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Fawad S. Niazi Geosystems Engineering Division Civil & Environmental Engineering Georgia Institute of Technology April 27, 2010 Spatial Variability of.

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Presentation on theme: "Fawad S. Niazi Geosystems Engineering Division Civil & Environmental Engineering Georgia Institute of Technology April 27, 2010 Spatial Variability of."— Presentation transcript:

1 Fawad S. Niazi Geosystems Engineering Division Civil & Environmental Engineering Georgia Institute of Technology April 27, 2010 Spatial Variability of CPT Data and Soil Parameters at NGES, Texas A&M et al. 2010

2 2 Spatial variability of CPT readings for horizontal & vertical variability in soil profiles (all soundings, each 10 cm depth):  Mean, min, max  Moment statistics (variance, skewness, kurtosis)  Residuals of principal comp. analysis of CPT readings (space and depth)  Test of normality ( χ 2 test) Comparison of measured and evaluated soil unit weight,  t  LS regression, correlation coefficient  LS, principal component and reduced major axis regression  Higher order regression and residuals analysis Scope of Study

3 3 qcqc u2u2 fsfs VsVs Site characterization:  Conventional boring/sampling methods  Lab investigations on disturbed samples Cone penetration test:  Fast, economical, and continuous data  up to 4 separate readings in one sounding  Soil parameter interpretation I c,  t, OCR,  p ', K o, s u,  ', D R, G max q c, f s, u 2, V s Cone Penetration Test – a Hybrid Method

4 qtqt fsfs u2u2 VSVS Typical Cone Penetration Sounding 4

5 National Geotechnical Experimentation Site Riverside Campus, Texas A&M University Geotechnical Experimentation Site College Station Texas A&M University

6 Location of Clay and Sand Sites on Riverside Campus, Texas A&M University Clay Site Sand Site

7 Field Investigations at NGES Clay Site, Texas A&M University 1997 Twelve MCPT Six CPT Three SCPT Testing Program 1977 to 1995 Nine CPT 1995 to 1996 Three CPTu CPT: 10 cm 2 Cone Penetration Test CPTu:Piezocone Penetration Test MCPT:2 cm 2 Mini Cone Penetration Test SCPT: 15 cm 2 Seismic Piezocone Penetration Test BH:Borehole 15 m Clay Control N CPT CPTu MCPT SCPT BH Legend

8 Horizontal Variability of Tip Resistance Profiles Critical χ2 Value = 11.08

9 Spatial Variability Trend of Tip Resistance Profiles for 33 CPT Soundings Critical χ2 Value = 11.08

10 Horizontal Variability of Sleeve Friction Profiles Critical χ2 Value = 11.08

11 Spatial Variability Trend of Sleeve Friction Profiles for 33 CPT Soundings

12 Residuals of Principal Comp. Analysis of q t at 0.16 m Critical χ2 Value = 11.08

13 Residuals of Principal Comp. Analysis of q t at m Critical χ2 Value = 11.08

14 Residuals of Principal Comp. Analysis of Tip Resistance at CPT4 Critical χ2 Value = 11.08

15 Residuals of Principal Comp. Analysis of Tip Resistance at MCPT13 Critical χ2 Value = 11.08

16 Results of Horizontal Variability Study 0 – 1.1 m 4.9 – 8.7 m 10.5 – 13.6 m

17 1997 Twelve MCPT Six CPT Three SCPT Testing Program 1977 to 1995 Nine CPT 1995 to 1996 Three CPTu CPT: 10 cm 2 Cone Penetration Test CPTu:Piezocone Penetration Test MCPT:2 cm 2 Mini Cone Penetration Test SCPT: 15 cm 2 Seismic Piezocone Penetration Test BH:Borehole 15 m Clay Control N CPT CPTu MCPT SCPT BH Legend A A’ Results of Vertical Variability Study

18 18  t = Total unit weight (kN/m 3 )  w = Unit weight of water (kN/m 3 ) q t = Cone tip resistance (kPa) f s = Sleeve friction (kPa) z = Depth (m)  vo ’ = Effective vertical overburden stress (kPa)  atm = Atmospheric pressure (kPa) Correlations: CPT Readings and Soil Unit Weight,  t Mayne et al. 2010

19 Measured and Evaluated Soil Unit Weight Profiles

20 Least Square Regression, Correlation Coefficient, 95% Confidence Bounds r = r =

21 1997 Twelve MCPT Six CPT Three SCPT Testing Program 1977 to 1995 Nine CPT 1995 to 1996 Three CPTu CPT: 10 cm 2 Cone Penetration Test CPTu:Piezocone Penetration Test MCPT:2 cm 2 Mini Cone Penetration Test SCPT: 15 cm 2 Seismic Piezocone Penetration Test BH:Borehole 15 m Clay Control N CPT CPTu MCPT SCPT BH Legend Results of Vertical Variability Study

22 Least Square Regression, Correlation Coefficient, 95% Confidence Bounds p = p =

23 Least Squares, Principal Component And Reduced Major Axis Regression Analyses

24 Higher Order Regression Analysis

25 25 Horizontal and vertical variability of CPT readings for better site characterization CPT-based relationship for evaluating soil unit weight Conclusions Mayne et al. 2010

26 Fawad S. Niazi Geosystems Engineering Division Civil & Environmental Engineering Georgia Institute of Technology April 27, 2010 Spatial Variability of CPT Data and Soil Parameters at NGES, Texas A&M et al. 2010

27 Depth (m) Very Stiff Clay Sand Very Stiff Clay Hard Clay (Shale)  t = 19.6 kN/m 3 s u = 110 kPa  t = 19.5 kN/m 3 s u = 140 kPa  t = 18.9 kN/m 3 s u = 160 kPa After Briaud 2000 Stratigraphy at the NGES TAMU Clay Site

28 Autocorrelation of Residual Higher Order Regression


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