--- title: "Well foundation: sinking, brick, sand filling, PCC" subject: "Estimating and Costing" chapter: 6 key: "semester_7/estimating_and_costing:well-foundation-g-sand-filling" source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/well-foundation-g-sand-filling site: BCT Engineering --- # Well foundation: sinking, brick, sand filling, PCC Estimating and Costing · Chapter 6: Detailed Estimate - Asked in: 2079 Bhadra, 4×2 marks - 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-g-sand-filling - Whole chapter: https://www.bctengineer.com/md/semester_7/estimating_and_costing/chapter-6 ## Question Work out quantity of well foundation for bridge. 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 be sealed with 0.45 m thick (1:4:8) cement concrete as well cover. Estimate quantities for the following works. a) Sinking of well. b) Brick masonry work in (1:6) cement sand mortar. c) Sand filling. d) PCC for RCC in well cover. ## Short answer Outer area 5.309 m², inner 3.142 m², ring 2.168 m². Sinking: outer area × 14 m = 74.33 m³. Brickwork: ring area × 14.20 m = 30.78 m³. Sand filling: inner area × 13.75 m = 43.20 m³. PCC cover: inner area × 0.45 m = 1.414 m³. ## Answer **Data.** Internal dia 2.0 m; wall 0.30 m, so outer dia = 2.60 m. Depth of well below GL = 14.0 m (curb included); well rises 0.6 m above GL; curb 0.4 m; cover 0.45 m thick placed inside the top of the bore. - Outer area $A_o=5.309$ m²; inner area $A_i=\frac{\pi}{4}\times 2^2=3.142$ m²; ring area $2.168$ m². #### a) Sinking of well $A_o\times 14.0 = 5.309\times 14 =$ **74.33 m³** (of this, 3.8 m is above the water table: 20.18 m³ and 54.15 m³ below it, which is priced separately if required). #### b) Brick masonry (1:6) Height = 14.0 − 0.4 + 0.6 = 14.20 m; volume = 2.168 × 14.20 = **30.78 m³**. #### c) Sand filling Filling goes from the top of the curb to the underside of the cover: height = 14.0 + 0.6 − 0.4 − 0.45 = 13.75 m; volume = 3.142 × 13.75 = **43.20 m³**. #### d) PCC (1:4:8) in well cover Volume = $A_i\times 0.45=3.142\times 0.45=$ **1.414 m³**. **Answer:** Sinking 74.33 m³; brickwork 30.78 m³; sand filling 43.20 m³; well cover concrete 1.414 m³. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which expression gives total sinking of well? A. Outer area 5.309 x 14.0 = 74.33 m3 B. Ring area 2.168 x 14.0 C. Inner area 3.142 x 14.0 D. Outer area x 14.2 Answer: A. Sinking covers the full outer cross-section down to founding depth of 14.0 m. (Key point: Sinking quantity) 2. How is the sand fill height 13.75 m found? A. 14.0 + 0.6 - 0.4 - 0.45 B. 14.0 - 0.4 C. 14.0 + 0.6 D. 14.0 - 0.45 only Answer: A. Fill runs from top of curb to underside of cover: total 14.6 less 0.4 curb and 0.45 cover. (Key point: Sand filling height) 3. Which cross-section is used for sand filling? A. Outer area 5.309 m2 B. Inner area 3.142 m2 C. Ring area 2.168 m2 D. Area for 2.3 m dia Answer: B. Sand fills the hollow core inside the masonry, i.e. the 2 m internal diameter. (Key point: Sand filling area) 4. What is the volume of the 0.45 m thick (1:4:8) cover? A. 3.142 x 0.45 = 1.414 m3 B. 5.309 x 0.45 = 2.39 m3 C. 2.168 x 0.45 = 0.976 m3 D. 3.142 x 0.40 = 1.257 m3 Answer: A. The cover fills the inner circle: 3.142 x 0.45 = 1.414 m3. (Key point: Well cover) ## Close variants set in other exams - [Well foundation: excavation, sinking, brick, PCC curb](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Awell-foundation-d-four-items) — Estimating and Costing, chapter 6, asked 2× ## Related in Estimating and Costing - [Well foundation, 5 m internal diameter](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Awell-foundation-5m-k) — Estimating and Costing, chapter 6, asked 2× - [Well foundation, 4.5 m internal diameter](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Awell-foundation-4-5m-p) — Estimating and Costing, chapter 6, asked 2× - [Building: excavation, PCC, brick, wood work](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Abuilding-f-fig3-four-items) — Estimating and Costing, chapter 6 - [Well foundation of pier: PCC and steel](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Awell-foundation-dia-7-pier) — Estimating and Costing, chapter 6 - [Two-room building: excavation, PCC, brick, plaster](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Abuilding-h-two-room-fig1) — Estimating and Costing, chapter 6 - [Building: brick 1:6, ceiling plaster, PCC](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Abuilding-l-fig1-ceiling-plaster) — Estimating and Costing, chapter 6 ## Related in other subjects - [Brick and mortar for 230 mm wall (100 kN/m)](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Awall-eccentric-230mm-100kn-5m) — Concrete Technology and Masonry Structure, chapter 8, asked 7× - [Brick and mortar for 250 mm wall (350 kN/m)](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Awall-eccentric-250mm-350kn) — Concrete Technology and Masonry Structure, chapter 8, asked 7×