• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.15-23
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• 2015

An experimental study has been conducted to evaluate the effects of average and cyclic shear stresses on the undrained failure behaviors of dense marine silty sand by using the Cyclic Direct Simple Shear apparatus. The results show that when the average shear stress ratio is zero, symmetric cyclic shear deformation is the major component of deformation, and permanent shear deformation is relatively small. On the other hand, when the average shear stress ratio is larger than zero, asymmetric permanent shear deformation is the major component, and cyclic shear deformation does not change much as the number of cyclic loads increases. The average shear stress ratio has less effects on the number of cyclic loads needed to fail, as compared with the cyclic shear stress ratio. The proposed stress-dependent failure contour can effectively be used to assess the cyclic shear strength of soil beneath the foundation for the design of offshore structures.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.315-322
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• 2003

Cyclic simple shear tests were performed to find out the effect of preshear on dynamic strength of the sandy soil. Tests were performed for the specimens with 40% and 60% of relative density, under three different effective vertical stress of 50, 100 and 200kPa. For 50 and 100kPa, preshear ratios 0.00, 0.08, 0.12 and 0.16 were given, respectively, For low and high relative densities, two different results are shown in dynamic tests. Under the dense conditions, the maximum shear stress ratio($\tau$$\_$cyc//$\sigma$$\_$vo/) and the cyclic shear stress ratio($\tau$$\_$cyc//$\sigma$$\_$vo/) causing a certain shear strain increase with augmenting preshear ratio(${\alpha}$). However, the maximum shear stress ratio and the cyclic shear stress ratio increase or decrease with increasing preshear ratio under the loose conditions. Correction factor(K$\_$${\alpha}$/) for preshear increases at an early stage and then decreases with increasing preshear ratio at loose condition and increase with increasing preshear ratio at dense condition. Correction factor (K$\_$${\alpha}$,Max/) for preshear increases with the increasing preshear ratio irrespective of relative density, and the value of has same behavior as K$\_$${\alpha}$/.

• Journal of the Korean Geosynthetics Society
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• v.13 no.2
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• pp.49-57
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• 2014

In this study, in order to take advantage of samples collected in the Jangbogo station, and to grasp the liquefaction resistance characteristics of the dynamic load was performed cyclic triaxial test. Also, through the comparison with the existing literature. The test results, for the relationship between number of cycles for the same cyclic shear stress ratio and the cyclic shear stress ratio to produce an axial strain of 5%, in all samples, the cyclic shear stress ratio to liquefaction for the specimen, which has been liquefied, was increased, whereas number of cycles were reduced. The cyclic shear stress ratio of samples first decrease up to the fine content of about 10%. After this strength level, there is a little increase in cyclic shear stress ratio with increasing fine content. In addition, the cyclic shear stress ratio between cohesive strength, mean particle size, and friction angle decrease but some time later, there was a tendency that cyclic shear stress ratio is a little increased.

• Geomechanics and Engineering
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• v.7 no.3
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• pp.297-316
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• 2014

This paper presents a detailed study focused on investigating the effects of silt content on the static and dynamic properties of sand-silt mixtures. Specimens with a low-plastic silt content of 0, 15, 30 and 50% by weight were tested in static triaxial, cyclic triaxial, and resonant columns in addition to consolidation tests to determine such parameters as compression index, internal friction angle, cohesion, cyclic stress ratio, maximum shear modulus, normalized shear modulus and damping ratio. The test procedures were performed on specimens of three cases: constant void ratio index, e = 0.582; same peak deviator stress of 290 kPa; and constant relative density, $D_r$ = 30%. The test results obtained for both the constant-void-ratio-index and constant-relative-density specimens showed that as silt content increased, the internal friction angle, cyclic stress ratio and maximum shear modulus decreased, but cohesion increased. In testing of the same deviator stress specimens, both cohesion and internal friction angle were insignificantly altered with the increase in silt content. In addition, as silt content increased, the maximum shear modulus increased. The cyclic stress ratio first decreased as silt content increased to reach the threshold silt content and increased thereafter with further increases in silt content. Furthermore, the damping ratio was investigated based on different silt contents in three types of specimens.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.2
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• pp.95-101
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• 2018

The objective of this study is to evaluate the liquefaction cyclic shear stress ratio considering the soil uncertainty. In this study, the probabilistic ground response analysis and the cyclic shear stress ratio analysis for the liquefaction potential evaluation are performed considering the soil variability. The statistical properties of input ground parameters were analyzed to investigate the parameters affecting the seismic response analysis. The Probabilistic analysis was carried out by Monte Carlo Simulation method. The ground response analysis was performed considering the soil variability and the probability distribution characteristics of the ground acceleration. The probability distribution of the peak ground acceleration by seismic characteristics was presented. The differences of liquefaction shear stress ratio results according to soil variability were compared and analyzed. The maximum acceleration of the ground by the deterministic method was analyzed to be overestimation of the ground amplification phenomenon. Also, the shear stress ratio was overestimated.

• Journal of the Korean Geotechnical Society
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• v.33 no.1
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• pp.79-91
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• 2017

An experimental study has been conducted by using the Cyclic Direct Simple Shear apparatus to evaluate the influence of average and cyclic shear stresses on the undrained shear failure behavior of marine silty sand considering various relative densities. The obtained results show that despite using different relative densities, similar trends were gained in the cyclic shear deformation. Moreover, the cyclic shear deformation is affected mainly by the average and cyclic shear stresses. The number of cyclic loads for failure is significantly affected by the cyclic shear stress ratio and relative density, and is less affected by the average shear stress ratio. The proposed three-dimensional stress-dependent failure contour can be used effectively to assess the soil shear strength considering various relative densities in the design of foundation used for offshore structures.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.3
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• pp.73-79
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• 2010

In the present study, the loading frequency dependencies of cyclic shear strength and elastic shear modulus of reconstituted clay were examined by performing undrained cyclic triaxial tests and undrained cyclic triaxial tests to determine deformation properties. The result of undrained cyclic triaxial test of reconstituted and saturated clay shows that a faster frequency leads to higher stress amplitude ratio, but when the frequency becomes fast up to a certain point, the stress amplitude ratio will reach its maximum limit and the frequency dependence becomes insignificant. And also, the result of undrained cyclic triaxial deformation test shows a fact that a faster loading frequency leads to higher equivalent shear modules and smaller hysteresis damping ratio, and confirms the frequency dependence of cohesive soil. Meanwhile, the result of the creep test shows that continuing creep is created in the undrained cyclic triaxial test with slow loading frequency rate, and since loading rate becomes slower at the vicinity of the maximum and the minimum deviator stress due to sine wave loading, the vicinity of the maximum and the minimum deviator stress shall be more influenced by creep.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.277-285
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• 2009

A series of undrained cyclic triaxial tests were carried out to investigate the cyclic shear stress strength characteristics of sands with respect to the silt content. Silty sand was collected around the basin of Nak-Dong River and remolded in laboratory with the range of silt content 0~50% in sand located. As results, with the change of silt content cyclic shear stress ratio (CSR) at N=10 showed the maximum value at 5% and the minimum at 20% in all relative density. The development tendency of the pore water pressure analyzed by the relationship cyclic ratio and pore water pressure ratio is unrelated the change of CSR varying silt content. Comparing the results of the void ratio and skeleton void ratio after consolidation, CSR varying silt content was much affected by skeleton void ratio which is known to affect shear behavior of silty sand.

• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.151-163
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• 2006

This paper presents the interrelationship between undrained static and cyclic shear behavior. Laboratory works were performed through the undralned static and cyclic triaxial test using Nak-Dong River sand. And static triaxial test involved the triaxial extension test for comparison with cyclic shear behavior Cyclic triaxial test was performed with a variety of combination conditions of initial static shear stress $(q_{st})$ and cyclic stress $(q_{cy})$. In this result, the stress path of cyclic shear behavior was correspondent with static shear behavior passing the critical stress ratio (CSR) line because of the development of flow deformation. After that, a failure occurred according to failure line (FL) of static shear behavior. The stress path of cyclic shear behavior showed essentially the same with static shear behavior, although it appears a little different in test method.

• Computers and Concrete
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• v.1 no.1
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• pp.77-98
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• 2004

This paper presents a numerical model for simulating the nonlinear response of reinforced concrete (RC) shear walls subject to cyclic loadings. The material behavior of cracked concrete is described by an orthotropic constitutive relation with tension-stiffening and compression softening effects defining equivalent uniaxial stress-strain relation in the axes of orthotropy. Especially in making analytical predictions for inelastic behaviors of RC walls under reversed cyclic loading, some influencing factors inducing the material nonlinearities have been considered. A simple hysteretic stress-strain relation of concrete, which crosses the tension-compression region, is defined. Modification of the hysteretic stress-strain relation of steel is also introduced to reflect a pinching effect depending on the shear span ratio and to represent an average stress distribution in a cracked RC element, respectively. To assess the applicability of the constitutive model for RC element, analytical results are compared with idealized shear panel and shear wall test results under monotonic and cyclic shear loadings.