Civil Engineering August 2021 | Vol 29 No 7

20 August 2021 Civil Engineering REDUCING EMISSIONS FROM GEOTECHNICAL PROJECTS Geotechnical engineering is an impor- tant part of civil engineering and the construction industry, providing an interface between human society and the surrounding environment. According to Pantelidou et al. (2012), the opportunity for sustainable solutions is highest during the initial stages of the project. Geotechnical engineering, typically positioned at the inception stages of projects, provides excellent opportunities for sustainable solutions. Carbon emission can be reduced in four ways: 1. Completely eliminate sources which emit carbon dioxide 2. Reduce emissions through optimised design, improved operational ef- ficiency, etc. 3. Substitute by using recycled or recy- clable material 4. Compensate through negative carbon solutions. Cement is a major contributor of emis- sions in construction. For piles, which consist mainly of concrete and steel, the common interventions would be to reduce the cementitious content by sub- stituting with blast furnace slag (GGBS) or fly ash. Production of one ton of ce- ment produces around 800 kg to 900 kg of CO 2 per ton compared to GGBS which generates 80 kg CO 2 per ton. Fly ash is a byproduct of burning coal and has no linked emissions. For steel reinforcement, using recycled steel can reduce CO 2 emissions from approximately 2 000 kg per ton to 500 kg per ton. GROUND IMPROVEMENT AS A SUSTAINABLE ALTERNATIVE TO PILING Ground improvement is one way to eliminate or reduce cement usage in foundation construction. In the South African context, ground improvement is synonymous with dynamic compaction. There are, however, many other methods available for foundation construction, such as vibro compaction, stone col- umns, rigid inclusions, soil mixing and vertical drains. Most consultants consider ground improvement only applicable for light structures and maintain that for heavy structures, piled foundation should be used. Topolnicki and Chang (2019) have demonstrated that there are some common applications where both solu- tions are feasible, which they illustrated with numerous case studies. Ground im- provement solutions often have an added cost and programme benefit, but for practical implementation, it is important that ground improvement solutions be considered at the conceptual design stage of the project. CONCLUDING REMARK Tesla is transforming the car industry by introducing energy-efficient electric vehicles. Apple, Google, Amazon and Microsoft are moving to renewable energy to power offices and data centres. As companies around the world rapidly innovate to reduce their impact on the environment, the construction industry in South Africa has an opportunity to make our contribution.  REFERENCES IEA. 2019. Global Status Report for Buildings and Construction: Towards a zero-emission, efficient and resilient buildings and construction sector. Global Alliance for Buildings and Construction (GlobalABC), International Energy Agency (IEA), and UN Environment programme. Pantelidou, H., Nicholson, D., and Gaba, A. 2012. Sustainable geotechnics. In Manual of geotechnical engineering. Vol. 1. Institute of Civil Engineers, UK. Topolnicki, M. & Chang, H.N. 2019. Ground improvement, an alternative to pile foundations, Proceedings, 17th ARCSMGE, Cape Town, 2019. Planning stage Design stage Construction stage eg: Q Q Alignment choice Q Q Structures choice eg: Q Q Material choice Q Q Design optimisation eg: Q Q Energy efficiency on site Q Q Machinery choice Potential for sustainable decisions Project stage Figure 4 Opportunities for sustainable solutions during the life of a project (Credit: Pantelidou et al., 2012) Settlement Foundation load GI without binders Piling GI with binders Piling GI GI and Piling equally possible 1 1’ 2 2’ Figure 5 Tentative ranges of piling and ground improvement solutions for foundation support Production of one ton of cement produces around 800 kg to 900 kg of CO 2 per ton compared to GGBS which generates 80 kg CO 2 per ton