1. The Flat Dilatometer Test (DMT): and Recent Developments
Design Applications
and Recent Developments
P. Monaco, S. Marchetti & G. Totani
University of L'Aquila, Italy

2. KEY DMT REFERENCES
ORIGINAL PAPER
MARCHETTI S. (1980). In Situ Tests by Flat Dilatometer.
J. Geotech. Engrg. Div. ASCE, 106(GT3),
STANDARDS
ASTM D (2001). Standard Test Method for Performing the Flat Plate Dilatometer.
EUROCODE 7 – Geotechnical Design – Part 2: Ground Investigation and Testing. EN :2007
SOA REPORT
TC16 (2001). The Flat Dilatometer Test (DMT) in Soil Investigations. May 2001, 41 pp. Reprint in Proc. 2nd Int. Conf. on Flat Dilatometer, Washington D.C., 7-48
INTERNET
biblio site (download papers)

3. FLAT DILATOMETER (DMT)
BLADE
FLEXIBLE MEMBRANE

4. GENERAL LAYOUT of DMT  DMT blade  Push rods (e.g. CPT)
Push force provided by penetrometer or drill rig
 DMT blade
 Push rods (e.g. CPT)
 Pneumatic-electrical cable
 Control unit
 Pneumatic cable
 Gas tank
 MEMBRANE EXPANSION
p0 & p1 readings at 20 cm depth intervals

5. SOILS that can be TESTED by DMT
CLAY, SILT, SAND – But can cross through GRAVEL layers  0.5 m
Soils from VERY SOFT to VERY STIFF (upper limit is push capacity of rig)
Clays: Cu = 2-4 to 1000 kPa (marls)
Moduli: up to 400 MPa

6. Basic DMT reduction formulae (TC16 2001)

7. DMT results KD = 2  NC clay ID  M Cu   KD  soil type
  KD 
soil type
(clay, silt, sand)
common use
shape similar to OCR helps understand history of deposit

8. Design using soil parameters
In most cases DMT used to determine common geotechnical design parameters
Experience has shown undrained shear strength Cu and constrained modulus M by DMT generally accurate and dependable for design
Comparisons at several research sites indicate quite good agreement between profiles of Cu and M by DMT and reference values by other tests ( see TC )

9. Comparisons Cu DMT vs. Cu reference
Nash et al. (1992)
AGI (1991)
Research Site Bothkennar (UK)
Research Site
Fucino (Italy)

10. Comparisons MDMT vs. Mreference
M back-calculated
Marchetti et al. (2006)
Lacasse (1986)
M by DMT vs. M back-calculated from local vertical strains measured under Treporti full-scale test embankment (Italy)
M by DMT vs. M by high quality oedometers
Onsøy (Norway)

11. Settlement prediction
No. 1 DMT application
by Boussinesq
Classic linear elastic 1-D approach – or 3-D with E  0.8 MDMT (similar predictions)
Settlement under working loads (Fs  )

12. Summary of comparisons DMT-predicted vs. observed settlements
Large No. of case histories  good agreement for wide range of soil types, settlements, footing sizes
Average ratio DMT-calculated/observed settlement  1.3
Band amplitude (ratio max/min) < i.e. observed settlement within ± 50 % from DMT-predicted
Monaco et al. (2006)

13. Compaction control
Experience suggests DMT well suited to detect BENEFITS of SOIL IMPROVEMENT due to its high sensitivity to changes of stresses/density in soil
Several comparisons of CPT and DMT before/after compaction
Schmertmann et al. (1986), Jendeby (1992)  increase in MDMT after compaction of sand  2 increase in qc (CPT)
Pasqualini & Rosi (1993) ...

14. DMT vs. CPT before/after compaction
MDMT qc
Ratio MDMT /qc before/after compaction of a loose sand fill (Jendeby 1992)

15. Detecting slip surfaces in clay slopes
DMT-KD method  Verify if an OC clay slope contains ACTIVE (or old QUIESCENT) SLIP SURFACES
(Totani et al. 1997)

16. Validation of DMT-KD method
LANDSLIDE "FILIPPONE" (Chieti)
DOCUMENTED SLIP SURFACE
LANDSLIDE "CAVE VECCHIE" (S. Barbara)
DOCUMENTED SLIP SURFACE
(inclinometers)

17. DMT for LIQUEFACTION
Correlations for evaluating Cyclic Resistance Ratio CRR from KD developed in past 2 decades, stimulated by:
Sensitivity of KD to factors known to increase liquefaction resistance: Stress History, prestraining/aging, cementation, structure …
Correlation KD – Relative Density
Correlation KD – In situ State Parameter
Key element supporting well-based CRR-KD correlation: ability of KD to reflect aging in sands (1st order of magnitude influence on liquefaction) + sensitivity of KD to non-textbook OCR crusts in sands

18. Curves for evaluating CRR from KD
(Seed & Idriss 1971 simplified procedure)
Summary + latest version CRR-KD correlation see Monaco et al. (2005 ICSMGE Osaka)
Magnitude M = 7.5 – Clean sand

19. LATERALLY LOADED PILES
DMT for DESIGN of
LATERALLY LOADED PILES
Robertson et al. (1987)
Marchetti et al. (1991)
2 methods recommended for deriving P-y curves for laterally loaded piles from DMT (single pile, 1st time monotonic loading)
Independent validations  2 methods provide similar predictions, in very good agreement with observed full-scale pile behaviour

20. DMT for DESIGN of DIAPHRAGM WALLS
Monaco & Marchetti (2004 – ISC'2 Porto)
Tentative correlation for deriving the coefficient of subgrade reaction Kh for design of multi-propped diaphragm walls from MDMT
Indications on how to select input moduli for FEM analyses (PLAXIS Hardening Soil model) based on MDMT

21. Subgrade compaction control
Bangladesh Subgrade Compaction Case History
90 km Road Rehabilitation Project
MDMT acceptance profile
(max always found at cm)
Acceptance MDMT profile fixed and used as alternative/fast acceptance tool for quality control of subgrade compaction, with only occasional verifications by originally specified methods (Proctor, CBR, plate)

22. Seismic Dilatometer (SDMT)
Combination S + DMT
2 receivers spaced 0.5 m
Vs determined from delay arrival of impulse from 1st to 2nd receiver (same hammer blow)
Signal amplified + digitized at depth
Vs measured every 0.5 m
Hepton 1988
Martin & Mayne 1997, (Georgia Tech, USA)

23. Validation of Vs by SDMT
AGI (1991)
SCPT
Cross Hole
SASW
Comparison of Vs profiles by SDMT and by other tests Fucino research site (Italy)

24. SDMT profiles at the site of Fiumicino (Italy)
SDMT results
Vs (m/s)
SHEAR WAVE
VELOCITY
SDMT profiles at the site of Fiumicino (Italy)
SDMT  accurate and highly repeatable Vs (in addition to usual DMT results)

25. In situ G- decay curves by SDMT
Mayne (2001)
Ishihara (2001)
SDMT  small strain modulus G0 from Vs
working strain modulus MDMT (settlements)
Tentative methods to derive in situ G- curves by SDMT
Two points help in selecting the G- curve

26. SDMT for LIQUEFACTION
SDMT  2 parallel independent evaluations of CRR from VS e KD
(Seed & Idriss 1971 simplified procedure)
CRR from Vs
CRR from KD
Andrus & Stokoe (2000)
Andrus et al. (2004)
Monaco et al. (2005)
ICSMGE Osaka

27. FINAL REMARKS
DMT  quick, simple, economical, highly reproducible in situ test
Executable with a variety of field equipment
Dependable estimates of various design parameters/information
– soil type
– stress state/history
– constrained modulus M
– undrained shear strength Cu in clay
– consolidation/flow parameters
– ...

28. Special thanks to Allan McConnell (IGS)
FINAL REMARKS
Variety of design applications
Most effective vs. common penetration tests when settlements/deformations important for design (e.g. strict specs or need to decide: piles or shallow ?)
SDMT  accurate measurements of Vs (and G0) + usual DMT results – greatly enhances DMT capability
Special thanks to Allan McConnell (IGS)