gravel bed

基本解释

Whenever they heard his tires crunch on the gravel driveway they would scramble to hide under their beds.
只要一听到他的轮胎碾过车道上的碎石路他们就会赶紧爬到他们的床下躲起来。
The cool, clear waters with loose gravel beds hold some 2, 000 bull trout nests, among the highest concentration in the world.
凉爽清澈的河水，还有松散的碎石河床拥有2000外欧鳟巢穴，是世界上欧鳟巢穴最密集的地方。
The tools were located in a series of gravel, sand, and mudstone beds and included picklike tools, basic hand axes, and broken pieces of stone left behind in the tool-making process.
这些工具遗迹位于一系列的砾石、沙滩和泥岩床上，包括类似镐的工具、基本手持工具和在工具制造过程中残留的碎石片等。

砾石层
After the survey of gravel beds,we know the area and the age of the two gravel beds,the ingredient,granularity,orientation of the gravels.
通过对砾石层的调查,了解其分布的范围、分析了砾石的成分、粒度、砾向、形成年代。