Civil Engineering October 2022 | Vol 30 No 9

34 October 2022 Civil Engineering The original design required a layer work thickness of 1.2 m. With the inclusion of geosynthetics the project saw a cost saving of 17%. Using a woven geotextile with a bi-directional strength of 40 kN/m, both separation and additional reinforcement were achieved. The use of this geosynthetic controlled the contamination of the base course by decreasing the ability of the fines to migrate from the subgrade to the subbase. Additionally, it resulted in a 30% reduc- tion of the required thickness of the base and subbase layers (see Figure 3). The reinforcement of the asphalt layer was enhanced using a fibreglass geogrid with a bi-directional tensile strength of 100 kN/m. This also meant that the same layer performance was achieved with a 20% reduction in the asphalt required. Ground stabilisation at Secunda The construction of RDP housing necessi- tated the rehabilitation of the road scheme at Velabahleke in Mpumalanga. During excavation the subgrade was found to be very soft and wet and would not allow for the construction of the initially designed pavement structure. Due to budgetary and time constraints, excavation and replace- ment of dump rock were not feasible at that depth. Using Maccaferri’s software, the pave- ment was analysed using the Leng-Gabr method and it was found that the pro- posed dump rock layer could be reduced by 57% with the use of geosynthetics. A combination of an extruded geogrid (which reduces stresses at the dump rock and G7 subbase interface), woven and nonwoven geotextiles was used to sustain the pavement loading and replace the subsurface drainage. The solution incor- porated reinforcement, separation, and filtration, providing a holistic approach to the problem. The use of geosynthetics allowed the project to continue without major delays. CONCLUSION The literature demonstrates that the use of geosynthetics in road applications can be used to reinforce, restrain, separate and act as a tensioned membrane. As the subgrade’s strength decreases and vehicle loads and passes increase, reinforcement becomes more necessary. With an in- crease in cost and a lack of material avail- ability, creative solutions to traditional design and construction become vital. The use of geosynthetics can be seen as a cost-effective and value-adding material in roads.  REFERENCE Ogundare, D.A., Adebara, S.A., Familusi, A.O., & Adewumi, B.E. 2018. Stabilization of subgrade using geosynthetics (case study – geotextile) under soaked condition . ANNALS of Faculty Engineering Hunedoara – International Journal of Engineering , 16(4): 157-162. The construction of RDP housing necessitated the rehabilitation of the road scheme at Velabahleke in Mpumalanga. During excavation the subgrade was found to be very soft and wet and would not allow for the construction of the initially designed pavement structure. Due to budgetary and time constraints, excavation and replacement of dump rock were not feasible at that depth. Figure 3 Layer work reduction at Ivato Airport 10 cm 35 cm 75 cm Beton Bitumineux GCNT 0/40 Decaissement zone P2 Subgrade 8 cm 25 cm 60 cm Subgrade Decaissement zone P2 Beton Bitumineux GCNT 0/40 MACGRID® AR10.7 MACTEX® W1 4S