Seismic Behavior of Gravel Drains and Compacted Sand Piles using ...

Figure 15. Foundation settlements observed in different tests
In all of the tests regarding the ten second shaking period, most of the foundation settlements occurred during shaking,
and a smaller portion of the total settlement was caused by post-shaking soil reconsolidation due to excess pore water
pressure dissipation. The less efficiency of gravel drains can be realized by comparing these two phenomena that excess
pore water pressure was reduced mostly after shaking and most of the settlement occurred during shaking. However,
more recently, gravel drains have been used to reduce post-earthquake settlements resulting from soil consolidation due
to excess pore pressure dissipation and secondary liquefaction (EERC, 1997).
NUMERICAL RESULTS
The numerical analysis presented in figures 16-18 illustrate that the numerical method was only able to predict the excess
pore pressure ratio correctly in test O. In the other tests using gravel drains and compacted sand piles, the computed
excess pore pressure ratios were much smaller than the measured values. However the trends in each test were predicted
correctly i.e. the excess pore pressure ratios in deeper layers were larger than those in shallower layers.