back cavity造句

• ( 3 ) some destroy is likely to occur to existing tunnel before new construction , that is to say , the tunnel perhaps holds some flaw , therefore , a structure mechanics method is used in this thesis to analyze the safety of existing tunnel vvhich is under the condition of back cavity and insufficient thickness
  ( 3 ) 、在邻近隧道施工之前，既有隧道可能已经受到一定程度的破坏，既有隧道可能存在各种缺陷，通过结构力学计算，分析了有空洞存在或隧道衬砌结构厚度不够时隧道安全性。