Caracterização química, mineralógica e geotécnica de solos do município de Areia-PB.

Abstract

For geotechnical engineering, an adequate investigation of the soil covers the assessment of the nature and behavior of all geological and geotechnical aspects of the study area as well as the environmental conditions to which this area may be exposed, as such factors have a direct influence on the design of engineering projects. In an assessment carried out by the Mineral Resources Research Company - CPRM, in 2015, four areas at risk of mass movements were identified in the urban area in the municipality of Areia/PB. Thus, the aim of this study was to analyze the soils of the risk areas identified by CPRM in the municipality of Areia - PB from the geotechnical point of view with intent to support studies on the occurrence of mass movements on the slopes. Only two of the four areas proved to be accessible for the study, and these were identified by the initials of the street names such as JL and MM. For this, disturbed and undisturbed samples were collected from these areas, for laboratory tests. Simple recognition in-situ dynamic penetration tests (SPT - Standart Penetration Test) were also carried out in these areas. Soil classification, chemical, physical and microstructural characterization; Crumb test (NBR-13601/96); Direct shear strength (ASTM D3080 / D3080M - 2011); Edometric consolidation test (ASTM D2435 / D2435M - 2011); Collapsibility (Simple Oedometric) and Suction Tests (ASTM D5298 - 16) were carried out. The soils were analyzed in non-flooded and flooded conditions, in order to determine their behavior in the presence of water. Due to field conditions, the soils were identified as residual soils. The soils in both areas were considered collapsible soils, confirmed by numerical methods and laboratory tests: crumb test and collapse test (simple oedometer). The collapse potential of these soils was high, with values between 3 and 13.06. From a geotechnical point of view, the soils proved to be quite compressible, corroborating the high values of initial voids index that they presented. High values of cv were found for the soils, demonstrating that the pore pressures resulting from the shear deformations suffered in the field, probably process very quickly. Very low preconsolidation stresses were also found. The soils, when flooded, showed total loss of the cohesion portion, and their shear strengths showed large decreases, indicating that these soils are unstable, especially when in the presence of water. This fact is of concern, due to the confirmed collapsibility of the soils, combined with the condition of unsaturation that they are in the field and low water retention capacity, indicated by the suction test.