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Base acceleration, excess pore pressure ratio, vertical displacement, and angular distortion time histories measured during the Kobe earthquake motion.
Source publication
This paper presents preliminary results from four centrifuge tests, performed at the University of Colorado Boulder, to evaluate the relative influence of different mitigation mechanisms provided by dense granular columns (DGC) on the seismic performance of embankments founded on liquefiable soil deposits. The first test was designed as the baselin...
Contexts in source publication
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... 3 compares the results among different tests in terms of the time history of accelerations and Arias Intensities as well as response spectra in the center array below the embankment. Figure 4 compares the results in terms of the time history of excess pore pressure ratio (i.e., r u = Δu/σ′ z , where Δu is the excess pore water pressure and σ′ z is the initial vertical effective stress at a given depth) in the center and edge arrays as well as the settlement and angular distortion of the embankment. ...
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... response may be explained by the large excess pore pressure recordings at lower elevations, which in a way, reduced the seismic demand transferred to higher elevations. Figure 4 showed that creating a more uniformly dense deposit in RF-DS led to larger r u values within the lower dense layer of Ottawa sand similar to those measured in Test BS (with no DGCs or densification) and significantly greater than those measured in Tests RF-DR and RF. Even though increased density of the top Ottawa sand layer reduced the extent of softening within that layer, greater pore pressures at lower elevations in Test RF-DS reduced soil's strength and stiffness, de-amplifying highfrequency accelerations that propagated upward toward the embankment. ...
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... though increased density of the top Ottawa sand layer reduced the extent of softening within that layer, greater pore pressures at lower elevations in Test RF-DS reduced soil's strength and stiffness, de-amplifying highfrequency accelerations that propagated upward toward the embankment. Figure 4 also shows the time histories of vertical displacement (settlement) D v recorded at the top and bottom of the embankment along its centerline. Overall, the embankment itself did not experience notable volumetric strains, as it was placed at a very dense initial state. ...
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... the embankment itself did not experience notable volumetric strains, as it was placed at a very dense initial state. As a result, total embankment settlements were almost entirely due to the settlement of the soil deposit below (as shown in Figure 4), which was caused by a combination of volumetric and shear type deformations ( Dashti et al. 2010). DGCs used in Tests RF-DR, RF, and RF-DS were successful in reducing settlements with respect to the unmitigated case, BS, with the common denominator of shear reinforcement. ...
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... quantify changes in the angle of embankment's slope over time, its angular distortion was approximated as the difference in vertical displacements between the edge (D v edge ) and the toe (D v toe ) of the embankment slope, divided by the horizontal distance (d) between those two locations after construction or before shaking. Figure 4 shows the angular distortion time histories experienced by the north and south slopes of the embankment during the Kobe motion. In general, Tests BS and RF-DS showed a non-symmetrical deformation pattern, whereas Tests RF-DR and RF exhibited similar combinations of volumetric and shear deformations at both slopes. ...
