Boring, Ramming & Jacking Overview

Auger Boring - Method consists of the use a dry rotating auger driven normally through a jacked steel casing. Casing is jacked in as the auger advances. Boring machine typically is placed in a pit on grade with the bore profile and exits into an exit pit. Using a two casing system, some steerage is possible. Method is widely used for road crossings up to 60" in diameter and remains the most cost effective crossing method in many areas. Can be a more expensive option when water table is high, entry or exit pits require sheet-piling or when pits must be excavated in rock.

Wet Boring/Guided Boring - Typically from an entry pit, a boring machine using hollow bore rod excavates using a pressurized jet of water or drilling fluid. A cutting head and dry percussive drill head can also be used. Bore head can be angled and steered by rotating the bore rod. A locating sonde (transmitter) can be placed behind the bore head for guidance. Bore hole can be reamed larger by pulling back a reamer. Method is normally used for smaller diameter, shorter installations. When conducted from the surface, guided boring may be called directional boring.

Directional Boring - Also called horizontal directional drilling or HDD. See Directional Boring Overview for more info.  
Pipe Ramming - Involves the use a pneumatic hammer (impact mole) to drive a steel casing through the ground. Soil is typically excavated from the casing with compressed air, an auger or jetting. With small diameters it is sometimes possible to ram closed-end pipes. This method is frequently used to cross roads, railways, embankments.

Impact Moling - Most commonly used for small diameter lines under sidewalks, driveways and other short crossings, impact moling involves the use of a pneumatic piercing tool which drives itself through the ground by an air driven piston. The friction of the ground on the mole body prevents the mole from being driven backwards. Some types of moles can use different types of heads for various soil types. Mole is typically launched from a pit from a launching cradle. Monitoring equipment can determine the path of the mole.

Pipe Jacking - Pipe Jacking involves the jacking of steel or clay jacking pipe through a bore by means of a hydraulic ram. The ram is braced against a thrust wall/thrust block opposite the bore hole in the drive shaft. Spoil from the bore hole may be excavated by an auger, slurry or conveyor.

Microtunneling is a process by which a remote controlled tunneling machine is driven from a drive shaft to a receiving shaft by means of a hydraulic jack. Tunneling machine is launched from the pit through an entrance ring which isolates the ground from the pit. Excavated soil is carried by a slurry mixture to the surface. Ground pressures are equalized with slurry and jacking pressure. As the tunneling machine is driven forward, jacking pipe is added onto the back of the machine. Steerage is accomplished by means of a laser and hydraulic steering jacks inside the tunneling machine. Microtunneling can be used where grade must be maintained and where the installation is deep. Diameters of 12" up to 12' can be installed.