建 base course ; base ; grass-roots
grassroots democracy ; local democratic system; community-level democracy ; primary-level democracy ; basic level democracy
systems of community-level self-governance; the system of community-level self-governance ; the system of community-level self-governance ; Community-level self-governance ; the system of people's self-governance at grassroots
基岩是冲积层之下较坚硬的岩石,一般是灰岩、花岗岩、砂岩和页岩等。其表面是致密的黏土层,通常称为假底。当基岩为灰岩时,矿床底板常呈现四凸不平,也称喀斯特底板,使矿床开采困难。