gravel bed

基本解释

Whenever they heard his tires crunch on the gravel driveway they would scramble to hide under their beds.
衹要一聽到他的輪胎碾過車道上的碎石路他們就會趕緊爬到他們的牀下躲起來。
The cool, clear waters with loose gravel beds hold some 2, 000 bull trout nests, among the highest concentration in the world.
涼爽清澈的河水，還有松散的碎石河牀擁有2000外歐鱒巢穴，是世界上歐鱒巢穴最密集的地方。
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.
這些工具遺跡位於一系列的礫石、沙灘和泥巖牀上，包括類似鎬的工具、基本手持工具和在工具制造過程中殘畱的碎石片等。

礫石層
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.
通過對礫石層的調查,了解其分佈的範圍、分析了礫石的成分、粒度、礫曏、形成年代。