Using slippage theory to analyze shear behavior of loop-formed fiber reinforced soil composites

Abstract

Since composite structures with soft-material matrix do not have adequate pullout resistance with flat-type reinforcements such as fibers, there are increasing cases where reinforcements with passive resistance are used in conjunction. So, loopformed polyethylene fibers were used to reinforce soil against shear loading. Afterward, shear behavior of both fiber and loop-formed fiber-reinforced soil composite samples was modeled by using ''force-equilibrium method'' and ''slippage theory'' of short fiber composites. The proposed model indicated that both fiber parameters and ambient conditions determine shear strength of a fiber-soil composite. In the next step, a set of laboratory direct shear tests was performed on different samples including neat soil, loop-formed fiber and fiber-reinforced treatments. Thus, it was found that the performance of polyethylene looped fibers in shear strength improvement of soil composite is more than that of the ordinary polyethylene fibers. In addition, a novel apparatus based on fiber pullout test was designed to determine the interfacial shear stress between fiber and soil. Finally, an artificial neural network technique and least square method were used to calculate ''fiber reinforcing amplitude'' and ''slippage ratio'', as input parameters required for the model. Consequently, both the proposed models and established artificial neural network adequately predicted shear behavior of loop-formed fiber and fiber reinforced soil composite.

Shear modeling of polypropylene-fiber-reinforced soil composite using electrical conductivity contour technique

“…Randomly distributed fiber-reinforced soils have recently attracted increasing attention in geotechnical engineering for the second time [1,2]. Therefore, it is emphasized that short fiber composite soil is still a relatively new technique in geotechnical projects as a mimics of the past [3].…”

Micromechanical analysis of loop-formed fiber-reinforced soil composite

“…At this stage it can be concluded that pullout resistance of loop-formed fibers has two major components: (a) the friction between soil matrix and vertical elements of looped fiber (the fiber effect) and (b) shear resistance of soil matrix within the loop (the loop effect). Therefore, the total improvement in shear strength of soil composite (ÁS t ) can be written in the following format [5]…”

“…A hole (D = 4 mm) was entrenched on the mold, 15 mm above the horizon. More details can be found in the study of Hejazi et al [5]. On the base of optimum moisture content (OMC) (13.82%), the soil should be statically compacted in the mold to fill 30 mm of the mold.…”

“…The contribution of the fibers has been typically quantified by an equivalent friction angle and cohesion of soil [2]. Therefore, composite models have been proposed by several investigators including mechanistic models [3][4][5], a statistical model [6], and an energy-based limit analysis model [7].…”

“…On the other hand, since composite structures with soft-material matrix do not have adequate pullout resistance with flat-type reinforcements such as fibers, there are increasing cases where reinforcements with passive resistance are used in conjunction [5,19]. Therefore, in this research, loop-formed fiber is introduced as a novel reinforcement method for soil composites instead of ordinary fibers.…”