ISKRIT / Site investigation & geotechnics / Plate load test
Site investigation & geotechnics
Plate load test calculator: deformation modulus, Ev1 and Ev2
Enter the load steps of a plate bearing test and get the deformation modulus and the modulus of subgrade reaction. Pick the standard first: ASTM D1196 uses the rigid circular plate formula and reports E together with the subgrade reaction k, DIN 18134 fits a second-degree curve to each loading cycle and reports Ev1, Ev2 and their ratio. The pressure-settlement curve is drawn, and the pressure range used for the slope is printed with the result, so the number can be audited.
Data current as of 2026-08-24
Standards
ASTM D1196: rigid circular plate on an elastic half-space, E = (1 − ν²)·(π/4)·D·Δp/Δs, modulus of subgrade reaction k = Δp/Δs, no embedment correction. DIN 18134: Ev = 1.5·r/(a1 + a2·σmax) from the second-degree fit of the loading cycle, with Ev1, Ev2 and the Ev2/Ev1 ratio as the compaction criterion.
Input
Load steps as pressure and settlement pairs, plate diameter, soil type for the Poisson ratio, and the pressure range of the linear segment. For DIN 18134, mark each step with its cycle, 1 or 2.
Output
Deformation modulus, modulus of subgrade reaction, Ev1, Ev2 and Ev2/Ev1, the slope of the chosen segment, and the pressure-settlement curve.
What it does
- Deformation modulus E by the rigid circular plate formula of ASTM D1196
- Modulus of subgrade reaction k for a Winkler foundation model
- Ev1, Ev2 and the Ev2/Ev1 ratio from two loading cycles per DIN 18134
- Least-squares slope over the linear segment you select
- Pressure-settlement curve with the segment used marked on it
- Load steps pasted by hand or imported from a spreadsheet
The tool and the platform
The tool
- Both standards: ASTM D1196 and DIN 18134
- Curve, segment slope and every intermediate value on screen
- Load field tests from Excel, export the schedule to XLSX
- Calculations are stored on the server and reopen next time, company letterhead with signatures
- Works instantly, no sign-up required
ISKRIT·Geo demo
The work of a whole department: roles, history and modules linked together.
- Field tests are tied to the points and boreholes of the site
- Field moduli are compared with laboratory ones for the same unit
- One schedule of field tests across the site
Questions
Which standard should I pick?
ASTM D1196 when you need a deformation modulus or a subgrade reaction for design. DIN 18134 when the test is compaction acceptance on a subgrade or a fill layer, because there the criterion is the Ev2/Ev1 ratio and not the modulus alone.
What does the Ev2/Ev1 ratio mean?
It compares the stiffness of the second loading cycle with the first. A ratio close to 1 means the layer took almost no further compaction under the plate, so it was already compacted. The limiting value belongs to the project specification, and the tool reports the measured ratio rather than a verdict.
Why is there no embedment coefficient?
ASTM D1196 applies none: the formula is written for a plate at the test surface. The tabulated embedment coefficient for a plate at the bottom of a borehole belongs to the Russian GOST 20276 procedure, which is offered on the Russian version of the calculator.
Why does a larger plate give a lower k?
A larger plate stresses a deeper zone, and the deeper material is usually softer than the compacted surface layer. The modulus of subgrade reaction is not a soil property: a value measured on a 300 mm plate cannot be carried over to a 3 m footing without a size correction.
Which steps count as the linear segment?
You set the range by its start and end pressure. The first step is usually left out because it contains seating of the plate, and the last steps are left out once the curve bends into yielding. The range used is printed with the result.