Hi I have a compaction grouting project and I would like guidance on the things to observe or record in the field and if possible a form which l can use.
You need to record grout flow volume and pressure at each hole by use of a digital meter on the grout line.Also you should record existing ground elevations and any movement as grout pressure might raise the ground elevations.If pressure is to high the grout will not only compact the ground but startto fracture the ground or rock.
Grouting this way can do some unusual things if you are not wAtching everything.
If there are any buried pipes, conduits, etc. anywhere nearby, look carefully at them. All sewers should have some form of monitoring in case the grout gets in them.
On one of the first such jobs I watched was the raising of a settled area at one end of a long nursing home. After some work was done, grout came out of a basement floor drain AT THE OTHER END OF THE BUILDING.
For Ground Densification purposes here is what you look for;
1. Prior to pumping any grout check the SLUMP. Compaction grout slump should NOT be greater than 3-inch. Higher slump grout will not displace and densify the in-situ soils properly. High slump grout will also travel laterally and potentially case impacts elsewhere outside of the intended improvement zone. Higher grout mobility can result in uncontrolled travel thereby causing a blanketing effect which can cause adverse vertical heave at amazingly low pumping pressures.
2. PUMPING PRESSURE. Does not necessarily need to be digital but does need to be near the point of injection (grout header). Watch for a gradual increase in pumping pressure with continuous pumping at a given depth. Also watch closely this trend of pressure or ground response to grout injection for you may potentially see a sudden drop in pressure that may be attributed to ground fracture. The ground can only be displaced and densified so much until the effective vertical stress is overcome thus causing heave which defeats the purpose of the compaction grouting work.
3. PUMPING RATE. An acceptable pumping rate must not be exceeded. Visualize the ground displacing, time must be given for pore pressures to dissipate. Since time is money Contractors like to force grout in quickly. Simple rule of thumb, for work less than 50-ft in depth the pumping rate should not exceed 3-cft/min. Pumping rate can be discussed and debated in great depth since there are many influencing factors but one factor remains the same, slower is better.
4. GROUT VOLUME. Grout volume should be consistantly recorded in depth intervals of 1 to 2-ft.
5. GROUND HEAVE. Record when ground heave is observed, correlating to depth of injection, pumping rate, stage volume etc.
6. ANY OTHER GENERAL NOTES OR OBSERVATIONS.
A compaction grout field log is just a simple excel spreadsheet that anyone can make. Knowing and understanding the work before you is key.
