WORKSHOP ON PENETRATION TESTING AND OTHER GEOMECHANICAL ISSUES Pisa 14 June 2016 ROOM F8 CPTU IN UNUSUAL SOILS

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1 WORKSHOP ON PENETRATION TESTING AND OTHER GEOMECHANICAL ISSUES Pisa 14 June 2016 ROOM F8 CPTU IN UNUSUAL SOILS Diego Lo Presti, Barbara Cosanti, Ilaria Giusti, Nicola Perilli UNIVERSITA DI PISA 1

2 LECTURE OUTLINE DEFINITION OF UNUSUAL SOILS CHARACTERIZATION (IDENTIFICATION) OF PARTIALLY SATURATED FINE- GRAINED SOILS UNDERCONSOLIDATED SILTY SOILS 2

3 UNUSUAL SOILS LAYERED; PARTIALLY SATURATED; UNDERCONSOLIDATED; INTERMEDIATE PERMEABILITY; COMPACTED SOILS 3

4 EQUIPMENT AT UNIPI 4

5 CPTU EQUIPMENTS 5

6 SCPTU EQUIPMENT 6

7 SCPTU - ROTOSEIS 7

8 SCPTU INTERPRETATATION 8

9 SCPTU INTERPRETATION 9

10 ARRIVAL TIME PICKUP 10

11 HOMOGENEOUS ELASTIC ISOTROPIC MEDIUM 11

12 INTERPRETATION METHODS ARRIVAL TIME PICKUP PSEUDO INTERVAL TRUE INTERVAL CROSS CORRELATION 12

13 CORRECTED-TIME VS. DEPTH 13

14 USE OF Vp IN PARTIALLY SATURATED SOILS 14

15 ANY REASON TO MESURE Vp? 15

16 JAMIOLKOWSKI 2013 RANKINE LECTURE 16

17 JAMIOLKOWSKI 2013 RANKINE LECTURE 17

18 CC TESTS ON TICINO SAND 1 18

19 CC TESTS ON TICINO SAND 2 19

20 INHERENT ANISOTROPY 20

21 STRESS-INDUCED ANISOTROPY 21

22 EFFECTS OF SATURATION ON SANDS CC DATA S=0% OR S=100% (FINE TO MEDIUM SANDS) NEGLIGIBLE EFFECTS (BELLOTTI ET AL ISOPT I; SCHMERTMANN 1976, JAMIOLKOWSKI ET AL. 2001) 22

23 EFFECTS OF SATURATION ON SANDS JAMIOLKOWSKI ET AL (UNDERESTIMATE 7 10%) 23

24 PARTIALLY SATURATED FINE GRAINED SOILS - BRONI 24

25 CPTu1 TEST CONDUCTED DURING THE WET SEASON (BRONI). 25

26 CPTu2 TEST CONDUCTED DURING THE DRY SEASON (BRONI). 26

27 MISS CLASSFICATION AT BRONI 27

28 MISS CLASSFICATION: LOOSE SILTY SOILS (SERCHIO RIVER LEVVES) 28

29 MK MODEL Kovacs (1981) and Aubertin, et al. (2002). The MK model has been used to evaluate, from simple soil parameters, the matrix suction (ψ r ) at the residual water content and the equivalent capillary height above the water table (h co ). (Aubertin et al. 1998; Mbonimpa et al. 2000, 2002). 29

30 EQUATIONS For clayey soil (ρ s = dry density) 30

31 EFFEECTS OF EFFECTIVE STRESS ON Ic 31

32 MODIFICATION OF THE VERTICAL EFFECTIVE STRESS TO GET A CONSTANT Ic (BRONI) Estimate of vertical effective stress at Broni 0 vertical effective stress (kpa) depth (cm) CPTu1 CPTu2 32

33 PRACTICAL MEANING OF THE CORRECTION THE SBT INTERPRETATION COULD GIVE AN ASSESSMENT OF THE EFFECTIVE STRESS-STATE MODIFYING A SBT INTERPRETATION INTO A SOIL TYPE INTERPRETATION, THE DIFFERENCES IN Ic SHOULD REFLECT WHAT IS MISSING IN SOIL TYPE INTERPRETATION (i.e.ocr) 33

POSSIBLE IDENTIFICATION OF PRECONSOLIDATION PRESSURE (PORCARI LUCCA) vertical effective stress kpa 1 10 100 σ' p 1000 10000-2 0 2 vertical

34 POSSIBLE IDENTIFICATION OF PRECONSOLIDATION PRESSURE (PORCARI LUCCA) vertical effective stress kpa σ' p vertical strain (%) Ic 1 1,5 2 2, z (cm Preconsolidation pressure From oedometer: kpa From CPTu: 296 kpa 34

35 EMPIRICAL CORRECTION Define Ic from borehole data (grain size curve) The new classification system is not SBT but depends on texture Criteria: AGI 1997 Example: Silt with clay (2.6<Ic<2.95) 35

36 ASSESSMENT OF Ic FROM BOREHOLE Borehole # Soil classification from borehole (AGI 1997) Ic from borehole Ic from CPTu ΔIc SBTn Soil classification from CPTu 1 Clayey and sandy silt Sand Mixtures Silty sand Sand Silty sand Sand Mixtures Sand, gravel and fine gravel Sand Silty sand Sand Mixtures 36

37 DATABASE SERCHIO RIVER LEVEE SYSTEM AND FOUNDATION SOIL DREDGED SEDIMENTS IN ARTICICIAL BASINS (PORT OF LIVORNO) 37

38 Ic FROM BOREHOLES AND CPTu 38

39 HOW TO CORRECT 39

40 ΔIc FUNCTION ΔIc (-) Serchio River Livorno Port Best Fit Total tip resistance MPa 40

41 Ic AFTER CORRECTION 41

42 ACKNOLEDGEMENTS DATA HAVE BEEN MADE AVAILABLE BY PROF. C. MEISINA (UNIPV), DR. BARSANTI (GEOPROVE - LUCCA), DR. COSCO & SPADARO (GEOSERVIZI- PISA). THE HELP GIVEN BY THE FOLLOWING STUDENTS IS ALSO ACKNOWLEDGED: M. ROSIGNOLI, N. FULCINITI, M. MARCONCINI, D.BUSONI, M. PONZANELLI, A. SCARDIGLI, C. ZACCAGNINO 42

CPT: Geopractica Contracting (Pty) Ltd Total depth: m, Date:

CPT: Geopractica Contracting (Pty) Ltd Total depth: m, Date: The plot below presents the cross correlation coeficient between the raw qc and fs values (as measured on the field). X axes presents the lag distance (one lag is the distance between two sucessive CPT