Small-Strain Behaviour of Cem Singapore Marine C. Dr. Yao Kai

Transcription

1 Small-Strain Behaviour of Cem Singapore Marine C Dr. Yao Kai

2 Outline Introduction Literature Review Experimental Methodology and Setup Maximum Shear Modulus Strain-Dependent Shear Modulus

3 Introduction Properties of Singapore Marine Clay: Low shear strength, high water content and high compressibility.

4 Literature Review G max of Natural Soil Factors affecting G max of soil: p, e, OCR. Hardin and Black (1969) : Viggiani and Atkinson (1995) : Hoyos et al. (2004) : G/G max of Natu Chong (2002) : Ho (2011) :

5 Factors Influencing the Stiffness of Cement-Treated Soil Stiffness and Strength: Correlated parameters. Terashi (1997): Characteristics of stabilizing agent and soil, mixing conditio Consoli (1999): The stiffness and strength of improved soil increase with th Babasaki et al. (1996): Lower total water content leads to higher unconfine Lee et al. (2005): qu depends on both soil-cement ratio (s/c) and water-ceme Kamruzzaman et al. (2009): qu increases with curing time, even upto 1 year

6 Effect of Confining Pressure on Gmax of Cemented Soil (Delfosse-Ribay et al. 2004)

7 Outstanding Issues and Scope of Study

8 Scope of Study: To get a clear perspective of the evolution of shear modulus with strai combined apparatus (bender element, resonant column and local strain To study the effects of factors such as cement content, total water conte and stress history on the small-strain shear modulus of cement-treated To develop some empirical relations for the G max and G/ G max of cement

9 Experimental Methodology and Setup Materials Singapore Marine Clay Ordinary Portland Cement Sample Preparation Procedure Equipment Setup and Experimental Procedure Bender Element Test

10 Materials Singapore Marine Clay Hydration reaction: Pozzolanic reaction: Ordinary Portland Cement

11 Sample Preparation Procedure Mix ratio s:c:w; cement content=c/s; total water content=. Hobart mixer Mixture after 10mins of mixing by Hobart mi

12 Bender Element Test Set u Schematic diagram of bender element system

13 Travel time of shear wave (Chan, 2010) First Arrival Method Peak to P

14 Effect of Slot Cutting and Filler Materials (Pantazopoulos and Atmatzidis, 2012)

15 Slot depth=0.5mm Slot depth Slot depth=1.5mm Slot depth

16 1.5 mm Slot depth=1.5mm

17 Influence of Excitation Frequency

18 Comparison of Bender Element and Resonant Column Results

19 Shear strain varies from zero along the axis of surface of the rod. Resonant Column Test Drnevich Long-Tor resonant column setup Lissajous figure of resonance on oscilloscope

20 Comparison of Hollow and Solid Cylindrical Specimens Hollow specimen for resonant column test Advantage: For a given applied torque, higher shear strain could be achieved. The use of average of the internal and external radius may lead to

21 Local Strain Test Sources of errors in external strain measurement (Baldi et al., 1988) Problems without Anchor Pins Components of local

22 Setting Up of Local Strain Transducer Specimen for local strain measurement Mounts and transducer guide for setting up

23 Effect of Dimension of Anchor Pins

24 Results Comparison of Local Strain Test with Resonant Column Test

25 Maximum Shear Modulus G max G max of Unconfined Specimen G max of Confined Specimen Influence of Mean Effective Stress Influence of Void Ratio

26 G max of Unconfined Specimen (Cement Content, Water Content, Curing Period)

27 G max of Confined Specimen

28 Influence of Mean Effective Stress Viggiani and Atkinson (1995): fine-grained soils G p max r p ' A pr n Cement-treated soils

29 Influence of Void Ratio

30 Strain-Dependent Shear Modulus Strain-Dependent Shear Modulus of Cement Unconfined Condition Factors Influencing Shear Modulus Degradation Curv Correlation of Shear Modulus Degradation Curves an Shear Modulus Degradation Curve under Co Influence of Effective Confining Pressure

31 Factors Influencing Shear Modulus Degradation Curve Cement Content Total Water Content

32 Curing Period

33 Correlation of Shear Modulus Degradation Curves and q

34 G G max 1 Gmax m Gmax 1 c 1 c m 1 c G G c=f 1(q u) m=f 2(q u) m G G max Log( 1) Logc mlog

35 G G max m 1 c 0.1

36 G G max 1 1 ( / ) G/ G 0.5 max

37 G G max / (1.571 qu ) / (1.571 qu ) q u q u G ( 0.5) G max G ( 0.5) G max

38 Shear Modulus Degradation Curve under Confined Influence of Mean Effective Stress

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40 Conclusion Bender Element Test 1. Exact-cut plus filler materials 2. High input frequency 3. L/λ>1 4. Aspect ratio=2 Resonant Column Test 1. Calibrated by BET and LST 2. ε<0.01%, representative radius of 0.8R is available

41 Maximum Shear Modulus 1. Maximum shear modulus in unconfined condition: 2. Gmax vs p (yield condition) Gmax q 1 3. Gmax vs e: G G max max e Strain-Dependent Shear Modulus 1. G/G max vs q u 2. Effective confining pressure p (yield condition)

42 Thank You