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S Lirer - One of the best experts on this subject based on the ideXlab platform.
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small strain shear modulus of undisturbed Gravelly Soils during undrained cyclic triaxial tests
Geotechnical and Geological Engineering, 2013Co-Authors: A Flora, S LirerAbstract:The determination of the small strain shear modulus G0 of gravels is a very important issue, both under monotonic or cyclic loading conditions. In the paper, the results of a series of triaxial tests carried out in a large apparatus on frozen (undisturbed) specimens of gravel are presented, along with the description of a new experimental device developed to measure the velocity of the shear waves Vs. During undrained cyclic tests, Vs values were measured before and after liquefaction, to analyse the effect of this peculiar stress history on the small strain stiffness G0 of coarse grained Soils. The small strain shear stiffness decreases as pore pressure in the specimen builds up. However, even in tests in which liquefaction was attained during the cyclic loading phase, G0 showed to depend only on the current value of the effective stress: its values become smaller than the initial one (before cyclic loading was applied) but not nil, depending on the transient value of the pore pressure and therefore of the effective stress. Furthermore, the experimental results showed that, since there was no sudden drop of G0 upon liquefaction triggering, the gravel did not have a structure which significantly affected its mechanical behaviour.
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undrained cyclic resistance of undisturbed Gravelly Soils
Soil Dynamics and Earthquake Engineering, 2012Co-Authors: A Flora, S Lirer, F SilvestriAbstract:Abstract The paper presents the results of laboratory tests carried out on undisturbed specimens of a Gravelly soil sampled by in situ freezing. Because of the heterogeneity of the natural deposit, the grain size distribution of the specimens ranged from uniform sand with a very low percentage of gravel to well-graded sandy gravel, and could be divided into three different families (respectively, named A, B and C). The testing programme consisted of drained and undrained monotonic triaxial tests and undrained cyclic triaxial tests, carried out on both isotropically and anisotropically ( K 0 ) consolidated specimens. Because of the coarse gradations of the Soils, a large triaxial cell was used. The monotonic and cyclic tests showed that the two finer materials (soil A and B) behave in a similar way, confirming that the fabric matrix dominates the overall mechanical behavior when coarser particles are few and floating. The results also confirmed that the coarsest material (soil C) has a lower tendency to liquefy. The tendency to undergo liquefaction or cyclic mobility during undrained cyclic tests was referred to initial soil conditions expressed through the state parameter ψ , which proved once more to be a parameter very useful to this aim.
Takeji Kokusho - One of the best experts on this subject based on the ideXlab platform.
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correlation of pore pressure b value with p wave velocity and poisson s ratio for imperfectly saturated sand or gravel
Soils and Foundations, 2000Co-Authors: Takeji KokushoAbstract:Field data indicate that the P-wave velocity in sand or gravel is sometimes much lower than that of water, even if the soil is below the water table. It is well understood that a slight decrease in saturation normally evaluated by the B-value has a significant effect on undrained shear behavior like liquefaction of saturated soil. In the first part of this research, theoretical formulations of the B-value, P-wave velocity and Poisson's ratio are made by taking into account the decrease in bulk modulus of water due to a mixture of air bubbles. Then, computations are carried out using formulas based on the soil properties of a typical sand or Gravelly Soils and Masa soil from the Kobe area to make charts correlating the variables. These charts indicate that a small decrement in the B-value in the interval of B=1.0 to 0.8 will considerably decrease the P-wave velocity. Thus, the P-wave velocity which is easily measured in the field can serve as a convenient index to quantitatively evaluate the insitu soil B-value.
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spt n value and s wave velocity for Gravelly Soils with different grain size distribution
Soils and Foundations, 1997Co-Authors: Takeji Kokusho, Yasuo YoshidaAbstract:ABSTRACT SPT N-value and S-wave velocities for Gravelly Soils with widely varying grain size distribution were measured in a large container test and formulated as functions of gradation, relative density and confining stresses. These values have been found to be very sensitive to the difference in gradation. It has also been found that well-graded Gravelly Soils, despite the much smaller void ratio than sand, can have an N-value and shear wave velocity as low as loose sand if it is loosely deposited. It has also been found that the formulae can readily estimate N-values with the factor of 1.5 ~ 1 /1.5 and S-wave velocity with that of 1.2 ~ 1 /1.2 for a wide range of Gravelly Soils and can give a direct relationship between the two variables which is consistent with previous research based on field data.
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UNDRAINED CYCLIC STRENGTH OF Gravelly SOIL AND ITS EVALUATION BY PENETRATION RESISTANCE AND SHEAR MODULUS
Soils and Foundations, 1992Co-Authors: Yukihisa Tanaka, Yasuo Yoshida, Kouji Kudo, Takeji KokushoAbstract:Undrained cyclic triaxial tests and drained triaxial compression tests were conducted on undisturbed samples of diluvial dense Gravelly Soils obtained by in-situ freeze sampling at four sites. These test results, together with test results by other researchers indicate that undrained cyclic strengths of Gravelly Soils depend not only on the modified blow count of penetration tests but also on effective confining pressure. By considering the effect of effective confining pressure on undrained cyclic strength, a method to evaluate undrained cyclic strength of natural Gravelly deposits using the blow count of Large Penetration Test (LPT) is proposed. Furthermore, the possibility of evaluating undrained cyclic strength of natural Gravelly deposits using initial shear modulus was investigated. It was found that although initial shear modulus can be used for this purpose, the accuracy is much less than that based on LPT penetration resistance.
Munenori Hatanaka - One of the best experts on this subject based on the ideXlab platform.
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permeability characteristics of high quality undisturbed Gravelly Soils measured in laboratory tests
Soils and Foundations, 2001Co-Authors: Munenori Hatanaka, Akihiko Uchida, Yuji Taya, Naoto Takehara, Tsuyoshi Hagisawa, Noriaki Sakou, Shinya OgawaAbstract:A series of permeability tests on both high-quality undisturbed samples and reconstituted samples was performed using a large-scale triaxial cell. Based on the test results and discussion, the following conclusions were noted. (1) The coefficient of permeability in the horizontal direction is larger than that in the vertical direction. However, its difference is between 10% and 70% and not so large. (2) The coefficient of permeability decreases with increasing confining stress. The effect of the confining stress can be understood as the effect of the void ratio. And the small change of the void ratio due to consolidation only leads to a small change of the coefficient of permeability. (3) There is no clear correlation between the physical properties and the coefficient of permeability. (4) The coefficient of permeability of Gravelly Soils is almost the same as that of sandy Soils, even though the 50% diameter of Gravelly Soils is about ten to a hundred times that of sandy Soils. This result implies that the large size particles of Gravelly Soils have no significant effect on permeability characteristics of Gravelly Soils. (5) A new definition for determination of D10, D20 and fines content only from those soil particles with a diameter smaller than 2mm was introduced. A correlation similar to sandy Soils can be seen between the coefficient of permeability and D10, D20, and fines content based on the new definitions. (6) The effect of the small size particles of the Gravelly Soils on the coefficient of permeability was found significant based on the test results using samples with a special blend of particle size and density reconstituted from undisturbed samples. (7) The coefficient of permeability of multi-layer Gravelly Soils, in the direction perpendicular to the sedimentation, was significantly affected by the lowest permeability. And the coefficient of permeability of the multi-layer in total agrees well with the theoretical estimation. (8) Although the data is limited, there was no significant different of coefficient of permeability between undisturbed and reconstituted samples. This result accords with that reported for sandy Soils by Hatanaka et al. (1997). This result also means that the coefficient of permeability of Gravelly soil is not affected by the soil fabric. As a result, the in-situ coefficient of permeability of Gravelly Soils can be well estimated for practical purposes from the reconstituted samples with the same gradation properties.
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estimating k0 value of in situ Gravelly Soils
Soils and Foundations, 1999Co-Authors: Munenori Hatanaka, Akihiko Uchida, Yuji TayaAbstract:ABSTRACT Hatanaka and Uchida (1996) developed a simple method (named G0-equal method) for estimating K0-value of cohesionless Soils by equalizing the initial shear modulus calculated from the shear wave velocity measured in the field (GOF) and that measured in laboratory (GO l ) for high-quality undisturbed samples. It is clear that to directly equalize the shear wave velocity obtained both in the laboratory and the field is more convenient. As a result, the G0-equal method was modified as a VS-equal method in the present study. In the VS-equal method, the K0-value can be described in Eq. (1) . (1) K 0 = 3 / σ v ′ ⋅ V SF / a ′ 1 / n ′ − 1 / 2 (2) V SL = a ′ σ m ′ n ′ where, K0 is the coefficient of earth pressure at rest, σ'v is the effective vertical stress at depth for measuring the shear wave velocity, VSF is the shear wave velocity measured in the field, σ'm is the effective mean principal stress, and a' and n' are the soil constants in Eq. (2) . In order to examine the validity of the Vs-equal method, the effects of the principal stress ratio and the stress history on the VsL-σ′m correlation were verified by performing a series of laboratory tests on undisturbed and reconstituted sand and gravel samples. The K0-value of in-situ Gravelly Soils was measured by using the Vs-equal method. High-quality undisturbed Gravelly samples for the determination of the K0-value were recovered at six sites. Based on the test results and discussion, the following were concluded. 1. A simple testing method was successfully created for reliably measuring the shear wave velocity of gravel samples in the laboratory. This method has the following advantages; ① without bedding error, ② little personal error, ③ easy to use and ④ adjustable to specimen height. 2. The effect of the principal stress ratio (R = σ3′/σ1′, σ3′ : radial stress, σ1′: axial stress) on the VSL − σm′ relation was found to be negligibly small in the range of R tested (R = 0.5 ~ 1.5). The effect of the stress history on the VSL − σm′ relation was also found to be very small. These results indicate that the Es-equal method modified from the G0-equal method is a useful tool to determine the K0-value for sandy and Gravelly Soils. 3. The K0-values measured by the VS-equal method were 0.19 to 0.40 for untreated Gravelly fill, 0.55 to 1.0 for compacted Gravelly fill, and 0.83 to 1.14 for Holocene Gravelly Soils. Test results indicate that the K0-value of compacted Gravelly Soils almost correspond to the range of the K0-value usually adopted in practical use (K0 = 0.5 to 1.0). However, the K0-values for Gravelly fill are much lower than that for common use. Holocene gravel has relatively high K0-values. 4. Based on the test results, a simple equation (Eq. (3) ) is newly proposed for the estimation of the K0-value for in-situ Gravelly Soils by only using the shear wave velocity measured in the field (VSF). (3) K 0 = 0.0058 V S F − 0.53 ( 150 ≤ V S F ≤ 350 ( m / s ) )
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correlation between undrained cyclic shear strength and shear wave velocity for Gravelly Soils
Soils and Foundations, 1997Co-Authors: Munenori Hatanaka, Akihiko Uchida, Yoshio SuzukiAbstract:ABSTRACT A series of undrained cyclic triaxial tests were performed on various types of high-quality undisturbed Gravelly samples recovered by the in-situ freezing method. The undrained cyclic shear strength obtained from these tests was reviewed and related to shear wave velocity measured in the field. Similar test results determined by other investigators were also adopted for establishing a correlation. Based on the review of these test results, the following conclusions were drawn. For the case of gravels of Holocene Epoch, a fairly good correlation could be found between the undrained cyclic shear strength and shear wave velocity, in such a way that the undrained cyclic shear strength increases with an increase in the shear wave velocity. The data for Pleistocene gravel, however, indicated two separate groups. One basically coincides with the correlation of Holocene gravel. The data from the other group indicated that the liquefaction strength is much higher than that of Holocene gravels for the same value of shear wave velocity. In order to correct the effect of confining stress on this correlation, a normalized shear wave velocity, VS1, in terms of the effective vertical stress was introduced. Similar good correlations were found between VS1 and the undrained cyclic shear strength. These correlations can be well expressed with empirical equations proposed by the authors. In the case of Pleistocene gravel, however, these equations indicate the lower boundary of undrained cyclic shear strength.
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correlation between strengths and penetration resistances for Gravelly Soils
Soils and Foundations, 1993Co-Authors: Yoshio Suzuki, Munenori Hatanaka, Shigeru Goto, Kohji TokimatsuAbstract:High-quality undisturbed gravel samples, 30 cm in diameter and 60 cm high, are obtained by the in-situ freezing method at four sites. Both the undrained cyclic shear strength and drained shear strength of these samples are measured by using a large scale triaxial test apparatus. The standard penetration test (SPT) and large penetration test (LPT) are conducted at each site to obtain possible correlations between their penetration resistances and the in-situ shear strengths. The data of gravels obtained by other investigators are also reviewed and discussed. The laboratory test results and the review of previous studies lead to the following conclusions. (1) The liquefaction resistance (the shear stress ratio required to cause 2 or 2.5% double amplitude axial strain in 15 load cycles) of the high-quality undisturbed gravel samples shows a good correlation with the value of Nl1 (normalized for the effective vertical stress of 1 kgf/cm squared) over a range of Nl1 between 20 and 50 in such a way that the liquefaction resistance increases with an increase in Nl1. The correlation appears to be independent of effective vertical stress. (2) The liquefaction resistance of the high-quality undisturbed gravel samples is overestimated particularly for Nl1-values larger than 30, if correlations between the liquefaction strength and the blowcount from the conventional SPT obtained for sands are directly applied. (A)
Jeanmarie Konrad - One of the best experts on this subject based on the ideXlab platform.
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a unified constitutive model for simulating stress path dependency of sandy and Gravelly soil structure interfaces
International Journal of Non-linear Mechanics, 2018Co-Authors: Miad Saberi, Charlesdarwin Annan, Jeanmarie KonradAbstract:Abstract A plasticity constitutive model is proposed to simulate the monotonic and cyclic behavior of granular soil–structure interfaces. The model is built on two-surface plasticity models previously developed for interfaces between Gravelly Soils and structural materials (Saberi et al., 2016, 2017), which simulate strain hardening, stress degradation and phase transformation behavior. The proposed model in this study incorporates the softening behavior likely to occur in dense sandy soil–structure interfaces under monotonic and cyclic loading, and it provides a unified formulation for simulating the behavior of both sandy and Gravelly soil–structure interfaces. The model accounts for the stress path dependency behavior of interfaces, and it requires a single set of nine calibration parameters, which can readily be obtained from standard interface shear tests. The interface model’s performance is evaluated for Constant Normal Load, Constant Normal Stiffness, and Constant Normal Height stress path conditions by comparing its predictions with experimental data.
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A unified constitutive model for simulating stress-path dependency of sandy and Gravelly soil–structure interfaces
International Journal of Non-linear Mechanics, 2018Co-Authors: Miad Saberi, Charlesdarwin Annan, Jeanmarie KonradAbstract:Abstract A plasticity constitutive model is proposed to simulate the monotonic and cyclic behavior of granular soil–structure interfaces. The model is built on two-surface plasticity models previously developed for interfaces between Gravelly Soils and structural materials (Saberi et al., 2016, 2017), which simulate strain hardening, stress degradation and phase transformation behavior. The proposed model in this study incorporates the softening behavior likely to occur in dense sandy soil–structure interfaces under monotonic and cyclic loading, and it provides a unified formulation for simulating the behavior of both sandy and Gravelly soil–structure interfaces. The model accounts for the stress path dependency behavior of interfaces, and it requires a single set of nine calibration parameters, which can readily be obtained from standard interface shear tests. The interface model’s performance is evaluated for Constant Normal Load, Constant Normal Stiffness, and Constant Normal Height stress path conditions by comparing its predictions with experimental data.
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Constitutive Modeling of Gravelly Soil–Structure Interface Considering Particle Breakage
Journal of Engineering Mechanics-asce, 2017Co-Authors: Miad Saberi, Charlesdarwin Annan, Jeanmarie KonradAbstract:AbstractThe mechanical behavior of the interface between Gravelly Soils and structures may play a significant role on the response of many soil-structure systems to loading. Under cyclic excursion ...
A Flora - One of the best experts on this subject based on the ideXlab platform.
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small strain shear modulus of undisturbed Gravelly Soils during undrained cyclic triaxial tests
Geotechnical and Geological Engineering, 2013Co-Authors: A Flora, S LirerAbstract:The determination of the small strain shear modulus G0 of gravels is a very important issue, both under monotonic or cyclic loading conditions. In the paper, the results of a series of triaxial tests carried out in a large apparatus on frozen (undisturbed) specimens of gravel are presented, along with the description of a new experimental device developed to measure the velocity of the shear waves Vs. During undrained cyclic tests, Vs values were measured before and after liquefaction, to analyse the effect of this peculiar stress history on the small strain stiffness G0 of coarse grained Soils. The small strain shear stiffness decreases as pore pressure in the specimen builds up. However, even in tests in which liquefaction was attained during the cyclic loading phase, G0 showed to depend only on the current value of the effective stress: its values become smaller than the initial one (before cyclic loading was applied) but not nil, depending on the transient value of the pore pressure and therefore of the effective stress. Furthermore, the experimental results showed that, since there was no sudden drop of G0 upon liquefaction triggering, the gravel did not have a structure which significantly affected its mechanical behaviour.
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undrained cyclic resistance of undisturbed Gravelly Soils
Soil Dynamics and Earthquake Engineering, 2012Co-Authors: A Flora, S Lirer, F SilvestriAbstract:Abstract The paper presents the results of laboratory tests carried out on undisturbed specimens of a Gravelly soil sampled by in situ freezing. Because of the heterogeneity of the natural deposit, the grain size distribution of the specimens ranged from uniform sand with a very low percentage of gravel to well-graded sandy gravel, and could be divided into three different families (respectively, named A, B and C). The testing programme consisted of drained and undrained monotonic triaxial tests and undrained cyclic triaxial tests, carried out on both isotropically and anisotropically ( K 0 ) consolidated specimens. Because of the coarse gradations of the Soils, a large triaxial cell was used. The monotonic and cyclic tests showed that the two finer materials (soil A and B) behave in a similar way, confirming that the fabric matrix dominates the overall mechanical behavior when coarser particles are few and floating. The results also confirmed that the coarsest material (soil C) has a lower tendency to liquefy. The tendency to undergo liquefaction or cyclic mobility during undrained cyclic tests was referred to initial soil conditions expressed through the state parameter ψ , which proved once more to be a parameter very useful to this aim.
