Road or railway construction method by digging trench to form tunnel - material excavated from front end of trench is used to cover trench further behind to restore ground to its original level, leaving only small part of trench uncovered

摘要

Material excavated from the front end of the trench is used to cover the trench further behind to form the tunnel, whilst essentially restoring the ground height to its original level prior to the road or railway being built. Only a small part of the trench is left uncovered. MECHANICAL ENGINEERING - PREFERRED FEATURES : The tunnel area immediately adjacent to the front end is left open.