Skip to main content

Well foundation, 5 m internal diameter

Short answer

Outer area 34.212 m², inner 19.635 m². Sinking: outer area × 15 m = 513.18 m³. Brickwork: ring area × 15 m = 218.65 m³. Bottom plug (1:4:8): inner area × 1.5 m = 29.45 m³. Top seal (1:2:4): inner area × 1.0 m = 19.63 m³. Sand filling: inner area × (15-1.5-1.0)=245.44 m³.

Workout the quantity of well foundation of a bridge. The well is to be circular of 5 m internal diameter with 800 mm wall in 1:6 cement and sand mortar. The well is to be founded on strata 15 m below bed of river which is dry during winter. Bottom of the well is to be plugged with 1.5 m thick cement concrete 1:4:8 and the top to be sealed with 1 m thick cement concrete 1:2:4 and central portion is to be sand filled.

Data. Internal dia 5.0 m, wall 0.80 m, so outer dia = 5.0 + 2 × 0.8 = 6.60 m. Founding depth = 15.0 m below river bed (dry river, so no water-table complication). Assumptions: the top of the well is at river-bed level and the steining includes the curb (a separate RCC curb would be deducted from the brickwork).

  • Ao=π4(6.60)2=34.212A_o=\frac{\pi}{4}(6.60)^2=34.212 m²; Ai=π4(5)2=19.635A_i=\frac{\pi}{4}(5)^2=19.635 m²; ring area =14.577=14.577 m².
ItemWorkingQuantity
Excavation / sinking34.212 × 15.0513.18 m³
Brick masonry 1:6 in steining14.577 × 15.0218.65 m³
Bottom plug, CC 1:4:819.635 × 1.529.45 m³
Top seal, CC 1:2:419.635 × 1.019.63 m³
Sand filling (15.0 − 1.5 − 1.0 = 12.50 m)19.635 × 12.50245.44 m³

Answer: Excavation 513.18 m³; brickwork 218.65 m³; bottom plug 29.45 m³ (1:4:8); top seal 19.63 m³ (1:2:4); sand filling 245.44 m³.

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Estimating and Costing chapter 6 questions →