Calculators for grouting work
These give planning estimates from the numbers you enter. Each one shows its formula and the assumptions behind it, so you can check the working before you use a result.
Polyurethane (PU) grouting is our main line, so the PU calculators come first; cement grout and a unit converter are further down. Metric units throughout. The results open after a one-time email check, and the numbers you type stay in your browser.
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Calculator 1 of 8
PU grout mix and quantity
Use it for the parts of a polyurethane (PU) grout, two-component or single-component with an accelerator, and the resin and packs for a grouting job.
How this is worked out
Formula
fA = a / (a + b), fB = b / (a + b)ρ = fA × ρA + fB × ρBRatio by mass = 100 : 100 × (b × ρB) / (a × ρA)One pack of A: VA = MA / ρA, VB = VA × b / a, mixed = VA + VBV = groups × holes × length × take × (1 + waste) (holes)V = points × take per point × (1 + waste) (injection points)V = volume needed × (1 + waste) (known volume)Part A = V × fA × ρA, Part B = V × fB × ρB (kg)Packs of each part = mass / pack size, rounded up- a, b
- parts of A and B by volume. A single-component resin is worked as a = 100 parts of resin to b = the accelerator dose in per cent
- ρA, ρB
- densities of the two parts, kg/L
- ρ
- density of the mixed resin, kg/L
- MA
- mass of one pack of Part A, or of the resin, kg
- V
- mixed resin, litres
- waste
- as a fraction: 10 % is 0.10
If the data sheet gives the mix ratio by mass, divide each part by its density to get the ratio by volume. For example, 100 : 120 by mass, with densities of 1.0 and 1.2 kg/L, is 100 : 100 by volume, or 1 : 1.
Assumptions
- Mix ratios, densities and pack sizes come from the product data sheet. The values shown are a worked example, not the figures for a particular product.
- The volumes of the parts add up when they are mixed. All volumes are of liquid resin, before any foaming: for foam filling a void, use the void filling calculator.
- The take must come from trials on this site. With water-reactive resins it can vary widely from hole to hole.
- Each part is rounded up to whole packs. Trials, flushing and stoppages need more.
Calculator 2 of 8
Void or annulus filling with expanding PU
Use it for estimating the resin to fill a void, a cavity or an annulus with expanding polyurethane foam.
How this is worked out
Formula
V = L × W × H (rectangular void)V = π / 4 × (D² − d²) × length (annulus)Effective expansion = E × cResin (litres) = V (litres) / (E × c) × (1 + waste)Mass (kg) = resin (litres) × density (kg/L)- E
- free-rise expansion ratio from the product data sheet
- c
- confinement factor, usually 0.3 to 1.0
- V
- void volume; 1 m³ is 1,000 litres
Confinement reduces expansion. Foam rising freely in a cup reaches its full free-rise volume. Foam pushing against the ground, the walls of a closed void or water pressure does not, so its effective expansion is E × c. Use c close to 1 where the foam can rise freely, and lower values where it is closed in or working against water.
Assumptions
- E is the free-rise figure from the product data sheet. Choose c from trials or experience: 0.8 is a starting value, not a rule.
- The void is taken as empty. Water or loose material in it changes the result, and water-reactive resins react with the water they meet.
- Foam lost into joints, open ground or drains is not included. Allow for it in the waste.
Calculator 3 of 8
Crack injection with drilled packers
Use it for setting out drilled packers along a crack in concrete or masonry, and estimating the resin.
How this is worked out
Formula
N = ⌈L / s⌉ + 1a = (t / 2) / tan θℓ = (t / 2) / sin θVcrack = L × t × wVholes = N × (π d² / 4) × ℓResin = (Vcrack + Vholes) × (1 + waste)- ⌈ ⌉
- round up to a whole number
- a
- distance of the hole from the crack, measured along the face
- ℓ
- length of the hole from the face to where it crosses the crack, at half the thickness
Assumptions
- Set the packers on alternate sides of the crack, so that neighbouring holes cross it from opposite sides.
- The crack runs square to the face, through the full thickness, at the width measured on the face. Most cracks narrow with depth, so the crack volume errs on the high side.
- Each hole is counted full of resin. The packer takes up part of it.
- Resin lost through the face, into voids or into other cracks is not included. Seal the face where needed and allow for losses in the waste.
Calculator 4 of 8
Injection holes under a footing or slab
Use it for setting out inclined holes from outside a footing or slab, to reach the ground under its centre.
How this is worked out
Formula
x = (H + z) / tan θ − t / 2L = (H + z) / sin θclearance below the edge = z − (t / 2) × tan θsteepest angle beneath the footing = atan(2z / t)- x
- from the footing face to where the hole starts, on the ground
- clearance
- depth of the hole below the underside where it passes the footing face
Assumptions
- The hole starts on the ground, in a vertical plane at right angles to the footing face, and is aimed at the centre line.
- The ground and the underside of the footing are level.
- If x is negative, the hole would start inside the footprint: use a flatter angle, or drill through the slab.
- If the clearance is negative, the hole passes through the edge of the footing rather than beneath it.
- Drilling deviation is not included. Check the alignment of long holes, and locate buried services before drilling.
Calculator 5 of 8
Permeation grouting volume
Use it for estimating the grout needed to permeate a block of soil, or a set of grouted columns.
How this is worked out
Formula
Vsoil = L × W × D (block)Vsoil = N × π × r² × h (columns)Vgrout = Vsoil × n × α × (1 + waste)- n
- porosity: volume of the pores divided by the total volume
- α
- filling ratio: share of the pores the grout fills
- waste
- as a fraction: 10 % is 0.10
Assumptions
- Porosity must come from site data, such as laboratory tests on samples from the ground investigation. The answer changes in direct proportion to n.
- The grout fills a share α of the pores and stays inside the treated volume. Losses go in the waste allowance.
- Columns are counted as separate cylinders. Where they overlap, the overlap is counted twice: use a block for the whole treated zone instead.
- This does not check whether the ground will take the grout. That depends on the grain size of the soil and on the grout.
Calculator 6 of 8
Packer test: Lugeon value
Use it for turning a water pressure (packer) test reading into a Lugeon value, an indicative class and a rough permeability.
How this is worked out
Formula
Lu = (Q / L) × (10 / P)k ≈ Lu × 1.3 × 10⁻⁷ m/s (approximation)P = Pg + 0.0981 × h − Pf- Q
- water take, L/min
- L
- length of the test section, m
- P
- effective pressure at the middle of the section, bar
- Pg
- gauge pressure, bar
- h
- height of water in metres from the gauge down to the groundwater level, or to the middle of the section if the section is above the groundwater; each metre of water adds 0.0981 bar
- Pf
- friction loss in the pipes and the packer at this flow, from a calibration, bar
Assumptions
- 1 Lu is a water take of 1 litre per minute, per metre of test section, at an effective pressure of 10 bar.
- One pressure stage at a time. In a five-stage test, work out Lu for each stage and choose the value to report from the pattern of the stages, as set out by Houlsby (1976).
- The flow is steady when it is read.
- k assumes laminar flow through uniform rock around the hole. Treat it as an order of magnitude, not a design value.
- The classes follow Quiñones-Rozo (2010) and are indicative only.
Calculator 7 of 8
Cement grout mix and quantity
Use it for the yield, water and density of a neat cement grout, and the cement for a grouting campaign.
How this is worked out
Formula
Yield per bag (litres) = bag × (1 / RD + r)Bags per m³ = 1000 / yield per bagWater per bag (litres) = bag × rDensity (kg/L) ≈ (1 + r) / (1 / RD + r)Grout (litres) = groups × holes × length × take × (1 + waste)Bags = grout / yield per bag, rounded up- r
- water-cement ratio by mass
- RD
- relative density (specific gravity) of the cement
- bag
- bag mass, kg
Assumptions
- Neat cement and water only: no bleed, no entrapped air and no additives. Thin mixes bleed, so less grout sets than is mixed.
- Water is taken as 1 kg per litre.
- The take per metre must come from trial holes on this site. It can vary widely from hole to hole.
- Bags are rounded up to whole bags. Trials, testing and stoppages need more.
Calculator 8 of 8
Unit converter
Use it for converting the pressure, flow and volume units found on gauges, pumps and data sheets.
How this is worked out
Formula
1 bar = 100 kPa = 0.1 MPa1 psi = 0.0689476 bar1 kg/cm² = 0.980665 bar1 m of water = 0.0980665 bar1 L/s = 60 L/min1 m³/h = 1000 / 60 = 16.6667 L/min1 US gal = 3.78541 litres1 imperial gal = 4.54609 litresAssumptions
- kg/cm² means kilogram-force per square centimetre, the unit on many pressure gauges.
- Metres of water assumes water at 1,000 kg/m³ and standard gravity.
- Results are shown to six significant figures.
Before you use a result
Planning estimates, not a design
These calculators give planning estimates from the numbers you enter. They are not a design. Ground, water and materials vary from site to site, and every treatment we carry out is designed by our engineers from site data and set out in a method statement. Check any result before you rely on it.
Planning a grouting job?
Send us your numbers and what you are trying to treat. An engineer reviews them and replies with the next step.