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Retaining structures hold back soil or other loose material where an abrupt change in ground elevation occurs. The retained material or backfill exerts a push on the structure and thus tends to overturn or slide it, or both. The cantilever is the most common type of retaining wall and is used for walls in the range of 3to 6m in height. This study presents analyses and design of cantilever retaining wall which is made from an internal stem of steel-reinforced, cast-in-place concrete (often in the shape of an inverted T). In this work a detailed analyses and design for this type of walls which include estimation of primary dimensions of the wall, then these dimensions were checked.The factor of safety against sliding, overturning and bearing were calculated.the shear resistance for the base,the tension stresses in the stem andthe tension stresses for the base were checked. Calculation of reinforcement for each part of the wall were done. All analysis and design are based on the ACI code
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This project investigates the underlying theory of a non-circular, curved-in-plan embedded retaining wall (referred to as an arched retaining wall for this report). The project used a method of analysis used to predict the behaviour of arched dams (the trial load method), and applied it to the arched retaining wall to estimate its deflection behaviour. This project also used PLAXIS 3D to predict the behaviour of an arched retaining wall when the embedment depth & stiffness of the wall were altered and also to measure the impact of different modelling techniques and also the use of the arches on large excavations (by placing the arches in series). This project also followed on from the work done previously by the author (Gilmore, 2015) to find a beneficial prestressing arrangement using different prestressing techniques. Due to time constraints a true estimation of the behaviour of an arched retaining wall using the trial load method could not be obtained. However from observing the behaviour of the arched retaining wall and straight retaining walls it was seen that the trial load method could have potential to be applied to both arched and straight cantilever retaining walls. From the PLAXIS 3D results similar conclusions to Gilmore (2015) were found, showing that the arched retaining wall has a lower displacement than a straight retaining wall (with a 15-25% reduction in the maximum horizontal displacements of the wall). A prestressing arrangement using either props or jacks at the edges of the wall was found to be most beneficial, but found that the reduction in displacements was considered unsatisfactory for the effort (with only a 5% reduction in displacements), however when this prestressing arrangement was placed at the mid height of the wall, the results improved substantially(with an 8.8% reduction when compared to propping at just the ground level). The project also found that the arched cantilever retaining wall has a shallow centre of rotation, potentially allowing for economical savings compared to straight retaining walls due to a lower embedment depth This report also raised questions about the current methods of sizing retaining walls using the vertical stiffness only (as done by Addenbrooke et al (2000)), with this project finding that the lateral stiffness of a retaining wall a more defining variable.
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A case study: cantilever retaining wall founded on concrete blocks (counterforts) A large number of relatively high cantilever retaining structures in BiH were built in last 10 years. These walls were part of motorway route “Vc” project, regional road remediation project and in private sector as well. Many were constructed like cantilever walls founded on concrete block (so called counterforts). The construction phases for this type of retaining structures were defined in special chapter of this manual. Since these walls are found as cost effective solution that is adopted to local construction companies for more than 40 years, it is not surprising that it was involved in mentioned project as well. One of the walls is selected as case study for this manual. The details like construction sequence, geotechnical investigations, numerical analysis and practical construction details are presented in order to promote this type of structures. On the other side, the shortcomings of these structures are highlighted to draw the attention to practical engineers that will built these walls in the future.
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International Journal of Engineering Research and Technology (IJERT)
https://www.ijert.org/analysis-and-design-of-stepped-cantilever-retaining-wall https://www.ijert.org/research/analysis-and-design-of-stepped-cantilever-retaining-wall-IJERTV4IS020033.pdf A retaining wall is one of the most important types of retaining structures. It is extensively used in variety of situations such as highway engineering, railway engineering, bridge engineering and irrigation engineering. Reinforced concrete retaining walls have a vertical or inclined stem cast with base slab. These are considered suitable up to a height of 6m. It resists lateral earth pressure by cantilever action of stem, toe slab and heel slab. The tendency of wall to slide forward due to lateral earth pressure should be investigated and a factor of safety of 1.5 shall be provided against sliding. Cantilever retaining walls are found best up to a height of 6m.For greater heights earth pressure due to retained fill will be higher due to lever arm effect, higher moments are produced at base, which leads to higher section for stability design as well as structural design. This proves to be an uneconomical design. As an alternative to this, one may go for counter fort retaining wall, which demands greater base area as well as steel. As a solution to this difficulty, a new approach that is to minimize effect of forces coming from retained fill , short reinforced concrete members in the form of cantilever steps are cast along the stem on the retaining face. Addition of these steps would counterbalance the locally appearing forces and will result into lesser moment and shear forces along the stem. Also it will reduce the bending action that is pressure below the base. The objectives of the study are To reduce the stresses on the retaining face of the cantilever retaining wall, it is proposed to introduce reinforced concrete steps along the stem. 2)Decide the most economical location of step along length and also along height of wall from number of trials. 3)Decide cross section of the R. C. step as per the stresses due to frictional forces in step. 4)Stability analysis of Cantilever retaining wall with steps for unit width will be done. Check for minimum and maximum stresses will be observed. 5)Cost comparison shall be carried out for these three different alternatives to give most economical retaining wall type. Index Terms-Mechanism of Concrete plates; Concrete quantity; Steel reinforcement and Cost comparison of Counter fort and Stepped Cantilever retaining wall.
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