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Thepresent experimental study is a preliminary step towards a newdesign approach for conventional and geosynthetic-reinforced soilretaining walls that takes into account the foundation settlement.2. Test set-upFig. 2 schematically shows the cantilever model retaining wall(CW). The stemof thewall consists of 10 steel blocks onwhich two-component loadcells are attached to their inner sides. These facingblocks are fixed to two steel stiffeners to form a rigid facing. Thebase slab consists of a planar steel block with five two-componentloadcells and a shear key attached to its bottom. This slab plate isrigidly joined to the facing block and the stiffener.Six springs are spaced 260 mm (center-to-center) apart at100 mm below the base slab to simulate a homogeneous yieldingsubgrade. The deformability of the subgrade varied from a ‘non-deformable’ condition simulated using screw jacks to variousdegrees of deformability using three springs with spring constantsof ks ¼ 78.8, 38.6, and 27.7 N/mm, respectively. These springconstants were selected based on targeted maximum subgradesettlements (Smax) of approximately 2.5, 5.0, and 10% of the wallheight (H), respectively. The corresponding values of the subgradereaction coefficient, kv, are 3.6, 1.8, and 1.3 kPa/mm (or MN/m3),respectively, as summarized in Table 1. Values of spring constant kslisted in Table 1 were provided by the manufacturer. Values ofsubgrade reaction modulus kv were calibrated directly on the foundation plate prior to each test. In the calibration, settlements ofthe foundation plate under uniform surcharges were measured.Values of kv were obtained by piding specific overburden pres-sures with corresponding settlements. A consistent value of kv wasobtained for each spring-supported foundation regardless of thechange of surcharge intensity.Four displacement sensors (DB1–DB4) were installed at thelocation of the springs tomeasure the settlement of the foundation;three displacement sensors (DW1–DW3) were installed in front ofthe facing to measure the horizontal displacements of the facing;two displacement sensors (DT1, DT2) were installed tomeasure thesettlement of the crest of the backfill. The two-component loadcell,originally developed by Tani et al. (1983), has been successfullyused in the past (Tatsuoka et al., 1986; Huang and Tatsuoka, 1990; Huang et al., 1999). The small coupling effects of the two-compo-nent loadcell allow the normal and shear loads against facing to beaccurately measured simultaneously. All monitoring devices wereconnected to a data logger (YOKOGAWA DC-10) with a samplingrate of 1 Hz. Fig. 3 shows a schematic view of the geosynthetic-reinforced wall with block facing (GRS-RW). In this case, 10 steelblocks and loadcells, the same as those used for the stemof the CW,were used except that the outside stiffeners and the base slab wereremoved. Steel rods were inserted at the block–block interface toprovide overall shear and bending resistance to simulate a rigidpanel facing condition. Steel rods were placed layer by layer from(1) Active thrust Pa and passive thrust Pp are calculated based on Coulomb’s activeearth and passive pressure coefficients (Ka ¼ 0.245, Kp ¼ 7.914, f ¼ 35 , andfw ¼ 18 ); also assuming passive resistance acting in front of the shear key. (2) Armsof rotation are calculated based on the assumption that resultant lateral earthpressure is at 1/3 of the backfill height. (3) fb ¼ 18 for the base of CWs, and fb ¼ 22 for the base of GRS-RWs; based on results of direct shear tests. right-bottom corner to the left-upper corner, in a rhombic patternwhich is the densest packing of uniform diameter steel rods. Thebackfill has a uniformunit weight (g) of 68.5 kN/m3and a void ratioof 0.103. To build the cantilevermodelwall, a full-heightmodelwallwas first placed on a 100 mm-thick level steel rod foundation, andthe wall was backfilled with uniform diameter steel rods. To buildthe reinforced model wall, 500 mm-high block units of facing wereplaced progressively with the rising of backfill. During construc-tions of all model walls, facings were unpropped源'自^优尔;文,论`文'网]www.youerw.com