The aim of this study is to characterize soil/reinforcement interaction in reinforced earth structures. The study showed that the internal behavior of this type of structure depends on a number of factors, including t...The aim of this study is to characterize soil/reinforcement interaction in reinforced earth structures. The study showed that the internal behavior of this type of structure depends on a number of factors, including the engineering backfill, the reinforcement and the soil/reinforcement interaction. The study also showed that the soil-reinforcement interaction phenomenon is a fairly complex mechanism that depends on the applied load, the geometry of the structure, the characteristics of the soil and a set of parameters characterizing the nailing: density, number and length of reinforcements, inclination of the reinforcements in relation to the sliding surface, mechanical characteristics of the reinforcements and, in particular, the relative stiffness of the reinforcements and the soil. The results showed that the tensile forces developed in the reinforcement are not entirely reversible, and that the soil at the interface undergoes permanent deformation, leading to the appearance of irreversible tensile forces in the reinforcement.展开更多
Given the complexities of reinforced soil materials’constitutive relationships,this paper compares reinforced soil composite materials to a sliding structure between steel bars and soil and proposes a reinforced soil...Given the complexities of reinforced soil materials’constitutive relationships,this paper compares reinforced soil composite materials to a sliding structure between steel bars and soil and proposes a reinforced soil constitutive model that takes this sliding into account.A finite element dynamic time history calculation software for composite response analysis was created using the Fortran programming language,and time history analysis was performed on reinforced soil retaining walls and gravity retaining walls.The vibration time histories of reinforced soil retaining walls and gravity retaining walls were computed,and the dynamic reactions of the two types of retaining walls to vibration were compared and studied.The dynamic performance of reinforced earth retaining walls was evaluated.展开更多
Because of its excellent seismic performance, reinforced soil retaining walls are increasingly used in civil engineering. Although many countries have published corresponding design codes, the differences between them...Because of its excellent seismic performance, reinforced soil retaining walls are increasingly used in civil engineering. Although many countries have published corresponding design codes, the differences between them are still relatively large. Using the FHWA Code and the Code for Seismic Design of Railway Engineering(CSDRE), stability calculations of reinforced soil retaining walls were carried out and the similarities and differences between these two design codes were analyzed. According to the comparative analysis, the following conclusions are drawn: the inertia force, the earth pressure and the tensile force of reinforcements calculated from the CSDRE are less than those from the FHWA Code, and the safety factor calculated from the former is larger. Although the M-O method is recommended to calculate the dynamic earth pressure, the FHWA Code suggests a higher action point as compared to the CSDRE.展开更多
Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites in nitrogen atmosphere protection. Microstructures and mechanical properties of ...Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites in nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It was indicated that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550 ℃ and 28 MPa for 30 min were improved evidently. Besides mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistants, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All of the above were beneficial for improving the mechanical properties of alumina matrix ceramic composites.展开更多
The interaction between geogrid and soil is crucial for the stability of geogrid-reinforced earth structure. In finite element （FE） analysis, geogrids are usually assumed as beam or truss elements, and the interacti...The interaction between geogrid and soil is crucial for the stability of geogrid-reinforced earth structure. In finite element （FE） analysis, geogrids are usually assumed as beam or truss elements, and the interaction between geogrid and soil is considered as Coulomb friction resistance, which cannot reflect the true stress and displacement developed in the reinlbrcement. And the traditional Lagrangian elements used to simulate soil always become highly distorted and lose accuracy in high-stress blocks. An improved geogrid model that can produce shear resistance and passive resistance and a soil model using the Eulerian technique, in combination with the coupled Eulerian-Lagrangian （CEL） method, are used to analyze the interaction between geogrid and soil of reinforced foundation test in ABAQUS. The stress in the backfill, resistance of geogrid, and settlement of foundation were computed and the results of analysis agree well with the experimental results. This simulation method is of referential value for FE analysis of reinforced earth structure.展开更多
Back-to-back mechanically stabilized earth walls （BBMSEWs） are encountered in bridge approaches, ramp ways, rockfall protection systems, earth dams, levees and noise barriers. However, available design guidelines fo...Back-to-back mechanically stabilized earth walls （BBMSEWs） are encountered in bridge approaches, ramp ways, rockfall protection systems, earth dams, levees and noise barriers. However, available design guidelines for BBMSEWs are limited and not applicable to numerical modeling when back-to-back walls interact with each other. The objective of this paper is to investigate, using PLAXIS code, the effects of the reduction in the distance between BBMSEW, the reinforcement length, the quality of backfill material and the connection of reinforcements in the middle, when the back-to-back walls are close. The results indicate that each of the BBMSEWs behaves independently if the width of the embankment between mechanically stabilized earth walls is greater than that of the active zone. This is in good agreement with the result of FHWA design guideline. However, the results show that the FHWA design guideline underestimates the lateral earth pressure when back-to-back walls interact with each other. Moreover, for closer BBMSEWs, FHWA design guideline strongly overestimates the maximum tensile force in the reinforcement. The investigation of the quality of backfill material shows that the minor increase in embankment cohesion can lead to significant reductions in both the lateral earth pressure and the maximum tensile force in geosynthetic. When the distance between the two earth walls is close to zero, the connection of reinforcement between back-to-back walls significantly improves the factor of safety.展开更多
Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites with nitrogen atmosphere protection. Microstructures and mechanical properties o...Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites with nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It is indicates that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550℃ and 28 MPa for 30 min are improved evidently. Based on mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistant, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All the above are beneficial to the improvement of mechanical properties of alumina matrix ceramic composites.展开更多
In this paper, field measurements and pullout tests of a new type of reinforced earth retaining wall, which is reinforced by trapezoid concrete blocks connected by steel bar, are described. Field measurements included...In this paper, field measurements and pullout tests of a new type of reinforced earth retaining wall, which is reinforced by trapezoid concrete blocks connected by steel bar, are described. Field measurements included settlements of the earth fill, tensile forces in the ties and earth pressures on the facing panels during the construction and at completion. Based on the measurements, the following statements can be made: (1) the tensile forces in the ties increased with the height of backfill above the tie and there is a tensile force crest in most ties; (2) at completion, the measured earth pressures along the wall face were between the values of the active earth pressures and the pressures at rest; (3) larger settlements occurred near the face of the wall where a zone of drainage sand and gravel was not compacted properly and smaller settlements occurred in the well-compacted backfill. The results of field pullout tests indicated that the magnitudes of pullout resistances as well as tensile forces induced in the ties were strongly influenced by the relative displacements between the ties and the backfill, and pullout resistances increased with the height of backfill above the ties and the length of ties.展开更多
Approximately, 75% of constructed dams in the world are earth dams. The use of an earth dam is restricted by its geometrical area, weir restriction, and the availability of sufficient amount of earth material. These r...Approximately, 75% of constructed dams in the world are earth dams. The use of an earth dam is restricted by its geometrical area, weir restriction, and the availability of sufficient amount of earth material. These restrictions can be alleviated by the use of reinforced soil. In this research study the use of geotextile to stabilize and increase the shear strength of clay soils has been investigated. The results show an increase of about 25% in shear strength and cause an enhancement of stability in sandy soil in earth dams.展开更多
Rising temperatures are causing melting of glaciers around the world.ShivaLingam,the most sacred pilgrimages of the Hindus,which formed naturally for thousands of years has melted due to unusual hot climatic condition...Rising temperatures are causing melting of glaciers around the world.ShivaLingam,the most sacred pilgrimages of the Hindus,which formed naturally for thousands of years has melted due to unusual hot climatic conditions.In Indian tradition,the Earth is worshipped as the compassionate Mother Goddess. We need to take urgent affirmative collective measures as we have only"One Earth to Live On".展开更多
文摘The aim of this study is to characterize soil/reinforcement interaction in reinforced earth structures. The study showed that the internal behavior of this type of structure depends on a number of factors, including the engineering backfill, the reinforcement and the soil/reinforcement interaction. The study also showed that the soil-reinforcement interaction phenomenon is a fairly complex mechanism that depends on the applied load, the geometry of the structure, the characteristics of the soil and a set of parameters characterizing the nailing: density, number and length of reinforcements, inclination of the reinforcements in relation to the sliding surface, mechanical characteristics of the reinforcements and, in particular, the relative stiffness of the reinforcements and the soil. The results showed that the tensile forces developed in the reinforcement are not entirely reversible, and that the soil at the interface undergoes permanent deformation, leading to the appearance of irreversible tensile forces in the reinforcement.
基金supported in part by the Chongqing Social Science Planning Project(2021BS064)Chongqing Construction Science and Technology Plan Project(Grant 2023-0187)+1 种基金Special Foundation of Chongqing Postdoctoral Research(2021XM2052)Scientific and Technological Research Program of Chongqing Municipal Education Commission(Grant KJQN202304703).
文摘Given the complexities of reinforced soil materials’constitutive relationships,this paper compares reinforced soil composite materials to a sliding structure between steel bars and soil and proposes a reinforced soil constitutive model that takes this sliding into account.A finite element dynamic time history calculation software for composite response analysis was created using the Fortran programming language,and time history analysis was performed on reinforced soil retaining walls and gravity retaining walls.The vibration time histories of reinforced soil retaining walls and gravity retaining walls were computed,and the dynamic reactions of the two types of retaining walls to vibration were compared and studied.The dynamic performance of reinforced earth retaining walls was evaluated.
基金sponsored by the Project of Science and Technology Research and Development Plan of China Railway Corporation(Grant No.2014G003-C)
文摘Because of its excellent seismic performance, reinforced soil retaining walls are increasingly used in civil engineering. Although many countries have published corresponding design codes, the differences between them are still relatively large. Using the FHWA Code and the Code for Seismic Design of Railway Engineering(CSDRE), stability calculations of reinforced soil retaining walls were carried out and the similarities and differences between these two design codes were analyzed. According to the comparative analysis, the following conclusions are drawn: the inertia force, the earth pressure and the tensile force of reinforcements calculated from the CSDRE are less than those from the FHWA Code, and the safety factor calculated from the former is larger. Although the M-O method is recommended to calculate the dynamic earth pressure, the FHWA Code suggests a higher action point as compared to the CSDRE.
基金the Outstanding Young Scientist Rewards of Shandong Province (05BS04008)the Natural Science Fund of Shandong Province (Y2007F29)
文摘Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites in nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It was indicated that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550 ℃ and 28 MPa for 30 min were improved evidently. Besides mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistants, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All of the above were beneficial for improving the mechanical properties of alumina matrix ceramic composites.
基金Supported by National Natural Science Foundation of China (No. 50678032)
文摘The interaction between geogrid and soil is crucial for the stability of geogrid-reinforced earth structure. In finite element （FE） analysis, geogrids are usually assumed as beam or truss elements, and the interaction between geogrid and soil is considered as Coulomb friction resistance, which cannot reflect the true stress and displacement developed in the reinlbrcement. And the traditional Lagrangian elements used to simulate soil always become highly distorted and lose accuracy in high-stress blocks. An improved geogrid model that can produce shear resistance and passive resistance and a soil model using the Eulerian technique, in combination with the coupled Eulerian-Lagrangian （CEL） method, are used to analyze the interaction between geogrid and soil of reinforced foundation test in ABAQUS. The stress in the backfill, resistance of geogrid, and settlement of foundation were computed and the results of analysis agree well with the experimental results. This simulation method is of referential value for FE analysis of reinforced earth structure.
文摘Back-to-back mechanically stabilized earth walls （BBMSEWs） are encountered in bridge approaches, ramp ways, rockfall protection systems, earth dams, levees and noise barriers. However, available design guidelines for BBMSEWs are limited and not applicable to numerical modeling when back-to-back walls interact with each other. The objective of this paper is to investigate, using PLAXIS code, the effects of the reduction in the distance between BBMSEW, the reinforcement length, the quality of backfill material and the connection of reinforcements in the middle, when the back-to-back walls are close. The results indicate that each of the BBMSEWs behaves independently if the width of the embankment between mechanically stabilized earth walls is greater than that of the active zone. This is in good agreement with the result of FHWA design guideline. However, the results show that the FHWA design guideline underestimates the lateral earth pressure when back-to-back walls interact with each other. Moreover, for closer BBMSEWs, FHWA design guideline strongly overestimates the maximum tensile force in the reinforcement. The investigation of the quality of backfill material shows that the minor increase in embankment cohesion can lead to significant reductions in both the lateral earth pressure and the maximum tensile force in geosynthetic. When the distance between the two earth walls is close to zero, the connection of reinforcement between back-to-back walls significantly improves the factor of safety.
文摘Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites with nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It is indicates that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550℃ and 28 MPa for 30 min are improved evidently. Based on mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistant, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All the above are beneficial to the improvement of mechanical properties of alumina matrix ceramic composites.
文摘In this paper, field measurements and pullout tests of a new type of reinforced earth retaining wall, which is reinforced by trapezoid concrete blocks connected by steel bar, are described. Field measurements included settlements of the earth fill, tensile forces in the ties and earth pressures on the facing panels during the construction and at completion. Based on the measurements, the following statements can be made: (1) the tensile forces in the ties increased with the height of backfill above the tie and there is a tensile force crest in most ties; (2) at completion, the measured earth pressures along the wall face were between the values of the active earth pressures and the pressures at rest; (3) larger settlements occurred near the face of the wall where a zone of drainage sand and gravel was not compacted properly and smaller settlements occurred in the well-compacted backfill. The results of field pullout tests indicated that the magnitudes of pullout resistances as well as tensile forces induced in the ties were strongly influenced by the relative displacements between the ties and the backfill, and pullout resistances increased with the height of backfill above the ties and the length of ties.
文摘Approximately, 75% of constructed dams in the world are earth dams. The use of an earth dam is restricted by its geometrical area, weir restriction, and the availability of sufficient amount of earth material. These restrictions can be alleviated by the use of reinforced soil. In this research study the use of geotextile to stabilize and increase the shear strength of clay soils has been investigated. The results show an increase of about 25% in shear strength and cause an enhancement of stability in sandy soil in earth dams.
文摘Rising temperatures are causing melting of glaciers around the world.ShivaLingam,the most sacred pilgrimages of the Hindus,which formed naturally for thousands of years has melted due to unusual hot climatic conditions.In Indian tradition,the Earth is worshipped as the compassionate Mother Goddess. We need to take urgent affirmative collective measures as we have only"One Earth to Live On".
