Series Of Resonant Column Tests Research Articles

Measurements of Shear Wave Velocity for Collapsible Soil

This paper examines the effects of collapsible soil structure on shear wave velocity. The study attempts to simulate hydraulic fill sand deposits, which represent a natural soil deposition process that can result in a collapsible soil structure. A series of resonant column tests and bender element tests on Ottawa sand was conducted on sand specimens and prepared by dry pluviation and simulated hydraulic fill methods subjected to various confining pressures. Shear wave velocities measured from both methods of deposition are compared and discussed. Results from this study show that for soil specimens with the same void ratio, samples prepared by simulated hydraulic fill have a lower shear modulus and shear wave velocity than the specimens prepared by dry pluviation, and the differences are more pronounced at higher confining pressures. The resonant column test results performed in this study were consistent with results from the discrete element analysis, full-scale testing, and centrifuge testing. The discrete element analysis suggests that soil fabric and number of particle contacts are the key factors affecting the shear wave velocity. These factors are dependent on the methods of deposition. Results from this study examining hydraulic fill collapsible structure shear wave velocity provide a step forward toward a better correlation between soil dynamic properties measured in field and laboratory tests.

Shear modulus of sand-rubber mixtures: element testing and constitutive modeling

In this study, a series of resonant column tests was conducted to measure the shear modulus of sand-rubber mixtures at small strain amplitudes (i.e. between 10−4% and 10−4%), considering different rubber percentages and confining stress levels. The results were then combined with data obtained by dynamic hollow cylinder tests to investigate shear modulus degradation of the mixtures over a wider shear strain range. Based on the test results, a new expression was proposed to improve the prediction of maximum shear modulus of sand-rubber mixtures using the modified equivalent void ratio concept. A new constitutive model was also developed for estimation of strain-dependent shear modulus of the mixtures based on the modified hyperbolic framework. The shear modulus of the mixtures was found to be a function of rubber percentage, confining stress, the modified equivalent void ratio and the relative shear stiffness of rubber and sand. The experimental data and the developed models showed that the shear modulus decreased with rubber percentage and increased with confining stress. Moreover, the reference shear strain of the modified hyperbolic model increased with both rubber percentage and confining stress while its curvature coefficient increased more considerably with rubber percentage compared to the confining stress.

Shear modulus and damping ratio of granulated rubber-sand mixtures: Influence of relative particle size

Rubber-sand mixtures (RSM) have gained recognition as a valuable, lightweight, and cost-efficient energy-absorbing material with extensive potential application in engineering construction. However, the small-strain dynamic properties and prevailing mechanisms of RSM have not been thoroughly understood. This study conducted a series of resonant column tests on the small-strain dynamic modulus and damping ratio of RSM, considering the effects of particle size ratio (PSR), rubber content (RC), and confining pressure. The results reveal that the dynamic shear modulus of RSM generally decreases with increasing RC and increases with rising confining pressure. For all RC and confining pressure levels, the maximum dynamic shear modulus of RSM reaches the minimum value as the PSR approaches 1.0. In this case, the dynamic shear modulus of RSM decreases most gently with the strain. The addition of rubber consistently augments the damping ratio, whereas the PSR initially diminishes the damping ratio before eventually enhancing it. Simultaneously, as the PSR is nearing 1.0, the damping ratio achieves its lowest point. Furthermore, new empirical equations were developed to quantitatively analyze the dynamic properties of RSM, in which the predicted values of the dynamic shear modulus and the modulus attenuation coefficient show good agreement with the observed values. This work will facilitate the preparation of artificial RSM-cored geotechnical seismic isolation layers tailored to specific engineering requirements.

Experimental investigation on dynamic shear modulus of undisturbed marine soils in the east coast of China

The dynamic shear modulus G is one of the vital parameters for the dynamic properties of marine soils and is crucial for marine geotechnical engineering design. In order to investigate the G characteristics of various marine soils, a series of resonant column tests were performed on undisturbed marine soils with various depths taken from Bohai Bay, Yangtze River estuary, and Jintang Strait, respectively. In addition, the maximum dynamic shear modulus Gmax and strain-compatible G of the tested marine soils were compared with the marine and terrestrial soils from the published literature. A remarkable finding is that, compared with terrestrial soils, the marine soils in different sea area present the stronger nonlinear behavior with lower shear modulus due to the special depositional environment. With the increasing of H, G in each strain range increase, and the dynamic characteristics of the marine soils gradually transition from nonlinear to linear, the Gmax and reference shear strain γ0 value of marine soils in different sea areas increases linearly with the increasing H, but the Gmax and γ0 growth rate varied with the sea environment and soil type. Based on the quantitative prediction equation of the Gmax and G attenuation relationship (G/Gmax ∼ γ) of various marine soils, a new prediction equation can be also established to predict G value in different depth and strain levels of various marine soils. The proposed equation are validated by independent experimental data of marine and terrestrial soils from the literature. In this regard, the proposed procedure provides a significant advantage in the evaluation of dynamic properties of marine soils in practice.

Mechanical Properties and Engineering Applications of Special Soils—Dynamic Shear Modulus and Damping of MICP-Treated Calcareous Sand at Low Strains

Calcareous sand deposits are widespread along the shoreline in tropical and subtropical regions. Microbially induced calcite precipitation (MICP) treatment is a new method for improving the soil’s stiffness and strength. The small-strain shear modulus and damping ratio of MICP-treated calcareous sand, two critical parameters for predicting the dynamic behavior of soil, are little known. This study conducts a series of resonant column tests to investigate the dynamic characteristics of MICP-treated calcareous sand, emphasizing the influence of treatment duration and confining stress on the stiffness and damping characteristics. It analyzes the relationship between the initial dynamic shear modulus and unconfined compressive strength. In addition, empirical relationships between the reference shear strain and treatment duration or confining stress are provided. The results show that the normalized shear modulus G/G0 of MICP-cemented calcareous sand has a higher strain sensitivity than that of untreated sand, and the Hardin–Drnevich model can describe its attenuation pattern. The effective confining stress σc affects the degradation characteristics of the dynamic shear modulus of MICP-treated calcareous sand with a low cementation level; however, its impact decreases as the treatment duration increases. There is a linear relationship between the reference shear strain and confining stress. While the relationship between the reference shear stain and treatment duration is a power law.

Effect of Mean Grain Size on the Small-Strain Dynamic Properties of Calcareous Sand

Calcareous sand was selected as the prior material for island reclamation in many coastal regions. The mechanical properties of the granular materials are greatly affected by their grain size distribution conditions. The shear modulus and damping ratio are two important parameters for earthquake ground response analysis and liquefaction evaluation. A series of resonant column tests had been performed on calcareous sands with varying median grain diameter and uniform coefficient. The dependence of the shear modulus and damping ratio of the calcareous sand on grain size has been confirmed in this examination. The test results reveal that the shear modulus decreases with a rise in shear strain for calcareous sand samples at a given confining pressure and relative density. The maximum shear modulus tends to increase with confining pressure and relative density. On the maximum shear modulus and void ratio plane, the trend lines of the measured results shift toward up and right position with a rise in grain diameter. The measured results indicate that the influence of uniform coefficient on the maximum shear modulus is neglectable. A revised empirical equation based on the Hardin model had been proposed considering the influence of grain diameter to estimate the maximum shear modulus of calcareous sand. The predicted values show satisfactory agreement with the measured results. The results manifest that the effect of grading condition on small-strain dynamic properties of calcareous sands cannot be neglected for the evaluation of seismic safety for reclamation engineering sites.

Dynamic shear modulus and damping ratio of rubber-sand mixtures with a wide range of rubber content

The binary mixture of rubber and clean sand has been used as a synthetic porous material characterized by such advantages as light density, strong compressibility and good durability compared to the natural sandy soil. Previous research researches mainly focused on the static properties of this binary mixture. In this paper, the dynamic properties of the binary mixture including dynamic shear modulus and damping ratio, were investigated through a series of resonant column tests. The results indicated that the addition of rubber particles into clean sand significantly improves the dynamic performance of the host sandy soil. A unified model was proposed to describe the dynamic shear modulus and damping ratio of the rubber-sand mixtures with a wide range of rubber content. The synthetic mixture showed a great potential in the applications of the seismic isolation and reduction technique.

Small-strain dynamic properties of silty clay stabilized by cement and fly ash

This study examines the small-strain dynamic properties of cement-stabilized silty clay (CSC) and cement-fly ash-stabilized silty clay (CFSC). A series of resonant column tests were performed to investigate the effect of confining pressure, binder content and curing age on the small-strain dynamic shear modulus (G) and damping ratio (D) of CSC and CFSC. Furthermore, the maximum dynamic shear modulus (Gmax) and maximum damping ratio (Dmax) of CSC and CFSC were also evaluated. The results showed that the G of CSC and CFSC increased with the increase of confining pressure, binder content and curing age. The G decreased slowly and then rapidly with shearing strain (γ), and the γ of 10−4 was the turning point of evaluating the small-strain dynamic behavior of CSC and CFSC. Using 5% cement together with 30% fly ash as stabilizer has advantageous over using 15% cement alone in improving the stiffness properties of silty clay. The D of CSC and CFSC decreased with the increase of confining pressure and curing age, but increased with an increase in cement and fly ash content. This was attributed to the weakly cemented and rough of soil particles led to more energy dissipation of vibration wave propagating through the sample. The microstructural analysis revealed that the micro-aggregate effect and hollow structure of fly ash particles not only contributed to the improvement in G, but also effectively improve the energy dissipation performance of CFSC.

Dynamic Properties of Carbon-Fiber-Reinforced Clay Soil

To study the dynamic characteristics of carbon-fiber-reinforced soil, carbon fiber was uniformly dispersed into clay soil. A series of resonant column tests was carried out at constant soil dry density. Samples prepared with fiber contents of 0%, 0.05%, 0.10% and 0.15% and water contents of 12%, 16% and 20% were studied. Scanning electron microscopy was used to examine the carbon-fiber-reinforced clay soil at the microscopic level. The results show that the maximum dynamic shear modulus increases and the damping ratio decreases with decreasing soil water content. With increasing fiber content, the maximum dynamic shear modulus increases at first and then decreases; the optimal carbon fiber content was 0.10%. The damping ratio increases with increasing soil fiber content. Scanning electron microscopy analysis indicated two reinforcement mechanisms: friction effect and limiting lateral deformation. Results of this study indicate that carbon fiber is conducive to the dissipation of vibration energy.

Small and intermediate strain properties of sands containing fines

The goal of this paper is to find the influence of fines content, fc, on the fitting parameters of Hardin's relationship to predict shear modulus and damping ratio at small and intermediate shear strain (G(γ) and η(γ)). Therefore, a series of resonant column tests were conducted on dry Hostun sand mixed with 0, 5, 10, 20, 30 and 40 % of fines content. Tests were carried out using the resonant column device at Ruhr- Universität Bochum. Experimental data on the adopted material revealed that maximum shear modulus decreases with an increase in fc. Analysis of data showed that fitting parameters of Hardin's relationship must be correlated to fc. In addition, experimental results for an intermediate strain region revealed the significant effect of fc on damping ratio and shear modulus. The results showed that damping ratio increased with fines content up to fc = 20 % and then decreases with further increase of fc. Reference shear strain is a key parameter to describe nonlinear behavior of soils and damping ratio. The analyses of results showed that the reference shear strain decreased with fc up to fc = 20 % and it then increases with further increase of fc for the adopted mixtures.

Investigation on shear modulus and damping ratio of transparent soils with different pore fluids

Transparent soil, manufactured with transparent granular particles and pore fluid with matching refractive index, used to mimic the behavior of natural saturated soil, is widely used in visualization model tests. The properties of transparent soils are not only affected by granular particles’ characteristics, but also influenced by pore fluids’ characteristics. However, the researches focused on the dynamic properties of transparent soil influenced by pore fluids are relatively rare in the literature. In this paper, the dynamic shear modulus and damping ratios of transparent soils manufactured by fused quartz and three different pore fluids (mixed oil, calcium bromide $$(\hbox {CaBr}_{2})$$ solution, and sucrose solution) were measured through a series of resonant column tests and dynamic torsional shear tests. The laboratory tests on dry fused quartz specimens were also carried out for comparative analysis. It is found that the transparent soils have a certain similar dynamic behaviors as those of natural soil, and the values of dynamic shear modulus and damping ratios are influenced by pore fluids. With the test results, transparent soil manufactured by fused quartz and mixed oil shows a great potential as a substitute for natural sand and is expected to be widely used in dynamic model tests.

Investigation on the dynamic shear modulus and damping ratio of steel slag sand mixtures

This paper aims to investigate the dynamic shear modulus (G) and damping ratio (D) of steel slag sand mixture (SSM), and compared with the cement sand mixture (CSM) under the same conditions. A series of resonant column tests were conducted to explore the effects of confining pressure, mix proportion and curing age on the dynamic shear modulus and damping ratio. The results show that the dynamic shear modulus increases with the increase of confining pressure, whereas the damping ratio is found to be less influenced by confining pressure. An increase in curing age leads to an increase in dynamic shear modulus and a slowly decrease in damping ratio. The mix proportion significantly affects the dynamic shear modulus and damping ratio of SSM and CSM. The dynamic shear modulus of SSM initially increases and then decreases with the increase of steel slag content, and reaches the maximum when steel slag content is 40%. The dynamic shear modulus of CSM gradually increases with the increase of cement content. As the increase of steel slag and cement in the mixture, the damping ratios of SSM and CSM tend to increase first and then decrease, and the maximum damping ratio (Dmax) also shows similar trend. When the steel slag content is 15%, the maximum dynamic shear modulus (Gmax) and maximum damping ratio (Dmax) of SSM are close to those of CSM with the 15% cement content. With the test findings, it is feasible to use 40% steel slag instead of 15% or less cement to mix with sand as the foundation treatment materials, which can not only improve the dynamic characteristics of the foundation, but also save resources and protect the environment.

Regional subsidence effects on seismic soil-structure interaction in soft clay

Regional subsidence effects on dynamic soil properties and ground layering deformation are often ignored in practice, when dealing with seismic soil-structure interaction analyses. Nevertheless, these effects can substantially change the frequency content and spectral accelerations in both free field and in the soil-structure system. Pore pressure variations over the project economic life are due to both regional subsidence as well as dissipation of excess pore pressure caused by the structure weight. These variations lead to changes in effective stresses, which in turn, modify the dynamic properties such as shear wave velocity distribution and modulus degradation and damping curves, as well as soil layer thickness and shape. These changes can be substantial in highly compressible very soft clay, such as that found in Mexico City valley. This paper presents a numerical study on the seismic response of a conventional five-story building supported by a compensated box foundation built in soft clay, considering these effects. Three-dimensional finite difference models were developed with the software FLAC3D. Initially, the evolution of effective stresses with pore pressure was established based on in-situ piezometer measurements of an instrumented site, and laboratory data. Then, changes in dynamic properties were taken into account based on the results gathered from series of resonant column tests conducted for several effective consolidation stresses, and a PS suspension logging test. The static behavior of the soil-structure system was assessed. For the cases studied herein, the complex interplay between soil nonlinearities, which lead to fundamental period elongation of the soil deposit, Tp, and the overall tendency of ground consolidation to shorten it, controls the variations in the spectral ordinates depending on how close Tp is of the predominant period of the excitation.

Experimental study on dynamic properties of sand-rubber mixtures in a small range of shearing strain amplitudes

Sand-rubber mixtures has characteristics of light weight, cheap and environmental-friendly, thereby it has a great potential to be used in geotechnical engineering for sustainable development. Dynamic properties (i.e. shear modulus and damping ratio) of sand-rubber mixtures in a small range of shearing strain amplitudes (i.e. 10-6-10-4) were investigated in this study through a series of resonant column tests. The effects of shearing strain amplitude, confining pressure and rubber content on dynamic shear modulus (G), maximum dynamic shear modulus (Gmax), damping ratio (D) and dynamic shear modulus ratio G/Gmax of the mixtures were also discussed. Based on the analyses of the relationship among confining pressure, rubber content and Gmax, an empirical formula for predicting Gmax considering the effects of confining pressure and rubber content was also proposed. The model prediction agreed with the experimental results very well.

Dynamic soil properties for seismic ground response studies in Northeastern India

Stiffness and damping properties of soil are essential parameters for any dynamic soil structure interaction analysis. Often the required stiffness and damping properties are obtained from the empirical curves. This paper presents the stiffness and damping properties of two naturally occurring sandy soils collected from a river bed in a highly active seismic zone in the Himalayan belt. A series of resonant column tests are performed on the soil specimens with relative densities representative of the field and with varying confining pressures. The test results are compared with the available empirical curves. Furthermore, a ground response analysis study is also carried out for a bridge site in the region using both the empirical curves and experimentally obtained curves. It has been observed that the application of empirical modulus and damping curves in ground response prediction often leads to underestimation of the seismic demands on the structures. The established soil curves can thus be utilized in performing seismic ground response studies for the design of new structures or requalification/reassessment of existing structures in the northeastern part of India.

Effect of saturation on dynamic properties of compacted clay in a resonant column test

ABSTRACTIn the present study, a series of resonant column (RC) tests was performed on compacted clayey soils to study the effect of saturation on the dynamic properties of soil, including shear modulus (G) and damping ratio (D). The Poisson’s ratio () of the compacted clays is also determined. Cylindrical samples measuring 50 mm × 100 mm were prepared in a constant volume mould at optimum moisture content under a static compaction. Two series of RC tests were performed; in the first series samples were compacted at optimum moisture content while in the second series, samples were fully saturated. A reduction in shear modulus and increase in damping ratio with saturation were observed. This is due to the suction present in the partially saturated soils. It was observed that this effect is noticeable at low isotropic confining pressures; however, it reduces considerably with an increase in isotropic confining pressure. Similar observations were made with respect to the shear strain applied. For the partially saturated soils, Poisson’s ratio decreases with an increase in confining pressure and increases with an increase in shear strain. However, Poisson’s ratio obtained for the saturated sample, as expected, is close to 0.5 and remains constant for all confining pressures and shear strains applied.

Shear modulus and damping ratios of transparent soil manufactured by fused quartz

The mixture of fused quartz and pore fluid with the same refractive index has been used as a synthetic transparent soil to mimic the behavior of natural soil. Previous research has focused on its static properties. In this paper, the dynamic properties of fused quartz (dry samples and oil saturated samples), including shear modulus and damping ratio, were examined through a series of resonant column tests and dynamic torsional shear tests. It was found that fused quartz has similar dynamic behavior to that of natural soil. With the test results, fused quartz shows a great potential as a substitute for natural soil and is expected to be widely used in dynamic transparent soil model tests.

Influence of Shear Strain on the Poisson’s Ratio of Clean Sands

In the present study, a series of resonant column tests was performed to determine the influence of confining pressure, shear strain and relative density on the dynamic properties and Poisson's ratio of poorly graded clean sand. The tests were performed on the sand specimens of size 50 × 100 mm compacted at relative densities 30, 50 and 75 %. To achieve the corresponding relative density, sand was compacted in 5 equal layers with a specific number of blows. A fixed-free type resonant column apparatus was used to determine the dynamic soil properties at various confining pressures. It has been inferred from the data that the shear modulus ( $$G$$ ) increases with an increase in confining pressure and relative density; and decreases with an increase in shear strain. In addition, damping ratio ( $$D$$ ) decreases with an increase in confining pressure and relative density; and increases with an increase in shear strain. In addition, Poisson’s ratio ( $$\nu$$ ) decreases with an increase in confining pressure and relative density and increases with an increase in the shear strain. The variation of shear modulus with Poisson’s ratio is also discussed. It has been found that there has been a decrease in shear modulus with an increase in Poisson’s ratio of the soil. It is noticed that the small strain shear modulus determined from the present study closely matches with the value determined using the correlations from the literature.

Reliability Evaluation of Dynamic Characteristics of Clean Sand Soils Based on Soft Computing Methods

This study was conducted to estimate the dynamic characteristics of clean sand under low strains using fuzzy expert systems and neural network approximations. A series of resonant column tests were conducted on clean sand specimens to create a large database. The effects of various factors, such as effective pressure, saturation, void ratio and shear strain levels, were simulated using fuzzy expert systems and neural networks. The neuro-fuzzy inference method was employed to predict the initial shear modulus of clean sand samples as a substitute for time-consuming laboratory testing. Additionally, the maximum shear modulus results were compared with the existing empirical relationships. From these observations, it can be observed that certain relationships significantly underestimate the initial shear modulus. Simple empirical relationships to estimate the initial shear modulus were formulated. It is concluded that neuro-fuzzy-based models provide useful guidelines for the preliminary estimation of the dynamic shear modulus for clean sand soils.

A study on the rheological properties of recycled rubber-modified asphalt mixtures.

Using waste rubber in asphalt mixes has become a common practice in road construction. This paper presents the results of a study on the rheological characteristics of rubber-modified asphalt (RMA) concrete under static and dynamic loading conditions. A number of static and dynamic creep tests were conducted on RMA mix specimens with different rubber sizes and contents, and a series of resonant column tests were conducted to evaluate the shear modulus and damping values. To simulate the stress-strain response of traffic-induced loading, the measurements were taken for different confining pressures and strain levels. The results of the study indicated that rubber modification increases stiffness and damping ratio, making it a very attractive material for use in road construction. However the grain size of the rubber is very important. Although RMA may cost up to 100% more than regular asphalt, the advantages it brings, such as an increased service life of the road and proper waste utilization contributing to a more sustainable infrastructure, may justify the added cost.