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Friction angle and overconsolidation ratio of soft clays from cone penetration test
Abstract The cone penetration test (CPT) is a method widely used for site characterization as measurements are continuous, fast and economical compared to laboratory testing. However unlike laboratory testing that quantifies soil properties directly, readings obtained from CPT are indirect and needs to be interpreted. Hence many correlations have been proposed to infer a wide range of soil properties from CPT readings. Existing correlations have discovered separate relationships between normalized cone tip resistance (Q t) and effective friction angles (ϕ’), as well as Q t and overconsolidation ratio (OCR). This study employs the press-replace method (PRM), a novel simplified numerical technique, to perform systematic and extensive undrained investigations of CPT in a modified Cam-clay (MCC) soil model. It is the first comprehensive numerical study with an advanced soil model that considers rough cone-soil interactions. The PRM numerical approach overcomes the need to assume the CPT process as analogous to spherical or cylindrical cavity expansions, therefore produces results that are more authentic to real CPT. From the large database of numerical results, an equation is formulated that provides a framework on how Q t is related to both ϕ’ and OCR, rather than separately to ϕ’ or OCR as described in previous correlations. The proposed equation is then simplified so that ϕ’ and OCR can be easily estimated from Q t. Numerical results and predictions from the new equations are then compared to soil behaviour charts, other correlations and field data from different sites.
Highlights 57 numerical simulations of undrained cone penetration test in modified cam-clay. Systematic investigation of ϕ’, OCR, σ vo’, λ, κ, eo, Ko and su on CPT measurements. Cone tip resistances and excess water pressures were determined and validated. Results are unified (R2 = 0.99) through a newly proposed equation. Newly proposed equation simplified for ease of application: Qt ≈ 1.8C M0.70 OCRΛ.
Friction angle and overconsolidation ratio of soft clays from cone penetration test
Abstract The cone penetration test (CPT) is a method widely used for site characterization as measurements are continuous, fast and economical compared to laboratory testing. However unlike laboratory testing that quantifies soil properties directly, readings obtained from CPT are indirect and needs to be interpreted. Hence many correlations have been proposed to infer a wide range of soil properties from CPT readings. Existing correlations have discovered separate relationships between normalized cone tip resistance (Q t) and effective friction angles (ϕ’), as well as Q t and overconsolidation ratio (OCR). This study employs the press-replace method (PRM), a novel simplified numerical technique, to perform systematic and extensive undrained investigations of CPT in a modified Cam-clay (MCC) soil model. It is the first comprehensive numerical study with an advanced soil model that considers rough cone-soil interactions. The PRM numerical approach overcomes the need to assume the CPT process as analogous to spherical or cylindrical cavity expansions, therefore produces results that are more authentic to real CPT. From the large database of numerical results, an equation is formulated that provides a framework on how Q t is related to both ϕ’ and OCR, rather than separately to ϕ’ or OCR as described in previous correlations. The proposed equation is then simplified so that ϕ’ and OCR can be easily estimated from Q t. Numerical results and predictions from the new equations are then compared to soil behaviour charts, other correlations and field data from different sites.
Highlights 57 numerical simulations of undrained cone penetration test in modified cam-clay. Systematic investigation of ϕ’, OCR, σ vo’, λ, κ, eo, Ko and su on CPT measurements. Cone tip resistances and excess water pressures were determined and validated. Results are unified (R2 = 0.99) through a newly proposed equation. Newly proposed equation simplified for ease of application: Qt ≈ 1.8C M0.70 OCRΛ.
Friction angle and overconsolidation ratio of soft clays from cone penetration test
Lim, Yi Xian (author) / Tan, Siew Ann (author) / Phoon, Kok-Kwang (author)
Engineering Geology ; 274
2020-06-14
Article (Journal)
Electronic Resource
English
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