Schools are one of the land uses that are sensitive to traffic noise. While schools must be silen... more Schools are one of the land uses that are sensitive to traffic noise. While schools must be silent zones, many are located in urban areas and are exposed to high noise levels. In this study, an assessment of traffic noise around multiple schools in the city of Doha, Qatar was conducted during school hours. The results indicated that the noise is positively correlated with the traffic volume around the schools, indicating that locations with higher traffic volumes tend to have higher noise. The results also showed that the noise levels exceed the reference value of 53 dBA according to the World Health Organization. Furthermore, the measured noise levels exceeded the Qatar local standards for residential area and public corporation daytime noise level (55 dBA). To address this problem, several solutions were recommended.
Advances in Intelligent Systems and Computing, 2020
Although hospitals are sensitive to noise and are considered silent zones, many are located in ur... more Although hospitals are sensitive to noise and are considered silent zones, many are located in urban areas and are subject to high levels of noise. In this study, an assessment of traffic noise, around a major hospital in the city of Doha, Qatar, was conducted during the morning and evening periods. The results indicated that the noise values exceeded the World Health Organization’s reference value of 50 dBA for both morning and evening times, and were higher than the 55 dBA limit at which serious annoyance is generated. Additionally, it exceeded the Qatar local standards for both daytime (55 dBA) and nighttime (45 dBA) noise levels. The results indicated that one of the main sources of noise was road traffic. Different solutions were proposed for a possible action plan to reduce the high level of noise.
The patent-pending integrated waste-to-energy system comprises both a novel biohydrogen reactor w... more The patent-pending integrated waste-to-energy system comprises both a novel biohydrogen reactor with a gravity settler (Biohydrogenator), followed by a second stage conventional anaerobic digester for the production of methane gas. This chemical-free process has been tested with a synthetic wastewater/leachate solution, and was operated at 37o C for 45 days. The biohydrogenator (system (A), stage 1) steadily produced hydrogen with no methane during the experimental period. The maximum hydrogen yield was 400 ml H2 / g glucose with an average of 345 ml H2 / g glucose, as compared to 141 and 118 ml H2 / g glucose for two consecutive runs done in parallel using a conventional continuously stirred tank reactor (CSTR, System (B)). Decoupling of the SRT from the HRT using the gravity settler showed a marked improvement in performance, with the maximum and average hydrogen production rates in system (A) of 22 and 19 L H2/d, as compared with 2-7 L H2/d in the CSTR resulting in a maximum yiel...
Pile capacity installed in Dubai rock formation is calculated based primarily on socket shaft res... more Pile capacity installed in Dubai rock formation is calculated based primarily on socket shaft resistance. During preliminary design, socket resistance is estimated by using correlations with rock strength that do not reflect the behavior of Dubai rock formations as well as construction practices. Consequently, large discrepancy is often noticed between predicted pile capacity and that determined from the results of pile load tests. In this study, a new predictive model is developed for socket shaft resistance of piles constructed in rock formations of Dubai area. Five (5) instrumented piles of different diameters and socket lengths ranging from 10 to 15 m are tested. The proposed model takes into account the compressive strength of the rock in addition to the pile movement at the top of socket to predict its side resistance. The average side resistance of the socket predicted using the proposed model compared well with the results of load transfer along the sockets of the test piles...
Helical screw anchors have been utilized in uplift forces applications for many years and they ha... more Helical screw anchors have been utilized in uplift forces applications for many years and they have gained popularity for bearing load, seismic performance and dynamic applications and evolved into Helical Screw Piles (HSPs). The speed and ease of their installation, as well as the low cost for new construction and repair, make them versatile for many rehabilitation or new construction applications and as an efficient alternative for deep foundations in infrastructure projects when it is suitable. The main objectives of this paper are to explore the available helical piles systems as well the performance of the helical pile foundation systems under monotonic and cyclic axial and lateral loads. In addition, to explore the new helical screw pile systems suitable for seismic retrofitting of existing foundations and for new structures construction; and to explore their design methodology. Among the helical piles configurations available the circular steel shaft helical piles and the squ...
Helical piles are increasingly used to support structures subjected to axial compressive loads. T... more Helical piles are increasingly used to support structures subjected to axial compressive loads. This paper presents the results of full-scale field testing of reinforced helical pulldown micropiles (RG-HSP) installed in clayey soils and resting on sandy soils. The piles were tested under monotonic and one way cyclic axial loadings. It was found that the addition of the reinforced grouted column resulted in a significant increase in the failure load of the pile. Also, during 15 cycles of loading, the piles showed no signs of performance deterioration and experienced minimal increase in displacement. The piles' axial stiffness and capacity were not affected after being subjected to 15 cycles of loading. The experimental results show that the reinforced helical pulldown micropile is a viable deep foundation option for axial monotonic and cyclic loading applications.
Abstract This paper investigates the static and cyclic characteristics of a fouled sub-ballast ma... more Abstract This paper investigates the static and cyclic characteristics of a fouled sub-ballast material using static and cyclic triaxial tests. Static triaxial tests were conducted first to determine the peak strength, which was used as the applied stress in the cyclic tests. Moreover, the results of the displacement-controlled static triaxial test were used to assess the shear stiffness and strength during the cyclic stress-controlled loading cycles. Isotropically consolidated drained (CD) compression cyclic triaxial tests were conducted to simulate the long-term response of fouled railway substructure under progressive repetitive loading and unloading cycles. The accumulated plastic strains of the fouled railroad sub-ballast were determined under cyclic loading and unloading conditions. The obtained results indicated that the soil plasticity and effective confining pressure, and relative density are not the only important factors in shaping the damping curves but also the loading rate, and particle size. Both parameters play a major role in determining the behaviour of fine contaminated sub-ballast. The railway operational speed limits were deduced from the stress-strain behaviour of the fouled sub-ballast interlayer zone. It is recommended that the maximum speed of trains in fouled railroad segments be limited to a maximum of 32 km/h. The developed guidelines are aimed to prolong the service lifespan of the fouled track segments, while maintaining safety standards to avoid train derailments, track deterioration, and high maintenance costs.
The research on the deformation mechanism of monopile foundation supporting offshore wind turbine... more The research on the deformation mechanism of monopile foundation supporting offshore wind turbines is significant to optimize the design of a monopile foundation under wave and current load. In this paper, a three-dimensional wave-pile-soil coupling finite element model is proposed to investigate the deformation mechanism of monopile undercurrent and fifth-order Stokes wave. Different from the conventional assumption that there is no slip at the pile-soil interface, Frictional contact is set to simulate the relative movement between monopile and soil. Numerical results indicate that under extreme environmental conditions, the monopile foundation sways within a certain range and the maximum displacement in the loading direction is 1.3 times the displacement in the reverse direction. A further investigation has been made for a large-diameter pipe pile with various design parameters. The finite element analyses reveal that the most efficient way to reduce the deflection of the pile hea...
Abstract The multistage triaxial compression test was mainly utilized in this research to investi... more Abstract The multistage triaxial compression test was mainly utilized in this research to investigate the degradation in the strength of swelling shale under different wetting conditions. Shale samples were tested in four different conditions: (1) under their natural moisture content denoted as intact, and after soaking in, (2) water, (3) polymer solution, and (4) bentonite solution, separately. The experimental results showed that a considerable decrease in the shale’s strength was noted after soaking in water and the lubricant fluids (LFs). The polymer solution caused the least decrease in the strength compared to other fluids. Strength envelopes of the tested shale were constructed for intact and soaked states. These envelopes showed fair agreement between the single stage and the multistage triaxial compression test results, indicating suitability of the multistage triaxial compression test for the tested swelling shale.
Journal of Geotechnical and Geoenvironmental Engineering
AbstractBox culverts can be subjected to considerable induced earth pressure from overlaying stru... more AbstractBox culverts can be subjected to considerable induced earth pressure from overlaying structures and foundations. Therefore, the effect of surface foundations on soil pressures around box culverts needs to be properly investigated and incorporated into the analysis and design of culverts. In this study, the effect of a surface foundation on the response of box culverts was investigated experimentally and numerically. A series of centrifuge tests were performed to evaluate the additional soil pressures around box culverts installed in sand due to adjacent surface foundations. The experimental results were used to calibrate and verify a two-dimensional (2D) numerical model developed using computer software. This model was then used for a parametric study to investigate the effect of the relative foundation location on various aspects of the culvert response. The soil pressures, culvert bending moments, and soil-culvert interaction factors were all considered for different soil depths and surface foun...
Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, 2017
A novel piling system is proposed involving a spun-cast ductile iron SCDI tapered shaft fitted wi... more A novel piling system is proposed involving a spun-cast ductile iron SCDI tapered shaft fitted with a lower helical plate. The pile combines the compressive and lateral efficiency of the tapered section, the competitive cost, effectiveness and durability of spun cast ductile iron with a rough surface and the construction advantages of screw piles. The monotonic uplift and lateral performance of the proposed pile in a silty sand profile is investigated using a three dimensional finite element model developed using the software Abaqus (Hibbitt et al., 2008). The model was established and calibrated using full scale experimental data. The performance of steel straight shaft helical piles was also simulated for comparison purpose. The developed models simulated the response of steel and SCDI piles with different configurations when subjected to different loading conditions including uplift, lateral and combined moment-horizontal. Different loading sequences were mimicked to assess the effect of prior cyclic and monotonic loading on the piles' performance. The effects of installation technique on the piles behavior are quantified. The results showed that the tapered helical piles exhibited a stiffer response than the straight piles at lower displacements. At greater displacements, the presence of the helical plate avoided the dislodge of the tapered shaft from the ground. The value of the lateral earth pressure coefficient was found to significantly decrease during the uplift loading of tapered helical piles whereas no significant change was found for the straight shaft ones. The uplift performance of the SCDI tapered helical configuration was found to more efficient for greater pile length providing higher uplifttocompression ratio compared to straight helical piles. The results also showed that SCDI tapered helical piles exhibited a stiffer lateral response and offered higher ultimate capacity compared to the straight-shaft piles owing to the greater flexural rigidity along the top portion of the pile. As well, the addition of a helical plate to a short pile was found to significantly increase its lateral capacity due to the provided fixation to the bottom of the piles resulting from the passive bearing pressures developed on the helix surfaces. On the other hand, the helical plate had no influence the lateral performance of long piles. Moment-horizontal force interaction diagrams were developed and design equations were provided to aid in design of the proposed piling system as well as straight helical piles subjected to a combination of significant moment and horizontal loads. The results of the present study revealed the improved performance of the proposed piling system in various loading conditions compared to the conventional piling alternatives. The study also demonstrated that the spun cast iron with rough surface is a viable material for piling products.
Seismic shaking can cause slope instability in otherwise relatively stable permafrost terrains. I... more Seismic shaking can cause slope instability in otherwise relatively stable permafrost terrains. In addition, rapid ice melting in low-permeability fine-grained soils can lead to excess pore-water pressure build-up and cause instability in slopes even at small angles. This study addresses the active-layer detachment (ALD) slope instability hazard and develops a systematic risk assessment framework for existing and future linear infrastructures, such as energy pipelines, bridges, and roads traversing permafrost regions. Mild slopes, with average gradient of 7°, are considered in this study as the most representative of actual field conditions. The potential for earthquake-triggered ALD is analytically quantified. State-of-the-art ALD morphological statistics for northern Canada are combined with seismic slope stability analyses to determine (i) the probability of linear infrastructure exposure to permanent ground deformations (PGDs) caused by ALD and (ii) the extent of the potential P...
International Journal of Solids and Structures, 2004
Structures with inappropriate distributions of strength and stiffness have performed poorly in re... more Structures with inappropriate distributions of strength and stiffness have performed poorly in recent earthquakes, and most of the observed collapses have been related to some extent to configuration problems or a wrong conceptual design. Shear building models of multi-story structures are considered in this study and are subjected to a group of severe earthquakes. It is shown that the strength
Despite the large volume of experimental studies on the dynamic behavior of sands and silty sands... more Despite the large volume of experimental studies on the dynamic behavior of sands and silty sands, the dynamic undrained characteristics of cohesionless silts and sandy silts are less understood. A comprehensive laboratory testing program is conducted to characterize the dynamic properties of silt and sandy silt soils with 75% and 50% silt contents. The elastic soil behavior at very small shear strains ( < 10%) is investigated through shear wave velocity (Vs) measurements using bender elements at vertical stresses ranging from 50 to 300 kPa. In addition, strain-controlled constant-volume cyclic ring shear tests are carried out to establish shear modulus (G) and damping ratio (D) at larger shear strain amplitudes ( > 0.01%) and investigate the influence of silt content and γ on these parameters. The results demonstrate that Vs and the maximum shear modulus (Go) increase with increasing silt content. Vs is also found to vary with the effective overburden stress to the power of...
Abstract The liquefaction behavior and cyclic resistance ratio (CRR) of reconstituted samples of ... more Abstract The liquefaction behavior and cyclic resistance ratio (CRR) of reconstituted samples of non-plastic silt and sandy silts with 50% and 75% silt content are examined using constant-volume cyclic and monotonic ring shear tests along with bender element shear wave velocity ( V s ) measurements. Liquefaction occurred at excess pore water pressure ratios ( r u ) between 0.6 and 0.7 associated with cumulative cyclic shear strains ( γ ) of 4% to 7%, after which cyclic liquefaction ensued with very large shear strains and excess pore water pressure ratio ( r u >0.8). The cyclic ring shear tests demonstrate that cyclic resistance ratio of silt and sandy silts decreases with increasing void ratio, or with decreasing silt content at a certain void ratio. The results also show good agreement with those from cyclic direct simple shear tests on silts and sandy silts. A unique correlation is developed for estimating CRR of silts and sandy silts (with more than 50% silt content) from stress-normalized shear wave velocity measurements ( V s1 ) with negligible effect of silt content. The results indicate that the existing CRR– V s1 correlations would underestimate the liquefaction resistance of silts and sandy silt soils.
In recent years large number of mega projects were constructed using the piled raft foundation sy... more In recent years large number of mega projects were constructed using the piled raft foundation system concept. hence a noticeable attention have been drawn toward better understanding of the performance of piled raft foundation systems subjected to vertical loading. Piled raft foundations have a complex soil-structure interaction scheme including the pile-soil interaction, pile-pile interaction, raft-soil interaction, and finally the pile-raft interaction. Consequently, there is a need for 3D numerical models that is capable of studying this complex interaction. In this paper, a 3D finite element model was verified using published geotechnical centrifuge test data. The study was performed on cohesionless soil with linearly increasing stiffness with depth. The developed 3D model was able to capture the behavior of the piled raft foundation system. In addition, an extended parametric study in which the effect of different parameters, such as pile spacing, piled diameter, raft width, a...
[Journal of Composites for Construction 9, 274 (2005)]. M. Sakr, MH El Naggar, M.ASCE, M. Nehdi. ... more [Journal of Composites for Construction 9, 274 (2005)]. M. Sakr, MH El Naggar, M.ASCE, M. Nehdi. Abstract. ... Geoenviron. Eng., 125(8), 633640. FukushimaS., and TatsoukaF. (1982). Deformation and strength of sand in torsional simple shear. Proc., IUTAM Conf. ...
Schools are one of the land uses that are sensitive to traffic noise. While schools must be silen... more Schools are one of the land uses that are sensitive to traffic noise. While schools must be silent zones, many are located in urban areas and are exposed to high noise levels. In this study, an assessment of traffic noise around multiple schools in the city of Doha, Qatar was conducted during school hours. The results indicated that the noise is positively correlated with the traffic volume around the schools, indicating that locations with higher traffic volumes tend to have higher noise. The results also showed that the noise levels exceed the reference value of 53 dBA according to the World Health Organization. Furthermore, the measured noise levels exceeded the Qatar local standards for residential area and public corporation daytime noise level (55 dBA). To address this problem, several solutions were recommended.
Advances in Intelligent Systems and Computing, 2020
Although hospitals are sensitive to noise and are considered silent zones, many are located in ur... more Although hospitals are sensitive to noise and are considered silent zones, many are located in urban areas and are subject to high levels of noise. In this study, an assessment of traffic noise, around a major hospital in the city of Doha, Qatar, was conducted during the morning and evening periods. The results indicated that the noise values exceeded the World Health Organization’s reference value of 50 dBA for both morning and evening times, and were higher than the 55 dBA limit at which serious annoyance is generated. Additionally, it exceeded the Qatar local standards for both daytime (55 dBA) and nighttime (45 dBA) noise levels. The results indicated that one of the main sources of noise was road traffic. Different solutions were proposed for a possible action plan to reduce the high level of noise.
The patent-pending integrated waste-to-energy system comprises both a novel biohydrogen reactor w... more The patent-pending integrated waste-to-energy system comprises both a novel biohydrogen reactor with a gravity settler (Biohydrogenator), followed by a second stage conventional anaerobic digester for the production of methane gas. This chemical-free process has been tested with a synthetic wastewater/leachate solution, and was operated at 37o C for 45 days. The biohydrogenator (system (A), stage 1) steadily produced hydrogen with no methane during the experimental period. The maximum hydrogen yield was 400 ml H2 / g glucose with an average of 345 ml H2 / g glucose, as compared to 141 and 118 ml H2 / g glucose for two consecutive runs done in parallel using a conventional continuously stirred tank reactor (CSTR, System (B)). Decoupling of the SRT from the HRT using the gravity settler showed a marked improvement in performance, with the maximum and average hydrogen production rates in system (A) of 22 and 19 L H2/d, as compared with 2-7 L H2/d in the CSTR resulting in a maximum yiel...
Pile capacity installed in Dubai rock formation is calculated based primarily on socket shaft res... more Pile capacity installed in Dubai rock formation is calculated based primarily on socket shaft resistance. During preliminary design, socket resistance is estimated by using correlations with rock strength that do not reflect the behavior of Dubai rock formations as well as construction practices. Consequently, large discrepancy is often noticed between predicted pile capacity and that determined from the results of pile load tests. In this study, a new predictive model is developed for socket shaft resistance of piles constructed in rock formations of Dubai area. Five (5) instrumented piles of different diameters and socket lengths ranging from 10 to 15 m are tested. The proposed model takes into account the compressive strength of the rock in addition to the pile movement at the top of socket to predict its side resistance. The average side resistance of the socket predicted using the proposed model compared well with the results of load transfer along the sockets of the test piles...
Helical screw anchors have been utilized in uplift forces applications for many years and they ha... more Helical screw anchors have been utilized in uplift forces applications for many years and they have gained popularity for bearing load, seismic performance and dynamic applications and evolved into Helical Screw Piles (HSPs). The speed and ease of their installation, as well as the low cost for new construction and repair, make them versatile for many rehabilitation or new construction applications and as an efficient alternative for deep foundations in infrastructure projects when it is suitable. The main objectives of this paper are to explore the available helical piles systems as well the performance of the helical pile foundation systems under monotonic and cyclic axial and lateral loads. In addition, to explore the new helical screw pile systems suitable for seismic retrofitting of existing foundations and for new structures construction; and to explore their design methodology. Among the helical piles configurations available the circular steel shaft helical piles and the squ...
Helical piles are increasingly used to support structures subjected to axial compressive loads. T... more Helical piles are increasingly used to support structures subjected to axial compressive loads. This paper presents the results of full-scale field testing of reinforced helical pulldown micropiles (RG-HSP) installed in clayey soils and resting on sandy soils. The piles were tested under monotonic and one way cyclic axial loadings. It was found that the addition of the reinforced grouted column resulted in a significant increase in the failure load of the pile. Also, during 15 cycles of loading, the piles showed no signs of performance deterioration and experienced minimal increase in displacement. The piles' axial stiffness and capacity were not affected after being subjected to 15 cycles of loading. The experimental results show that the reinforced helical pulldown micropile is a viable deep foundation option for axial monotonic and cyclic loading applications.
Abstract This paper investigates the static and cyclic characteristics of a fouled sub-ballast ma... more Abstract This paper investigates the static and cyclic characteristics of a fouled sub-ballast material using static and cyclic triaxial tests. Static triaxial tests were conducted first to determine the peak strength, which was used as the applied stress in the cyclic tests. Moreover, the results of the displacement-controlled static triaxial test were used to assess the shear stiffness and strength during the cyclic stress-controlled loading cycles. Isotropically consolidated drained (CD) compression cyclic triaxial tests were conducted to simulate the long-term response of fouled railway substructure under progressive repetitive loading and unloading cycles. The accumulated plastic strains of the fouled railroad sub-ballast were determined under cyclic loading and unloading conditions. The obtained results indicated that the soil plasticity and effective confining pressure, and relative density are not the only important factors in shaping the damping curves but also the loading rate, and particle size. Both parameters play a major role in determining the behaviour of fine contaminated sub-ballast. The railway operational speed limits were deduced from the stress-strain behaviour of the fouled sub-ballast interlayer zone. It is recommended that the maximum speed of trains in fouled railroad segments be limited to a maximum of 32 km/h. The developed guidelines are aimed to prolong the service lifespan of the fouled track segments, while maintaining safety standards to avoid train derailments, track deterioration, and high maintenance costs.
The research on the deformation mechanism of monopile foundation supporting offshore wind turbine... more The research on the deformation mechanism of monopile foundation supporting offshore wind turbines is significant to optimize the design of a monopile foundation under wave and current load. In this paper, a three-dimensional wave-pile-soil coupling finite element model is proposed to investigate the deformation mechanism of monopile undercurrent and fifth-order Stokes wave. Different from the conventional assumption that there is no slip at the pile-soil interface, Frictional contact is set to simulate the relative movement between monopile and soil. Numerical results indicate that under extreme environmental conditions, the monopile foundation sways within a certain range and the maximum displacement in the loading direction is 1.3 times the displacement in the reverse direction. A further investigation has been made for a large-diameter pipe pile with various design parameters. The finite element analyses reveal that the most efficient way to reduce the deflection of the pile hea...
Abstract The multistage triaxial compression test was mainly utilized in this research to investi... more Abstract The multistage triaxial compression test was mainly utilized in this research to investigate the degradation in the strength of swelling shale under different wetting conditions. Shale samples were tested in four different conditions: (1) under their natural moisture content denoted as intact, and after soaking in, (2) water, (3) polymer solution, and (4) bentonite solution, separately. The experimental results showed that a considerable decrease in the shale’s strength was noted after soaking in water and the lubricant fluids (LFs). The polymer solution caused the least decrease in the strength compared to other fluids. Strength envelopes of the tested shale were constructed for intact and soaked states. These envelopes showed fair agreement between the single stage and the multistage triaxial compression test results, indicating suitability of the multistage triaxial compression test for the tested swelling shale.
Journal of Geotechnical and Geoenvironmental Engineering
AbstractBox culverts can be subjected to considerable induced earth pressure from overlaying stru... more AbstractBox culverts can be subjected to considerable induced earth pressure from overlaying structures and foundations. Therefore, the effect of surface foundations on soil pressures around box culverts needs to be properly investigated and incorporated into the analysis and design of culverts. In this study, the effect of a surface foundation on the response of box culverts was investigated experimentally and numerically. A series of centrifuge tests were performed to evaluate the additional soil pressures around box culverts installed in sand due to adjacent surface foundations. The experimental results were used to calibrate and verify a two-dimensional (2D) numerical model developed using computer software. This model was then used for a parametric study to investigate the effect of the relative foundation location on various aspects of the culvert response. The soil pressures, culvert bending moments, and soil-culvert interaction factors were all considered for different soil depths and surface foun...
Proceedings of the 2nd World Congress on Civil, Structural, and Environmental Engineering, 2017
A novel piling system is proposed involving a spun-cast ductile iron SCDI tapered shaft fitted wi... more A novel piling system is proposed involving a spun-cast ductile iron SCDI tapered shaft fitted with a lower helical plate. The pile combines the compressive and lateral efficiency of the tapered section, the competitive cost, effectiveness and durability of spun cast ductile iron with a rough surface and the construction advantages of screw piles. The monotonic uplift and lateral performance of the proposed pile in a silty sand profile is investigated using a three dimensional finite element model developed using the software Abaqus (Hibbitt et al., 2008). The model was established and calibrated using full scale experimental data. The performance of steel straight shaft helical piles was also simulated for comparison purpose. The developed models simulated the response of steel and SCDI piles with different configurations when subjected to different loading conditions including uplift, lateral and combined moment-horizontal. Different loading sequences were mimicked to assess the effect of prior cyclic and monotonic loading on the piles' performance. The effects of installation technique on the piles behavior are quantified. The results showed that the tapered helical piles exhibited a stiffer response than the straight piles at lower displacements. At greater displacements, the presence of the helical plate avoided the dislodge of the tapered shaft from the ground. The value of the lateral earth pressure coefficient was found to significantly decrease during the uplift loading of tapered helical piles whereas no significant change was found for the straight shaft ones. The uplift performance of the SCDI tapered helical configuration was found to more efficient for greater pile length providing higher uplifttocompression ratio compared to straight helical piles. The results also showed that SCDI tapered helical piles exhibited a stiffer lateral response and offered higher ultimate capacity compared to the straight-shaft piles owing to the greater flexural rigidity along the top portion of the pile. As well, the addition of a helical plate to a short pile was found to significantly increase its lateral capacity due to the provided fixation to the bottom of the piles resulting from the passive bearing pressures developed on the helix surfaces. On the other hand, the helical plate had no influence the lateral performance of long piles. Moment-horizontal force interaction diagrams were developed and design equations were provided to aid in design of the proposed piling system as well as straight helical piles subjected to a combination of significant moment and horizontal loads. The results of the present study revealed the improved performance of the proposed piling system in various loading conditions compared to the conventional piling alternatives. The study also demonstrated that the spun cast iron with rough surface is a viable material for piling products.
Seismic shaking can cause slope instability in otherwise relatively stable permafrost terrains. I... more Seismic shaking can cause slope instability in otherwise relatively stable permafrost terrains. In addition, rapid ice melting in low-permeability fine-grained soils can lead to excess pore-water pressure build-up and cause instability in slopes even at small angles. This study addresses the active-layer detachment (ALD) slope instability hazard and develops a systematic risk assessment framework for existing and future linear infrastructures, such as energy pipelines, bridges, and roads traversing permafrost regions. Mild slopes, with average gradient of 7°, are considered in this study as the most representative of actual field conditions. The potential for earthquake-triggered ALD is analytically quantified. State-of-the-art ALD morphological statistics for northern Canada are combined with seismic slope stability analyses to determine (i) the probability of linear infrastructure exposure to permanent ground deformations (PGDs) caused by ALD and (ii) the extent of the potential P...
International Journal of Solids and Structures, 2004
Structures with inappropriate distributions of strength and stiffness have performed poorly in re... more Structures with inappropriate distributions of strength and stiffness have performed poorly in recent earthquakes, and most of the observed collapses have been related to some extent to configuration problems or a wrong conceptual design. Shear building models of multi-story structures are considered in this study and are subjected to a group of severe earthquakes. It is shown that the strength
Despite the large volume of experimental studies on the dynamic behavior of sands and silty sands... more Despite the large volume of experimental studies on the dynamic behavior of sands and silty sands, the dynamic undrained characteristics of cohesionless silts and sandy silts are less understood. A comprehensive laboratory testing program is conducted to characterize the dynamic properties of silt and sandy silt soils with 75% and 50% silt contents. The elastic soil behavior at very small shear strains ( < 10%) is investigated through shear wave velocity (Vs) measurements using bender elements at vertical stresses ranging from 50 to 300 kPa. In addition, strain-controlled constant-volume cyclic ring shear tests are carried out to establish shear modulus (G) and damping ratio (D) at larger shear strain amplitudes ( > 0.01%) and investigate the influence of silt content and γ on these parameters. The results demonstrate that Vs and the maximum shear modulus (Go) increase with increasing silt content. Vs is also found to vary with the effective overburden stress to the power of...
Abstract The liquefaction behavior and cyclic resistance ratio (CRR) of reconstituted samples of ... more Abstract The liquefaction behavior and cyclic resistance ratio (CRR) of reconstituted samples of non-plastic silt and sandy silts with 50% and 75% silt content are examined using constant-volume cyclic and monotonic ring shear tests along with bender element shear wave velocity ( V s ) measurements. Liquefaction occurred at excess pore water pressure ratios ( r u ) between 0.6 and 0.7 associated with cumulative cyclic shear strains ( γ ) of 4% to 7%, after which cyclic liquefaction ensued with very large shear strains and excess pore water pressure ratio ( r u >0.8). The cyclic ring shear tests demonstrate that cyclic resistance ratio of silt and sandy silts decreases with increasing void ratio, or with decreasing silt content at a certain void ratio. The results also show good agreement with those from cyclic direct simple shear tests on silts and sandy silts. A unique correlation is developed for estimating CRR of silts and sandy silts (with more than 50% silt content) from stress-normalized shear wave velocity measurements ( V s1 ) with negligible effect of silt content. The results indicate that the existing CRR– V s1 correlations would underestimate the liquefaction resistance of silts and sandy silt soils.
In recent years large number of mega projects were constructed using the piled raft foundation sy... more In recent years large number of mega projects were constructed using the piled raft foundation system concept. hence a noticeable attention have been drawn toward better understanding of the performance of piled raft foundation systems subjected to vertical loading. Piled raft foundations have a complex soil-structure interaction scheme including the pile-soil interaction, pile-pile interaction, raft-soil interaction, and finally the pile-raft interaction. Consequently, there is a need for 3D numerical models that is capable of studying this complex interaction. In this paper, a 3D finite element model was verified using published geotechnical centrifuge test data. The study was performed on cohesionless soil with linearly increasing stiffness with depth. The developed 3D model was able to capture the behavior of the piled raft foundation system. In addition, an extended parametric study in which the effect of different parameters, such as pile spacing, piled diameter, raft width, a...
[Journal of Composites for Construction 9, 274 (2005)]. M. Sakr, MH El Naggar, M.ASCE, M. Nehdi. ... more [Journal of Composites for Construction 9, 274 (2005)]. M. Sakr, MH El Naggar, M.ASCE, M. Nehdi. Abstract. ... Geoenviron. Eng., 125(8), 633640. FukushimaS., and TatsoukaF. (1982). Deformation and strength of sand in torsional simple shear. Proc., IUTAM Conf. ...
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Papers by Hesham El Naggar