【正文】 e ?eld and laboratory: (a,b) piles in the reclaimed island of Kobe during the 1995 Kobe earthquake (after Refs. [2,5])。 (c,d) piles for the Struve Slough Crossing during the 1989 Loma Prieta earthquake ((c) after [2] and (d) photographed by H. G. Wilshire)。 (e) gap observed in shaking table test (after [11])。 and (f) gap observed in shaking table test (after [2]).Fig. 2. (a) A photograph of the soil–pile–structure system used。 (b) an elevated side viewof the system showing the sizes and the laminated soil tank。 and (c) crosssections used for piles and columns, and for constructing the laminar frame of the tank.To simulate the shaking of soil in the free ?eld, a rectangular minated soil tank is constructed by stacking up 32 laminar ctangular steel frames made by welding four rectangular hollow ctions of together (see Fig. 2(c)). The minar rectangular frame has an internal size of . To duce the friction and allow sliding between adjacent frames, two 1mmthick layers of Te?on (or polytetra?uoroethylene) are glued to the top and bottom of each steel frame section. The frictional coef?cient between two Te?on surfaces is found equal to . The height of the soil tank is about . To ensure the overall sliding stability, the bottom frame section is welded to a bottom steel plate of 12mm thickNess, on which another threedimensional (3D) steel box frame with cross bracing is constructed to limit the maximum translation of the laminated soil tank, as shown in Fig. 2(a). This box frame also provides a reference for measuring the horizontal distance of the soil tank at various levels (see Fig. 3).Four concrete piles are cast independently using a template of PVC pipe of 100mm in diameter. The piles are long, which gives a slenderness ratio of the piles as 17. The Young’s modulus, Poisson ratio and the 28day cube strength of the concrete are , , and , respectively. The reinforcement in the pile consists of eight vertical mild steel bars of diameter 6mm (or a steel ratio of %). Circular stirrups made of 9mm mild steel with a spacing of 20mm are ?xed to the vertical bars. Eight strain gauges were attached to the vertical steel bars near the top of the piles, shown as S1–S8 in Fig. 3, with a pair of strain gauges is installed on the surfaces of each pile along the shaking direction. After the concrete is cast, eight more strain gauges were installed to the surface of the concrete piles, again on the surface of each pile along the shaking direction (shown as C1–C8 in Fig. 3). The spacing of the piles along the shaking direction is 800mm while the spacing along the transverse direction is 500mm. Therefore, since the spacing for inline shaking piles is larger than six diameters of the pile, the pile–pile interaction can be neglected [16]. The piles are ?xed to the bottom steel plate by a wooden template of 10mm thickNess when soil is put into the laminated soil tank. Thus, the piles can be considered as hinged endbearing piles.Fig. 3. A vertical crosssection showing the piles and soil within the laminated tank with a horizontal crosssection cut at the bottom level of the pile cap. Locations of thestrain gauges for steel bars (S1–S8) and for concrete surfaces (C1–C8), the nine displacement transducers, and the ?ve accelerometers are also showed.The soil used is poorly graded river sand imported from the Mainland China. The D10, D30, D50, and D60 of the sand are about , , , and mm, respectively, with all particles smaller than 1 mm. The speci?c gravity of the sand is . The ?ne content (. particles smaller than mm) is less than %. Therefore, it can be considered as pure sand, 35% coarse (–2 mm), 61% medium (– mm) and 4% ?ne sand (– mm). From the results of seven triaxial tests, the Young’s modulus of the soil is estimated to range from to about 5 MPa depending on the con?ning stress and the strain level. Before the sand is packed into the laminated soil tank, an expansible waterresistant nylon bag is custom made to ?t the size of the soil tank to prevent the loss of soil particles through the joints of the laminated tank. A total of 3622 kg of sand is used to ?ll the laminated tank in 11 layers. When each sublayer is ?lled, an electric hammer of kg is used to pact the soil to a speci?c thickNess of about 154 mm. The hammer is the Kango Type 628 Light Demolition Hammer, and the base of the hammer is a ?at disk of 145 mm diameter. The overall density of the soil is Mg/m3. The ?ll is relatively loose and should resemble the condition of loose hydraulic ?ll found in the reclaimed areas of Hong Kong. The water content of the sand in the laminated shear tank is about 4%, therefore, it can be basically considered dry. Thus, no capillary stress needs to be considered, and the sandy soil can be considered as cohesionless. After the soil is ?lled, a concrete pile cap for all four piles iscast. The size of the pile cap is 1200 mm (length) 194。 800 mm (width) 194。 200 mm (thickNess). Mild steel bars of 4 mm diameter are placed at 20 mm spacing along both the shaking direction and its orthogonal direction, and at both the top and bottom of the cap. The pile cap can, therefore, be considered as rigid.A singlestorey structure made of steel frame is then attached to the pile cap by four tiedown bolts. Two steel plates of 1200 mm (length) 194。 800 mm (width) 194。 20 mm (thickNess) are used as the base and top of the frame structure. Four columns of hollow square section of 90 mm 194。 90 mm 194。 mm are welded to both the upper and lower plates (see Fig. 2(c)). The Young’s modulus, Poisson ratio and yield strength of the mild steel are 206 GPa, , and 215 MPa, respectively. Additional mass of 2 ton is added to the top plate of the structures (see Fig. 2(a)) and the total mass of the structure is 2358 kg. Five accelerometers are installed at various locations of the soil–pile–structure systems, shown as triangles in Fig. 3. The accelerometers a0, a1, a2, ap and as are installed at the surface of the shaking table, at the soil tank at an elevat