AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT

1. WORKSHOP ON PENETRATION TESTING October 9th, 2014 Auditorium Opera Primaziale, Pisa • AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION • OF RIVER EMBANKMENTS • USING CPT BARBARA COSANTI N. SQUEGLIA D.C.F. LO PRESTI • Universityof Pisa – D.E.S.T.eC.

2. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT Presentationoutline 1 introduction 2 THE method 3 HYPOTHESES 4 THE EQUIPMENT 5 LABORATORY TESTS 6 RESULTS 7 CONCLUSIONS Barbara Cosanti, PhD

3. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT 1 introduction 2 THE method 3 HYPOTHESES 4 THE EQUIPMENT 5 LABORATORY TESTS 6 RESULTS 7 CONCLUSIONS Barbara Cosanti, PhD

4. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT 1 Introduction Compaction = Densification of soil by removing air voids using mechanical equipment • Improving soil strength by increasing the unit weight • Increasing the bearing capacity of foundations • Decreasing the undesirable settlement of structures • Controlundesirable volume changes • Reduction in hydraulicconductivity • Increasing the stability of slopes Objectives Barbara Cosanti, PhD

5. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT River embankments ASSESSMENT of the SAFETYDEGREE DESIGN CAUSES of FAILURE Saturated for only a short period of time Different erosion mechanisms and slope instability Definition of design values for strength and permeability characteristics POORATTENTION POORDEGREE OFCOMPACTION = PREDISPOSINGFACTOR DEPENDENCY ON THE DEGREEOFCOMPACTION NEED FOR AN EXPEDITIOUS AND ACCURATE METHOD TO EVALUATEDEGREEOFCOMPACTION Barbara Cosanti, PhD

6. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT 1 introduction 2 THE method 3 HYPOTHESES 4 THE EQUIPMENT 5 LABORATORY TESTS 6 RESULTS 7 CONCLUSIONS Barbara Cosanti, PhD

7. 2 AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT The method EVALUATIONOF THE DEGREEOFCOMPACTION OF RIVER EMBANKMENTS After completion • CPT TESTS IN LABORATORY • in a mini CC with a mini CPT • using samples at given densities ) ( In situ stress state when relevant + • TIP RESISTANCE TARGET PROFILE • qcLAB • CPTtests in situ • Vs • QUALITYCONTROL • Existingembankments: evaluationof the degreeofcompaction • Embankments under construction: it is possible (a‒priori) to establish which is the expected qc corresponding to a prescribed density Barbara Cosanti, PhD

8. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT 1 introduction 2 THE method 3 HYPOTHESES 4 THE EQUIPMENT 5 LABORATORY TESTS 6 RESULTS 7 CONCLUSIONS Barbara Cosanti, PhD

9. 3 AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT Hypotheses I. The tip resistance is not affected by the tip diameter  qcfromCPT (d= 35.7 mm) qcLABfrommini-CPT (d= 8 mm) Evenif: Vmini-CPT = 1/4  VCPT Normalized velocity (Finnie & Randolph, 1994) Where: v: velocity of the penetrometer d: diameter of the penetrometer cv: coefficient of consolidation of the soil UNSATURATED SILTMIXTURES Barbara Cosanti, PhD

10. 3 AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT Hypotheses II. FOR DRY SAND→ (Baldi et al. 1986, Jamiolkowskiet al. 1988, Garizio 1997, Jamiolkowskiet al. 2000, 2001) III. IN SITU STRESS STATE→ Estimate of the vertical effective stress component v At-rest earth pressure coefficient →DMT test (Jamiolkowskiet al. 1988) Barbara Cosanti, PhD

11. 3 AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT Hypotheses IV. The effects of the mini–chamber sizes can be considered negligible if: CCdiameter = 40 Mini-CPTdiameter When the horizontal distance between DMT and CPT is  20 times the cone diameter the DMT is no more sensitive to the passage of the cone DMT blade location CPT at 15d distance CPT at 30d distance V. It is acceptable: Mini-CPTdiameter  4 Diameterof the biggest particle Barbara Cosanti, PhD

12. 3 AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT Hypotheses The method has been successfully used in some case histories CPT n°3 CPT n°2 CPT n°1 qcLAB,90% qcLAB,80% (Modified Proctor) Barbara Cosanti, PhD

13. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT CPT n°1 CPT n°2 partially disturbed samples qcLAB,90% qcLAB,80% CPT n°3 CPT n°4 Barbara Cosanti, PhD

14. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT 1 introduction 2 THE method 3 HYPOTHESES 4 THE EQUIPMENT 5 LABORATORY TESTS 6 RESULTS 7 CONCLUSIONS Barbara Cosanti, PhD

15. AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT 4 The equipment Developed by the Geotechnical Laboratory of the University of Pisa in partnership with Pagani Geotechnical Equipment Barbara Cosanti, PhD

16. AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT THE EQUIPMENT Diameter = 320 mm; Height = 210 mm Top boundary → rigid Lateral and bottom boundaries → flexible → provided with latex membranes Barbara Cosanti, PhD

17. AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT THE EQUIPMENT The membranes allow the independent application of horizontal and vertical stresses through a compressed air system. Manual air pressure regulators for the vertical and horizontal stresses. All the possible chamber boundary conditions can beapplied: - BC1 = h = cost; v = cost - BC2 = h = 0; v = 0 - BC3 = h = 0; v = cost - BC4 = h = cost; v = 0. Barbara Cosanti, PhD

18. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT THE EQUIPMENT step by step electric motor aluminum frame locking system Barbara Cosanti, PhD

19. AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT THE EQUIPMENT • Mini CPT: • 60° conicaltip • conediameter = 8 mm • external sleeve • - standard rate of 20 mm/s • load cell external to the cone Barbara Cosanti, PhD

20. AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT Barbara Cosanti, PhD

21. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT 1 introduction 2 THE method 3 HYPOTHESES 4 THE EQUIPMENT 5 LABORATORY TESTS 6 RESULTS 7 CONCLUSIONS Barbara Cosanti, PhD

22. 5 AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT Laboratory tests dry partially saturated CRUSHEDSAND (Calibration material) FINE GRAINEDSOILS (Building materials) d50 = 0,5 mm Cu = 2 min = 1,419 kg/dm3 ; max = 1,663 kg/dm3 Only the particle size fraction which pass the 2 mm sieve DD A4; dmax= 18.2 kN/m3; wopt=13.2% Dry sand samples are reconstituted inside the CC to a given DRbypluvialdeposit. PC A4; dmax= 19.5 kg/m3; wopt=10.8% FR A6; dmax= 20.5 kN/m3; wopt=9.43% Barbara Cosanti, PhD

23. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT partially saturated FINE GRAINEDSOILS • Fine grained soil samples are reconstituted in 5 layers at a known unit weight using static compaction (hydraulic ram) in a mold • The compaction effort, required to consolidate each layer and the sample, is registered: Barbara Cosanti, PhD

24. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT 1 introduction 2 THE method 3 HYPOTHESES 4 THE EQUIPMENT 5 LABORATORY TESTS 6 RESULTS 7 CONCLUSIONS Barbara Cosanti, PhD

25. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT TIP RESISTANCE STRESS DEPENDENCE dry sand σ’h = costant Barbara Cosanti, PhD

26. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT TIP RESISTANCE STRESS DEPENDENCE dry sand σ’v = costant Barbara Cosanti, PhD

27. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT TIP RESISTANCE STRESS DEPENDENCE AT A GIVEN DR VALUE hIS THE MOST INFLUENTIAL PARAMETER ON qcLAB Barbara Cosanti, PhD

28. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT DD; PC; → d = 8092%dmax (Modified Proctor) w = wopt FR → d = 80%dmax (ModifiedProctor) w= 4; 8; 12% Suction→ evaluatedaccordingtoAubertinet al. (2003) Barbara Cosanti, PhD

29. AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT There is a clear relationship between tip resistance ‒ degree of compaction ‒ compaction energy, while, confinement pressures and suction have little effect on the tip resistance Barbara Cosanti, PhD

30. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT FR → d = 80%dmax (ModifiedProctor) w= 4; 8; 12% (wopt  10%) Barbara Cosanti, PhD

31. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT Very high values of qc in the shallower layers of the embankments ? EVAPO - TRANSPIRATION PHENOMENA (DESSICATION) Variation of tip resistance with water content Barbara Cosanti, PhD

32. AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT Laboratory tests Barbara Cosanti, PhD

33. AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT CPTu LFWD + Correlation between Ed and qc Averageqcmeasured within the influence depth for the LFWD (approximately 1.5 times the diameter of the loading plate = 45cm) Simple prevision method for quality control Barbara Cosanti, PhD

34. AN INNOVATIVE METHOD TO EVALUATE DEGREE OF COMPACTION OF RIVER EMBANKMENTS USING CPT As the water content decreases, Ed value increases Barbara Cosanti, PhD

35. Conclusions AN INNOVATIVE METHOD TO EVALUATEDEGREEOFCOMPACTIONOF RIVER EMBANKMENTSUSINGCPT DRY SANDS qc = f (σ’h) PARTIALLY SATURATED FINE GRAINED SOILS ( ) qc = f COMPACTION ENERGY w For a given soil and water content: • a correlation exists between qc and soil density that can be used to define a target tip resistance profile • it is possible to predict the dry density from the measured qc irrespective of the boundary stresses TIP RESISTANCE INCREASES WITH TIME BECAUSE OF DESSICATION

36. Thankyou barbara.cosanti@for.unipi.it