۱۸ فروردین ۱۳۹۹
دسته:
کد : 536
CPT

» عنوان : Cone Penetration Testing (CPT) Interpretation – Soil Type

تعداد صفحات : ۲۲

فرمت : PDF

Advantages of CPT
Advantages over traditional combination of boring, sampling and other testing
• Fast
• Continuous or near continuous data
• Repeatable and reliable data
• Cost savings

CPTu Interpretation Soil Type
– Soil behavior type (SBT) & stratigraphy In-situ State
– Relative density (Dr) or State Parameter and OCR
Strength
– Peak friction angle and undrained strength (Su)
Stiffness/compressibility
– Shear (Go), Young’s (E’) and 1-D constrained (M)
Consolidation/permeability
– Coeff of consolidation (Cv) and permeability (k)

Role of CPT
CPThas three main applications:
• Determine sub-surface stratigraphy and identify materials present (Soil Type – SBT)
• Estimate soil parameters
• Provide results for direct geotechnical design
Primary role is soil profiling and can be supplemented by samples, other in-situ tests and laboratory testing

CPT- Soil Behavior Type (SBT)

CPT/SBT based on insitu soil behavior (strength, stiffness, compressibility) – not the same as classification based Atterberg Limits and grain size carried out on disturbed samples

Generalized CPT-Soil Behaviour Type

CPT Soil Behaviour
A: Drained-dilative
B: Drained-contractive
C: Undrained-dilative
D: Undrained-contractive

SBT from-CPT
• Soil behavior influenced by fines content and plasticity of fine
– e.g. soils with small amount of high plastic fines behave more like a clay and soils with large amount of low plastic fines behave more like sand
• CPT Soil Behavior Type Index Ic captures combined influence of fines content and plasticity of fines

Fines content alone can not capture correct soil response

CPT-Normalization
• Early normalization based on theory for clays
• Recently normalization based on soil type, density and stress level

Summary
• CPT (Cone Penetration Testing) is a fast, reliable method to determine soil stratigraphy and soil type in a cost effective manner.
• CPT-based Soil Behaviour Type (SBT) charts available to estimate soil type, based on either tip-friction and/or tip-pore pressure measurements
• CPT equipment can be used to take small diameter push-in soil samples to verify soil type

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