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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

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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

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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

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qtqt fsfs u2u2 VSVS Typical Cone Penetration Sounding 4

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

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

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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

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Horizontal Variability of Tip Resistance Profiles Critical χ2 Value = 11.08

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

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Horizontal Variability of Sleeve Friction Profiles Critical χ2 Value = 11.08

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Spatial Variability Trend of Sleeve Friction Profiles for 33 CPT Soundings

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

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

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

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

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

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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

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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

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Measured and Evaluated Soil Unit Weight Profiles

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

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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

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

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Least Squares, Principal Component And Reduced Major Axis Regression Analyses

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Higher Order Regression Analysis

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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

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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

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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

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Autocorrelation of Residual Higher Order Regression

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