But for triple stratum foundation, if the topsand layer is relatively thin, piping is vertical. The damage zones are large in width and depth that expand to the sand layer and gravel layer.
The sand falls from the top of the sand glasses to the bottom.
沙子从沙漏的顶部落到底部。
3
Relentless winds have scored fine lines into the top of a dune and swept sand into a mangrove forest, smothering trees that are now reduced to denuded trunks.