Retaining wall | Cost estimation 3 steps

Retaining wall cost estimation can be done on the basis of the plan, cross-section details and local rates for various works involved.

Retaining wall specifications, cross-section details

The following are the specifications of the retaining wall.

• For RCC work M25 grade concrete is utilised.
• Height of the retaining wall is 30 m and the height is 6 m.
• Main bars 20 mm Dia @ 400 mm c/c,200 mm c/c is utilised in three curtailments and Distribution bars 12 mm Dia @ 250 mm c/c, Vertical bars 12 mm @300 mm C/C, distribution bars 10 mm @ 300 mm c/c is utilised in retaining wall.
• In grade slab, top mat: 16 mm dia main bars @100 c/c, 10 mm dia @200 c/c distribution bars are utilised.
• In grade slab, bottom mat: 16 mm dia main bars @150 mm c/c,10 mm dia distribution bars 250 mm c/c is utilised.
• Depth of grade slab is 500 mm and the length is 3 m.
• The top width of the retaining wall is 200 mm, the bottom width is 600 mm.

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RCC Retaining wall quantity estimation 3 steps

1. RCC quantity estimation
2. Reinforcement quantity estimation
3. Cost estimation

1. RCC Quantity estimation

For RCC  M25 grade concrete is utilised.

From the cross-section details,Grade slab length =30 m,width=3 m,depth=0.5 m

Wall length =30 m,height=6 m, width is average of top and bottom.

RCC quantity in grade slab = 30 m x 3 m x 0.5 m = 45 cum

RCC quantity of retaining wall is 30 m x (0.6+0.2)*0.5*6=72 cum.

So Total RCC quantity = 45 cum + 72 cum =117 cum.

2. Reinforcement quantity estimation

20 mm dia main bars

Estimation of 20 mm dia main bars @ 400 mm c/c up to the full height

From the cross-section details,20 mm dia  @ 400 mm c/c spacing is utilised up to full height 6.5 m.

Number of bars = (Total length-clear cover/spacing) +1 =((30 m- 0.05-0.05)/0.4)+1=(29.9/0.4)+1=76No’s, where,Clear cover =50mm

Cutting length =6.5 m -top cover-bottom cover+2 hooks+0.75 =6.5-0.05-0.07+20×0.020+0.75=7.53 m, where 2 hooks length = 20 x d (dia of bars).

So total cutting length of 20 mm dia  @ 400 mm c/c spacing bars =7.53 m x 76 no’s =572.28 m.

Estimation of 20 mm dia main bars @ 400c/c spacing up to 3.6 m height

From the cross-section details,20 mm dia  @ 200 mm c/c spacing is utilised up to 3.6 m height.

Number of bars = (Total length-clear cover/spacing) +1 =((30 m- 0.05-0.05-2*0.2)/0.4)+1=(29.5/0.4)+1=75 No’s.

Cutting length =6.5 m -top cover-bottom cover+2 hooks+0.75 -2.4 m=6.5-0.05-0.07+20×0.020+0.75-2.4 m =5.13 m, where 2 hooks length = 20 x d (dia of bars).

So total cutting length of 20 mm dia  @ 400 mm c/c spacing bars =5.13 m x 75 no’s =384.75 m.

Estimation of 20 mm dia main bars @ 200c/c spacing up to 1.8 m height

From the cross-section details,20 mm dia  @ 200 mm c/c spacing is utilised up to 1.8 m height.

Number of bars = (Total length-clear cover/spacing) +1 =((30 m- 0.05-0.05-2*0.1)/0.2)+1=(29.7/0.2)+1=150 No’s.

Cutting length =6.5 m -top cover-bottom cover+2 hooks+0.75 -4.2 m=6.5-0.05-0.07+20×0.020+0.75-4.2 m =3.33 m, where 2 hooks length = 20 x d (dia of bars).

So total cutting length of 20 mm dia  @ 200 mm c/c spacing bars =3.33 m x 150 no’s =499.50 m.

So Total cutting length of 20mm dia =572.28 m +384.75 m +499.5 m=1456.53 m

Unit weight of steel =d x d/162 =20 x 20/162 =2.46 kg/m,where d=dia of steel.

So total weight of 20mm dia steel =1456.53 x 2.46 =3583.06 kg.

12 mm dia Bars

12mm dia distribution bars at 250 mm c/c

From the cross-section details,distribution bars12 mm dia  @ 200 mm c/c spacing is utilised.

Number of bars = (Total length-clear cover/spacing) +1 =((6.5 m- 0.05-0.07)/0.25)+1=(6.38/0.25)+1=27 No’s.

Cutting length =30 m -2 covers+2 overlaps +6 hooks=30 m-0.05-0.05+2 x 40×0.012+6x10x0.012=31.58 m, where  hooks length = 10 x d (dia of bars),overlap lenght=40xd (dia of bars)

So total cutting length of 12 mm dia  @ 250 mm c/c spacing bars =31.58 m x 27 no’s =852.66 m.

12mm dia vertical bars at 300 mm c/c

From the cross-section details, vertical bars12 mm dia  @ 300 mm c/c spacing is utilised.

Number of bars = (Total length-clear cover/spacing) +1 =((30 m- 0.05-0.05)/0.25)+1=(29.9/0.3)+1=101 No’s.

Cutting length =6.5m -top and bottom covers +2 hooks=6.5 m-0.05-0.07+2x10x0.012=6.62 m, where  hooks length = 10 x d (dia of bars)

So total cutting length of 12 mm dia  @ 300 mm c/c spacing bars =6.62 m x 101 no’s =668.62 m

So total cutting length of 12 mm dia bars = 852.66 m + 668.62 =1521.28 m

Unit weight of steel =dxd/162=12×12/162=0.88 kg/m,where d=dia of steel

So total weight of 12 mm dia steel =1521.28 mx 0.88 kg/m=1338.72 kg

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10 mm dia Bars

10 mm dia Bars in wall

From the cross-section details,distribution bars 10 mm dia  @ 300 mm c/c spacing is utilised.

Number of bars = (Total length-clear cover/spacing) +1 =((6.5 m- 0.05-0.07)/0.3)+1=(6.38/0.3)+1=22No’s.

Cutting length =30 m -2 covers +2 over laps +6 hooks=30 m-0.05-0.05+2x40x0.01+6x10x0.010=31.3 m, where  hooks length = 10 x d (dia of bars)

So total cutting length of 10 mm dia  @ 300 mm c/c spacing bars =31.3 m x 22 no’s =688.6 m

10 mm dia Bars in Grade slab bottom mat

From the cross-section details,distribution bars 10 mm dia  @ 250 mm c/c spacing is utilised.

Number of bars = (Total length-clear cover/spacing) +1 =((0.75 m+0.6 m +0.3 m- 0.05)/0.25)+1=(1.6/0.3)+1=7 No’s.

Cutting length =30 m -2 covers +2 over laps +6 hooks=30 m-0.05-0.05+2x40x0.01+6x10x0.010=31.3 m, where  hooks length = 10 x d (dia of bars)

So total cutting length of 10 mm dia  @ 250 mm c/c spacing bars =31.3 m x 7 no’s =219.1 m

10 mm dia Bars in Grade slab top mat

From the cross-section details,distribution bars 10 mm dia  @ 200 mm c/c spacing is utilised.

Number of bars = (Total length-clear cover/spacing) +1 =((1.56 m+0.6 m +0.25 m- 0.05)/0.20)+1=(2.36/0.2)+1=13 No’s.

Cutting length =30 m -2 covers +2 over laps +6 hooks=30 m-0.05-0.05+2x40x0.01+6x10x0.010=31.3 m, where  hooks length = 10 x d (dia of bars)

So total cutting length of 10 mm dia  @ 250 mm c/c spacing bars =31.3 m x 13 no’s =406.9 m

So total cutting length of 10 mm dia =688.6 m +219.1 m +406.9 m=1314.6 m

Unit weight of steel=dxd/162=10×10/162=0.617 kg/m

So total weight of 10 mm dia steel =1314.6 m x 0.617 kg/m =811.10 kg

16 mm dia Bars