Frontiers of Architecture and Civil Engineering in China, 2009
Concrete box culverts are widely used in expressways in mountain areas. Many problems frequently ... more Concrete box culverts are widely used in expressways in mountain areas. Many problems frequently take place due to improperly estimated vertical earth pressures on culverts. The prevailing Chinese General Code for Design of Highway Bridges and Culverts (CGCDHBC) stipulates the computation of the design load on culverts primarily based on the linear earth pressure theory, which cannot accurately describe the
Piled embankments provide an economic solution to the problem of constructing embankments over so... more Piled embankments provide an economic solution to the problem of constructing embankments over soft soils. The piles and geosynthetic combination can alleviate the uneven surface settlements that sometimes occur in embankments supported by piles without reinforcement. The main focus of this paper is to present a new method for analysis of an embankment of granular fill on soft ground supported by a rectangular grid of piles and geosynthetic. This method is based on consideration of the arching effect in granular soil and similar to the method proposed by Low, B.K., Tang, S.K., Arching in piled embankments. Journal of Geotechnical Engineering 120 (11), 1917-1938]. The main refinements are: inclusion of a uniform surcharge load on the embankment fill, individual square caps were used, and taking into account the skin friction mechanism, which contributes to soil-geosynthetic interface resistance. Using this method, the influence of embankment height, soft ground depth, soft ground elastic modulus, and geosynthetic tensile stiffness on efficiency, stress concentration ratio, settlement ratio, tension of geosynthetic, and axial strain of geosynthetic are investigated. The results show that inclusion of a geosynthetic membrane can increase the fill load carried by piles. As a result, both the total and differential settlements of the embankment can be reduced. The new design method was verified against several current design methods. Theoretical solution showed that BS8006 [1995. Code of Practice for Strengthened/Reinforced Soils and other Fills. British Standards Institution, London, p. 162] and Guido, V.A., Kneuppel, J.D., Plate loading tests on geogrid-reinforced earth slabs. In: Proceedings of the Geosynthetics '87, New Orleans, USA, IFAI, pp. 216-225] methods overpredict the vertical stress acting on the geosynthetic due to that the reaction of the soft ground on the geosynthetic is not considered in their methods. It also showed that the present method is in good agreement with Low, B.K., Tang, S.K., . Arching in piled embankments. Journal of Geotechnical Engineering 120 (11), 1917-1938] method.
Geosynthetics in Civil and Environmental Engineering, 2009
ABSTRACT The vertical reinforcement (pile walls) is combined with the horizontal reinforcement (g... more ABSTRACT The vertical reinforcement (pile walls) is combined with the horizontal reinforcement (geosynthetics) to provide an economical and effective solution for ground treatment of high embankments constructed on soft soil. Theoretical and numerical analyses were conducted to investigate the interaction among geosynthetics, pile walls and soft soil. The differential settlement between pile wall and soft soil will generate soil arching in embankment fill. Soil arching and tensioned membrane of geosynthetics are combined to transfer embankment loads from soft soil to competent substratum (such as bedrock) through pile walls, which minimize the yielding of the soft soil and potentially reduce the total and differential settlements. The soil arching efficiency, the pile wall efficiency, the differential settlement of the embankment, and the distribution of tension force in the geosynthetics have been analyzed with the consideration of four major influencing factors: the elastic modulus of the pile wall, the tensile stiffness of the geosynthetics, the height of the embankment fill, and the area ratio of the pile wall. Some conclusions are drawn as a reference for the design and construction of geosynthetic-reinforced and pile wall-supported embankment over soft ground.
ABSTRACT A multi-column composite foundation is a new concept utilizing different column types wi... more ABSTRACT A multi-column composite foundation is a new concept utilizing different column types with varying lengths and diameters to support the embankment fill and to mobilize the strength and stiffness of the soil at shallow depths. This study presents the results of finite element analyses using the finite element software PLAXIS to investigate the consolidation behavior of a road embankment constructed on a multi-column composite foundation. The finite element results are calibrated for a period of 200 days. The settlement, horizontal displacement, differential settlement, column axial force, and the development and dissipation of excess pore pressure are presented and discussed in detail. It is concluded that a multi-column composite foundation allows a fast rate of consolidation and significantly increases the embankment stability. A multi-column composite foundation formed by CFG–lime columns is more effective than one formed by SC–lime columns. The CFG–lime columns improve the long-term stability of the embankment because the compression modulus of CFG columns is significantly greater than that of SC columns.
The increasing application of conventional geosynthetic-reinfor ced and pile-supported (GRPS) emb... more The increasing application of conventional geosynthetic-reinfor ced and pile-supported (GRPS) embankments (called CT embankments) for ground improvement has resulted in many problems, for example, intolera ble total or differential settlements, large lateral displac ements, local instabilities, and low efficiencies of the geosynthetic. In this study, a new ground improveme nt technique, referred to as fixedgeosynthetic-rein forced and pile-supported embankment (called FGT embankment), is proposed. A two-dimens ional numerical simulation that uses coupled mechanical and hydraulic modeling is conducted to investigate the performance of an FGT embankment. A sensitivity analysis is performed to investigate influencing factors, such as the tensile stiffness of the geosynthetic, the pile wall spacing, the elastic modulus of the soft clay, the elastic modulus of the pile wall and the pile wall width. The numer ical results show that the FGT embankment can sufficiently reduce the total and differential settlements, lateral displacement and excess pore water pressure , and enhance the stability of the embankment.
Piled embankments provide an economic solution to the problem of constructing embankments over so... more Piled embankments provide an economic solution to the problem of constructing embankments over soft soils. The piles and geosynthetic combination can alleviate the uneven surface settlements that sometimes occur in embankments supported by piles without reinforcement. The main focus of this paper is to present a new method for analysis of an embankment of granular fill on soft ground supported by a rectangular grid of piles and geosynthetic. This method is based on consideration of the arching effect in granular soil and similar to the method proposed by Low, B.. The main refinements are: inclusion of a uniform surcharge load on the embankment fill, individual square caps were used, and taking into account the skin friction mechanism, which contributes to soil–geosynthetic interface resistance. Using this method, the influence of embankment height, soft ground depth, soft ground elastic modulus, and geosynthetic tensile stiffness on efficiency, stress concentration ratio, settlement ratio, tension of geosynthetic, and axial strain of geosynthetic are investigated. The results show that inclusion of a geosynthetic membrane can increase the fill load carried by piles. As a result, both the total and differential settlements of the embankment can be reduced. The new design method was verified against several current design methods. Theoretical solution showed that BS8006 [1995. Code of Practice for Strengthened/Reinforced Soils and other Fills. British Standards Institution, London, p. 162] and Guido, V.A., Kneuppel, J.D., Sweeny, M.A. [1987. Plate loading tests on geogrid-reinforced earth slabs. In: Proceedings of the Geosynthetics '87, New Orleans, USA, IFAI, pp. 216–225] methods overpredict the vertical stress acting on the geosynthetic due to that the reaction of the soft ground on the geosynthetic is not considered in their methods. It also showed that the present method is in good agreement with Low, B.
Frontiers of Architecture and Civil Engineering in China, 2009
Concrete box culverts are widely used in expressways in mountain areas. Many problems frequently ... more Concrete box culverts are widely used in expressways in mountain areas. Many problems frequently take place due to improperly estimated vertical earth pressures on culverts. The prevailing Chinese General Code for Design of Highway Bridges and Culverts (CGCDHBC) stipulates the computation of the design load on culverts primarily based on the linear earth pressure theory, which cannot accurately describe the
Piled embankments provide an economic solution to the problem of constructing embankments over so... more Piled embankments provide an economic solution to the problem of constructing embankments over soft soils. The piles and geosynthetic combination can alleviate the uneven surface settlements that sometimes occur in embankments supported by piles without reinforcement. The main focus of this paper is to present a new method for analysis of an embankment of granular fill on soft ground supported by a rectangular grid of piles and geosynthetic. This method is based on consideration of the arching effect in granular soil and similar to the method proposed by Low, B.K., Tang, S.K., Arching in piled embankments. Journal of Geotechnical Engineering 120 (11), 1917-1938]. The main refinements are: inclusion of a uniform surcharge load on the embankment fill, individual square caps were used, and taking into account the skin friction mechanism, which contributes to soil-geosynthetic interface resistance. Using this method, the influence of embankment height, soft ground depth, soft ground elastic modulus, and geosynthetic tensile stiffness on efficiency, stress concentration ratio, settlement ratio, tension of geosynthetic, and axial strain of geosynthetic are investigated. The results show that inclusion of a geosynthetic membrane can increase the fill load carried by piles. As a result, both the total and differential settlements of the embankment can be reduced. The new design method was verified against several current design methods. Theoretical solution showed that BS8006 [1995. Code of Practice for Strengthened/Reinforced Soils and other Fills. British Standards Institution, London, p. 162] and Guido, V.A., Kneuppel, J.D., Plate loading tests on geogrid-reinforced earth slabs. In: Proceedings of the Geosynthetics '87, New Orleans, USA, IFAI, pp. 216-225] methods overpredict the vertical stress acting on the geosynthetic due to that the reaction of the soft ground on the geosynthetic is not considered in their methods. It also showed that the present method is in good agreement with Low, B.K., Tang, S.K., . Arching in piled embankments. Journal of Geotechnical Engineering 120 (11), 1917-1938] method.
Geosynthetics in Civil and Environmental Engineering, 2009
ABSTRACT The vertical reinforcement (pile walls) is combined with the horizontal reinforcement (g... more ABSTRACT The vertical reinforcement (pile walls) is combined with the horizontal reinforcement (geosynthetics) to provide an economical and effective solution for ground treatment of high embankments constructed on soft soil. Theoretical and numerical analyses were conducted to investigate the interaction among geosynthetics, pile walls and soft soil. The differential settlement between pile wall and soft soil will generate soil arching in embankment fill. Soil arching and tensioned membrane of geosynthetics are combined to transfer embankment loads from soft soil to competent substratum (such as bedrock) through pile walls, which minimize the yielding of the soft soil and potentially reduce the total and differential settlements. The soil arching efficiency, the pile wall efficiency, the differential settlement of the embankment, and the distribution of tension force in the geosynthetics have been analyzed with the consideration of four major influencing factors: the elastic modulus of the pile wall, the tensile stiffness of the geosynthetics, the height of the embankment fill, and the area ratio of the pile wall. Some conclusions are drawn as a reference for the design and construction of geosynthetic-reinforced and pile wall-supported embankment over soft ground.
ABSTRACT A multi-column composite foundation is a new concept utilizing different column types wi... more ABSTRACT A multi-column composite foundation is a new concept utilizing different column types with varying lengths and diameters to support the embankment fill and to mobilize the strength and stiffness of the soil at shallow depths. This study presents the results of finite element analyses using the finite element software PLAXIS to investigate the consolidation behavior of a road embankment constructed on a multi-column composite foundation. The finite element results are calibrated for a period of 200 days. The settlement, horizontal displacement, differential settlement, column axial force, and the development and dissipation of excess pore pressure are presented and discussed in detail. It is concluded that a multi-column composite foundation allows a fast rate of consolidation and significantly increases the embankment stability. A multi-column composite foundation formed by CFG–lime columns is more effective than one formed by SC–lime columns. The CFG–lime columns improve the long-term stability of the embankment because the compression modulus of CFG columns is significantly greater than that of SC columns.
The increasing application of conventional geosynthetic-reinfor ced and pile-supported (GRPS) emb... more The increasing application of conventional geosynthetic-reinfor ced and pile-supported (GRPS) embankments (called CT embankments) for ground improvement has resulted in many problems, for example, intolera ble total or differential settlements, large lateral displac ements, local instabilities, and low efficiencies of the geosynthetic. In this study, a new ground improveme nt technique, referred to as fixedgeosynthetic-rein forced and pile-supported embankment (called FGT embankment), is proposed. A two-dimens ional numerical simulation that uses coupled mechanical and hydraulic modeling is conducted to investigate the performance of an FGT embankment. A sensitivity analysis is performed to investigate influencing factors, such as the tensile stiffness of the geosynthetic, the pile wall spacing, the elastic modulus of the soft clay, the elastic modulus of the pile wall and the pile wall width. The numer ical results show that the FGT embankment can sufficiently reduce the total and differential settlements, lateral displacement and excess pore water pressure , and enhance the stability of the embankment.
Piled embankments provide an economic solution to the problem of constructing embankments over so... more Piled embankments provide an economic solution to the problem of constructing embankments over soft soils. The piles and geosynthetic combination can alleviate the uneven surface settlements that sometimes occur in embankments supported by piles without reinforcement. The main focus of this paper is to present a new method for analysis of an embankment of granular fill on soft ground supported by a rectangular grid of piles and geosynthetic. This method is based on consideration of the arching effect in granular soil and similar to the method proposed by Low, B.. The main refinements are: inclusion of a uniform surcharge load on the embankment fill, individual square caps were used, and taking into account the skin friction mechanism, which contributes to soil–geosynthetic interface resistance. Using this method, the influence of embankment height, soft ground depth, soft ground elastic modulus, and geosynthetic tensile stiffness on efficiency, stress concentration ratio, settlement ratio, tension of geosynthetic, and axial strain of geosynthetic are investigated. The results show that inclusion of a geosynthetic membrane can increase the fill load carried by piles. As a result, both the total and differential settlements of the embankment can be reduced. The new design method was verified against several current design methods. Theoretical solution showed that BS8006 [1995. Code of Practice for Strengthened/Reinforced Soils and other Fills. British Standards Institution, London, p. 162] and Guido, V.A., Kneuppel, J.D., Sweeny, M.A. [1987. Plate loading tests on geogrid-reinforced earth slabs. In: Proceedings of the Geosynthetics '87, New Orleans, USA, IFAI, pp. 216–225] methods overpredict the vertical stress acting on the geosynthetic due to that the reaction of the soft ground on the geosynthetic is not considered in their methods. It also showed that the present method is in good agreement with Low, B.
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