•Segmental Post Tensioned Mechanically Stabilised Earth Wall (PT-MSEW) was introduced.•Finite element models were developed and verified against test results.•Design recommendations for the proposed ...PT-MSEW system were provided.
This study reports on a numerical investigation on the behaviour of an innovative retaining wall system named Post Tensioned Mechanically Stabilised Earth Wall (PTMSEW). In the proposed system, Post-Tensioning (PT) technique was integrated into the common retaining wall and the Mechanically Stabilised Earth Wall (MSEW) construction method to improve the performance of MSEWs and limit their failure modes. The variables of this study were wall height, PT force, pre-cast segment size, surcharge load, foundation size, and soil reinforcement length. The study found that incorporating PT stress into the MSEW improved the performance of the retaining wall by decreasing horizontal displacement of the wall face, soil reinforcement tensile forces, and backfill settlements and significantly enhanced the passive resistance of the wall. The introduction of a small amount of PT force prevented local failures caused by the relative movement of face segments. It was observed that by applying only a small level of post-tensioning, the lateral load-carrying capacity and passive resistance of the proposed PT-MSEW system can be significantly improved over that of its conventional counterpart. This opens new possibilities for the use of MSEW in the construction of taller retaining walls.
In the design of a deep retaining wall, it is necessary to consider the blocking effect on groundwater seepage of retaining walls in aquifers. In this study, both laboratory tests and numerical ...simulation with finite element method (FEM) were adopted to investigate the blocking effect on groundwater seepage under different insertion depths of retaining wall in aquifer. Laboratory tests were conducted to analyze this blocking effect in an unconfined aquifer. The test results indicate that the effective insertion depth ratio (J) of a retaining wall in Shanghai aquifer sand is about 70%. A three-dimensional numerical model (3D-FEM) was conducted to analyze the laboratory test results. The FEM results show that FEM is a reliable method to analyze the blocking effect on groundwater seepage in an aquifer. Based on the same aforementioned procedure, a 3D FEM model is established to investigate the blocking effect in the confined aquifer in Shanghai deposit. Both laboratory test and FEM results show that drawdown of groundwater level decreases with an increase of the insertion depth ratio, J, of retaining structures in an aquifer. The optimal value of J (approximately 70%) is achieved for retaining wall based on the synthetic results from laboratory test, FEM analysis, and the equation of Pujades et al. for either unconfined aquifers or confined aquifers of Shanghai.
•We conducted a series of laboratory tests to investigate the blocking effect of retaining walls on groundwater flow.•Numerical simulation was conducted to analyze the test procedure and the parameters were determined.•Numerical simulation was applied to the deposit of Shanghai based on the aforementioned procedure.•The effective insertion depth of a retaining wall to blocking seepage for the soil of Shanghai was obtained.
Abstract
The concept and study of a cantilever retaining wall and a cantilever retaining wall with relieving platform with elevations varying from 5 to 8 meters and having a safe bearing capacity of ...160 KN/m2 are presented in this paper. It also depicts relative research such as bending moment, safety against overturning and sliding, expense and economy, between the retaining walls. The cost and optimal cost are calculated as part of the relative analysis. Software and analytical results such as bending moment, deflection, and stresses are also discussed in this paper. Laterally acting total earth pressure is depicted to be reduced due to the provision of relieving platform (RP). The retaining wall with relieving platform (RW with RP) is shown to be cost-effective, more stable, and relieve the BM of the stem and heel portions than cantilever retaining wall (CRW). The findings of this research is drawn based on the results obtained using different models prepared in software, comparison of bending moments, requirement of tension reinforcement and these results are verified by manual analysis. The research shows that the CRW with RP is more economical and is more worthy than CRW.
Shallow slope failure in mountainous regions is a common and emergent hazard in terms of its damage to important traffic routes and local communities. The impact of dry granular flows consisting of ...rock fragments and other particles resulting from shallow slope failures on retaining structures has yet to be systematically researched and is not covered by current design codes. As a preliminary study of the impact caused by dry granular flows, a series of dry granular impact experiments were carried out for one model of a retaining wall. It was indirectly verified that the total normal force exerted on a retaining wall consists of a drag force (
F
d
), a gravitational and frictional force (
F
gf
), and a passive earth force (
F
p
), and that the calculation of
F
d
can be based on the empirical formula defined in NF EN Eurocode 1990 (
Eurocode structuraux. Base de calcul des structures
, AFNOR La plaine Saint Denis,
2003
). It was also indirectly verified that, for flow with Froude number from 6 to 11, the drag coefficient (
C
d
) can be estimated using the previously proposed empirical parameters.
Abstract
In order to solve the difficulties in the construction design of pile foundation and cushion cap of bridge substructure caused by marsh geology and tidal environment abroad, according to the ...European standard EN 1997, a new form of integrated design of retaining wall and cofferdam construction is creatively proposed. The whole process of structural design is studied in detail from the aspects of structural selection, determination of load and load partial coefficient, checking calculation of component design details. Taking the Brunei project as a case, the results show that the integrated design method of retaining wall and cofferdam construction can effectively improve the performance of the pile foundation of the beam substructure, meet the requirements of European standard EN 1997, and provide technical reserves for the construction of similar bridge projects abroad.
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•A new retaining wall system (PSRW) is proposed.•Experimental study on post-tensioned segmental retaining walls (PSRWs) is presented.•Different axial stress ratio and wall-footing ...interface materials are examined.•Force-displacement and energy dissipation responses of PSRWs is analyzed.•Precast PSRWs can potentially be used for accelerated construction of retaining walls.
This paper reports on an experimental study on nine Post-tensioned Segmental Retaining Walls (PSRWs). All the walls were post-tensioned and tested under incrementally increasing cyclic loading. Each test wall was constructed using four T-shaped precast concrete blocks, assembled on top of each other with dry joints. The integrity of the system was maintained using post-tensioning (PT). Different levels of PT forces were applied to investigate the effect of it. Different wall-footing interface materials were used including steel plate, concrete and neoprene pad. Conventional concrete and crumb rubberized concrete was used to investigate the effect of concrete properties on the structural behavior of retaining walls. Three walls with confinement (confined with either Carbon Fiber Reinforced Polymer (CFRP), steel reinforcement or steel face plate) were tested. The force–displacement responses, energy dissipation, post-tensioning stresses, gap rotation, lateral stiffness, and normal strains were observed and compared. The results from this study showed that the level of axial stress ratio, eccentricity of pre-stressing as well as the properties of the wall-footing interface material is critical to provide enough lateral strength and stiffness for engineering design of the PSRW. The wall with steel plate on compression face had the largest ultimate strength. The specimen having largest PT force generated largest initial and secant stiffness. Additional reinforcement of the bottom most segment is also required to avoid sudden failure and increase ductility in T-shaped blocks. Lateral stiffness increases in conventional concrete was much higher than rubberized concrete when PT force was increased. None of concrete confinement methods applied (CFRP confinement, steel reinforcement and steel face plate) affected energy dissipation characteristics of the tested walls. Using neoprene as the interface material for wall-footing significantly increased energy dissipation and concrete wall-footing interface showed more energy dissipation in comparison to steel interface material. Stiffness degradation of all walls had similar rate against wall lateral displacement. This paper concluded that the proposed segmental retaining wall system is potentially a practical alternative to accelerate the construction of retaining walls using precast concrete blocks.
Six centrifuge models were tested as part of the Liquefaction Experiments and Analysis Projects (LEAP-2020 and LEAP-2022). The models consisted of saturated Ottawa F65 sand deposits supported by ...sheet-pile walls. The objective of this study is to confirm the reproducibility of the experiments and evaluate the model responses to the testing parameters, including the soil density, embedment depth of the sheet pile, and input acceleration. This study quantitatively addresses the significance of the degree of saturation by highlighting the increase in unwanted liquefaction resistance due to imperfect saturation. Duplicate models confirmed the experimental reproducibility of the excess pore pressure response and sheet pile displacement. The stability of the sheet pile was evaluated using a simple pseudo-static model that considered dynamic earth and hydrodynamic pressures.
•Six centrifuge models were tested as part of the LEAP-2020 and LEAP-2022.•The degree of saturation of the model and liquefaction resistance of sand were evaluated.•The results of the duplicate models confirmed the experimental reproducibility.•The stability of sheet-pile wall was evaluated using a simple pseudo-static model.
Strut-free retaining walls are an efficient and cost-effective technology for large-scale excavations, but their application at excavation depths of more than 10 m in soft soils has rarely been ...reported. An innovative multibench retaining system composed of an inclined–vertical framed retaining wall (IVFRW) and a cantilever wall with anchors was used in a 14.7-m-deep excavation in soft clay in Tianjin, China. To analyze the pile–soil interaction considering the influence of the second stepped excavation, indicators were monitored to provide comprehensive measured data. Field measurements included the lateral deflection and vertical displacement of the retaining wall, the ground water level variation, the ground settlement, and the axial force of the piles within the IVFRW. The measured results indicated that the wall displacements and the ground movements caused by the excavations were small in comparison to those of previous projects and empirical formulas. The influence of the second stepped excavation on the soil|structure interaction and its influence on the axial force of the IVFRW were analyzed. The optimal values of the first stepped excavation depth (H1) for different site conditions were further investigated.
In this paper, a thorough numerical study is conducted to rigorously evaluate the lateral earth pressures exerted on the retaining walls backfilled with geosynthetic-reinforced soil strata. With this ...aim, the lower bound theorem of limit analysis is exploited in conjunction with the finite element discretization method. The computational programming adopting second-order cone optimization is employed to model the Mohr-Coulomb yield criterion in its respective nonlinear form. The reinforcement layers are assumed to bear solely axial tension; but not bending moment, which is the common characteristic of all geosynthetic materials. Results show that the horizontal stress field behind retaining structures is heavily disturbed by placing geosynthetic layers, especially in close proximity to the retaining structure. Accordingly, the failure zone shrinks in size and the lateral earth pressure decreases by either adding more reinforcement layers or increasing their relative lengths. Through a comprehensive parametric survey, the influence of several parameters, including internal friction angle, soil-wall and soil-reinforcement interface friction angles, length and number of reinforcements, soil inherent anisotropy and surface loading on the lateral earth pressure is meticulously examined. The employed formulations are rigorously compared with results published in the literature. A design table is also provided so as to effectively estimate the active earth pressure coefficient of geosynthetic-reinforced walls accounting for all contributing parameters.
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