CONE PENETRATION TEST Flashcards
it is originally known as Dutch cone penetration test
cone penetration test
Cone penetration test is a versatile ___________ test that can be carried out in most soil conditions.
in situ
The original Dutch cone penetration test developed in _______________ in 1932 was a _____ degree mechanical cone with a ______ mm outside diameter, with approximately _____ cm^2 projected area.
Holland, 60, 35, 10
When a cone is pushed to the ground, the resistance at the cone, known as the __________ and the ____________ is measured separately.
cone resistance (qc). sleeve friction (fc)
____________________ is the force required to push the cone tip into the soil per unit cross-sectional area.
Cone Resistance
Standard CPT tests use a rate of _____ mm/s.
20
In CPT with piezocone (CPTu), what does the pore pressure sensor measure?
The pressure of water within the soil pores during penetration
In Dutch penetration test, the measurement is recorded at larger intervals in the order of ________ mm
200
Electrical cone measurements are made using ________________ and ______________ generally for every 20 mm.
strain gauges, transducers
Who developed the first electric cone in 1965 as an improvement to the mechanical cone.
Fugro
_____________ is the resistance measured along the friction sleeve of the CPT probe as it penetrates the soil. It is an important parameter used to determine soil type and estimate ______________.
Sleeve friction, shear strength
Helps distinguish between cohesive (clay) and non-cohesive (sand) soils.
Sleeve Friction
Used to determine undrained shear strength of clay.
Sleeve Friction
The modern cones which are also able to measure pore water pressure, are known as ______________
piezocones
The standard cone of _____ cm^2 has a friction sleeve area of ________ cm^2
10, 150
The __________ mm long frictional sleeve has an outer diameter of ________ mm.
133.7, 35.7
______________ are the modern electric friction cones. With the addition of sensors such as geophones, seismic cone penetration tests can now also measure shear wave velocity vs, and hence the ________________.
Piezocones, shear modulus G
A _____________ pushes the cone into the ground
hydraulic ram
High sleeve friction in a Cone Penetration Test (CPT) typically indicates that the soil has a significant amount of ________.
cohesion
________ friction ratio = More clay, silt, or organic soil
High
_________friction ratio = More sand or gravel
Low
Friction ratio varies in the range of 0- ___ %, with the lower end of the range for ________ soil and the upper end for ________ soil.
10, granular, cohesive
The friction ratio varies in the rang of 0 - ___% with the lower end of the range for ________ soil and the upper end for ________ soil.
10, granular, cohesive
In a recent study on several soil in Greece, Anagnostopoulos et al expressed Fr as ____________________ for electric cone
Fr = 1.45-1.36 log (D50)
In a recent study on several soil in Greece, Anagnostopoulos et al expressed Fr as ____________________ for mechanical cone.
Fr = 0.7811 - 1.611 log (D50)
Kulhawy and Mayne (1990) proposed the following relationship to correlate Dr, qc, and the vertical effective stress (O’o):
In this equation,
OCR = overconsolidation ratio
pa= _______________________
Qc = _______________________
The recommended values of Qc are as follows:
Highly compressible sand = _____
Moderately compressible sand = 1.0
Low compressible sand = ____
Dr = Sqr ( (1/305 (Qc) (OCR)^1.8)((qc/pa)/(O’o/pa)^0.5))
atmospheric pressure
compressibility factor
0.91
1.09
The precding relationship between Dr, qc pa, and O’o can be rewritten as
Dr(%) = 68(log (qc/sqr(pa * O’o)) - 1)
On the basis of experimental results, Robertson and Campanella (1983) suggested the variation of Dr, O’o, and drained friction angle for normally consolidated quartz sand. This relationship can be expressed as (Kulhawy and Mayne, 1990)
drained friction angle = tan-1 ( 0.1 + 0.38 log (qc/O’o)
Based on the cone penetration tests on the soil in the Venice Lagoon (Italy), Ricceri et al. (2002) proposed a similar relationship for soil with classifications of ML and SP-SM fro correlation between qc and drained fricion angle for sand
drained friction angle = tan-1 (0.38 + 0.27 log (qc/O’o))
Lee et al. (2004) developed a correlation among drained friction angle, qc, and the horizontal effective stress (O’h) in the form
drained friction angle = 15.575 (qc/O’h)^0.1714
The undrained shear strength, cu, can be expressed as
Nk =
Mayne and Kemper
Nk (electric) = ______________
Nk (electric) = ______________
Greece
Nk (electric)= ____________
Nk (mechanical) = ______________
These field tests also showed that
Cu (mechanical) =
Cu (electrical) =
cu = (qc -Oo)/Nk
bearing capacity factor
15
20
17.2
18.9
Cu= fs/1.26 (mechanical)
Cu = fs (electrical)
Mayne and Kemper (1988) provided correlations for preconsolidation pressure (sc9) and overconsolidation ratio (OCR) as
O’c = ?
OCR =?
O’c = 0.243 (qc)^0.96
OCR = 0.37 ( (qc-Oo)/O’o)^1.01
