Compared comprehensively, enclosed supports are better than non-enclosed supports; supports of square annular shape or Ushape are better than supports of semicircle arch.
Compared comprehensively, enclosed supports are better than non-enclosed supports; supports of square annular shape or Ushape are better than supports of semicircle arch.
综合比较来看，封闭式支架要优于不封闭支架；马蹄形或方环形支架要比半圆拱等支护形式好。