3 Definitions and symbols

3.1 Definitions

The definitions given in this chapter cover only the most important terms involved in geotechnical grouting. Further definitions are given in the glossary in annex B.


bulk filling

fr: injection de comblement

de: Hohlraumverfüllung

bulk filling is the placement of grout with a high particulate content to fill substantial voids


compaction grouting

fr: injection solide

de: Verdichtungsinjektion (Kompaktionsinjektion)

displacement grouting method which aims at forcing a mortar of high internal friction into the soil to compact it without fracturing it


contact grouting

fr: injection de contact

de: Kontaktinjektion

injection of grout into the interface between man-made structures and the ground


displacement grouting

fr: injection avec déplacement des terrains

de: Verdrängungsinjektion

injection of grout into a host medium in such a manner as to deform, compress, or displace the ground


effective pressure

fr: pression effective

de: wirksamer Druck

actual grout pressure acting in the ground


fissure grouting

fr: injection de fissure

de: Kluftinjektion

injection of grout into fissures, joints, fractures and discontinuities, particularly in rock


gravity grouting

fr: injection gravitaire

de: drucklose Verfüllung

grouting under no applied pressure other than the height of grout fluid. Sometimes referred to as tremie grouting



fr: coulis

de: Injektionsgut

pumpable material (suspension, solution, emulsion or mortar), injected into soil or rock, which stiffens and sets with time


grouting pressure

fr: pression d'injection

de: Injektionsdruck

pressure applied during the grouting process and measured at defined locations (usually at the pump or the borehole collar)


hydraulic fracturing (hydraulic fracture, claquage grouting)

fr: fracturation hydraulique (injection de claquage)

de: Hydraulische Rissbildung (Claquage)

fracturing of a ground initiated by the injection of water or grout under a pressure in excess of the local tensile strength and confining pressure; also called hydrofracturing, hydrosplitting, hydrojacking or claquage


penetration grouting

fr: injection de pénétration

de: Eindringinjektion

grout injection of joints or fractures in rock, or pore spaces in soil, without displacing the ground. The term includes permeation (impregnation), fissure and contact grouting


permeation (impregnation) grouting

fr: injection d'imprégnation

de: Poreninjektion (Imprägntion durch Porenverfüllung)

replacement of interstitial water or gas of a porous medium with a grout at injection pressures low enough to prevent displacement


non-displacement grouting

fr: injection sans déplacement des terrains

de: Verdrängungsfreie Injektion (Injektion ohne Baugrundverdrängung)

substitution of the natural interstitial fluid in the accessible existing voids of the ground by a grout or mortar without any significant displacement of the ground. The term includes penetration grouting and bulk filling


stable suspension

fr: suspension stable

de: stabile Suspension

stable suspensions exhibit in 2 hours less than 5 per cent bleeding of clear water at the top of a 1 000 ml cylinder with an internal diameter of 60 mm at a temperature of 20 °C

3.2 Symbols and units

The following symbols and units are used in this standard.

Symbols Denomination Unit
T Temperature [°C]
V Volume injected [m3]
P Injection pressure [Pa]
Q Injection or flow rate [m3/s] or [l/s]
k Intrinsic (absolute) permeability1) [m2]
K Coefficient of hydraulic conductivity [m/s]
i Hydraulic gradient [dimensionless]
d10, d15
D85, D90
Largest particle size of the smallest 10, 15 % of grout
Largest grain size of the smallest 85, 90 % of the medium
t Setting time [s]
Compressive strength
Shear strength
Normal stress
Shear stress
ε Strain [dimensionless]
Shear rate [s–1]
Viscosity (apparent)
[Pa·s], [kg/m·s]
C Cohesion [Pa]
τ0 Yield shear stress [Pa]
ρ Density [kg/m3]
γ Specific or unit weight [kN/m3]
tM Outflow time (Marsh) [s]
R Action radius [m]
1 Pa = 1 N/m2 = 10–5 bar
1) It is common practice in geotechnical engineering to use k for hydraulic conductivity. Nevertheless, this refers to the parameters generally used in rock and fluid mechanics.


4 Information needed

4.1 All information relevant to the execution of the grouting works should be provided with the work specifications.

4.2 The following technical information shall be available on site before the commencement of the works:

  • site conditions and limitations, e.g. size, gradients, access;
  • working restrictions, including any environmental, legal or statutory restrictions;
  • any underground contamination or hazard which could affect the method of execution or the safety of the working environment;
  • design and specifications for the works.

4.3 The following technical information should be available on site before the commencement of the works:

  • geological and geotechnical conditions (see chapter 5);
  • the co-ordinate locations of the site with respect to the national grid;
  • existence, location and conditions of any adjacent structures, e.g. buildings, roads, utilities or services, underground structures and their foundations;
  • any concurrent or subsequent activities which could affect the works (e.g. groundwater extraction or recharge, tunnelling, other deep excavations);
  • any previous experience with grouting or other underground works on or adjacent to the site, or relevant experience in the execution of comparable works under similar conditions;
  • any information relevant for the production of drawings and method statements (where required);
  • any additional requirements for the supervision, monitoring or testing of the works.

4.4 The following aspects shall be established before the commencement of the works and shall be available in written form on site:

  • the requirement, and assignment, for any survey of the condition of adjacent structures, roads, services, etc. to be carried out prior to, during and after the works;
  • specific procedures and criteria for the verification, control and acceptance of the grouting works;
  • the clear division of tasks with respect to the design, execution, interpretation of results and approval of the works.

EN 12715:2000 Execution of special geotechnical work – Grouting