Site investigation · In-situ testing
Flat dilatometer (DMT) data reduction calculator
Corrects the A and B readings, then gives the intermediate parameters ID, KD, ED, soil description, constrained modulus and the usual clay or sand correlations.
Standard: Marchetti (1980, 2001) · ID, KD, ED, RM; Marchetti correlations for OCR, K0, cu, φ′
Open the live calculator → All site investigation calculators
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| A reading | 300 | kPa |
| B reading | 700 | kPa |
| Membrane calibration ΔA | 15 | kPa |
| Membrane calibration ΔB | 40 | kPa |
| Gauge zero offset zm | 0 | kPa |
| Test depth | 6 | m |
| Unit weight γ | 18 | kN/m³ |
| Water table depth | 1.5 | m |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| p0 = 1.05(A − zm + ΔA) − 0.05(B − zm − ΔB) | 297.8 | kPa |
| p1 = B − zm − ΔB | 660.0 | kPa |
| Pore pressure | 44.15 | kPa |
| σ′v0 | 63.86 | kPa |
| Material index ID | 1.43 | |
| Horizontal stress index KD | 3.97 | |
| Dilatometer modulus 34.7(p1 − p0) | 12.57 | MPa |
| Soil description | SILT | |
| OCR = (0.5KD)^1.56 (ID < 1.2) | n/a | |
| K0 = (KD/1.5)^0.47 − 0.6 (ID < 1.2) | n/a | |
| cu = 0.22σ′v0(0.5KD)^1.25 (ID < 1.2) | n/a | kPa |
| φ′ = 28 + 14.6logKD − 2.1log²KD (ID > 1.8) | n/a | ° |
| RM by ID | 1.60 | |
| RM (KD > 10 rule, ≥ 0.85) | 1.60 | |
| Constrained modulus M = RM·ED | 20.15 | MPa |
- ✓ Valid reading: p1 > p0 > u0
Method, formulas and assumptions
- p0 = 1.05(A − zm + ΔA) − 0.05(B − zm − ΔB) = 1.05*(300-0+15)-0.05*(700-0-40) = 297.75 kPa
- p1 = B − zm − ΔB = 700-0-40 = 660 kPa
- Pore pressure = 9.81*MAX(0,6-1.5) = 44.145 kPa
- σ′v0 = 18*6-44.145 = 63.855 kPa
- Material index ID = (660-297.75)/(297.75-44.145) = 1.4284
- Horizontal stress index KD = (297.75-44.145)/63.855 = 3.9716
- Dilatometer modulus 34.7(p1 − p0) = 34.7*(660-297.75)/1000 = 12.57 MPa
- Soil description = IF(1.4284<0.6,"CLAY",IF(1.4284<1.8,"SILT","SAND")) = SILT
- OCR = (0.5KD)^1.56 (ID < 1.2) = IF(1.4284<1.2,(0.5*3.9716)^1.56,"n/a") = n/a
- K0 = (KD/1.5)^0.47 − 0.6 (ID < 1.2) = IF(1.4284<1.2,(3.9716/1.5)^0.47-0.6,"n/a") = n/a
- cu = 0.22σ′v0(0.5KD)^1.25 (ID < 1.2) = IF(1.4284<1.2,0.22*63.855*(0.5*3.9716)^1.25,"n/a") = n/a kPa
- φ′ = 28 + 14.6logKD − 2.1log²KD (ID > 1.8) = IF(1.4284>1.8,28+14.6*LOG10(3.9716)-2.1*LOG10(3.9716)^2,"n/a") = n/a °
- RM by ID = IF(1.4284<=0.6,0.14+2.36*LOG10(3.9716),IF(1.4284>=3,0.5+2*LOG10(3.9716),0.14+0.15*(1.4284-0.6)+(2.5-0.14-0.15*(1.4284-0.6))*LOG10(3.9716))) = 1.6034
- RM (KD > 10 rule, ≥ 0.85) = MAX(0.85,IF(3.9716>10,0.32+2.18*LOG10(3.9716),1.6034)) = 1.6034
- Constrained modulus M = RM·ED = 1.6034*12.57 = 20.155 MPa
Related site investigation calculators
- SPT corrections & correlations — Raw N to N60 and (N1)60 with energy, rod, borehole and overburden corrections, and common correlations…
- CPT interpretation (Robertson SBTn) — Normalised cone resistance and friction ratio, Ic, soil behaviour type plotted on the Robertson chart and as…
- DCP to CBR — Penetration per blow by layer and estimated in-situ CBR, plotted with depth.
- Plate load test — Pressure–settlement curve to deformation modulus and modulus of subgrade reaction.
- Ménard pressuremeter: modulus, bearing and settlement — Ménard modulus from two points on the pseudo-elastic part of the test curve, net limit pressure, soil class…
- CPTu dissipation test: ch and kh — Horizontal coefficient of consolidation from the time to 50 % dissipation, with an optional estimate of…
- Borehole log builder — Draws a borehole log from a layer table (base depth, soil type code, SPT N, description) with groundwater…
For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.