Comparison of Mechanical Properties ofFiber-Reinforced Sand under Triaxial Compressionand Direct Shear

Abstract

This research investigates the behavior of sand reinforced with polypropylene fiber. To do this, 40 direct shear tests and 40 triaxial tests were performed on the coastal beaches of Babolsar, a city in the North of Iran. The effect of parameters such as fiber content, length of fiber and normal or confining pressure on the behavior of Babolsar sand have been studied. In this study, four various fiber contents (0, 0.25, 0.5 and 1 percent), three different lengths of fiber (6, 12 and 18 mm) and four normal or confining pressures (50, 100, 200 and 400 kPa) have been employed. The test results show that fiber inclusion has a significant effect on the behavior of sand. In both direct shear and triaxial tests, the addition of fibers improved shear strength parameters (C, φ), increased peak shear strength and axial strain at failure, and also limited the amount of post-peak reduction in shear resistance. The comparison of the test results revealed that due to better fiber orientation toward the direction of principal tensile strain in triaxial test as compared to direct shear tests, the fiber efficiency and its effect on soil behavior is much more significant in triaxial specimens.

Effect of Polypropylene Fiber on Shear Strength Parameters of Sand

“…Randomly distributed fibers offer strength isotropy and limit potential planes of weakness that can develop in parallel to oriented reinforcement (Yetimoglu and Salbas,) [6]. Noorzad and Ghoreyshi Zarinkolaei [9] performed laboratory triaxial and direct shear tests to determine the static stress-strain response of sands reinforced with discrete randomly distributed fibers. The test results revealed that in both direct shear test and triaxial tests, the addition of fibers improved shear strength parameters and also limited the amount of post-peak reduction in shear resistance.…”

Influence of randomly oriented fibres on shear strength of mineral soils

“…The brittleness index for samples at optimum moisture content was on average 0.03 (soil without the reinforcement), 0.05 (soil with fibres) and from 0.01 to 0.04 (soil with foil stripes). Such low values of the brit-tleness index for non-cohesive soils are also given by, among others, Consoli et al (2002) and Noorzad and Zarinkolaei (2015), whereas for cohesive soils -by The values of shear strength indicate that in most of the tests the addition of the fibre reinforcement increased shear strength and the higher the values of normal stresses, the greater this influence. In case of dry medium sand ( Fig.…”

“…up to 10°) and at the same time -increase cohesion (even up to 100 kPa). Results of the tests carried out byNoorzad and Zarinkolaei (2015) indicated that dispersed reinforcement increases the values of the angle of internal friction and cohesion (up to 8° and 19 kPa, respectively) in case of sand in loose state, which is in line with test results of loose and dense compacted sands obtained byDiambra et al (2010). On the other hand,Anagnostopoulus (2013) showed that in case of moderately compacted and compacted sand the influence of the reinforcement on shear strength is ambigu-Kąt tarcia wewnętrznegoAngle of internal friction, [°]Dodatek zbrojenia Addicitve of reinforcement[%] maximum value -polyolefine fibres residual value -polyolefine fibres maximum value -foil stripes residual value -foil stripes Relation between shear strength parameters of the medium sand and addition of the reinforcement at both moisture contents ous.…”

The Reinforcement of Sand by Fibres with a Non-Uniform Shape

“…Many authors have analyzed the behaviour of soil-fibre composites solely on an experimental basis by introducing so-called improvement factors, which quantify the degree of improvement of certain properties (e.g., shear strength and ductility). Noorzad and Zarinkolaei (2015) conducted a series of 40 triaxial and 40 direct shear tests with polypropylene fibres in fine sand. The fibre lengths, concentrations, and confining stresses were varied throughout the test campaign.…”