Retaining wall | Cost estimation 3 steps

Ashwini Kumar

4 years ago

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

RCC quantity estimation
Reinforcement quantity estimation
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

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

16 mm dia Bars in Grade slab bottom mat

From the cross-section details,distribution bars 16 mm dia @ 150 mm c/c spacing is utilised.

Number of bars = (Total length-clear cover/spacing) +1 =((30 m-0.05- 0.05)/0.15)+1=(29.9/0.15)+1=200 No’s.

Cutting length =0.75 m+0.6 +0.3 -0.05+20×0.016=1.92 m, where hooks length = 10 x d (dia of bars)

So total cutting length of 16 mm dia @ 150 mm c/c spacing bars =1.92 m x 200 no’s =384 m

16 mm dia Bars in Grade slab top mat

From the cross-section details,distribution bars 16 mm dia @ 100 mm c/c spacing is utilised.

Number of bars = (Total length-clear cover/spacing) +1 =((30 m-0.05- 0.05)/0.10)+1=(29.9/0.1)+1=300 No’s.

Cutting length =1.65 +0.6 +0.25-0.05+20 x 0.016=2.77 m, where hooks length = 10 x d (dia of bars)

So total cutting length of 16 mm dia @ 100 mm c/c spacing bars =2.77 m x 300 no’s = 831 m

So total cutting length of 16 mm dia =384 m +831 m=1215 m

Unit weight of steel=dxd/162=16×16/162=1.58 kg/m

So total weight of 16 mm dia steel =1215 m x 1.58 kg/m =1919.7 kg

So total weight of 20 mm,12 mm,10 mm,16 mm=3583.06 kg+1338.72 kg+811.10 kg+1919.7 kg=7652.58 kg=7.65 MT

3. Cost estimation

The retaining wall cost estimation of RCC work and steelwork can be done by utilising its quantity and item rates.

The cost estimation rate of RCC M25 grade work using RMC vehicle excluding steel and its bending, including centring and shuttering is Rs 6500 /cum

So the cost estimation of RCC work =rate x quantity =6500 x 117 =Rs 760500

The cost estimation of steel rate only labour excluding material is Rs 10200 / MT

So cost estimation of Steel work=rate x quantity = 10200 x 7.65 =Rs 78030.(Cost of steel not considered)

So total cost estimation of retaining wall =Rs 760500+Rs 78050=Rs 838530

Add contingency to cost estimation of about 5% =838530×0.05=Rs 41926.5

So Total cost estimation of RCC retaining wall =Rs 838530 + Rs 41926.5 =Rs 880456.5

Conclusion :

So from the above mentioned 3 steps retaining wall cost estimation can easily be calculated.

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