Cost effective sustainable slope protection solution of rural roads at flooding regions

Abstract

Bangladesh is a sandwich country between the Himalayas and the Bay of Bengal. The rivers of the country carry a huge amount of upstream water and therefore the rural roads along the rivers and the alluvial plains are often subjected to floods and erosion. Protection of road embankment slopes was difficult and sometimes construction of retaining wall was the only solution. LGED with assistance from a JICA Technical assistance project has developed a sustainable and cost effective solution for protection of steep slopes with soil bag. The cost of the slope protection works is nearly 40% of protection with retaining walls. The foundation of the protection should be in stable earth. Wooden piles may be used beneath the foundation to avoid scouring. The foundation is constructed with brick soling and a lean concrete above it. The protective materials are made of soil/sand bag. The bags can be made of jute or geosynthetic. The soil/sand cement ratio can be varied from 4:1 to 8:1. The stability of the protection work lies in correct positioning and placing of bags. Under different trial situation, the correct positioning of the bags has been found as 10° inclination at the first layer and 18°at all the upper layers. This method of slope protection can be replicated in flooded regions as well as in hilly region where stability of slope is a great concern