---
title: "Well foundation: excavation, sinking, brick, PCC curb"
subject: "Estimating and Costing"
chapter: 6
key: "semester_7/estimating_and_costing:well-foundation-d-four-items"
source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/well-foundation-d-four-items
site: BCT Engineering
---

# Well foundation: excavation, sinking, brick, PCC curb

Estimating and Costing · Chapter 6: Detailed Estimate

- Asked in: 2081 Baisakh, 8 marks
- Video: [HOW TO CALCULATE SHUTTERING QUANTITY OF WELL STENING ?](https://www.youtube.com/watch?v=1c7k16kqd-Q) — THE BRIDGE ENGINEER
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/estimating_and_costing/well-foundation-d-four-items
- Whole chapter: https://www.bctengineer.com/md/semester_7/estimating_and_costing/chapter-6

## Question

Work out quantity of well foundation of bridge foundation. The well is to be circular of 2 m internal diameter with 300 mm thick masonry wall in 1:6 cement sand mortar. The well is founded in strata 14.00 m thick. Water table remains at 3.80 m depth. Well curb at bottom is RCC with M25 grade concrete mix and is 400 mm deep. The well rises 60 cm above ground level. Top of well is to sealed with 0.45 m thick (1:4:8) cement concrete as well cover. Estimate quantities for the following works.
a) Earthwork in excavation
b) Sinking of well
c) Brick masonry work in (1:6) cement sand mortar
d) PCC for RCC in curb

## Short answer

Dry earthwork to water table is 20.18 m3; sinking below water table is 54.15 m3; brick masonry 1:6 steining is 30.78 m3; M25 RCC curb is 0.867 m3.

## Answer

**Data.** Internal dia = 2.0 m; masonry wall 0.30 m, so outer dia = 2.0 + 2 × 0.30 = 2.60 m. Founding depth below GL = 14.0 m (including the 0.4 m curb); water table at 3.8 m; well rises 0.6 m above GL.

- Outer cross-section $A_o=\frac{\pi}{4}(2.60)^2=5.309$ m²
- Annular area of steining $=\frac{\pi}{4}(2.60^2-2^2)=2.168$ m²

#### a) Earthwork in excavation (above water table)
Dry excavation from GL to 3.8 m: 5.309 × 3.8 = **20.18 m³**.

#### b) Sinking of well (below water table)
The remaining depth 14.0 − 3.8 = 10.2 m is sunk by dredging under water: 5.309 × 10.2 = **54.15 m³**. (If a single item is wanted, total = 74.33 m³.)

#### c) Brick masonry (1:6) in steining
Height of steining = 14.0 − 0.4 (curb) + 0.6 (above GL) = 14.20 m.

Volume = 2.168 × 14.20 = **30.78 m³**.

#### d) PCC (M25) for RCC curb
Curb ring area is the same, depth 0.4 m: 2.168 × 0.4 = **0.867 m³** (reinforcement is measured separately in kg).

The 0.45 m well cover (1:4:8) is not asked here; it is π/4 × 2.0² × 0.45 = 1.41 m³.

**Answer:** Excavation 20.18 m³; sinking 54.15 m³; brickwork 30.78 m³; curb concrete 0.867 m³.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Internal dia 2.0 m, wall 0.30 m. What area is used for excavation and sinking?
   A. pi/4 x 2.0^2 = 3.142 m2
   B. pi/4 x 2.6^2 = 5.309 m2
   C. ring area 2.168 m2
   D. pi/4 x 2.3^2
   Answer: B. Excavation and sinking cover the full outer circle of dia 2.0 + 0.6 = 2.60 m. (Key point: Outer area)

2. How are excavation and sinking divided?
   A. Dry excavation to 3.8 m above water table; sinking of remaining 10.2 m below it
   B. Excavation 14 m; sinking 3.8 m
   C. Both 14 m
   D. Excavation 10.2 m; sinking 3.8 m
   Answer: A. Earthwork above the water table (3.8 m) is excavation; the remaining 14.0 - 3.8 = 10.2 m is sunk by dredging. (Key point: Water table split)

3. What height is used for the masonry steining?
   A. 14.0 m
   B. 14.0 - 0.4 + 0.6 = 14.20 m
   C. 14.0 + 0.6 = 14.6 m
   D. 14.0 - 0.4 = 13.6 m
   Answer: B. The curb (0.4 m) is RCC, not masonry, and the well rises 0.6 m above GL. (Key point: Steining height)

4. How is the RCC curb concrete found?
   A. Outer area x 0.4
   B. Ring area 2.168 m2 x 0.4 m = 0.867 m3
   C. Inner area x 0.45
   D. Ring area x 14.2
   Answer: B. The curb is the same ring as the steining, 0.4 m deep. (Key point: Curb volume)

## Close variants set in other exams

- [Well foundation: sinking, brick, sand filling, PCC](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Awell-foundation-g-sand-filling) — Estimating and Costing, chapter 6, asked 2×

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