Resonant Column Tests Research Articles

Correction of Young’s Modulus Calculation in the Flexural Mode of Resonant Column Test

The resonant column test includes torsional and flexural modes that can be used to obtain reduction curves for the shear modulus and Young’s modulus of the soil, respectively. When the resonant column test is performed under flexural mode, Young’s modulus is calculated mainly using the measured resonant frequency following the formula proposed by Cascante et al. However, this formula does not consider the rotational inertia effect of the electromagnetic drive disk of the resonant column apparatus and thus may inaccurately calculate Young’s modulus. In this study, the formula was modified by considering the rotational inertia effect of the electromagnetic drive disk, and its accuracy was verified by using three aluminum calibration rods with different diameters as a dummy specimen for the resonant tests in flexural and torsional modes.

Laboratory Investigation of the Mechanical Properties of a Rubber–Calcareous Sand Mixture: The Effect of Rubber Content

This paper introduces a rubber–calcareous sand mixture as a lightweight building material in offshore engineering. The mechanical properties of mixtures of varying rubber contents were investigated by performing a one-dimensional (1-D) compression test in a modified oedometer cell, as well as a resonant column test. A discussion on the test results, along with detailed interpretations regarding the role of rubber chips in the mixtures, are provided. It was found that the virgin compression curves of the rubber–calcareous sand mixtures tended to converge at a certain stress level, whilst the stress level depended on the rubber content. Moreover, the relative breakage was examined by comparing the particle size distribution curves of the calcareous sand before and after the compression test. It was shown that the grain crushing of calcareous sand was less remarkable with the inclusion of rubber chips. Furthermore, the small strain shear modulus (G0) of the mixtures decreased with the rubber content, yet the modulus reduction and damping curves exhibited little difference for the specimens of varying rubber contents.

Torsional and flexural resonant column testing of grouted sands

Torsional and flexural resonant column tests were conducted on sands grouted with a fine cement and the effects of confining pressure, strain, grout water-to-cement ratio (W/C) and sand grain size and shape were evaluated. Both types of excitation were applied on a single grouted sand specimen without causing specimen failure. Flexural excitation of grouted sands has not been reported in the literature to date. The grout W/C ratio had the strongest effect on the dynamic properties of the grouted sands and on the improvement of clean sand properties due to grouting. Depending on grout W/C ratio and confining pressure, the shear and Young's moduli, the torsional and flexural damping ratios and the Poisson ratio of the clean sands were improved by a factor of 6–36, 1.1–7.3 and 1.02–1.82, respectively.

Characterization of seismic wave velocity and attenuation and interpretation of tetrahydrofuran hydrate-bearing sand using resonant column testing

Understanding the geophysical properties of hydrate-bearing sediments is critical for hydrate utilization such as prediction of hydrate distribution and concentration, as well as safety evaluation during hydrate production. Here, a customized resonant column is employed to test tetrahydrofuran (THF) hydrate-bearing sandy specimens. The results show that wave velocities of all tested specimens increase exponentially with increasing effective confining stress (V = α × σβ), whereas wave velocity evolution becomes almost stress-independent when critical hydrate saturation (Sh > 0.53 in this study) is reached, which transforms the hydrate morphology from non-cementing to cementing type. In addition, regardless of structure differences between tested specimens, an increased α factor and decreased β exponent follows a uniform equation β = 0.61 – 0.2 log[α/(m/s)]. Measured wave velocity differences between hydrate-bearing and hydrate-free specimens confirm the coexistence of various hydrate morphologies based on matching results of theoretical predictions from rock physics models and interpretation of volumetric proportions of hydrates with different morphologies in tested specimens. Wave attenuation of tested specimens generally decreases with increasing effective confining stress and increase with increasing hydrate saturation. The relationship between wave attenuation and hydrate saturation (QS−1 = 0.015 + 0.17 Sh) is confirmed to be a hydrate saturation indicator. Considering data from field seismic surveys, this type of monotonous relationship appears to be less sensitive for hydrate morphology. Nevertheless, through the combined interpretation of wave velocities and attenuations, it is theoretically feasible to not only predict hydrate saturation, but also illustrate the evolution of hydrate morphology. Our study contributes to a better understanding of stress-related geophysical properties of hydrate-bearing sediments, which can be useful for the characterization of hydrate reservoirs.

Electrical resistivity and elastic wave velocity of sand–cement–inorganic binder mixture

Cement-based grout has been used for ground improvement. Owing to environmental issues related to cement, its usage should be reduced. In this study, an inorganic binder is introduced to reduce the use of cement in grout. To evaluate the transient electrical and mechanical properties of the sand–cement admixture samples improved with the addition of inorganic binders, two non-destructive testing methods, the electrical resistivity and free–free resonant column tests, were adopted in addition to the unconfined compressive strength (UCS) test. Experimental tests were performed considering four different mixing ratios and three different cement contents, depending on the curing time. The results show that the mixing ratio and curing time have considerable effects on the electrical and mechanical properties of the mixture. The UCS decreases as the cement content decreases. However, sufficient UCS is expected to be obtained when the inorganic binder content is increased in the mixture. From the results, it is found that geotechnical properties of the mixture can be estimated in the field with proper non-destructive testing methods. It is expected that the data and trends proposed in this study can be used as a reference in predicting grouting quality in the field.

Experimental Investigation on Small-Strain Dynamic Properties and Unconfined Compressive Strength of Gyeongju Compacted Bentonite for Nuclear Waste Repository

Gyeongju bentonite is a Ca-bentonite and a highly compacted buffer material primarily considered in Korea, as a part of an engineered barrier system (EBS) of high-level radioactive waste (HLW) repository. During the repository lifetime, the buffer material should guarantee the safe disposal of HLW against any external mechanical impact, including seismic activity. Therefore, the dynamic deformation properties of buffer material is crucial to validate its lifetime effectiveness and performance. Even though there are some researches to investigate the dynamic properties of the bentonite buffer, there has been no researches for the Korean bentonite buffer. For this reason, the paper aims to evaluate the dynamic properties at small-strain of Gyeongju bentonite and correlate the small-strain deformation properties with unconfined compressive strength using seismic and static laboratory tests. Three sets of compacted cylindrical bentonite specimens with varying dry densities (1.50 g/cm3 to 1.77 g/cm3) were produced using a cold isostatic pressing technique under three different pressing loads. Free-free resonant column (FFRC) tests and unconfined compressive (UC) tests were performed. The FFRC tests measured deformation properties at small strain, including unconstrained and constrained compression velocities, Young's modulus (Emax), constrained modulus (Max), material damping ratio (Dmin), and Poisson's ratio. The UC tests evaluated the compressive strength and secant modulus (E50) at large-strain. In this study, it was found that the deformation properties (Emax and Mmax) and unconfined compressive strength increase with the increase in a design rage of dry density. Poisson's ratio measured at constrained boundary yields relatively constant value close to 0.4 for specimens at a range of dry density higher than 1.5 g/cm3. In addition, it was found that the elastic moduli have an almost linear relationship with the unconfined compressive strength. Finally, empirical equations between elastic moduli and unconfined compressive strength for Gyeongju compacted bentonite are proposed for a Koeran design guideline.

Dynamic Behaviour of Sand–Crumbed Rubber Mixture at Low Strain Level

In the present study, the dynamic behaviour of Barak river sand and sand crumbed rubber mixture is studied under different conditions. The resonant column test is used to study the dynamic behaviour of sand and sand mixed with varying percentages (1, 2, 3, 4, 5 and 6%) of crumbed rubber at the low strain level. The tests are conducted for different relative densities (40, 50, and 60%) under different confining pressures (50, 100 and 200 kPa). The effects of saturation, relative density (Dr), confining pressure (CP) and crumbed rubber content on the dynamic behaviour of local Barak river sand is investigated. Experimental results show that the difference of shear modulus for saturated and dry conditions is not much different for small strain level. Similar behaviour is observed for damping ratio as well. However, the effect of crumbed rubber content is significant on dynamic behaviour of sand. Further, an optimum percentage of crumbed rubber content is obtained from the present study.

An archive of data from resonant column and cyclic torsional shear tests performed on Italian clays

Measurement of soil properties under cyclic and dynamic loading conditions is a critical task in the solution of most geotechnical earthquake engineering problems. The main dynamic properties of soils are usually expressed in terms of shear modulus, G, and damping ratio, D, and they are generally obtained from laboratory tests at different strain levels. Dynamic geotechnical problems often require a site-level or territorial approach involving a considerable number of dynamic laboratory tests that might be too expensive and time-consuming. Thus, it is a common practice to use empirical relationships between dynamic parameters and measurements from routine geotechnical tests. Therefore, the availability of a large and reliable archive of multiple testing results constitutes a fundamental step for geotechnical earthquake engineers and researchers. To this aim, a large data-set of the index and dynamic parameters measured from 170 undisturbed clay samples obtained from 90 sites in Central and Northern Italy is made available, and its use and application are further described and discussed.

Experimental Study on Dynamic Properties of Nano-MgO-Modified Silty Clay

To study the dynamic properties of nano-MgO-modified soil, the contents of nano-MgO which were 0%, 1%, 2%, 3%, 4% and 5% of the dry weight for soil were added into the soil. The water content of soil samples were 16% and 22%. The variation of shear modulus and damping ratio of soil was analyzed through the resonant-column test of the modified soil. The results show that with the increasing of shear strain, the shear modulus of soil decreases and the damping ratio of soil increases, the shear modulus for nano-MgO-modified soil reaches the maximum when the content of nano-MgO is 5%. The maximum shear modulus of soil with water content of 22% is smaller than that of soil with water content 16% under the same confining pressure, the shear modulus of soil increases linearly with the increasing of nano-MgO content. The reinforcement mechanism of the nano-MgO-modified soil was analyzed such as pore filling effect of nano-MgO, effect of water content, effect of vibration compaction, interaction between a nano-MgO group and a soil particle, interaction between several nano-MgO groups and soil particles.

Exploration of a mechanistic model for the quantification of the resilient modulus using free-free resonant column testing

Resilient modulus (MR ) is one of the key properties used to characterise and quantify the mechanical behaviour of soil materials for pavement design purposes. Standard MR test procedures are often complex, lengthy, and cost-prohibitive for most routine daily applications. Therefore, correlative models relating to easy-to-obtain basic soil index properties, such as the Atterberg limits, have been historically used to predict and estimate MR ; such index properties, however, are not always effective for obtaining correct MR values. Alternatively, the California bearing ratio (CBR) and nonlinear stress–strain constitutive models have also been used to estimate MR . The work presented in this paper proposes the implementation of an enhanced hyperbolic constitutive model (eHCM) for the estimation of MR based on small-strain modulus measurements from the free-free resonant column (FFRC) test. The proposed approach aims to circumvent some of the challenges and complexity associated with the lengthy MR laboratory testing. Using the Texas flexible pavements and overlays database (namely the DSS) as the data source, the research methodology included: (a) formulating and developing the eHCM, (b) estimating MR values using the eHCM model along with FFRC test measurements, (c) calibrating and validating the eHCM model using modulus measurements obtained through conventional MR testing, and (d) establishing statistical correlations between eHCM model parameters and routinely measured soil properties. Ten in-service highway test sections from the DSS, encompassing both granular (flex) base and raw subgrade soil materials, were used for the study. From the corresponding results and findings, the eHCM model was found to be satisfactory in terms of adequately quantifying the mechanical behaviour of granular base and subgrade soil materials, yielding coefficient of variation values comparable to the literature. Overall, the proposed eHCM model indicated promising potential as a viable alternative, surrogate, and/or supplement for rapid MR estimation based on simple and inexpensive field or laboratory small-strain modulus testing such as the FFRC.

Assessment of a Hyperbolic Model for Undrained-Cyclic Shearing of Remolded Clay

AbstractThe behavior of remolded kaolin clay is examined using cyclic triaxial and resonant column tests. The damping of kaolin is shown to be largely hysteretic, and its cyclic degradation behavio...

Laboratory Characterization of a Compacted–Unsaturated Silty Sand with Special Attention to Dynamic Behavior

The dynamic properties of compacted non-cohesive soils are desired not only because of the risk of natural sources of dynamic excitations such as earthquakes, but mostly because of the anthropogenic impact of machines that are working on such soils. These soils are often unsaturated, which positively affects the soil’s mechanical properties. The information about the values of these parameters is highly desirable for engineers. In this article, we performed a series of tests, including oedometric tests, resonant column tests, bender element tests, and unsaturated triaxial tests, to evaluate those characteristic parameters. The results showed that sandy silt soil has a typical reaction to dynamic loading in terms of shear modulus degradation and the damping ratio curves’ characteristics, which can be modeled by using empirical equations. We found that the compaction procedure caused an over-consolidation state dependent on the moisture content during compaction effort. The article analyzed the soil properties that impact the maximum shear modulus G0 value. Those properties were suction s, confining pressure σ3, and compaction degree represented by the void ratio function f(e).

Seismic response of subway station in soft soil: Shaking table testing versus numerical analysis

As revealed by the collapse of the Daikai Metro station during the 1995 Kobe earthquake, underground structures are not immune to seismic loading. Shanghai Metro operates 16 lines of 676 km length, comprising 413 underground stations. An additional 1000 km with 600 underground stations are planned for the next 20 years, calling for improved understanding of their seismic response. This paper studies the seismic performance of a typical 2-storey, 3-span Shanghai Metro station in soft soil, combining shaking table testing and numerical modelling. Notwithstanding scale effects, shaking table testing is performed to allow detailed simulation of the complex structural system of the station. The structure is modelled using granular concrete and galvanized steel wires to simulate the RC prototype. To remedy the problem of scale effects, synthetic model soil (a mixture of sand and sawdust) is used, along with similitude relations derived considering dynamic equilibrium. The properties of the synthetic model soil are adjusted to satisfy similitude; target stiffness and density are attained by adjusting the mixture proportions. To quantify the transferability of the results to prototype scale, the experiments are simulated with nonlinear finite elements (FE), modelling the synthetic model soil with a kinematic hardening constitutive model, calibrated against resonant column and direct shear tests. The FE model is shown to compare adequately well with the shaking table tests. The validated FE model is used to predict the seismic response of the prototype, thus allowing indirect transfer of the results from model to prototype scale. The model in prototype scale is calibrated for the real soil layers against in situ (down-hole) and laboratory (resonant column) tests. Moving from model to prototype scale, the racking deformation remains qualitatively similar. The racking drift is reduced by 50% going from model to prototype scale, which is partly due to scale effects, but also related to differences between the idealized soil of the experiments and the multiple soil layers encountered in reality. The maximum bending moment also reduces by 30% going from model to prototype scale. The base of the lower-storey columns is proven to be the most vulnerable section, as was the case for Daikai.

Dynamic properties of a sand–nanoclay composite

The paper describes the influence of 1–3% (by dry mass of sand) Laponite, a highly plastic synthetic nanoclay, on the dynamic properties of Ottawa sand, based on undrained resonant column tests. The effect of Laponite depends on the amount added, the confining stress and consolidation time. With 1% Laponite, there is an increase in the very small-strain shear stiffness at all confining stresses, which increases with extended consolidation time, reflecting the thixotropic nature of the nanoclay. Added Laponite also produces an increase in small-strain damping, an extension of the linear strain threshold; and it delays the generation of excess pore pressure, degradation of shear modulus and increase in damping with shear strain. These effects, which become more significant with increasing Laponite content, can be attributed to the impact of the clay on the fabric and grain-to-grain contacts. Evidence is provided that Laponite interferes with direct interaction between the sand grains, and the thickness of the clay layer present at the contacts appears to control the small-strain behaviour of the sand–Laponite mixtures. The formation of a gel-like pore fluid from the hydration of Laponite in the voids, and the degree to which it occupies the pore space, are responsible for the behaviour in the non-linear region.

Dynamic properties of two historically liquefiable sands in the Lisbon area

The stiffness properties of soils, particularly shear modulus and damping ratio, play a fundamental role in predicting the ground deformation during cyclic and dynamic loading. The dynamic properties can be used for the assessment of seismic ground response and the analysis of soil–structure interaction. This study provides a detailed dynamic characterisation of two liquefiable sandy soils, which have experienced earthquake-induced liquefaction, as historically documented. The soils were collected in the greater Lisbon area, in the south of Portugal. For this purpose, a comprehensive laboratory testing programme, which included a series of bender-element and resonant-column tests, was conducted. During the study, the effects of void ratio and mean effective stress on the soil stiffness were examined, focusing on the small-strain response. Results show shear modulus degradation and damping ratio curves, at small and intermediate shear strain levels, for saturated reconstituted samples under different stress conditions. Data obtained in the laboratory of both materials were fitted into normalised models to estimate the dynamic properties for different stress and state conditions. In addition, damping ratio curves were compared against the typical bounds of quartz materials. Stress-dependent models for estimating the maximum shear modulus and threshold shear strain amplitudes of both sands are proposed in this paper. The data provided in this study are useful for numerical analyses and geotechnical design, particularly when involving dynamic or seismic approaches.

Characterization of the Dynamic Properties of Clay–Gravel Mixtures at Low Strain Level

In order to support the dynamic design of subgrade filling engineering, an experiment on the dynamic shear modulus (G) and damping ratio (D) of clay–gravel mixtures (CGMs) was carried out. Forty-two groups of resonant column tests were conducted to explore the effects of gravel content (0%, 10%, 20%, 30%, 40%, 50%, and 60%, which was the mass ratio of gravel to clay), gravel shape (round and angular gravels), and confining pressure (100, 200, and 300 kPa) on the dynamic shear modulus, and damping ratio of CGMs under the same compacting power. The test results showed that, with the increase of gravel content, the maximum dynamic shear modulus of CGMs increases, the referent shear strain increases linearly, and the minimum and maximum damping ratios decrease gradually. In CGMs with round gravels, the maximum dynamic shear modulus and the maximum damping ratio are greater, and the referent shear strain and the minimum damping ratio are smaller, compared to those with angular gravels. With the increase of confining pressure, the maximum dynamic shear modulus and the referent shear strain increase nonlinearly, while the minimum and maximum damping ratios decrease nonlinearly. The predicting equation for the dynamic shear modulus and the damping ratio of CGMs when considering confining pressure, gravel content, and shape was established. The results of this research may put forward a solid foundation for engineering design considering low-strain-level mechanical performance.

Effect of Plastic Fines on Liquefaction Resistance of Sandy Soil Using Resonant Column Test

Effect of Plastic Fines on Liquefaction Resistance of Sandy Soil Using Resonant Column Test

Small-strain dynamic properties of siliceous-carbonate sand under stress anisotropy

Small-strain dynamic properties of sands are commonly estimated through the correlations basically developed by the experimental results of isotropically consolidated specimens. In reality, however, the in-situ stress state of soils is not necessarily isotropic. Several resonant column tests were conducted on reconstituted samples of a coastal siliceous-carbonate sand in a variety of initial relative density and consolidation stress. The results indicate that despite the noticeable effect of initial stress anisotropy on the values of maximum shear modulus Gmax, the values of minimum damping ratio Dmin are almost independent of initial stress ratio. In a preceding paper, the authors proposed a correction factor for two siliceous and calcareous sands which correlates the shear modulus in anisotropic stress condition to the isotropic shear modulus. It is demonstrated herein that the proposed formula is precise for the siliceous-carbonate sand of the present study. The proposed empirical relationship is then compared with a correction factor proposed by others for shear modulus of sands in stress anisotropy condition.

A novel procedure to determine shear dynamic modulus and damping ratio for partial saturated compacted fine-grained soils

This paper presents a new procedure for the characterisation of the dynamic mechanical properties of unsaturated fine-grained soils (i.e., dynamic shear modulus and phase angle). The procedure uses a rheometer, which is a conventional device for the characterisation of viscous and viscoelastic materials but with limited used in the area of geotechnical engineering. Tests were carried out on cylindrical samples following a dynamic loading scheme under strain-controlled conditions. This research is divided into two phases. The first phase aims at validating the proposed experimental methodology. Thus, one sample of kaolin was tested using the proposed methodology, and the results were compared against those obtained from the conventional Resonant Column test. During the second phase, samples of kaolin were compacted at the optimum Proctor Standard; conditioned at different degrees of saturation, and tested using the proposed procedure to show its applicability on partially saturated soils. The dynamic shear modulus and phase angle of these samples were measured using a strain level ranging from 6×10-6 to 1×10-3 with different suction conditions and without confinement pressure. The results suggest that the newly developed procedure could be more versatile and accurate than available standardized tests.

Preliminary numerical study on long-wavelength wave propagation in a jointed rock mass

Non-destructive exploration using elastic waves has been widely used to characterize rock mass properties. Wave propagation in jointed rock masses is significantly governed by the characteristics and orientation of discontinuities. The relationship between spatial heterogeneity (i.e., joint spacing) and wavelength for elastic waves propagating through jointed rock masses have been investigated previously. Discontinuous rock masses can be considered as an equivalent continuum material when the wavelength of the propagating elastic wave exceeds the spatial heterogeneity. However, it is unclear how stress-dependent long-wavelength elastic waves propagate through a repetitive rock-joint system with multiple joints. A preliminary numerical simulation was performed in in this study to investigate long-wavelength elastic wave propagation in regularly jointed rock masses using the three-dimensional distinct element code program. First, experimental studies using the quasi-static resonant column (QSRC) testing device are performed on regularly jointed disc column specimens for three different materials (acetal, aluminum, and gneiss). The P- and S-wave velocities of the specimens are obtained under various normal stress levels. The normal and shear joint stiffness are calculated from the experimental results using an equivalent continuum model and used as input parameters for numerical analysis. The spatial and temporal sizes are carefully selected to guarantee a stable numerical simulation. Based on the calibrated jointed rock model, the numerical and experimental results are compared.