Technicrete’ s Armorflex 180 erosion control system was selected for stormwater channel management in a new housing development, The Orchards Ext 116 in Pretoria North. The Armorflex 180 system is a uniquely engineered alternative for a wide variety of erosion control and drainage projects which offers flexibility, adaptability to ground contours, settling of the concrete mat without breaking or spalling of individual blocks and with limited ground preparation work required. Technicrete supplied a total of 7,594 m2 of Armorflex for this project.
Armorflex 180 blocks are tied to adjacent blocks with galvanized wire threaded through the blocks and tied up like a zip to lock the system together. For steep installations and/or poor in situ sub-base structure, Armorflex can be anchored into the in-situ soil to further assist with stabilisation of the ground, blocks and system in general. The Armorflex blocks provide a loose but sophisticated interlocking design allowing the surface to remain flexible to movement without the cracking and spalling issues that occur with in situ cast concrete when exposed to any type movement or degradation of the supporting soil below the concrete layer.
“In order to manage existing stormwater challenges, it was proposed that the existing flood line path over the proposed development be redefined and shaped into a trapezoidal shape in order to have a better redefined/defined flow regime path for the 1:50-yr and 1:100-yr post development flood lines. Additionally, it was also suggested that a street be constructed with culverts along the Armorflex channel. These infrastructures will act as the proposed control point in order to protect existing downstream developments and to determine the post development 1:50-yr and 1:100-yr flows floodline. The flood lines will follow the refined flood area through the proposed township development as well as inside the Armorflex channel.” Commented Design Engineer, Charl Lemmer of Sotiralis Consulting Engineers.
“The material selection of the Armorflex blocks, for the trapezoidal shaped channel, was for compliance with the standard specifications of the City of Tshwane” Lemmer said.
Despite the challenges faced, the Armorflex performed its intended function effectively once the installation was completed commented Contracts Manager at Khavhakone Jorge Pacheao. “The quality of the Armorflex product is good, as was the delivery and technical assistance from Technicrete, “ he said.
“The Armorflex 180 blocks for the stormwater channel management at this residential development made technical and economic sense as they provide an excellent lining for drainage channels. At aprons at pipe inlets and outlets, Armorflex eliminates pipe undercutting that can lead to severe problems such as
surrounding bank failure and hence additional siltation downstream” said Lerato Modiba, Sales Consultant for Technicrete
The Armorflex 180 blocks are 340 x 294 x 115 mm in length, breadth and height with 11 blocks per square meter but a wider range of other specifications are also available with different footprint, height and mass per square meter. “Typical material selection of Armorflex blocks for a trapezoidal channel is based on balancing the overall mass per square meter of this concrete lining against the uplift force created by the flowing / moving water over the blocks. You must ensure that the blocks are thus heavier than the expectant uplift force to ensure stability of the system,” adds Justin Kretzmar, Technicrete Sales Engineer.
Technicrete offers a range of concrete products covering the building, infrastructure and mining sectors. The company, part of the Infrastructure Specialist Group, has ten manufacturing facilities across South Africa.
