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Well foundation, 4.5 m internal diameter

Short answer

Outer area 29.225 m², inner 15.904 m². Sinking: 29.225×15=438.37 m³. Brickwork: ring area ×15=199.81 m³. Bottom plug (1:4:8): 15.904×1.0=15.90 m³, top seal (1:4:8): 15.904×0.75=11.93 m³, total 27.83 m³. Sand filling: 15.904×(15-1-0.75)=210.73 m³.

Workout the quantity of well foundation of a bridge. The well is to be circular of 4.5 meter internal diameter with 800 mm wall in 1:6 cement and sand mortar. The well to be founded on strata 15 meter below bed of river which is dry during the hot weather. Bottom of the well to be plugged with 1.0 meter thick cement concrete 1:4:8 and the top to be sealed with 0.75 meter thick cement concrete 1:4:8 and central portion is to be sand filled.

Data. Internal dia 4.5 m, wall 0.80 m, so outer dia = 4.5 + 2 × 0.8 = 6.10 m. Founding depth 15.0 m below river bed (dry). Assumptions: top of the well at bed level and the steining includes the curb.

  • Ao=π4(6.10)2=29.225A_o=\frac{\pi}{4}(6.10)^2=29.225 m²; Ai=π4(4.5)2=15.904A_i=\frac{\pi}{4}(4.5)^2=15.904 m²; ring area =13.320=13.320 m².
ItemWorkingQuantity
Excavation / sinking29.225 × 15.0438.37 m³
Brick masonry 1:6 in steining13.320 × 15.0199.81 m³
Bottom plug, CC 1:4:8 (1.0 m)15.904 × 1.015.90 m³
Top seal, CC 1:4:8 (0.75 m)15.904 × 0.7511.93 m³
Sand filling (15.0 − 1.0 − 0.75 = 13.25 m)15.904 × 13.25210.73 m³

Total 1:4:8 concrete = 27.83 m³.

Answer: Excavation 438.37 m³; brickwork 199.81 m³; CC 1:4:8 = 27.83 m³ (bottom 15.90 + top 11.93); sand filling 210.73 m³.

✓ Answer checked by Claude Opus 5.5 (high effort)

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