从下面支撑 meaning in Chinese

underlay

I spar d no pains indeed , in this piece of fruitless toil , and spent , i think , three or four weeks about it ; at last finding it impossible to heave it up with my little strength , i fell to digging away the sand , to undermine it , and so to make it fall down , setting pieces of wood to thrust and guide it right in the fall
我不遗余力去干这件工作，最后只是白费心思和力气，却浪费了我整整三四个星期的时间。后来，我终于意识到，我的力气是微不足道的，根本不可能把小艇抬起。于是，我不得不另想办法，着手挖小艇下面的沙子，想把下面挖空后让小艇自己落下去同时，用一些木头从下面支撑着，让小艇落下来时翻个身。