International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 07 | July -2017
p-ISSN: 2395-0072
www.irjet.net
Effective Use of Shelves in Cantilever Retaining Walls A. C. Chougule1, Prof. J. P. Patankar 2, P. A. Chougule3 1Assistant
Professor, Dept. of Civil Engineering, Sharad Institute of Technology, College of Engineering, Yadrav-Ichalkaranji, Maharashtra, India 2Professor, Department of Applied Mechanics, Walchand College of Engineering, Sangli, Maharashtra, India 3Assistant Professor, Department of Applied Mechanics, Walchand College of Engineering, Sangli, Maharashtra, India ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - Reinforced concrete cantilever retaining walls
termed as the retaining wall with relief shelf. One or more relief platforms or shelves extended to the rupture surface may have an advantage of decreasing the overall lateral earth pressure on the wall and increasing the stability of the structure. This will be an economical design because less material goes into the wall as compared to massive structure of cantilever or even counterfort retaining walls without shelves. The study of such type of retaining wall is therefore important to see its performance.
(RCCRW) are used in a variety of engineering fields such as roads, dams, tunnels and mines. RCCRWs are usually favored due to their economic benefits when compared to counterfeited walls. When considering retaining walls of greater height, the RCCRW can be effectively used if shelves are provided in the stem. If the shelves are extended up to rupture surface, the effective lateral earth pressure on the wall decreases considerably (which is advantageous for stability of the wall) as compared to cantilever retaining wall without shelves. This paper conducts a thorough analysis of the design measures taken of RCCRWs with 1) Single and Double shelves, and 2) Without Shelves. The paper concludes that the best location for a shelf for single shelf retaining walls is at 7/12th of stem height from top and the best locations for two shelves for double shelf retaining wall is at 4/12th of stem height and 7/12th of stem height from top.
1.1 Change in pressure due to presence of shelf Retaining wall supports a “wedge� of soil. The wedge is defined as the soil which extends beyond the failure plane of the soil type present at the wall site, and can be calculated once the soil friction angle is known. As the setback of the wall increases, the size of the sliding wedge is reduced. This reduction lowers the pressure on the retaining wall.
Key Words: Retaining Wall, Effective lateral earth pressure, rupture surface, double shelf, best location
The most important consideration in proper design and installation of retaining walls is to recognize and counteract the tendency of the retained material to move down slope due to gravity. This creates lateral earth pressure behind the wall which depends on the angle of internal friction and the cohesive strength of the retained material, as well as the direction and magnitude of movement the retaining structure undergoes.
1. INTRODUCTION A retaining wall is a structure designed and constructed to resist the lateral pressure of soil when there is a desired change in ground elevation that exceeds the angle of repose of the soil. A. R. Jumikis[1], P. C. Varghese[3] suggested that the stability of counterfort wall can be considerably increased by providing one or more relief platforms or shelves in cross section of such a wall and by extending them up to rupture surface. The relief shelves have an advantage of decreasing lateral earth pressure on wall and increasing overall stability of the structure. This results in an economical design since less material has to go into the wall as compared with massive structure or cantilever, and even counterforted walls without shelves. Bhaskarai, P. R. and et all[2]stated that as the total active earth pressure on a retaining wall with relief shell is lower in magnitude than that of conventional type only if the shelf is extended upto the rupture surface.
Lateral earth pressures are zero at the top of the wall and in homogenous ground increase proportionally to a maximum value at the lowest depth. Earth pressures will push the wall forward or overturn it if not properly designed. Also, any groundwater behind the wall that is not dissipated by a drainage system causes hydrostatic pressure on the wall. The total pressure or thrust may be assumed to act at one-third from the lowest depth for lengthwise stretches of uniform height. Figure 1.1 and Figure 1.2 shows the change in pressure distribution due to presence of shelf
Retaining walls may be used economically by providing relief shelves on the back fill side of the wall. Such walls are
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