Filling cavities in the ground to protect structures.
Grouting is always injected by drilling, often using devices to control the flow of grout into the soil (injection tubes, obturator bags, “tubes à manchettes”, etc.)
Underground excavation has always provided the broadest scope of applications for impermeability and consolidation grouting. The grouting techniques used vary widely depending on the desired end result and soil type.
Tunnel construction work is very often accompanied by a range of different grouting types. They can be used – for example – to reduce the permeability of a working face (progress treatment), treat water ingress by grouting cracks in the rock, reduce surface settlement as a result of tunnel construction (compensation grouting) or to fill voids in the outer surfaces of tunnel segment assembly.
Grouting also has a role to play in soil improvement. Solid grouting is used to consolidate granular soils by mortar injection to reduce the void index.
Grouting is also widely used to create hydraulic barriers, for a slab construction, for example, a grouted cut-off at the foot of a diaphragm wall and an impermeable base level to limit pumping flows when excavating at extreme depths.
It is also used very frequently in dam construction and maintenance to consolidate the dam core or slopes, or for cut-off walls, for example.
Grouting can also be used to protect structures. Examples of this application include safety work to old mine shafts and the galleries of redundant underground quarries, and filling karstic and gypsum dissolution voids. It is also frequently used to consolidate old masonry walls.
Lastly, grouting techniques are essential tools for the securing of anchor bolts and micropiles.
It is an adaptable solution that can be used with all types of soil
The range of products and techniques available is very wide
The processes can be used for impermeability treatment, consolidation, reinforcement or even the protection of existing structures
The technique is fully compatible with the observational method
What are the different types of grouting and how are they used?
The scope of applications for grouting is extremely wide. So for the purposes of example, we can make a distinction between:
The “tube à manchettes” is a tube with a smooth internal surface and with perforations every 30 to 40cm. These perforations are covered by rubber sleeves, called «manchettes», which act as non return valves. The tube is sealed into the grout hole with a weak bentonite-cement slurry (the sleeve grout) to prevent the subsequent grout from travelling along the annular space.
When grouting into rock, the universally accepted method is called “split hole grouting”, which begins with primary drillings spaced at fairly wide intervals, followed by intermediate drillings (secondary, tertiary or more) to create an increasingly tight-knit matrix of drillings.
Grout is injected into alluvial soils using “tube à manchettes”. This is usually a two-phase process: the first involving injection of a bentonite/cement grout to fill the coarse grain size, and the second using a more penetrative grout (liquid or ultra-fine suspension grout). The main criterion is the quantity of grout needed to provide optimum filling of soil porosity.
Soletanche formed its first grout curtain on Morocco’s El Kansera dam in 1927