Abstract
It has been established that the matric suction is the portion of the total suction that affects, more directly, the mechanical behaviour of unsaturated soils, being less considered the effects of the osmotic suction. Considering that in the deeply weathered soils will occur, depending on its chemical-mineralogical characteristics, more or less ionic exchange between the soil particles and the chemical products to which the soil has been exposed to, the study of the osmotic suction and its impact on the soil textural and structural stability becomes relevant. In natural terrain and slopes, the chemical products come mostly from agricultural inputs, while in road constructions they come from additives such as lime and cement that are incorporated to the soil with the objective of enhancing its mechanical behaviour. In the case of cast in situ concrete foundations, part of the concrete’s chemical compounds migrates to the surrounding soil. In all of the above mentioned cases, the matric suction acts on the chemical compounds’ migration process, affecting soil’s osmotic suction. Aiming at assessing the impacts of these chemical compounds on the soil properties and behaviour, soil-water characteristics curves of a lateritic soil mixed with a dolomitic limestone and a fertilizer were evaluated. The results show that, in the case of the fertilizer mixture, the variation of osmotic suction contributed to the disaggregation of the soil.
Highlights
Weathered tropical soils stand out for presenting aggregations and microaggregations that interconnect through clay bridging and/or cements (Conciani et al 2015 [1])
According to the Unified Soil Classification System (USCS), it is a clay silt of low plasticity (Burgos 2016 [14]). This soil was mixed with a Dolomitic Limestone (DL), a substance widely employed as a soil acidity regulator and conditioner, and a compound denominated as SUC, which was obtained by mixing, in equal amounts, the following fertilizers: Single Superphosphate, Urea and Potassium Chloride
soil-water characteristic curve (SWCC) of total and matric suction were determined through the filter paper method to evaluate if the chemical transfer between the soil and these substances intervene on the osmotic suction
Summary
Weathered tropical soils stand out for presenting aggregations and microaggregations that interconnect through clay bridging and/or cements (iron and aluminium oxy-hidroxys) (Conciani et al 2015 [1]). Depending on its chemical-mineralogical characteristics and on the presence of organic matter, these soils will present greater or lesser cation exchange capacity (CEC) (Raij 2010 [2], Ronquim 2010 [3]), making them more or less susceptible to changes on their composition after interacting with other chemical compounds These soils are characterized by having a variable charge that depends on the environment pH (Tiecher 2015 [4]). When these soils absorb salts, particles’ superficial charges are affected along the changes of the point of zero charge (PZC) (Marchi et al 2006 [5]), condition that will interfere, for example, in the CEC. In the study of unsaturated soil, suction is one of the main phenomena to be considered, since it intervenes significantly in the mechanical behaviour of soils and alters itself due to variations in factors like porosity, moisture, degree of saturation and physical-chemical conditions of the soil and the environment
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