Definition - What does Thrust Block mean?
A thrust block can be defined as a structural member that is installed at the rear of the launching shaft for the purpose of transmitting the horizontal force transmitted from the pipe jacks to the surrounding soil.
Pipe ramming, pipe jacking and other methods of trenchless installation utilize hydraulic or pneumatic thrust force to drive casings into the ground. Thrust blocks ensure that the jacking force is evenly distributed to the ground.
Trenchlesspedia explains Thrust Block
The jacking system at the launching shaft is aligned and mounted on tracks. The drive shaft consists of a stable foundation and adequate thrust block. The design of the shaft is important in the jacking process because a misaligned track can cause the bore to deviate. The foundation supports the track so that the machine has sufficient traction to move forward and back without any vertical movement.
The horizontal jacking force from the tracks is transmitted to the thrust block and distributes the jacking force over the surrounding soil, such that it does not exceed the allowable compressive strength of the soil.
An unstable thrust block can compromise the accuracy and integrity of the borehole.