永冻层

běi jí yǒng dòng céng

北极永冻层

the permafrost of the North Pole

yǒng dòng céng zhī xià de tǔ rǎng yuè yìng suǒ xū yào de yào shì zhuāng yào liàng yě yuè dà

永冻层之下的土壤越硬，所需要的药室装药量也越大。

The harder the material under the permafrost is, the larger the chamber charge required.