Lub hnab ntim cov hnab yas sib xyaw ua ke ntau yam khoom siv nrog cov yam ntxwv sib txawv los txhim kho huab cua permeability, noo noo permeability, roj tsis kam, dej tsis kam thiab tshuaj tsis haum ntawm cov khoom ntim, kom nws tuaj yeem ua si tiv thaiv kab, plua plav pov thawj, tiv thaiv kab mob, los tiv thaiv lub teeb, Nws muaj zoo mechanical zog thiab kev siv tau, thiab muaj zoo luam ntawv thiab zoo nkauj teebmeem.