranular stress caused by capillary action, the variation in the Gmax could be divided into three segments of saturation: the boundary effect stage, the transition stage and the unsaturated residual stage.
|
| [7] |
徐子皓, 秦悠, 马维嘉, 等. 沉积方向对珊瑚砂动剪切模量及阻尼比的影响[J]. 防灾减灾工程学报, 2024, 44(3):535-543.
(
|
| [8] |
|
| [9] |
The influence of saturation on the Poisson’s ratio v of reservoir sediments has an engineering significance in the field of oil and nature gas exploration. Based on a self-developed combined (BE-EE-RC) test system, under the dehydration path, the Poisson’s ratio variation of reservoir silty-fine sand in Hangzhou Bay, China, was investigated. Results show that the P- and S-wave velocities vary non-monotonically with decreasing saturation at different net stresses, and reach a maximum at the optimum saturation Sr(opt); Biot’s theory with respect to variation in Vp with Sr matches well with the measured e data. With a small amount of gas intrusion, Poisson’s ratio of saturated sand shows a sudden drop and gradually stabilizes; then, it attenuates slowly and reaches the minimum value at Sr(opt). Once the saturation degree decreases to the level lower than Sr(opt), it rapidly increases. Based on the soil–water characteristic curve (SWCC) and mesoscopic evolution of internal pore water morphology, the variation in Poisson’s ratio v can be divided into four segments of saturation: the boundary effect stage, the primary transition stage, the secondary transition stage, and the unsaturated residual stage. Ultimately, a prediction model for Poisson ratio’s v of the silty-fine sand was proposed to consider the saturation variation.
|
| [10] |
This study reports on the significance of particle shape on the small-strain damping ratio of dry sands in shear (Ds,min) through a comprehensive set of torsional resonant column tests. Sands with a variety of grain shapes prepared at variable initial densities are studied. The samples are subjected to torsional resonant column tests under isotropic confining pressures (p′) ranging from 50 to 800 kPa. Small-strain damping ratios are derived based on the free-vibration decay mode of the samples and the results are compared with the half-power bandwidth method. The effects of grain size distribution, particle shape and effective confining stress on Ds,minare thoroughly discussed, and a new model for the prediction of small-strain damping ratio of dry sand is proposed.
|
| [11] |
|
| [12] |
|
| [13] |
王体强, 王永志, 梁小丛, 等. 超重力模型试验干-饱和砂动剪切模量阻尼比特性研究[J]. 岩石力学与工程学报, 2023, 42(6): 1546-1559.
(
|
| [14] |
王勇, 王艳丽. 细粒含量对饱和砂土动弹性模量与阻尼比的影响研究[J]. 岩土力学, 2011, 32(9): 2623-2628.
(
|
| [15] |
|
| [16] |
江洎洧, 饶锡保, 张伟, 等. 荆江大堤下伏饱和粉细砂动力特性试验研究[J]. 地震工程学报, 2015, 37(3):759-764.
(
|
| [17] |
|
| [18] |
|
| [19] |
薛龙. 吸力控制下非饱和土的动力特性[J]. 佳木斯大学学报(自然科学版), 2013, 31(1): 34-37, 42.
(
|
| [20] |
王晋宝, 刘校麟, 童焯煜, 等. 基于共振柱的海砂动剪切模量和阻尼比探究[J]. 广西大学学报(自然科学版), 2019, 44(4): 1044-1051.
(
|
| [21] |
|
| [22] |
王海东, 翁芬芬, 蔡长丰. 含水率与粒径对非饱和砂土动力特性影响的试验研究[J]. 铁道科学与工程学报, 2019, 16(2): 359-366.
(
|
| [23] |
A new and relatively simple equation for the soil‐water content‐pressure head curve, θ(h), is described in this paper. The particular form of the equation enables one to derive closed‐form analytical expressions for the relative hydraulic conductivity, Kr, when substituted in the predictive conductivity models of N.T. Burdine or Y. Mualem. The resulting expressions for Kr(h) contain three independent parameters which may be obtained by fitting the proposed soil‐water retention model to experimental data. Results obtained with the closed‐form analytical expressions based on the Mualem theory are compared with observed hydraulic conductivity data for five soils with a wide range of hydraulic properties. The unsaturated hydraulic conductivity is predicted well in four out of five cases. It is found that a reasonable description of the soil‐water retention curve at low water contents is important for an accurated prediction of the unsaturated hydraulic conductivity.
|
| [24] |
毕昇, 陈国兴, 周正龙, 等. 细粒含量及固结应力对饱和砂土动剪切模量和阻尼比影响试验研究[J]. 岩土工程学报, 2017, 39(增刊1): 48-52.
(
|
| [25] |
|
| [26] |
陈辉. 非饱和土水力特性测试理论与方法研究[D]. 武汉: 中国科学院武汉岩土力学研究所, 2010.
(
|
| [27] |
陈国兴, 刘雪珠. 南京及邻近地区新近沉积土的动剪切模量和阻尼比的试验研究[J]. 岩石力学与工程学报, 2004, 23(8): 1403-1410.
(
|
| [28] |
陈国兴, 刘雪珠, 朱定华, 等. 苏南地区新近沉积土的动力特性研究[J]. 地下空间与工程学报, 2005, 1(增刊1):1139-1142.
(
|
| [29] |
王海东, 李建文, 陈曦, 等. 非饱和重塑砂土动力特性循环单剪试验研究[J]. 岩土力学, 2016, 37(11): 3115-3122, 3190.
(
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