Complete the following sentences using your own ideas and the Word list below

1. Most existing tunnels were driven by the drill and blast method, which cannot escape the risk of...……………………………………………………………..

2. Technological advances in modern tunneling result in …………………………

3. TBMs can be used for soft and rock tunneling because…………………......…

4. Shields can be assembled either in the shop or …………………………………

5. Various geological conditions call for different tunneling techniques because …………………………………………………………………………………