subsoil

They embedded the pilings deep into the subsoil.

他把桩打进基土中。

He embedded the pilings deep into the subsoil.

他把桩打进基土中。

Earthworms burrow deep into the subsoil.

钻进底土。

Some movement in the building will occur as it settles into the subsoil.

楼房沉到层土时，楼里就会有动静。

In loessal regions and alluvial valley fills of the western United States, both surface soil and subsoil are commonly friable.

在美国西部黄土区和冲积河谷里，表土和底土一般是容易破碎。