| dc.description.abstract | This study considers the building′s performance at liquefaction sites and when using the centrifuge at National Central University. Six experiments are tested wherein the uniform liquefiable sand with 55% of relative density. Two kinds of foundations (shallow and pile foundations) with different widths and lengths were placed with the same contact pressure of 71 kPa. The large foundation (Foundation L) was 10.0 meters length and 6.8 meters width (prototype). The small foundation (Foundation S) was 6.8 meters length and 4.8 meters width (prototype). Furthermore, this study employs a cone penetration test to assess liquefaction-induced settlements (CPT). A simplified process for establishing the probability of exceeding settlement curve.
The results showed that (1) For the shallow foundation, when the foundation dimensions are larger (1.5 times difference), settlement dramatically decreases to 43% (0.033 m), 31% (0.030 m) and 12% (0.020 m) under the base input motions of 0.08g (AI = 0.4 m/s), 0.17g (AI = 1.7 m/s), and 0.35g (AI = 7.4 m/s). (2) For the shallow foundation, when the foundation dimensions are larger (1.5 times difference), the tilting angle of structure increases by 50%, 12% and 5% under the base input motion of 0.08g (AI = 0.4 m/s), 0.17g (AI = 1.7 m/s), and 0.35g (AI = 7.4 m/s). (3) For the pile foundation, when the foundation dimensions are larger (1.5 times difference), the settlement decreases to 69% (0.051 m), 55% (0.050 m), and 21% (0.034 m) under the base input motion of 0.08g (AI = 0.4 m/s), 0.17g (AI = 1.7 m/s), and 0.35g (AI = 7.4 m/s). (4) For the pile foundation, when the foundation dimensions are larger (1.5 times difference), the tilting angle of structure increases by 30%, 14%, and 8% under the base input motion of 0.08g (AI = 0.4 m/s), 0.17g (AI = 1.7 m/s), and 0.35g (AI = 7.4 m/s). (5) For the small structure, using the pile foundation instead of the shallow foundation reduces settlement by only 5%, 4%, and 3% under the base input motion of 0.08g (AI = 0.4 m/s), 0.17g (AI = 1.7 m/s), and 0.35g (AI = 7.4 m/s). For the large structure, when the pile foundation is used instead of the shallow foundation, settlement reduces by 48%, 38%, and 12% under the base input motion of 0.08g (AI = 0.4 m/s), 0.17g (AI = 1.7 m/s), and 0.35g (AI = 7.4 m/s). (6) During soil liquefaction, the vertical stress increment due to surface loading (∆σ_z) only affected with a depth equal to the foundation width (B). From the back analysis. a modified vertical stress increment due to surface loading curve established, which can be used to estimate the effective overburden pressure in the liquefaction soil layer, meaning that the soil′s effective overburden stress is not zero during liquefaction and retains some residual strength.
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