Which trenchless method uses a bore and casing to install a conduit under obstacles?

• A. Jack and bore
• B. Auger bore
• C. Missile bore
• D. Impact moling

Answer: (A)

This question tests understanding of trenchless methods that place a conduit under an obstacle by creating a guided bore and protecting the path with a casing. Jack and bore uses a boring machine launched from a pit to drill a controlled bore beneath the obstacle, and a steel casing is installed along that bore path. The conduit is then pulled through the casing, keeping the bore path stable and shielding it from surface loads. This combination—bore plus protective casing—is exactly what allows a conduit to pass under roads, railways, or bodies of water with minimal surface disruption while maintaining the integrity of the underground path.

Other methods don’t use a casing in the bore itself. An auger bore relies on an auger to create the bore and pull the pipe but typically doesn’t deploy a protective casing along the path. A missile bore uses a projectile to push through the ground and seldom involves installing a casing for a long, guided run. Impact moling drives a hammering tool through the soil to create a bore for pulling in a conduit, also without installing a continuous casing.