18) Which foundation is adopted when the loose soil extends to a great depth?

19) Which foundation is provided for heavy works at a depth of 12 m to 15 m below the level of standing water surface?

20) Which caisson the ratio of sinking effort to skin friction is maximum?

21) What is the minimum percentage of oxygen concentration in underground air quality for tunnel?

22) What is the maximum noise levels of ventilation fans while measure at the closest point of employee exposure?