Heaving occurs when the ground ahead of a pipe jack or directional drill is lifted up, causing a bulge on the surface. Heaving can cause damage to existing utility structures above the excavation path. Trenchless technology utilizes methods that excavate under the surface of the earth without the need for excavation.
To prevent problems like heaving, thorough soil investigation should be conducted and appropriate excavating tools should be used.
Trenchlesspedia Explains Heaving
Trenchless installation methods have gained popularity but have become a cause for concern to contractors because of the problem of surface heaving. It can cause damage to sub surface structures such as foundations, and pipelines passing above the path of the excavation, and to surface structures such as pavements.
Factors that contribute to surface heaving include:
- Borehole pressure
- Depth of excavation
- Geotechnical properties
- Downhole tooling
- Drill mud flow
- Annular space between excavation and pipeline
- Backreaming rate
- Excess grouting
During the process of pipe jacking, ground heaving can occur when grout pressure exceeds the overburden pressure and also when loose and highly porous soil is present. The slurry pressure and grout viscosity should be controlled to prevent heaving.