Desenvolvimento de uma placa helicoidal com capacidade de medida de poro-pressão, para o estudo do comportamento tensão-deformação dos solos.

Abstract

The present work consists of the development of a helical plate equipped with a pressure transducer, for the study of the geotechnical parameters of soft clays. The analysis of some alternatives related to constructive aspects of the equipment, proved to be technically feasible to incorporate a pressure transducer to the helical plate. For driving the helical plate into the ground and carrying out the test, a test driving and reaction system was also developed. The developed equipment was tested and, helical plate tests were performed in a deposit of cohesive, soft soil. The studied soil is located in a mangrove region in the city of João Pessoa, state of Paraíba. Helical plate tests were performed at 1.0m depth intervals along the sub-soil profile. The maximum depth reached in each drill hole was 14m. The tests were performed on 5 drillholes. At each depth, cyclic loading tests were performed with at least two loading cycles. Each loading curve was applied in 10 loading stages. After the introduction of the helical plate in the test depth, tests were carried out to dissipate the excess pore pressure generated by the crimping of the plate. Also, during the execution of the helical plate test, the variation of the pore - pressure with time. This methodology allowed obtaining the load-settlement curve of the test, both in terms of total stress and in terms of effective stress. Theoretical analyzes, based on the theory of elasticity, provide estimates of the undrained and drained deformation modules. The limit load or the breaking load of the test can be of the load-relay curve of the test and be used to assess the shear strength, not drained from the soil. In turn, the curve of recording the variation of settlements with time, at each stage of the test, allows estimating the "in situ" properties of densification. The developed equipment proved to be adequate and efficient for carrying out helical plate tests in soft, cohesive soils. The incorporation of a pressure transducer to the helical plate, proved effective in the study of the stress - deformation behavior, in terms of effective stress, as well as in "in situ" assessment of the density characteristics of the soil deposit.