No abstract

Large areas of Southern Brazil are covered by thick layers of colluvial soils that have been affected by the laterisation process; this is typical of tropical regions. In their natural unsaturated condition, these soils, with porosities of ∼50%, can experience large and sudden volume reductions upon wetting and are generally identified as collapsible soils. In contrast to this behaviour, when compacted, these soils exhibit good mechanical properties and are used as construction material in the base courses of roads, as well as in some major Brazilian dams and embankments. Compacted layers of these lateritic soils have also been successfully utilised to allow the use of shallow foundations in collapsible soils. An adaptation of this technique was evaluated in this study – that is, the use of compacted lateritic soil columns to improve collapsible soil performance. The efficacy of the method was verified by plate load tests carried out on collapsible lateritic soil, with and without a compacted soil column, at the University of São Paulo in São Carlos City, Brazil. The preliminary results encourage the authors to continue this research in order to confirm the findings and to define guidelines for the practical use of this method.

The use of shallow geothermal energy through energy piles for the air-conditioning of buildings is increasing worldwide. This type of renewable energy technology is still not utilized in Brazil, where the hot dominating weather regions and the air cooling demand predominate. In this case of unbalanced heat transfer to the ground, the efficiency of the system may decrease with time due to the excessive heat injection into the soil. In order to investigate the possibility of an efficient application of this technology in São Paulo city, a balanced use of the ground for a ground-source heat pump (GSHP) system utilizing energy piles is evaluated in the present paper. Energy foundations were designed to meet the balanced heating and cooling loads (air conditioning and water heating) of a hypothetical business hotel building located in a site at the campus of the University of São Paulo, where thermal response tests (TRTs) were conducted on different types of energy pile. The number of energy piles required to supply the building thermal loads were estimated using the pile heat exchanger modelling software PILESIM 2.1 and compared with an analytical model prediction. The evaluations were done for three different types of pile tested at the site chosen for this study: micropiles, steel pipe, and continuous flight auger (CFA) piles. The results indicate that the ground heat extraction should be considered for the use of GSHP systems with energy piles in air cooling-dominated scenarios similar to the case studied here.