4 - HKU Libraries

- 57-CHAPTER 8REINFORCED EARTH RETAINING WALLSThe technique of reinforced earth Is used for retailing walls invarious parts of the works. Such walls are relatively new to Hong Kong, andthere is little experience under Hong Kong conditions.It is recommended s at present, that designs should be in accordancewith the Technical Memorandum (Bridges) BE 3/78 (Department of Transport, UK,1978). It is also recommended that for the backfill, the grading and plasticityIndex requirements of the Federal Highways Administration (1978), outlined inTable 7 9 should also be met, because of the limited documented experience ofreinforced earth retaining walls constructed using materials with a high finescontent and plasticity index.It is considered that difficulty will be experienced in obtainingsuitable backfill material from natural sources. Decomposed volcanics willnot meet the specifications. For decomposed granites. It is likely that thevariability of grading and plasticity index within a local area will presentdifficulties. Consideration should therefore be given to the use of crusher-runor similar materials. Designers are advised not to commit the design of awall to a reinforced earth system until a sufficient source of fill thatwill meet the specification has been identified.Close supervision is required to ensure that construction proceedsaccording to specification, particularly all aspects of the backfillspecification. Difficulties with later provision of services and thesterilization of land above for building development may preclude the use ofreinforced earth in certain circumstances.