Gravity Wall 1.pptx

About gravity retaining wall

1. GRAVITY RETAINING WALL

2. CONTENTS Introduction Of Retaining Walls Types Gravity Retaining Wall. Materials used. Design Example. Conclusion.

3. RETAINING WALL A retaining wall is designed to hold in place a mass of earth , the edge of a terrace or excavation. The structure is 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.

4. Types Of Retaining Walls Some of the types of retaining walls are: Gravity Retaining Wall. Cantilever Retaining Wall. Counter Fort Or Buttress Retaining Wall. Anchored Retaining Wall. Pile Retaining Wall. Hybrid System.

5. Gravity Retaining Wall Gravity retaining wall depends on its self weight only to resist lateral earth pressure . Commonly, gravity retaining wall is massive because it requires significant gravity load to counter act soil pressure . Sliding, overturning, and bearing forces shall be taken into consideration while this type of retaining wall structure is designed . It can be constructed from different materials such as concrete, stone, and masonry units . It is economical for a height up to 3m . Crib retaining wall, gabions, and bin retaining wall are also type of gravity retaining walls

6. Gravity Retaining Wall

7. Materials used for gravity retaining wall

8. Design Example 4-foot (1.2 m) high gravity retaining wall equivalent fluid pressure of soil = 30 pcf (4.7 kN /m³) soil weight = 100 pcf (15.7 kN /m³) soil friction coefficient = 0.55 soil bearing capacity = 2000 lb /ft² (0.096 MPa ) 100% solid concrete masonry units, 120 pcf (18.9 kN /m³) concrete footing, 150 pcf (23.6 kN /m³)

9. DIAGRAM

10. First, determine the width of the wall base: where: H = height of gravity retaining wall, in. (mm ) L = width of gravity retaining wall at base, in. (mm ) Q = equivalent fluid pressure of retained material acting horizontally as overturning moment, pcf (kg/m³ ) W = average weight of masonry, soil and other material acting vertically

11. Figure 2 is employed in the selection of dimensions for gravity retaining walls up to eight ft (1.8 to 2.4 m) high. From Figure 2, the base of the wall is 24 in. (610 mm), which can be accomplished using three 8-inch (203 mm) block. Note that the footing weight was not included in the calculation of average unit weight of the materials acting vertically, so that the width determined from Figure 2 would be the width of the masonry wall at its base

12. Pressure At The Base Of The Wall p = total soil height x equivalent fluid pressure of soil p = (4.67 ft )(30 pcf ) = 140 lb /ft² (6703 Pa) resultant pressure, P = ½ (p)(total soil height) P = ½ (140 lb /ft²)(4.67 ft ) = 327 lb / ft (4.8 kN /m)

13. Element: Weight S 1 (0.67 ft)(1.33 ft)(100 pcf) = 89 lb (396 N) S 2 (0.67 ft)(2.67 ft)(100 pcf) = 179 lb (796 N) S 3 (0.33 ft)(4.0 ft)(100 pcf) = 132 lb (587 N) M 1 (0.67 ft)(4.0 ft)(120 pcf) = 322 lb (1432 N) M 2 (0.67 ft)(2.67 ft)(120 pcf) = 214 lb (952 N) M 3 (0.67 ft)(1.33 ft)(120 pcf) = 107 lb (476 N) F (2.67 ft)(0.67 ft)(150 pcf) = 268 lb (1192 N)

14. Element: Weight, lb (N) x Arm, ft (m) = Moment, ft-lb (N-m) S 1 89 (396) 1.33 (0.41) 118.5 (161) S 2 179 (796) 2.00 (0.61) 357.8 (485) S 3 132 (587) 2.50 (0.76) 330.0 (447) M 1 322 (1432) 0.67 (0.20) 215.5 (292) M 2 214 (952) 1.33 (0.41) 285.5 (387) M 3 107 (476) 2.00 (0.61) 213.9 (290) F 268 (1192) 1.33 (0.41) 356.4 (483) Total 1311 (5832) 1878 (2546)   Resisting Moment (About The Toe)

15. Determine the overturning moment about the base M = ( P )(⅓ x total height of soil) M = (327 lb / ft )(⅓ x 4.67 ft ) = 509 ft-lb/ ft (2.28 kN -m/m ) Check safety factors : overturning moment safety factor = 1878/509 = 3.7 3.7 > 2 OK sliding safety factor = (1311 lb )(0.55)/(327 lb / ft ) = 2.2 2.2 > 1.5 OK

16. Check Pressure On Soil

17. Conclusion Since the concrete masonry used in this example is assumed solid or fully grouted T he calculations do not include a check of shear stresses and flexural stresses in the wall because of low magnitude. Flexural and shear stresses in gravity retaining walls will almost always be of minor importance.

18. References Building Code Requirements for Masonry Structures, ACI 530-95/ASCE 5-95/TMS 402-95. Reported by the Masonry Standards Joint Committee, 1995. 2 . Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-95. American Society for Testing and Materials, 1995. 3 . Standard Specification for Mortar for Unit Masonry, ASTM C 270-92a. American Society for Testing and Materials, 1992.

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