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.An internal friction angle 4 of 35 , according to Coulomb’sfailure criterion, is applicable for the steel rod assembly undera confining pressure equal to the overburden pressure athalf-height of the wall (¼17 kN/m2) based on the plane-strainelement test results reported by Huang et al. (1999). Similarities ofthe mechanical behavior, in terms of ultimate shear strength andstress-strain relationships, between a steel rod assembly andcohesionless soils have been shown experimentally and analyti-cally by Rowe (1962, 1969) and Huang et al. (1999). An internalfriction angle 4 ¼ 35 and steel rod–geotextile reinforcement interface friction angle of 22 ; steel rod–steel plate interface fric-tion angle of 18 were also obtained in direct shear tests, assummarized in Table 2. Note that the steel rod–steel plate interfacefriction angle (¼18 ) is also applicable for the left and rightside-walls of the model frame, and for the base plate above thesprings or jacks. Similar steel rod assemblies have also been used byHuang et al. (2008a,b, 2009) in a series of tilting tests on reinforcedmodel slopes.The woven geotextile shown in Fig. 4a was used as thereinforcing material. The reinforcing material is a polyester multi-filament woven geotextile with an ultimate tensile strength Tf of22.8 kN/m, and a tensile strain at failure 3f of 17.9% based on theresult of wide-width tensile tests, as shown in Fig. 4b and Table 3.Similitude of the working strain of the reinforcing materialbetween the model wall and the prototype wall was examinedprior to the tests. The results show that at the completion of thebackfill and at the completion of surcharge, working strains in thelowest reinforcement layer were 3 and 5%, respectively. Theseworking strains of reinforcement fall within the range that iscommonly used in the design of full-scale reinforced soil walls.Strain gages were attached to three positions (25, 125, and 225 mmfrom the facing) of each reinforcement sheet. The present studyfocuses on the comparative behavior of conventional cantileverwalls and geosynthetic-reinforced walls with a rigid facing; rein-forcement strain measurements and their discussion are reportedelsewhere. A total of five layers of reinforcement at the depths,zi ¼ 0.1, 0.2, 0.3, 0.4, and 0.5 m, respectively, from the crest of thewall were placed during the bottom-up backfilling phase. Thevertical spacing of the reinforcing sheet, Sv ¼ 0.1 mwhich simulatesSv ¼ 0.4 m in a 2 m-high prototype wall, is consistent with thedesign practice of geosynthetic-reinforced soil retaining walls with a rigid panel facing (Japan Railway Technical Research Institute,JRTRI, 1992), in which an Sv of 0.3–0.5 m is commonly used. Allreinforcing layers were glued to the block–block interface tosimulate the very high connection strength condition used for RRRwalls. The GRS-RW model had a wall height H of 500 mm. For CW,a base slab with a thickness of 50 mm was included in the stabilitycalculations. Therefore, the CW has a total wall height Ht of555 mm. The model walls were designed based on the followingrequirements:(1) Thewall configurations are similar to those adopted in practice.(2) External stability of the wall is controlled by a similar failuremode, such as sliding or overturning, with a similar safetyfactor.(3) Internal failures of the CW and GRS-RW, such as the shearfailure of the structural component of CW, the pull-outand breakage of reinforcement, and the connection failure ofGRS-RW, are prevented.Based on the above requirements, a CWwith B/H ¼ 0.6 (B, widthof the wall base; H, height of backfill) and a GRS-RW withB/H ¼ 0.73 were built. Both CW and GRS-RW were controlled bysliding failure, with similar safety factors against sliding failure ofFs ¼ 2.98 and 2.90 under q ¼ 0 for CW and GRS-RW, respectively;Fs ¼ 1.68 and 1.52 under q ¼ 17 kN/m2for CW and GRS-RW,respectively, as summarized in Table 4. Stability analyses for CWareschematically shown in Fig. 5a, which was reported in detail byHuang and Luo (2009). Stability analyses are based on Coulomb’sactive thrust on the vertical line through the heel of CW (as shownin Fig. 5a), or on the vertical line delineating the reinforced zone(as schematically shown in Fig. 5b). For both CW and GRS-RW,Coulomb’s Ka ¼ 0.245 (using an internal friction angle of f ¼ 35 ,fw ¼ 18 ; fw, wall-backfill interface friction angle, as summarizedin Table 2) is used. Awall base-foundation friction angle of fb ¼ 18 for CW and a reinforcement-foundation interface friction angle offb ¼ 22 for GRS-RW were used in the stability analysis to obtainthe factor of safety against lateral sliding (Fs).