2018 Outstanding Achievement Award in Roadways/Infrastructure Category
2018 Outstanding Achievement Award
Geotextile Reinforced Soil Retaining Wall for MSW Incineration and Power Generation Plant
Project Details
Fabric: Mirafi®
Producer: TenCate Geosynthetics
Subcontractor Company: Yunnan Construction and Investment Holding Group
Please describe the project specifications
The Yuxi Municipal Solid Waste (MSW) Incineration and Power Generation Plant is a USD 50 million investment to manage the collection and incineration of MSW in a rural area of China. The incinerator will operate at a temperature of 800OC reducing the MSW to ashes and the associated heat energy generated will be converted to electricity using steam turbine generators. The site is located on rugged terrain at an elevation of about 1,800 m above sea level in Yunnan.
What was the purpose of this project? What did the client request?
The project involves the construction of a 33 m high multi-tiered geotextile reinforced soil retaining wall to create levelled platforms for the plant. Each tier consists of between 300 to 350 m long and about 8 m high near-vertical wall facings. The client wanted a solid looking retaining wall that could withstand tremors in this earthquake affected area. As the area is not easily accessed during construction, the client also wished to have a wall system that requires minimal importation of materials, avoids use of special construction equipment and does not require specialist skills for erection of wall. Our Mirafi® reinforced soil retaining wall system fits the request ideally. The wall system uses geotextile reinforcement to reinforce the locally available soil and is constructed as earthworks are carried out. It is well known to the industry that a geotextile reinforced soil retaining wall outperforms rigid wall systems like conventional reinforced concrete retaining walls during earthquake events.
Modular concrete blocks are used to provide a solid facing for the retaining wall. The modular concrete blocks can be made using onsite or offsite wet casting method using repetitively used steel moulds. The facing block unit measures 0.4 m wide, 0.4 m high and 0.5 m deep and has tongue and groove features at bottom and top of block respectively. The facing block can be handled manually and the tongue of the upper block fits into the groove of the lower block which mechanically locks in the interlaid geotextile reinforcement to the facing units. Backfill is placed in compacted layers using local excavated soil behind the facing blocks. Mirafi® SR2500 reinforcement geotextile is laid in vertical spacing of 0.4 m which corresponds to the tongue and groove interlocking levels of the modular facing blocks. The length of reinforcement geotextile extends behind the facing blocks up to a maximum of 24 m, depending on the design.
What is unique or complex about the project?
The TenCate Mirafi® reinforced soil retaining wall system is unique because apart from normal earthwork machinery for the backfilling and compaction of soil, the laying of Mirafi® geotextile reinforcement and the placement of modular concrete blocks can be done manually while yet achieving very exacting fascia profiles and aesthetics. The wall system required only transportation of Mirafi® SR geotextile reinforcement and modular concrete blocks to site. The lightweight Mirafi® SR geotextile reinforcement and the modular concrete blocks forms a small fraction either by volume or by weight, when compared with that of the concrete, steel and formwork needed for a conventional concrete retaining wall. This is a huge advantage for construction of retaining walls in rural environments. As the site is on rugged terrain, a modular block facing can conform to the ground contours much more easily than conventional cast-in-place reinforced concrete retaining wall options.
What were the results of the project?
The client was very satisfied with the finished retaining wall, which was truly solid looking and will survive earthquake events in the future. The design resulted in 11,000 m2 of good looking retaining wall completed within a short construction time of 7 months, which was truly remarkable by any standards. The contractors were also very happy as the fast installation rate achieved helped increased their profitability.
