--- title: "Short note: construction procedure of gravel road" subject: "Transportation Engineering II" chapter: 3 key: "semester_7/transportation_engineering_ii:gravel-road-construction-procedure" source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/gravel-road-construction-procedure site: BCT Engineering --- # Short note: construction procedure of gravel road Transportation Engineering II · Chapter 3: Road Construction Technology - Asked in: 2070 Chaitra (old course), 4 marks; 2068 Baisakh, 4 marks (asked 2 times) - Video: [How Modern Roads Are Built? Highway Construction Process](https://www.youtube.com/watch?v=juWc-DpFolY) — Civil Mentors - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/gravel-road-construction-procedure - Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-3 ## Question Write a short note on construction procedure of gravel road. ## Short answer Gravel road construction uses well-graded gravel (50–70% gravel, 20–40% sand, 8–15% fines, PI 4–12%, max size 40 mm) spread in 100–150 mm loose layers on a compacted subgrade with 4–5% camber, wetted to optimum moisture, shaped by grader, and compacted with an 8–10 t roller. Drainage and periodic regraveling every 3–5 years are needed. ## Answer **Gravel road** has a wearing course of naturally occurring gravel or an aggregate-soil mix compacted on the subgrade; it is the common low-cost road in rural Nepal (Nepal Rural Road Standards / DoLIDAR, IRC:SP:20). **Materials**: well-graded gravel with 50-70 percent gravel, 20-40 percent sand and 8-15 percent fines (plasticity index 4-12 percent, liquid limit below 35 percent), maximum size 40 mm (CBR above 30 percent for base, above 15 percent for sub-base). **Construction procedure** 1. Clear the site and set out the centre line and width; construct the subgrade to grade and camber (4-5 percent), compacting the top 150 mm to 95-97 percent of Proctor density; construct side drains and cross drains. 2. Haul gravel from the borrow pit or quarry and spread it by grader or manually to the required depth, usually 100-150 mm loose, in one or two layers. 3. Mix with water to near the optimum moisture content, adding fines or sand if the gravel is deficient in binder. 4. Shape with a grader to the camber and compact with an 8-10 t roller (or vibratory roller); repeat for the second layer. 5. Finish to the cross-fall, check the thickness and shoulders, and complete the drainage structures. 6. Open to traffic once compaction is complete. Maintain the surface by regular grading, and regravel (about 75-100 mm) every 3 to 5 years, because the gravel wears away at roughly 20-25 mm a year. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What material is suitable for a gravel road wearing course? A. Uniform single-size gravel with no fines B. Well-graded gravel-sand-fines mix with PI 4-12 percent and maximum size 40 mm C. Pure clay with PI above 30 percent D. Pure sand with no fines Answer: B. Some fines (8-15 percent) provide binding, while excessive plasticity is avoided. (Key point: Gravel material) 2. At what moisture content is the gravel compacted? A. Near optimum moisture content B. Completely dry C. Fully saturated D. Any content, as rolling squeezes water out Answer: A. Compaction is most effective near OMC, adding fines or sand if the gravel lacks binder. (Key point: Moisture) 3. What periodic maintenance does a gravel road need? A. Complete reconstruction each year B. Bituminous overlay every month C. Regravelling of 25-30 mm every 3 to 5 years as gravel wears away D. None, since gravel never wears Answer: C. Traffic and weather wear the gravel, so it is replenished every 3 to 5 years. 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