Reinforced Fill Applications in Hong Kong
In Hong Kong, the common applications of the reinforced fill technique have included the following:
- Highway bridge abutments
- Retaining walls for highways, railways and building platforms
- Embankments for highways and railways
- River training works
- Repairs of failed slopes
- Barriers for blast shelters and landslide/boulder fall mitigation
Since 1981, over 100 reinforced fill structures have been constructed in Hong Kong. Many of these structures are situated in the new towns such as Tuen Mun, Yuen Long and Tsing Yi, which were developed in the 1980s to accommodate the increasing population. Extensive use of the reinforced fill technique has been made on the West Rail Project. Most of the completed reinforced fill structures range between 5 to 15 m in height, but a reinforced fill structure up to about 40 m was constructed on the mountainous coastal terrain of North West Tsing Yi to support a highway interchange that links Route 3 with the North Lantau Expressway.
Common Reinforced Fill Products
The common reinforced fill products are formed from metallic or polymeric materials. Metallic products are usually made from galvanised steel and formed as strips, grids or anchors. Polymeric products in the forms of grid or strip are commonly manufactured from polyester fibres or high density polyethylene (HDPE). Polymeric grids can be manufactured from drawn polymer sheets containing holes or formed from woven/knitted or solid structural polymeric elements (e.g. polymeric strips/bars) welded or knitted together.
Assessment of Reinforced Fill Products
From March 2022 onwards, the Civil Engineering and Development Department ceases to certify polymeric reinforced fill products. The existing certificates for certified products have been replaced with Design Data Sheets which can be viewed here.
The Civil Engineering and Development Department (CEDD) of the Hong Kong SAR Government regulates polymeric reinforced fill products whose long-term tensile strength and stress-strain characteristics are temperature and/or time dependent through a product assessment and acceptance process. Metallic products, of which the tensile strength and stress-strain characteristics are not dependent on temperature and time in normal application, do not require assessment for prior acceptance. According to Chapter 4 of the Project Administration Handbook for Civil Engineering Works, only polymeric products accepted by CEDD or metallic products shall be used in permanent reinforced fill features in Government projects. Both metallic and accepted polymeric products may be used in private projects subject to the approval of Building Authority.
The assessment of polymeric reinforcing products is to ensure the safety of permanent reinforced fill features constructed with these products in Hong Kong. Permanent reinforced fill features are defined as structures or slopes constructed using the reinforced fill technique, with or without facing elements, and having an intended design life longer than two years. The assessment process ensures consistent and satisfactory standards in the provision of these products, facilitates their specification, and saves time for designers, contractors, manufacturers, product distributors and the Government by eliminating repetitive checking of project proposals. Notwithstanding the listing of a reinforced fill product in the Product Register, a permanent reinforced fill structure or slope incorporating polymeric products accepted by CEDD or metallic reinforced fill products will need to be adequately designed by the designer, and checked by the Geotechnical Engineering Office (GEO) of CEDD.
Application for prior acceptance of polymeric reinforced fill products requires the applicant to submit sufficient information to justify the long-term tensile strength of the submitted products. The applicant shall provide a submission containing physical description of the polymeric reinforced fill products, history of its use, manufacturer quality control and quality assurance programme, detailed assessment of the long-term tensile strength and the pullout and sliding resistance of the products. A detailed breakdown of the submission requirements can be viewed by clicking Download PDF. The submission shall be submitted to the Head of GEO. Design Data Sheets of the accepted products including product images can be viewed in the Product Register.
Guide to Reinforced Fill Structure and Slope Design
Geoguide 6 - Guide to Reinforced Fill Structure and Slope Design (2017) recommends a standard of good practice for the design and construction supervision of permanent reinforced fills structures and slopes in Hong Kong. It provides a model specification, which stipulates the general requirements on the quality of materials, standard of workmanship, testing methods and acceptance criteria for reinforced fill construction. It can be used as a reference for the preparation of particular specification.