• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3C
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• pp.103-108
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• 2011

In this study, the limitations of large strain resonant column and torsional shear tests apparatus are described and solutions to the limitations are also described. The limitations are rotational distance, limited torque, and measurable deformation system, respectively. To resolve the rotational distance, the bottom platen was modified. And the four-armed drive plate was modified into eight-armed drive plate and the drive coil connection was changed to obtain powerful torque.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.1-10
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• 2008

Conventional RC/TS(resonant column and torsional shear) device usesa specimen with an aspect ratio(height-to-diameter) of 2:1 and this generates a maximum shear strain in the sample of about 1.5% at the maximum rotation of the drives system. The objective of this study is to modify RC/TS device to generate higher strain amplitude. The modifications include a new base pedestal to overcome the limitations in the travel of the drive system and modification of coil wiring to increase torque. The effects of the new coil wire on torque in the electro magnetic drive system were evaluated and the application of modified device was illustrated using sand soil.

• Journal of the Korean Geosynthetics Society
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• v.10 no.2
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• pp.21-28
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• 2011

Several theoretical soil nonlinear models to predict damping ratio, which is one of the typical dynamic properties of soils, it is impractical to predict damping ratio. The resonant column and torsional shear test(RC-TS) is used to represent the dynamic behavior of soils from intermediate to medium shear strains. A limitation of RC-TS is measure precise shear strain in large strains and the modified equivalent radius($R_{eq}$) was obtained using both modified hyperbolic model and Ramberg-Osgood model. Bonneville clays were tested using RC-TS test to obtain rotation and torque. The measured rotation and torque were then compared with calculated rotation and torque using curve-fitting method. Then, the nonlinear soil model parameters were obtained and the equivalent radius was calculated using the model parameters.

• Geotechnical Engineering
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• v.11 no.1
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• pp.101-112
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• 1995

Deformational characteristics of soils, often expressed in terms of shear modulus and material damping ratios, are important parameters in the design of soil-structure systems subjected to cyclic and dynamic loadings. In this paper, deformational characteristics of dry sand at small to intermediate strains were investigated using resonant column/torsional shear(RC 175) apparatus. Both resonant column(dynamic) and torsional shear (cyclic) tests were performed in a sequential series on the same specimen. With the modification of motion monitoring system, the elastic zone, where the stress strain relationship is independent of loading cycles and strain amplitude, was veri tied and hysteretic damping was found even in this zone. At strains above cyclic threshold, shear modulus increases and damping ratio decreases with increasing number of loading cycles. Moduli and damping ratios of dry sand are independent of loading frequency and values obtained from pseudostatic torsional shear tests are Identical with the values from the dynamic resonant column test, provided the effect of number of loading cycles is considered in the conlparison. Therefore, deformational characteristics determined by RC/TS tests may be applied in both dynamic and static analyses of soil-structure systems.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.1
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• pp.43-55
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• 2008

The complexity of determining strain associated with shear modulus and damping ratio in torsional tests has been resolved by means of several approaches. Particularly, the modified equivalent radius approach is adequate to when generating the plots of equivalent radius ratio versus strain more effectively over any range of strains in resonant column and torsional shear (RC/TS) tests. The modified equivalent radius approach was applied for hyperbolic, modified hyperbolic, and Ramberg-Osgood models in evaluating damping ratio. Results showed that using a single value of equivalent radius ratio based on conventional equivalent radius approach is not appropriate. A new model was developed to consider the soil damping behavior at small strains as well as hysteretic damping and it was attempted to determine adjustments are required in evaluating strain associated damping when combining the two damping components.

• Geotechnical Engineering
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• v.11 no.1
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• pp.113-126
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• 1995

Both resonant column (RC) and torsional shear(TS) tests were performed at small to intermediate strain levels to investigate deformational characteristics of cohesive soils. The effects of variables such as strain amplitude, loading frequency, and number of loading cycles were studied. Plasticity index was found to be an important variables in evaluating these effects. Soils tested include undisturbed silts and clays and compacted subgrade soils. At small strains below the elastic threshold, shear modulus is independent of number of loading cycles and strain amplitude. Small strain material damping exists wi th ranges be tween 1.1% and 1.7% for 75 tests. The elastic threshold strain increases as confining pressure and plasticity index increases. Above the cyclic threshold strain, the modulus of cohesive soil decreases with increasing number of cycles while damping ratio is almost independent of number of load cycles. Moduli and damping ratios of cohesive soils obtanined by RC test are higher than those from 75 test because of the frequency effect. Shear modulus of cohesive soil increases linearly as a function of the logarithm of loading frequency.

• Geotechnical Engineering
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• v.13 no.6
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• pp.13-24
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• 1997

In Korea, granite is abundant and occupies around two-thirds of the country's ground. Bven though weathered granite residual soils are widely distributed, undisturbed sampling of this soil is extremely difficult because of the particultate structure. This difficulty has kept away the researchers from investigating !he deformational characteristics of weathered granite residual soil. Thus, a special undisturbed sampling device was developed and undisturbed samples were prepared for triaxial compression (TX), resonant column(RC), and torsional shear (75) tests. Local deformation transducer (LDT) was fabricated for internal strain measurements during TX tests. Both undisturbed samples and statically compacted samples of same density were tested by using TX with LDT, RC, and 75 test equipments. The behaviour of statically compacted specimens was almost the same as that of undisturbed samples in the strain ranges below 1 percent. The stiffness and strength decreased with increasing degree of weathering. In case of undisturbed specimens, strains at failure are widely varied from 2 percent to 11 percent, and planes of failure are irrelevant to the angle of internal friction due to the inhomogeneous nature.