Development of a Bio-Composite Interlocking Block System for River Revetment

In Malaysia, many types of revetment systems are used in channel lining. These systems are mostly manufactured and patented overseas or designed using technologies transferred from foreign countries. Development of an interlocking block with environmental consideration is a new approach that may help in river protection and restoration. It is important to design and develop locally a new revetment block which is economical, durable and environmentally friendly. In this study, a block has been developed to be used as river revetment. As it also incorporates a bio-material, it is called a bio-composite revetment block. The block has a dimension of 400 mm x 400 mm x 100 mm (length x width x thickness) and it is designed to resist forces developed after installation at site and it complies with the requirements of the design and theory of existing blocks. The bio-composite block is made of concrete and it consists of tongue and groove to provide self interlocking between the blocks. In the opening at the centre of the block, a 10 mm layer of coconut husk is held in its place by two layers of plastic meshes that are embedded in concrete. Laboratory tests carried out were the flexural and tensile strength test on a single and multiple blocks. To conduct these tests, a special testing set-up was used. Direct tensile tests for single blocks indicate the failure was at 9.16 kN while for a group of blocks, the system failed at 5.81 kN. A finite element software called ANSYS was used to validate the failure pattern obtained from the laboratory tests and it was found to be in agreement with the predicted failure pattern by ANSYS. Laboratory experiment on biological materials showed that the coconut husk was the best medium for grass to grow compared to other media (oil palm husk and sugar cane husk). Field tests were conducted in which a 15 m stretch of a stream inside Universiti Putra Malaysia with a top width of 7 m was selected to install the bio-composite block. The purpose of field test is to measure the flow velocity and Manning roughness coefficient for the bio-composite block after installation. The average value of Manning roughness coefficient was found to be 0.040. The stability of the block and the rate of grass growth were also monitored. There was no block failure observed and a rapid grass growth was noticed with a rate of growth of 1.4% to 15% per week.

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