Concha Riedel, José Ignacio; (2025) Characterisation of adobe blocks from the partially saturated soil mechanics framework: a Chilean housing case study. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

In recent years, the rise in global temperatures, scarcity of raw construction materials, and the increase in energy demands from the building sector have emerged as significant concerns for civil engineers. This has resulted in the necessity to identify alternatives with reduced environmental impact. The use of earth blocks has emerged as a potential cost-effective solution for housing, by reducing energy consumption and consequently carbon dioxide emissions in construction. Despite that considerable research has been conducted into it, there has been a lack of externalisation and application of specific knowledge drawn from the geotechnical framework. This study aims to address the existing knowledge gap by employing a partially saturated soil mechanics framework to ascertain the mechanisms by which an organic silty sandy soil-fibre composite known as Adobe gains its strength. The use of drained and undrained monotonic triaxial tests, in conjunction with oedometric and shear box tests, enabled the characterisation of the soil strength parameters. Conversely, customised designed constant water unconfined compression tests with suction measurements, coupled with an evaluation of the soil-water retention curves, were employed to obtain the unsaturated strength and properties of the soil. The results of the tests conducted at different ages indicate that the increase in adobe strength depends on several mechanisms, including its unsaturated state (moisture content), and the quantity and nature of the reinforcement. Age however, did not have a significant effect on the adobes’ strength. The presence of organic matter was identified as a critical factor in the peak dry strength of adobe blocks which differs from inert soils studied previously, where suction was the main driver of unsaturated strength. Reinforced soil showed similar saturated behaviour as tests performed previously on sands reinforced with polypropylene fibres. However, fibres resulted in a detriment to the peak strength of the soil in dry conditions.

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