1. Foundation engineering: down-the-hole drilling rigs are widely used in the field of foundation engineering. They are used to drill down-holes or drive pilings to support the foundations of buildings or other structures. Down-the-hole drilling rigs can be used in foundation engineering projects such as pile foundations, cast-in-place piles, and caps.

2. Bridge construction: In bridge construction, down-the-hole drilling rigs are often used for drilling and piling of pier foundations. They can be used to drill deep holes, install caps or pile foundations, and ensure the stability and safety of bridges.

3. Tunnel engineering: down-the-hole drilling rigs also have important applications in tunnel engineering. They can be used for drilling down-holes, installing support structures or underground curing piles to enhance the stability and safety of tunnels.

4. Port and wharf construction: Down-the-hole drilling rigs are widely used in the basic engineering of ports and wharves. They can be used for drilled pile foundations, rock-cured piles and more to support ship berthing facilities, retaining walls and wharf equipment.

5. Infrastructure construction: Down-the-hole drilling rigs are also used in other infrastructure construction projects. For example, in the basic engineering of highways, railways, airports, large industrial facilities, etc., down-the-hole drilling rigs can be used for piling, drilling foundation holes, etc.