The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform
R. Valceschini - One of the best experts on this subject based on the ideXlab platform.
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Peak UnDrained Resistance of Loose Sands
Transportation Research Record: Journal of the Transportation Research Board, 1997Co-Authors: G. Norris, R. Madhu, M. Ashour, R. ValceschiniAbstract:The peak unDrained resistance (σ d,upeak) of a loose sand during liquefaction under monotonic loading does not necessarily occur on or near the Mohr Coulomb failure envelope. Instead, it occurs as that combination or product of a decreasing effective confining pressure ([Formula: see text]) and an increasing stress level ( SL). The condition in which this product is a maximum occurs at a particular point on a plot of the deviator stress (σ d) versus volumetric strain (ε v) as assessed from a Drained triaxial Test. A method is presented whereby a single Drained Test with volume change measurement can be used to assess this unDrained peak. This is a refinement of a more complete effective stress method of liquefaction analysis that requires only Drained triaxial Testing.
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Peak UnDrained Resistance of Loose Sands
Transportation Research Record, 1997Co-Authors: G. Norris, R. Madhu, M. Ashour, R. ValceschiniAbstract:The peak unDrained resistance (σd, u peak) of a loose sand during liquefaction under monotonic loading does not necessarily occur on or near the Mohr Coulomb failure envelope. Instead, it occurs as that combination or product of a decreasing effective confining pressure (σ3) and an increasing stress level (SL). The condition in which this product is a maximum occurs at a particular point on a plot of the deviator stress (σd) versus volumetric strain (ϵv) as assessed from a Drained triaxial Test. A method is presented whereby a single Drained Test with volume change measurement can be used to assess this unDrained peak. This is a refinement of a more complete effective stress method of liquefaction analysis that requires only Drained triaxial Testing.
G. Norris - One of the best experts on this subject based on the ideXlab platform.
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Peak UnDrained Resistance of Loose Sands
Transportation Research Record: Journal of the Transportation Research Board, 1997Co-Authors: G. Norris, R. Madhu, M. Ashour, R. ValceschiniAbstract:The peak unDrained resistance (σ d,upeak) of a loose sand during liquefaction under monotonic loading does not necessarily occur on or near the Mohr Coulomb failure envelope. Instead, it occurs as that combination or product of a decreasing effective confining pressure ([Formula: see text]) and an increasing stress level ( SL). The condition in which this product is a maximum occurs at a particular point on a plot of the deviator stress (σ d) versus volumetric strain (ε v) as assessed from a Drained triaxial Test. A method is presented whereby a single Drained Test with volume change measurement can be used to assess this unDrained peak. This is a refinement of a more complete effective stress method of liquefaction analysis that requires only Drained triaxial Testing.
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Peak UnDrained Resistance of Loose Sands
Transportation Research Record, 1997Co-Authors: G. Norris, R. Madhu, M. Ashour, R. ValceschiniAbstract:The peak unDrained resistance (σd, u peak) of a loose sand during liquefaction under monotonic loading does not necessarily occur on or near the Mohr Coulomb failure envelope. Instead, it occurs as that combination or product of a decreasing effective confining pressure (σ3) and an increasing stress level (SL). The condition in which this product is a maximum occurs at a particular point on a plot of the deviator stress (σd) versus volumetric strain (ϵv) as assessed from a Drained triaxial Test. A method is presented whereby a single Drained Test with volume change measurement can be used to assess this unDrained peak. This is a refinement of a more complete effective stress method of liquefaction analysis that requires only Drained triaxial Testing.
Norris Gary - One of the best experts on this subject based on the ideXlab platform.
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Liquefaction and UnDrained Response Evaluation of Sands from Drained Formulation
9999Co-Authors: Ashour Mohamed, Norris GaryAbstract:Report No. CCEER-95-2The state of knowledge with regard to static and cyclic liquefaction has progressed tremendously since the mid-1960s. In fact, it is generally accepted, based on the steady-state concepts of Casagrande, Castro,and Poulos that the end or steady-state condition of a liquefied loose sand is the same whether due to monotonic, cyclic, or dynamic unDrained loading. Even so, a straightforward and fundamental explanation of the initiation and end-state liquefaction behavior is still needed. Toward that end, an effective stress approach that allows the assessment of the whole unDrained stress-strain curve (including the peak and residual strength values) and the unDrained effective stress path of a monotonic Test from Drained triaxial Tests is presented. Results from three series of Tests are shown to demonstrate the validity of the method. This method makes it possible for a geotechnical firm with the capability of performing the traditional Drained Test with volume change measurements to participate in static liquefaction and residual strength assessment. More importantly, it provides the conditions and logic for the development of complete versus limited liquefaction (and even dilative) response (Abstract by authors)
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Liquefaction and Residual Strength of Sands from Drained Triaxial Tests
9999Co-Authors: Norris Gary, Siddharthan Raj, Zafir Zia, Madhu R.Abstract:Report No. CCEER-92-6-AThe state of knowledge with regard to static and cyclic liquefaction has progressed tremendously since the mid-1960s. In fact, it is generally accepted, based on the steady-state concepts of Casagrande, Castro, and Poulos that the end or steady-state condition of a liquefied loose sand is the same whether due to monotonic, cyclic, or dynamic unDrained loading. Even so, a straightforward and fundamental explanation of the initiation and end-state liquefaction behavior is still needed. Toward that end, an effective stress approach that allows the assessment of the whole unDrained stress-strain curve (including the peak and residual strength values) and the unDrained effective stress path of a monotonic Test from Drained triaxial Tests is presented. Results from three series of Tests are shown to demonstrate the validity of the method. This method makes it possible for a geotechnical finn with the capability of performing the traditional Drained Test with volume change measurements to participate in static liquefaction and residual strength assessment. More importantly, it provides the conditions and logic for the development of complete versus limited liquefaction (and even dilative) response
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Liquefaction and Residual Strength of Loose Sands from Drained Triaxial Tests
9999Co-Authors: Norris Gary, Zafir ZiaAbstract:Report No. CCEER-92-6The state of knowledge with regard to static and cyclic liquefaction has progressed tremendously since the mid-1960s. In fact, it is generally accepted, based on the steady-state concepts of Casagrande, Castro,and Poulos that the end or steady-state condition of a liquefied loose sand is the same whether due to monotonic, cyclic, or dynamic unDrained loading. Even so, a straightforward and fundamental explanation of the initiation and end-state liquefaction behavior is still needed. Toward that end, an effective stress approach that allows the assessment of the whole unDrained stress-strain curve (including the peak and residual strength values) and the unDrained effective stress path of a monotonic Test from Drained triaxial Tests is presented. Results from three series of Tests are shown to demonstrate the validity of the method. This method makes it possible for a geotechnical firm with the capability of performing the traditional Drained Test with volume change measurements to participate in static liquefaction and residual strength assessment. More importantly, it provides the conditions and logic for the development of complete versus limited liquefaction (and even dilative) response (Abstract by authors)
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Liquefaction and UnDrained Response Evaluation of Sands from Drained Formulation
9999Co-Authors: Norris Gary, Ashour MohamedAbstract:Report No. CCEER-98-2A general approach has been established to assess the unDrained stress-strain curve and effective stress path under monotonic loading from Drained triaxial Tests. Appropriate formulation of Drained and Drained rebounded (i.e. over consolidated) triaxial Test response is developed that, in turn, allows the assessment of developing liquefaction and the unDrained behavior of saturated sands. The formulation presented is based upon reported experimental Drained Test results that were obtained from different investigators using different Testing techniques. This formulation is a function of the confining pressure and basic properties of the sand such as relative density, uniformity coefficient, and particle shape (roundness), which can be obtained from visual inspection. The approach is verified by comparing predicted and reported (observed) unDrained behavior. The developed formulas allow one to predict the potential of sand to liquefy, the type of liquefaction, the peak and residual strength values, as well as the whole unDrained stress-strain curve and effective stress path. The simplicity of this approach makes it an attractive general method to characterize the unDrained behavior of sands in a preliminary analysis with no need to run sophisticated experimental Tests (Abstract by authors)
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Liquefaction and Residual Strength of Loose Sands from Drained Triaxial Tests
9999Co-Authors: Norris Gary, Madhu R., Valceschini R., Ashour MohamedAbstract:Report No. CCEER-94-4The proposed method of effective stress evaluation of monotonic unDrained stress-strain and stress path behavior based upon the use of consolidated rebounded Drained triaxial Tests with volume change measurements is a straight forward and powerful approach to understanding the liquefaction behavior of loose sands. Based upon this approach and the fact that the resulting rebounded Drained volume change curves display essentially the same shape, a number of important distinctions result, i.e., the associated shape of the Drained volume change curves for complete liquefaction, the relationship between the steady state and critical state conditions, the relationship between the Drained and the unDrained effective stress friction angles, the conditions of the peak unDrained strength (i.e. the product of the stress level and effective confining pressure) , etc. In addition, commercial geotechnical labs can readily apply the proposed approach. Chapter 2 of the report provided the methodology and demonstrated the validity of the approach via four Test series. Chapter 3 dealt with the particular condition that leads to the unDrained peak resistance and provided a method by which it could be assessed from the results of a single Drained Tested. Chapter 4 provided the start of a Drained Test database that, with additions, will supply the means for assessing unDrained behavior based solely upon classifying the sand of interest
W.k. Leong - One of the best experts on this subject based on the ideXlab platform.
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Pre-failure instability of sand under dilatancy rate controlled conditions
Soils and Foundations, 2015Co-Authors: Jian Chu, Dariusz Wanatowski, W.l. Loke, W.k. LeongAbstract:Experimental results are presented in this paper to show that a runaway type of pre-failure instability can occur for sand under dilatancy rate controlled conditions when an appropriate strain increment ratio, dev/de1, is imposed. This type of instability is similar to the runaway type of instability observed for very loose sand under unDrained conditions. Whether a soil element will undergo pre-failure instability depends on the difference between the strain increment ratio of the soil obtained from Drained Test, under a specified effective confining pressure, (dev/de1)s, and the strain increment ratio imposed during the Test, (dev/de1)i, rather than the absolute magnitude of (dev/de1)i. Based on the experimental data obtained in this study it was found that an instability line can be determined from a series of strain path Tests conducted at different effective confining pressures but with the same dev/de1 by joining the peak points of the effective stress paths to the origin in the q–p′ stress space. This line is similar to the instability line obtained from unDrained Tests on loose sand. The instability Tests under dilatancy rate controlled conditions indicate that the stress ratio at the onset of instability obtained in the instability Tests coincide with the peak stress ratio line. This suggests that the peak stress line can be used to predict the onset of instability under dilatancy rate controlled conditions in the same way as the use of instability line to predict the onset of instability under unDrained conditions.
R. Madhu - One of the best experts on this subject based on the ideXlab platform.
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Peak UnDrained Resistance of Loose Sands
Transportation Research Record: Journal of the Transportation Research Board, 1997Co-Authors: G. Norris, R. Madhu, M. Ashour, R. ValceschiniAbstract:The peak unDrained resistance (σ d,upeak) of a loose sand during liquefaction under monotonic loading does not necessarily occur on or near the Mohr Coulomb failure envelope. Instead, it occurs as that combination or product of a decreasing effective confining pressure ([Formula: see text]) and an increasing stress level ( SL). The condition in which this product is a maximum occurs at a particular point on a plot of the deviator stress (σ d) versus volumetric strain (ε v) as assessed from a Drained triaxial Test. A method is presented whereby a single Drained Test with volume change measurement can be used to assess this unDrained peak. This is a refinement of a more complete effective stress method of liquefaction analysis that requires only Drained triaxial Testing.
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Peak UnDrained Resistance of Loose Sands
Transportation Research Record, 1997Co-Authors: G. Norris, R. Madhu, M. Ashour, R. ValceschiniAbstract:The peak unDrained resistance (σd, u peak) of a loose sand during liquefaction under monotonic loading does not necessarily occur on or near the Mohr Coulomb failure envelope. Instead, it occurs as that combination or product of a decreasing effective confining pressure (σ3) and an increasing stress level (SL). The condition in which this product is a maximum occurs at a particular point on a plot of the deviator stress (σd) versus volumetric strain (ϵv) as assessed from a Drained triaxial Test. A method is presented whereby a single Drained Test with volume change measurement can be used to assess this unDrained peak. This is a refinement of a more complete effective stress method of liquefaction analysis that requires only Drained triaxial Testing.
