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Mostefa Belkhatir - One of the best experts on this subject based on the ideXlab platform.

  • packing Density and overconsolidation ratio effects on the mechanical response of granular soils
    Geotechnical and Geological Engineering, 2020
    Co-Authors: Youcef Mahmoudi, Mostefa Belkhatir, Abdellah Cherif Taiba, Leila Hazout, Wiebke Baille
    Abstract:

    Liquefaction of sandy soils is associated with a sudden loss of the shear strength due to a dramatic increase of the excess pore water pressure in undrained conditions. Its occurrence usually causes significant damages to buildings and infrastructures during earthquakes. Therefore, the proposed laboratory research investigation aims to study the effects of the combined effects of sample depositional methods, Initial Relative Density and overconsolidation ratio on the undrained shear strength of Chlef sand samples under static loading conditions. For this purpose, a series of undrained monotonic triaxial tests were carried out on reconstituted saturated Chlef sand samples and subjected to different overconsolidation ratios (OCR = 1, 2, 4 and 8). The Initial confining pressure for all tests was kept constant (σ′3 = 100 kPa). The samples were prepared using two depositional methods named: dry funnel pluviation (DFP) and wet deposition (WD) at three selected Relative densities (Dr = 18%, 52% and 88%). The obtained data confirm the existence of a linear relationship between the undrained peak shear strength of overconsolidated Chlef sand samples (qpeak_OC) and undrained shear strength of normally consolidated Chlef sand (qpeak_NC) for the two sample preparation techniques (DFP and WD) and range of the Initial Relative Density (18% ≤ Dr ≤ 88%) under consideration. The overconsolidation (OCR) and Initial Relative Density (Dr) increase the dilativeness of the normally consolidated and overconsolidated sandy samples for the two sample reconstitution techniques. The dry funnel pluviated sandy samples exhibit higher undrained shear strength (liquefaction resistance) than the wet deposited sandy samples. Moreover, the obtained data reveal that the wet deposited sandy samples were more vulnerable to liquefaction resistance than dry funnel pluviated sandy samples for the range of the Initial Relative Density (18% ≤ Dr ≤ 88%) and lower overconsolidation ratios (1 ≤ OCR ≤ 4).

  • experimental characterization of the undrained instability and steady state of silty sand soils under monotonic loading conditions
    International Journal of Geotechnical Engineering, 2018
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Abdelkader Kadri, Tom Schanz
    Abstract:

    AbstractThis laboratory study aims to analyse the effects of gradation on the undrained instability using the undrained instability stress and steady-state ratios of silty sand soils. In this context, series of undrained compression triaxial tests were carried out on Fontainebleau (France) sand mixed with low plastic fines (I p  = 5%) range F c  = 0–30%. The samples were prepared at an Initial Relative Density (D r  = 52%) and subjected to three different confining pressures (  = 100, 200 and 300 kPa). The test results indicate that the gradation has a significant influence on instability stress and steady-state ratios of sand–silt mixtures. Moreover, the obtained data confirm the existence of simple correlations between undrained instability stress, steady-state ratios, fines content, void ratios and grading characteristics (D 10 , D 30 , D 50 , D 60 and C u ) of the materials under consideration. The introduced grading characteristics ratios (D 10R , D 50R and C UR ) and the equivalent state parameter a...

  • experimental investigation into the influence of roundness and sphericity on the undrained shear response of silty sand soils
    Geotechnical Testing Journal, 2018
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Tom Schanz
    Abstract:

    Particle shape represents one of the key parameters that significantly influences the mechanical response, shear strength, deformation, and settlement characteristics of cohesionless soil deposits when subjected to static or dynamic loading conditions. Shear behavior of coarse-grained soils (gravel, gravelly sand, sandy gravel, sand, silty sand, or sandy silt) depends heavily on the two essential particle shape characteristics, which are termed roundness and sphericity. However, there are limited published studies available in the literature that deal solely with the effects of particle shape on shear-strain characteristics and shear behavior of granular soil deposits. Therefore, the veritable role of the particle shape parameter on soil behavior remains incomplete and requires further investigation. The present research work attempts to investigate the effects of particle shape on shear response of different categories of sand-silt mixtures under static triaxial loading conditions. For this purpose, a series of undrained compression triaxial tests was carried out on mixtures of Chlef (Algerian) rounded sand, Fontainebleau (France) subrounded sand, and Hostun (France) subangular sand mixed with low-plastic (Ip=5 %) rounded silty fines. All the sand-silt mixture samples were reconstituted at an Initial Relative Density (Dr=52 %) and subjected to a constant confining pressure (P’c=100 kPa). An evaluation of particle shape characteristics of the tested materials (sand and silt) was performed using a digital microscope device. Two new indexes, termed combined roundness and combined sphericity based on the combination of sand and silt to account for the coupled effects of particle shape and fines content, were proposed. The test results are used to correlate the undrained shear strength of the silty sand soils to the particle shape characteristics. Therefore, particle shape appears to be an important soil index property that needs to be adequately identified, particularly for silty sand–silt mixture soils. The systematic identification of particle shape characteristics leads to a better understanding of silty sand behavior.

  • saturation effect on behaviour of sandy soil under monotonic and cyclic loading a laboratory investigation
    Geotechnical and Geological Engineering, 2016
    Co-Authors: Ahmed Arab, Mostefa Belkhatir, Marwan Sadek
    Abstract:

    This paper presents a laboratory study of the influence of saturation degree on the liquefaction potential of sand. The study is based on drained, undrained monotonic and cyclic triaxial tests. Tests were conducted on a medium dense Hostun RF sand (France) with an Initial Relative Density Dr = 4, 50, 64 and 78 % and the coefficient of Skempton ranging between 0.95 (saturated) and 0.25. For all Skempton’s coefficient B values, the tests were carried out for different loading levels. The monotonic tests show that an increase in the Skempton’s coefficient B leads to a reduction of liquefaction resistance. The decrement of the coefficient of saturation B does not affect the instability and steady state lines. The test results indicate that the liquefaction resistance increases with the decrease of Skempton’s coefficient B. For the high level of loading (RCC = 0.5), the number required to cause liquefaction varied little with the Skempton’s coefficient B (Nc = 9, 10 and 11 for B = 0.67, 0.36 and 0.25 respectively). For the low level (RCC < 0.40), the number of cycles needed for liquefaction increases susceptibly with the reduction of the coefficient of Skempton (B). A simple mathematical relation has been suggested to correlate the liquefaction resistance with the coefficient of Skempton B.

  • insight into the effect of granulometric characteristics on the static liquefaction susceptibility of silty sand soils
    Geotechnical and Geological Engineering, 2016
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Abdelkader Kadri, Tom Schanz
    Abstract:

    Silty sands are the most common type of soil that is involved in monotonic or dynamic loading induced liquefaction. It is associated with a sudden drop of the shear strength of the soil leading to important damages to civil engineering and hydraulics structures. Therefore, it is of great importance to identify the influencing parameters on the liquefaction of soils for the purpose to develop design strategies and therefore mitigate earthquake damages due to liquefaction phenomena. Published literature indicates that particle shape and gradation are the most important parameters that would affect the liquefaction behavior of granular sandy soils. For this purpose, a series of undrained compression triaxial tests were carried out on reconstituted Chlef sand (Algeria) and Fontainebleau sand (France) samples with low plastic fines ranging from 0 to 40 % and Initial Relative Density (Dr = 52 %) to study the liquefaction susceptibility of these soils. All the samples under study were subjected to an Initial confining pressure of (\(\upsigma_{c}^{'}\) = 100 kPa). The evaluation of the obtained data indicates that the gradation and particle shape have a significant influence on the undrained shear strength (liquefaction resistance) of different silty sand soils under study. Moreover, test results confirm the existence of simple correlations between liquefaction resistance and different grading characteristics (D10, D30, D50, D60, and Cu) of the soils under consideration. New soil granulometric ratios (D10R = D10sand/D10mixture , D50R = D50sand/D50mixture, and CUR = Cusand/Cumixture) were introduced to discuss the sand–silt mixture liquefaction resistance susceptibility response. The used grading characteristics ratios (D10R, D50R and CUR) appear as pertinent parameters to predict the undrained shear strength response of the sand–silt mixtures for soil gradation under study.

Abdellah Cherif Taiba - One of the best experts on this subject based on the ideXlab platform.

  • packing Density and overconsolidation ratio effects on the mechanical response of granular soils
    Geotechnical and Geological Engineering, 2020
    Co-Authors: Youcef Mahmoudi, Mostefa Belkhatir, Abdellah Cherif Taiba, Leila Hazout, Wiebke Baille
    Abstract:

    Liquefaction of sandy soils is associated with a sudden loss of the shear strength due to a dramatic increase of the excess pore water pressure in undrained conditions. Its occurrence usually causes significant damages to buildings and infrastructures during earthquakes. Therefore, the proposed laboratory research investigation aims to study the effects of the combined effects of sample depositional methods, Initial Relative Density and overconsolidation ratio on the undrained shear strength of Chlef sand samples under static loading conditions. For this purpose, a series of undrained monotonic triaxial tests were carried out on reconstituted saturated Chlef sand samples and subjected to different overconsolidation ratios (OCR = 1, 2, 4 and 8). The Initial confining pressure for all tests was kept constant (σ′3 = 100 kPa). The samples were prepared using two depositional methods named: dry funnel pluviation (DFP) and wet deposition (WD) at three selected Relative densities (Dr = 18%, 52% and 88%). The obtained data confirm the existence of a linear relationship between the undrained peak shear strength of overconsolidated Chlef sand samples (qpeak_OC) and undrained shear strength of normally consolidated Chlef sand (qpeak_NC) for the two sample preparation techniques (DFP and WD) and range of the Initial Relative Density (18% ≤ Dr ≤ 88%) under consideration. The overconsolidation (OCR) and Initial Relative Density (Dr) increase the dilativeness of the normally consolidated and overconsolidated sandy samples for the two sample reconstitution techniques. The dry funnel pluviated sandy samples exhibit higher undrained shear strength (liquefaction resistance) than the wet deposited sandy samples. Moreover, the obtained data reveal that the wet deposited sandy samples were more vulnerable to liquefaction resistance than dry funnel pluviated sandy samples for the range of the Initial Relative Density (18% ≤ Dr ≤ 88%) and lower overconsolidation ratios (1 ≤ OCR ≤ 4).

  • experimental characterization of the undrained instability and steady state of silty sand soils under monotonic loading conditions
    International Journal of Geotechnical Engineering, 2018
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Abdelkader Kadri, Tom Schanz
    Abstract:

    AbstractThis laboratory study aims to analyse the effects of gradation on the undrained instability using the undrained instability stress and steady-state ratios of silty sand soils. In this context, series of undrained compression triaxial tests were carried out on Fontainebleau (France) sand mixed with low plastic fines (I p  = 5%) range F c  = 0–30%. The samples were prepared at an Initial Relative Density (D r  = 52%) and subjected to three different confining pressures (  = 100, 200 and 300 kPa). The test results indicate that the gradation has a significant influence on instability stress and steady-state ratios of sand–silt mixtures. Moreover, the obtained data confirm the existence of simple correlations between undrained instability stress, steady-state ratios, fines content, void ratios and grading characteristics (D 10 , D 30 , D 50 , D 60 and C u ) of the materials under consideration. The introduced grading characteristics ratios (D 10R , D 50R and C UR ) and the equivalent state parameter a...

  • experimental investigation into the influence of roundness and sphericity on the undrained shear response of silty sand soils
    Geotechnical Testing Journal, 2018
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Tom Schanz
    Abstract:

    Particle shape represents one of the key parameters that significantly influences the mechanical response, shear strength, deformation, and settlement characteristics of cohesionless soil deposits when subjected to static or dynamic loading conditions. Shear behavior of coarse-grained soils (gravel, gravelly sand, sandy gravel, sand, silty sand, or sandy silt) depends heavily on the two essential particle shape characteristics, which are termed roundness and sphericity. However, there are limited published studies available in the literature that deal solely with the effects of particle shape on shear-strain characteristics and shear behavior of granular soil deposits. Therefore, the veritable role of the particle shape parameter on soil behavior remains incomplete and requires further investigation. The present research work attempts to investigate the effects of particle shape on shear response of different categories of sand-silt mixtures under static triaxial loading conditions. For this purpose, a series of undrained compression triaxial tests was carried out on mixtures of Chlef (Algerian) rounded sand, Fontainebleau (France) subrounded sand, and Hostun (France) subangular sand mixed with low-plastic (Ip=5 %) rounded silty fines. All the sand-silt mixture samples were reconstituted at an Initial Relative Density (Dr=52 %) and subjected to a constant confining pressure (P’c=100 kPa). An evaluation of particle shape characteristics of the tested materials (sand and silt) was performed using a digital microscope device. Two new indexes, termed combined roundness and combined sphericity based on the combination of sand and silt to account for the coupled effects of particle shape and fines content, were proposed. The test results are used to correlate the undrained shear strength of the silty sand soils to the particle shape characteristics. Therefore, particle shape appears to be an important soil index property that needs to be adequately identified, particularly for silty sand–silt mixture soils. The systematic identification of particle shape characteristics leads to a better understanding of silty sand behavior.

  • insight into the effect of granulometric characteristics on the static liquefaction susceptibility of silty sand soils
    Geotechnical and Geological Engineering, 2016
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Abdelkader Kadri, Tom Schanz
    Abstract:

    Silty sands are the most common type of soil that is involved in monotonic or dynamic loading induced liquefaction. It is associated with a sudden drop of the shear strength of the soil leading to important damages to civil engineering and hydraulics structures. Therefore, it is of great importance to identify the influencing parameters on the liquefaction of soils for the purpose to develop design strategies and therefore mitigate earthquake damages due to liquefaction phenomena. Published literature indicates that particle shape and gradation are the most important parameters that would affect the liquefaction behavior of granular sandy soils. For this purpose, a series of undrained compression triaxial tests were carried out on reconstituted Chlef sand (Algeria) and Fontainebleau sand (France) samples with low plastic fines ranging from 0 to 40 % and Initial Relative Density (Dr = 52 %) to study the liquefaction susceptibility of these soils. All the samples under study were subjected to an Initial confining pressure of (\(\upsigma_{c}^{'}\) = 100 kPa). The evaluation of the obtained data indicates that the gradation and particle shape have a significant influence on the undrained shear strength (liquefaction resistance) of different silty sand soils under study. Moreover, test results confirm the existence of simple correlations between liquefaction resistance and different grading characteristics (D10, D30, D50, D60, and Cu) of the soils under consideration. New soil granulometric ratios (D10R = D10sand/D10mixture , D50R = D50sand/D50mixture, and CUR = Cusand/Cumixture) were introduced to discuss the sand–silt mixture liquefaction resistance susceptibility response. The used grading characteristics ratios (D10R, D50R and CUR) appear as pertinent parameters to predict the undrained shear strength response of the sand–silt mixtures for soil gradation under study.

Youcef Mahmoudi - One of the best experts on this subject based on the ideXlab platform.

  • packing Density and overconsolidation ratio effects on the mechanical response of granular soils
    Geotechnical and Geological Engineering, 2020
    Co-Authors: Youcef Mahmoudi, Mostefa Belkhatir, Abdellah Cherif Taiba, Leila Hazout, Wiebke Baille
    Abstract:

    Liquefaction of sandy soils is associated with a sudden loss of the shear strength due to a dramatic increase of the excess pore water pressure in undrained conditions. Its occurrence usually causes significant damages to buildings and infrastructures during earthquakes. Therefore, the proposed laboratory research investigation aims to study the effects of the combined effects of sample depositional methods, Initial Relative Density and overconsolidation ratio on the undrained shear strength of Chlef sand samples under static loading conditions. For this purpose, a series of undrained monotonic triaxial tests were carried out on reconstituted saturated Chlef sand samples and subjected to different overconsolidation ratios (OCR = 1, 2, 4 and 8). The Initial confining pressure for all tests was kept constant (σ′3 = 100 kPa). The samples were prepared using two depositional methods named: dry funnel pluviation (DFP) and wet deposition (WD) at three selected Relative densities (Dr = 18%, 52% and 88%). The obtained data confirm the existence of a linear relationship between the undrained peak shear strength of overconsolidated Chlef sand samples (qpeak_OC) and undrained shear strength of normally consolidated Chlef sand (qpeak_NC) for the two sample preparation techniques (DFP and WD) and range of the Initial Relative Density (18% ≤ Dr ≤ 88%) under consideration. The overconsolidation (OCR) and Initial Relative Density (Dr) increase the dilativeness of the normally consolidated and overconsolidated sandy samples for the two sample reconstitution techniques. The dry funnel pluviated sandy samples exhibit higher undrained shear strength (liquefaction resistance) than the wet deposited sandy samples. Moreover, the obtained data reveal that the wet deposited sandy samples were more vulnerable to liquefaction resistance than dry funnel pluviated sandy samples for the range of the Initial Relative Density (18% ≤ Dr ≤ 88%) and lower overconsolidation ratios (1 ≤ OCR ≤ 4).

  • experimental characterization of the undrained instability and steady state of silty sand soils under monotonic loading conditions
    International Journal of Geotechnical Engineering, 2018
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Abdelkader Kadri, Tom Schanz
    Abstract:

    AbstractThis laboratory study aims to analyse the effects of gradation on the undrained instability using the undrained instability stress and steady-state ratios of silty sand soils. In this context, series of undrained compression triaxial tests were carried out on Fontainebleau (France) sand mixed with low plastic fines (I p  = 5%) range F c  = 0–30%. The samples were prepared at an Initial Relative Density (D r  = 52%) and subjected to three different confining pressures (  = 100, 200 and 300 kPa). The test results indicate that the gradation has a significant influence on instability stress and steady-state ratios of sand–silt mixtures. Moreover, the obtained data confirm the existence of simple correlations between undrained instability stress, steady-state ratios, fines content, void ratios and grading characteristics (D 10 , D 30 , D 50 , D 60 and C u ) of the materials under consideration. The introduced grading characteristics ratios (D 10R , D 50R and C UR ) and the equivalent state parameter a...

  • experimental investigation into the influence of roundness and sphericity on the undrained shear response of silty sand soils
    Geotechnical Testing Journal, 2018
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Tom Schanz
    Abstract:

    Particle shape represents one of the key parameters that significantly influences the mechanical response, shear strength, deformation, and settlement characteristics of cohesionless soil deposits when subjected to static or dynamic loading conditions. Shear behavior of coarse-grained soils (gravel, gravelly sand, sandy gravel, sand, silty sand, or sandy silt) depends heavily on the two essential particle shape characteristics, which are termed roundness and sphericity. However, there are limited published studies available in the literature that deal solely with the effects of particle shape on shear-strain characteristics and shear behavior of granular soil deposits. Therefore, the veritable role of the particle shape parameter on soil behavior remains incomplete and requires further investigation. The present research work attempts to investigate the effects of particle shape on shear response of different categories of sand-silt mixtures under static triaxial loading conditions. For this purpose, a series of undrained compression triaxial tests was carried out on mixtures of Chlef (Algerian) rounded sand, Fontainebleau (France) subrounded sand, and Hostun (France) subangular sand mixed with low-plastic (Ip=5 %) rounded silty fines. All the sand-silt mixture samples were reconstituted at an Initial Relative Density (Dr=52 %) and subjected to a constant confining pressure (P’c=100 kPa). An evaluation of particle shape characteristics of the tested materials (sand and silt) was performed using a digital microscope device. Two new indexes, termed combined roundness and combined sphericity based on the combination of sand and silt to account for the coupled effects of particle shape and fines content, were proposed. The test results are used to correlate the undrained shear strength of the silty sand soils to the particle shape characteristics. Therefore, particle shape appears to be an important soil index property that needs to be adequately identified, particularly for silty sand–silt mixture soils. The systematic identification of particle shape characteristics leads to a better understanding of silty sand behavior.

  • insight into the effect of granulometric characteristics on the static liquefaction susceptibility of silty sand soils
    Geotechnical and Geological Engineering, 2016
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Abdelkader Kadri, Tom Schanz
    Abstract:

    Silty sands are the most common type of soil that is involved in monotonic or dynamic loading induced liquefaction. It is associated with a sudden drop of the shear strength of the soil leading to important damages to civil engineering and hydraulics structures. Therefore, it is of great importance to identify the influencing parameters on the liquefaction of soils for the purpose to develop design strategies and therefore mitigate earthquake damages due to liquefaction phenomena. Published literature indicates that particle shape and gradation are the most important parameters that would affect the liquefaction behavior of granular sandy soils. For this purpose, a series of undrained compression triaxial tests were carried out on reconstituted Chlef sand (Algeria) and Fontainebleau sand (France) samples with low plastic fines ranging from 0 to 40 % and Initial Relative Density (Dr = 52 %) to study the liquefaction susceptibility of these soils. All the samples under study were subjected to an Initial confining pressure of (\(\upsigma_{c}^{'}\) = 100 kPa). The evaluation of the obtained data indicates that the gradation and particle shape have a significant influence on the undrained shear strength (liquefaction resistance) of different silty sand soils under study. Moreover, test results confirm the existence of simple correlations between liquefaction resistance and different grading characteristics (D10, D30, D50, D60, and Cu) of the soils under consideration. New soil granulometric ratios (D10R = D10sand/D10mixture , D50R = D50sand/D50mixture, and CUR = Cusand/Cumixture) were introduced to discuss the sand–silt mixture liquefaction resistance susceptibility response. The used grading characteristics ratios (D10R, D50R and CUR) appear as pertinent parameters to predict the undrained shear strength response of the sand–silt mixtures for soil gradation under study.

Tom Schanz - One of the best experts on this subject based on the ideXlab platform.

  • experimental characterization of the undrained instability and steady state of silty sand soils under monotonic loading conditions
    International Journal of Geotechnical Engineering, 2018
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Abdelkader Kadri, Tom Schanz
    Abstract:

    AbstractThis laboratory study aims to analyse the effects of gradation on the undrained instability using the undrained instability stress and steady-state ratios of silty sand soils. In this context, series of undrained compression triaxial tests were carried out on Fontainebleau (France) sand mixed with low plastic fines (I p  = 5%) range F c  = 0–30%. The samples were prepared at an Initial Relative Density (D r  = 52%) and subjected to three different confining pressures (  = 100, 200 and 300 kPa). The test results indicate that the gradation has a significant influence on instability stress and steady-state ratios of sand–silt mixtures. Moreover, the obtained data confirm the existence of simple correlations between undrained instability stress, steady-state ratios, fines content, void ratios and grading characteristics (D 10 , D 30 , D 50 , D 60 and C u ) of the materials under consideration. The introduced grading characteristics ratios (D 10R , D 50R and C UR ) and the equivalent state parameter a...

  • experimental investigation into the influence of roundness and sphericity on the undrained shear response of silty sand soils
    Geotechnical Testing Journal, 2018
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Tom Schanz
    Abstract:

    Particle shape represents one of the key parameters that significantly influences the mechanical response, shear strength, deformation, and settlement characteristics of cohesionless soil deposits when subjected to static or dynamic loading conditions. Shear behavior of coarse-grained soils (gravel, gravelly sand, sandy gravel, sand, silty sand, or sandy silt) depends heavily on the two essential particle shape characteristics, which are termed roundness and sphericity. However, there are limited published studies available in the literature that deal solely with the effects of particle shape on shear-strain characteristics and shear behavior of granular soil deposits. Therefore, the veritable role of the particle shape parameter on soil behavior remains incomplete and requires further investigation. The present research work attempts to investigate the effects of particle shape on shear response of different categories of sand-silt mixtures under static triaxial loading conditions. For this purpose, a series of undrained compression triaxial tests was carried out on mixtures of Chlef (Algerian) rounded sand, Fontainebleau (France) subrounded sand, and Hostun (France) subangular sand mixed with low-plastic (Ip=5 %) rounded silty fines. All the sand-silt mixture samples were reconstituted at an Initial Relative Density (Dr=52 %) and subjected to a constant confining pressure (P’c=100 kPa). An evaluation of particle shape characteristics of the tested materials (sand and silt) was performed using a digital microscope device. Two new indexes, termed combined roundness and combined sphericity based on the combination of sand and silt to account for the coupled effects of particle shape and fines content, were proposed. The test results are used to correlate the undrained shear strength of the silty sand soils to the particle shape characteristics. Therefore, particle shape appears to be an important soil index property that needs to be adequately identified, particularly for silty sand–silt mixture soils. The systematic identification of particle shape characteristics leads to a better understanding of silty sand behavior.

  • insight into the effect of granulometric characteristics on the static liquefaction susceptibility of silty sand soils
    Geotechnical and Geological Engineering, 2016
    Co-Authors: Abdellah Cherif Taiba, Mostefa Belkhatir, Youcef Mahmoudi, Abdelkader Kadri, Tom Schanz
    Abstract:

    Silty sands are the most common type of soil that is involved in monotonic or dynamic loading induced liquefaction. It is associated with a sudden drop of the shear strength of the soil leading to important damages to civil engineering and hydraulics structures. Therefore, it is of great importance to identify the influencing parameters on the liquefaction of soils for the purpose to develop design strategies and therefore mitigate earthquake damages due to liquefaction phenomena. Published literature indicates that particle shape and gradation are the most important parameters that would affect the liquefaction behavior of granular sandy soils. For this purpose, a series of undrained compression triaxial tests were carried out on reconstituted Chlef sand (Algeria) and Fontainebleau sand (France) samples with low plastic fines ranging from 0 to 40 % and Initial Relative Density (Dr = 52 %) to study the liquefaction susceptibility of these soils. All the samples under study were subjected to an Initial confining pressure of (\(\upsigma_{c}^{'}\) = 100 kPa). The evaluation of the obtained data indicates that the gradation and particle shape have a significant influence on the undrained shear strength (liquefaction resistance) of different silty sand soils under study. Moreover, test results confirm the existence of simple correlations between liquefaction resistance and different grading characteristics (D10, D30, D50, D60, and Cu) of the soils under consideration. New soil granulometric ratios (D10R = D10sand/D10mixture , D50R = D50sand/D50mixture, and CUR = Cusand/Cumixture) were introduced to discuss the sand–silt mixture liquefaction resistance susceptibility response. The used grading characteristics ratios (D10R, D50R and CUR) appear as pertinent parameters to predict the undrained shear strength response of the sand–silt mixtures for soil gradation under study.

Ahmed Arab - One of the best experts on this subject based on the ideXlab platform.

  • saturation effect on behaviour of sandy soil under monotonic and cyclic loading a laboratory investigation
    Geotechnical and Geological Engineering, 2016
    Co-Authors: Ahmed Arab, Mostefa Belkhatir, Marwan Sadek
    Abstract:

    This paper presents a laboratory study of the influence of saturation degree on the liquefaction potential of sand. The study is based on drained, undrained monotonic and cyclic triaxial tests. Tests were conducted on a medium dense Hostun RF sand (France) with an Initial Relative Density Dr = 4, 50, 64 and 78 % and the coefficient of Skempton ranging between 0.95 (saturated) and 0.25. For all Skempton’s coefficient B values, the tests were carried out for different loading levels. The monotonic tests show that an increase in the Skempton’s coefficient B leads to a reduction of liquefaction resistance. The decrement of the coefficient of saturation B does not affect the instability and steady state lines. The test results indicate that the liquefaction resistance increases with the decrease of Skempton’s coefficient B. For the high level of loading (RCC = 0.5), the number required to cause liquefaction varied little with the Skempton’s coefficient B (Nc = 9, 10 and 11 for B = 0.67, 0.36 and 0.25 respectively). For the low level (RCC < 0.40), the number of cycles needed for liquefaction increases susceptibly with the reduction of the coefficient of Skempton (B). A simple mathematical relation has been suggested to correlate the liquefaction resistance with the coefficient of Skempton B.

  • Undrained behavior of silty sand: effect of the overconsolidation ratio
    Arabian Journal of Geosciences, 2013
    Co-Authors: Ahmed Djafar Henni, Mostefa Belkhatir, A. Saaed Hamoudi, Ahmed Arab, Hamid Khelafi
    Abstract:

    This experimental study deals with the effect of the overconsolidation ratio on the monotonic undrained shear behavior of silty sand. The study is based on the undrained monotonic triaxial tests for the overconsolidation ratios (OCR = 1, 2, 4, and 8), with different silt contents ranging from 0% to 40%. The laboratory tests were carried out at an Initial Relative Density of Dr = 50%. The paper is composed of two parts. The first one presents the tested soils; the second one gives an analysis of the test results and discusses the influence of the overconsolidation ratio on the shear strength of the soil. The test results indicate that the shear strength of the soil increases with the increase of the overconsolidation ratio resulting in an increase of soil dilatancy. The increase in the amount of fines from 0% to 40% increases the phase of the contractancy and consequently reducing the phase of dilatancy of the tested material