Grouting in Karst Terrain
Grouting in Karst Terrain
(OP)
When grouting in karst terrain (relatively deep depth to bedrock, say 50-ft plus) for the purposes of mititgation
of sinkhole development, what is the most rational methodology for determining maximum grouting pressures and
preventing hydrofracture in clayey soils....assuming no groundwater?
Also, is cap grouting at the bedrock interface the best approach, or should pressure grouting start at rock
and continue to near surface.
of sinkhole development, what is the most rational methodology for determining maximum grouting pressures and
preventing hydrofracture in clayey soils....assuming no groundwater?
Also, is cap grouting at the bedrock interface the best approach, or should pressure grouting start at rock
and continue to near surface.





RE: Grouting in Karst Terrain
RE: Grouting in Karst Terrain
for the purposes of say filling voids; perhaps based on vertical or horizontal earth pressures with
consideration to hydrofracture??
Only thing I can find is broad ranges referenced from past projects.
RE: Grouting in Karst Terrain
1) you let the sikhole develop but you lay your slab on an array of rigid inclusions. The grid will be chosen accordingly with the most probable sinkhole diameter. This approach has already been used in France.
2) you grout. In this case, just like for any void, you start filling the voids with a mortar more than a grout in order to limit quantities. Once this phase is completed you do a pressure grouting phase with Bentonite cement. Don't worry about fracturing the soil, there is no such thing as permeation grouting ! ( see late articles by Cambefort ). Refusal criteria are established just as for any other pressure grouting jobs.
RE: Grouting in Karst Terrain
RE: Grouting in Karst Terrain
How big is the void and where does the void stop .It may be connected to other voids, usually impossible to tell.The volume of grout needed can be unknown.
Is water flowing and how fast. If it is flowing at any more than a crawl, it will wash out the grout.
You can pour anything you like into the hole from regular concrete to fine grout depends on what you want to achieve.
If the ground is full of interconnected voids and you just want to fill a specific hole, you can if necessary fill the void with a fabriform grout bag which will contain the grout flow and form a plug.
In previous projects where you have a lot of water flow our methods are usually to drill 6" or 8 "lined dia holes place a 1" grout tube to the bottom of the void and then fill l with 6" minus rock, then 2 " rock, vibrate it as much possible, then add pea gravel. This mixture will slow the water flow and then you grout from the bottom.
You then fine grout it from the bottom the mixture of rocks will help the grout bond. You can also add some expanders to you grout that will help block smaller voids
Intrusion Prepakt /marineconcrete.com
RE: Grouting in Karst Terrain
Let's say you are at 80 feet below grade; is 10 psi okay, 50 psi, or 500 psi?
RE: Grouting in Karst Terrain
Intrusion Prepakt /marineconcrete.com