The influences of geotextile reinforcement layer numbernon the deformation and strength properties of coarse-grained soil were investigated by using the consolidated-drained triaxial compression tests on the samples with differentn(n=0~3). The experimental results showed that the axial strain at failure increases by 0.91%~2.00% under different confining pressures, with the increment ofnof 1, indicating the improvement of toughness. The geotextile could inhibit the lateral deformation of soil samples. The deformation modulus increased averagely by 5 378 kPa with the increment ofnof 1 under different confining pressures. The reinforcement could increase the volumetric strain at phase transition. Both points at phase transition and at failure with the samencould be fitted by lines inp-qplane. The strength indexes increased with the increase ofngenerally. With respect to the linear indexcand nonlinear indexes such asφ0and Δφ, its relationship withnwas approximately linear, and the internal friction angle increased by 1.75 degrees with the increment ofnof 1. Finally, the index of reinforcement IRwas put forward by considering the description of the quantity of reinforcement conveniently, and the method to obtain IRby triaxial shear test was given. It was found that the relationships between cohesionc, pseudo-cohesion Δc(cohesion increment of reinforced earth) and IRcould be fitted by lines, and with the increment of IRof 1 m-1,cand Δcincreased by 9.1 kPa and 13.5 kPa, respectively. Using this parameter IR, the effect of strength increase to sands, clay and coarse-grained soil under triaxial test was analyzed and summarized. There were significant differences on the cohesion increment among these soils, where thecfor sands, clay and coarse-grained soil increased by 0.07, 0.50 and 8.75 kPa with the increment of IRof 1 m-1. Based on the pseudo-cohesion principle, the relationships betweenc, Δcand IRwere established, which can be used to evaluatecand Δcof reinforced earth directly.
