Estudo de grampos em cortinas em solos tropicais na cidade de Goiânia
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2014-08-11
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Universidade Federal de Goiás
Resumo
Retaining structures with nails have been used in recent decades to contain excavation works
in several Brazilian cities, including Goiânia. The nails are made of steel bars inserted in
inclined or horizontal drilling, with small diameter and involved in cement grout, to ensure
the stability of vertical excavations by frictional forces developed in the contact between the
soil and nail. Therefore, it is important to understand this friction to design retaining
structures. There are lots of calculation methods proposed by many authors to design nails and
verify the stability of these structures. The main objective of this work was to review some
calculation methods, conduct pullout tests in the field and laboratory tests with samples taken
in situ, to evaluate calculation methodologies or parameters that best apply to the soil studied
in Goiânia. Among several proposals to estimate the media shear stress in the soil-nail
interface (qs) based on SPT, that showed better results in this paper are those from graph
lower limit proposed by Ortigão e Palmeira (1997), Springer (2006) and a proposal based on
Décourt & Quaresma (1978) to calculate pile lateral friction, using the proper parameter b.
Other propositions based on soil type and parameters of the soil that showed good fits were
Wong (1995) and Juran et al. (1990). The relation between qs and the shear stress of soil (ts)
resulted values between 0,55 and 0,85. Displacement readings were performed during loading
and unloading phase, was observed that for small loads, plastic deformations occured in the
nail, so is recommended in cases of nail’s numerical analyzes adopt elastic-plastic models.
Predictions of nail's elastic deformation, based on piles theory showed good results, however
significant plastic deformation occured in nails. The results of shear tests were compared with
the pullout tests, indicating that the reduction factor of laboratory results is necessary.
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RESENDE, C. Estudo de grampos em cortinas em solos tropicais na cidade de Goiânia. 2014. 124 f. Dissertação (Mestrado em Geotecnia, Estruturas e Construção Civil) - Universidade Federal de Goiás, Goiânia, 2014.