SUSI is a research project supported by the Regional Research Fund Trøndelag. The project goal has been to find more environmentally friendly procedures for lime cement stabilization of sensitive clay in the Trøndelag region. SUSI aims to define a lower limit to the amount of binder added in lime cement columns and to quantify the environmental impact of this reduction in terms of CO2-emissions.
The primary goal was to find the most sustainable and economical amount and type of binder to improve strength and deformation properties of sensitive clays. This was done by:
- WP1: Laboratory testing to find the minimum amount of binder necessary to improve strenght and deformation properties of sensitive clays.
- WP2: Cost-benefit and environmental-benefit evaluation for the different binder types and amounts used in WP1.
- WP3: Establish recommendations for the practical application of the results obtained and relevance for the community by evaluating the outcomes in a real case in Lundamo, Melhus, Trøndelag.
Background and summary
Mixing the soil at a defined depth with binders as lime, cement or a combination of these is a ground improvement method that aims to increase the strength and deformation properties of clays. In Norway, this method has been applied to sensitive or quick clays to improve the stability of slopes, excavations, reduction of settlements or vibrations, and under foundations.
NGI has been researching a more efficient use of binders for stabilization of sensitive clays. NGI has focused on the development of strength in a stabilized clay. It has been observed that one can reduce the amount of binder from the standard amount but still gaining strength in the field. However, it has not been possible to quantify the extension of this reduction and its effect in terms of CO2-emissions. Cement and lime production results in large CO2-emissions: one-ton CO2/ton cement or lime.
Prior to excavation for the new E6 in Klett, one million meters of lime-cement columns were installed. They translated into an estimated cement consumption of approx. 7000 tons, being responsible for 28% of the total CO2-emissions from the project. The reduction in the amount of binder can therefore make a significant contribution to the carbon footprint of this ground improvement technique.
Reduction of CO2-emissions
SUSI will add knowledge towards a reduction of the CO2-emissions during the stabilization of sensitive clays by optimizing the resources needed to conduct ground improvement. The optimization is related to the amount of binder, the costs associated and the time in situ to perform the work. This will bring the stabilization of sensitive clays a step forward to more sustainable soil stabilization solutions in geotechnics.
The results will be put in practice by a case study in Lundamo, where a cost-benefit analysis of different stabilization methods will contribute in the decision making of the stabilization work and the future use of the area under treatment.
Outcomes and impacts
- SUSI aims for optimizing an existing method for ground improvement to reduce costs and environmental emissions
- SUSI will add knowledge and bring forward the traditional practices in soil stabilization
- SUSI will build up local experience on the use of stabilization methods to realize future projects in areas with sensitive clays and contribute in the decision making of a communal actor.
- Prevent landslides in clay slopes, thus increasing the safety of people on quick clay areas
- Contribute in the sustainable development of the traditional method of stabilization with lime-cement, and thus reduce their carbon footprint
- Ensure the feasibility of development projects
- Safeguard landscape (like ravine landscapes), environmental values and cultural monuments
- Make available areas that cannot currently be built because of danger of triggering quick clay landslides
- Increase safety during the construction phase.
See also presentation of the project at Melhus kommune's website (in Norwegian only).