The test results show that: (1) For low degree of compaction and moderate permeability of soil, sudden-ly landslides will occur at toe of slope due to the seepage of groundwater.

The latter one maintains stable globally with smaller deformation because of the effective reinforcement of piles, although the toe of slope slides locally due to liquefaction of saturated subgrade.

If skiers can traverse a slope on both the little toe edge side of the uphill and the big toe edge side of the downhill ski; they can ski with parallel movements.