短语词组短語clay central core 粘土心牆clay impervious core 粘土防滲牆clay -core gravel sand dam 砂礫石粘土心牆垻clay central core embankment dam 粘土心牆土石垻inclined clay -core wall 粘土斜牆clay sloping core roch -fill dam 粘土斜心牆堆石垻clay core wall 粘土心牆 返回 clay core