--- title: "Roadside structures and landslide stabilisation" subject: "Transportation Engineering I" chapter: 5 key: "semester_6/transportation_engineering_i:roadside-structures-landslide" source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/roadside-structures-landslide site: BCT Engineering --- # Roadside structures and landslide stabilisation Transportation Engineering I · Chapter 5: Hill Roads - Asked in: 2069 Bhadra, 8 marks - Video: [Landslide PREVENTION: DIY Slope Stabilization Techniques](https://www.youtube.com/watch?v=-QobxZDZjoc) — iSTRUKTURA TV - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/roadside-structures-landslide - Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-5 ## Question Discuss the road side structures to be provided for roadway stability. Explain how you will stabilize landslides along the road. ## Short answer Roadside stability structures include retaining walls, breast walls, drainage systems, toe walls, and bio-engineering. Landslide stabilization primarily requires drainage control (surface and subsurface), unloading the head, loading the toe, retaining structures, soil reinforcement, and realignment if needed. ## Answer #### Road-side structures for stability of the roadway 1. **Retaining walls** (masonry, gabion, RCC) on the valley side to hold fills. 2. **Breast walls** on the hill side to support cuts. 3. **Drainage structures** - catch water drains, side drains, culverts, chutes, French drains and horizontal drains to keep water out of the slope. 4. **Toe walls, buttresses and parapets** (guard walls) at the valley edge. 5. **Rock-fall and slope protection** - rock nets, shotcrete, catch ditches, turfing, stone pitching. 6. **Gully control works** - check dams, drop structures. 7. **Bio-engineering** works over the exposed slopes. 8. **Berms and benches** on high cuts. #### Stabilising landslides along the road First investigate: type of slide (rotational, translational, debris flow, rock-fall), cause (water, loading, toe cutting), extent, depth of slip plane, and monitor movement. 1. **Drainage control** (most effective) - divert surface water with catch drains and lined channels around the slide; remove subsurface water with horizontal drains, French drains, and cut-off trenches; seal cracks. 2. **Geometric changes** - unload the head (remove soil from the top), load the toe with a berm, flatten the slope, or construct benches. 3. **Retaining structures at the toe** - gabion/masonry walls, piles, anchors, and buttresses to resist the slide. 4. **Soil reinforcement** - soil nails, rock bolts, ground anchors, geogrids; grouting of fractured rock. 5. **Bio-engineering** - grasses, shrubs and trees to bind soil and absorb water, plus jute net, bamboo, and brush layering. 6. **Realignment** - if the slide is large, shift the road away or bridge over it; or use a bypass. 7. **Maintenance** - regular inspection, cleaning of drains and early repair after each monsoon. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What should be done first before stabilising a landslide along a road? A. Build a retaining wall immediately B. Investigate the type of slide, cause, extent and slip plane depth, and monitor movement C. Realign the road D. Plant trees on the slide Answer: B. The treatment depends on the type, cause and extent of the slide, so these are investigated and the movement monitored first. (Key point: Investigation first) 2. Why is drainage control the most effective landslide measure? A. Water raises pore pressure and drives sliding, so diverting and draining it reduces the cause B. It increases the load at the head of the slide C. It makes the slip plane deeper D. It replaces the need for monitoring Answer: A. Water is a main cause of slides; diverting surface water and removing subsurface water cuts off the cause. (Key point: Drainage control) 3. Which combination is a correct geometric change to stabilise a slide? A. Load the head and unload the toe B. Unload the head and load the toe with a berm C. Steepen the slope and remove the toe D. Load both head and toe heavily Answer: B. Removing soil from the top reduces the driving force and a berm at the toe adds resisting weight. (Key point: Geometric changes) 4. When is realignment, bridging or a bypass chosen for a landslide? A. For every small slide B. When the slide is large and cannot be economically stabilised C. Only when drains are blocked D. Only in the dry season Answer: B. If the slide is large, it is more practical to move the road away from it, bridge over it or bypass it. (Key point: Realignment) ## Related in Transportation Engineering I - [Hill road drainage structures](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahill-drainage-structures) — Transportation Engineering I, chapter 5, asked 4× - [Gully control and land stabilisation](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Agully-control) — Transportation Engineering I, chapter 5, asked 2× - [Design steps of side drain](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aside-drain-design) — Transportation Engineering I, chapter 4 - [Retaining and slope protection structures](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aretaining-slope-protection) — Transportation Engineering I, chapter 5 - [Setback on six lane road, 500 m radius](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3An-65c-setback-500) — Transportation Engineering I, chapter 3 ## Related in other subjects - [Side-long ground hill road, 0-400 m](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aside-long-road-n) — Estimating and Costing, chapter 6 - [All mass movements are landslides](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aall-mass-movements-are-landslides) — Engineering Geology I, chapter 6 - [Landslide causes and slip surface techniques](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Alandslide-causes-and-slip-surface) — Engineering Geology I, chapter 6 - [Landslide causes and mitigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Alandslide-causes-mitigation) — Engineering Geology II, chapter 5, asked 6×