2.衔接词的添加 E.g.2 Running sand and loose gravel or silt,which are practically cohesionless and which cannot be safely and efficiently by ordinary soft-ground tunneling techniques,can be handled by the use of shield,usually working in free air. 流沙、散砾石或淤泥，由于本身无任何黏着力，而 且又不能采用通常的软土层隧道挖掘技术进行安 全有效的开挖，因而只能采用盾构挖掘，并且通 常要在通风条件下进行。2. 衔接词的添加 E.g.2 Running sand and loose gravel or silt, which are practically cohesionless and which cannot be safely and efficiently by ordinary soft-ground tunneling techniques, can be handled by the use of shield, usually working in free air. 流沙、散砾石或淤泥，由于本身无任何黏着力，而 且又不能采用通常的软土层隧道挖掘技术进行安 全有效的开挖，因而只能采用盾构挖掘，并且通 常要在通风条件下进行