Abstract
Residual bimodal soils present great complexity of hydraulic and mechanical behaviour, due to the presence of aggregations, mineralogy and complex structures. These soils often present a clear bimodality with a wide difference between the size of intra-aggregate and inter-aggregate pores, of 2 to 3 orders of magnitudes. The objective of this work is to produce a soil with bimodal characteristics using Kaolin Clay, in order to eliminate possible mineralogical, particle size and structural variables, since the clay mineral present in this material is mainly Kaolinite. Analyses of the effect of stable aggregations on soil structural behaviour were carried out by means of soil water retention curve (SWRC). For this, a new methodology was developed for the production of stable aggregations, which were used to compose new bimodal soils. Then, a series of comparisons between the SWRC of the soil with and without aggregation were carried out. Results showed that the presence of aggregations had a direct impact on soil plasticity, particle size classification and compaction curve.
Highlights
Soils with dual-porosity, or bimodal soils, can be understood as soils that present two distinct dominant pore sizes, which may be naturally occurring or a result of compaction.Clayey or silty soils compacted on the dry side of the compaction curve display a bimodal pore structure while soils compacted on the wet side of the compaction curve or reconstituted slurries present unimodal pore structures [1].Many tropical residual soils have naturally bimodal pore structures
Red circular points are the stable samples while white circular points represent the samples that failed the crumble test by disaggregating when immersed in water. It can be observed the agreement between the compaction curve of Kaolin with normal energy and the Mini Proctor test, highlighting the validity of the Mini Proctor test
The materials presented mineralogy containing only kaolinite clay minerals, the presence of stable aggregations resulted in a decrease of the specific surface of the particles, reducing its plasticity
Summary
Many tropical residual soils have naturally bimodal pore structures In these cases, it is common to observe the presence of aggregations, forming inter-aggregate pores, and the existence of intra-aggregate pores, formed between aggregations. It is common to observe the presence of aggregations, forming inter-aggregate pores, and the existence of intra-aggregate pores, formed between aggregations This is the case of the porous clay soil of Brasilia, Brazil, which often exhibits collapsing behaviour. 2.1 Mineralogy of clays and interparticle forces In this sense, in order to understand soils with great mineralogical variability and complex structures it is fundamental to start by studying the behaviour of soils with simpler structures and that forms the basis for the complex soil, as well as the forces acting at a particle level. The forces that occur between the particles are important for the compression of the soil structure, since the structure is a combination of soil fabric and interparticle forces
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