Once a site has been established for pipe jacking, and the alignment of the auger boring machine has been set, the installation of the first casing into the ground is called collaring. Initial torque settings must be reduced in order to minimise any disturbance to the alignment as the first casing slowly penetrates the ground. One of the key purposes of collaring is to ensure the installation is started on the correct trajectory.
Trenchlesspedia Explains Collaring
In a pipe jacking trenchless installation, where directional control is limited during the bore, it is vital that the start of the bore is accurately aligned to the design trajectory. The installation of the first casing (called collaring) is the most critical step where this is controlled. If an alignment deviation is found during or after collaring, corrections will have to be made, and in severe cases the collaring may have to be redone. Once collaring is complete, the next casing is lowered into position and both the casings and augers are aligned in order to keep the installation on the desired trajectory.