The sand liquefaction problem has been one of the important topics in soil dynamics and geotechnical earthquake engineering. Based on a project of the Middle Route of South-to-North Water Transfer

physico-mechanical parameters of soil have been obtained through field and laboratory tests. And the dynamic numerical analysis on the liquefied sand foundation of the main canal which has been reinforced by compacted gravel piles is conducted with FLAC3D. The results show that

for the drainage of the compacted gravel piles

the excess pore water pressure and pore pressure ratio in the saturated sand foundation of the main canal bottom have been significantly reduced compared to ones before reinforcement. Monitoring curves of the saturated sand in the bottom of the main canal show that

with the duration of the seismic loading

the peak values of the excess pore water pressure and pore pressure ratio in the saturated sand foundation decrease significantly compared to ones before reinforcement; and the time-history curve declines quickly when to the peak value

which keeps essentially unchanged before reinforcement. For the drainage and compaction effect of the compacted gravel piles

the liquefaction of the sand layers

in the bottom of the main canal

and from the outside platform of the embankment to the bottom of the slope foot

is eliminated effectively. And no liquefaction occurs in the saturated sand foundation of the main canal bottom after reinforcement.