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Basic Cone PenetrationTest (CPT) Course
Joselet Jane U. Tumilap
13th & 14th February 2013
www.fugro.comDate 14 February 2013
TOPICS
Basic of Cone Penetration Test, CPTWhat is CPTCPT Processing using UNIPLOT
Copy Test from OperatorsOpening the CPT Raw DataTest DescriptionInsert ClipsOffset ChannelsCPT at ResfusalData PresentationCreating ASCII File
CPT Data Interpretation
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Basic of Cone Penetration Test, CPT
Continuous hydraulic push using
Rods pushed at a rate of 20mm/sec
Reading taken every 10mm
Figure 1-1 Schematic Presentation of a Cone Penetration Test
Figure 1-3 Fugros electric Piezo-CPT Probe equipped with pressure sensors
Figure 1-2 20-Tonne truck
Pore water pressure
Tip Resistance
Sleeve Friction Resistance
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What is CPT
The Cone Penetration Test (CPT) is a method used to determine:
Geotechnical engineering properties of soils Delineating soil stratigraphy
In the CPT, using a 200kN capacity electrical cone at the end of a rod is pushed or penetrated continuously into the ground at a constant rate of 20mm/sec equipped with internal sensor.
The measurements comprised of:
Penetration depth Cone resistance / tip resistance (qc), Sleeve friction (fs) Pore pressures, u (CPTU a piezocone test) (Optional) Friction Ratio, Fr (fs / qc) Inclination
CPT vs the Standard Penetration Test (SPT)
Continuous Operator Independent Repeatability
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CPT Processing
CPT Processing = Correcting / checking the raw CPT data
Processing using UNIPLOT.
The processing of CPTs consists of the following steps:
Copy Test from Operators Opening the CPT Raw Data Test Description Insert Clips Offset Channels CPT at refusal Data Presentation Creating ASCII File
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Copy Test from Operators
CPT data from site are saved in folders:
Processed Raw
Figure 2-1 Copying the test from operators
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Opening the CPT Raw Data
Figure 3-1 .1 Opening the CPT data in UNIPLOT for processing.
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Figure 3-1.1 UNIPLOT 05.19nl Rev.01 Main Menu
A B C D E F G H
A.New Selection CPT filesB.Open Selection ListC.Save CPT FilesD.Manual ProcessingE.ClassificationF. Select a Plot Command FileG.Plot on Screen (Preview)H.Plot on Printer
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Figure 3-1.2 Opening CPT Raw Data
1
2 3 4
5
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Figure 3-1.3 Selecting a command file
1
2
3
Select a Plot Command File
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Figure 3-1.4 Unprocessed CPT Log
A
B
D
C
Check for:
A. qc and fs < 0B. SpikesC. Fr
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Test Description
Filling the Test Description Data
Processor Data versus Operator Data
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Figure 4-1.1 Test Description in UNIPLOT
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Figure 4-2.2 Inserting of Coordinates and Elevations
1
2
34
5
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Insert Clips
Figure 5-1.1 During and after inserting the clip
1
2(Insert New Clip in CPT By clicking the right mouse button )
3
4(End of CPT By clicking the right mouse button)
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Offset Channels
Check for:
qc < 0 fs < 0
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2Offset (Cone, Sleeve)
fs
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CPT in Refusal
Figure 7-1.1 CPT not in refusal and in refusal
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Delete Clips
Figure 7-1.2 Deleting Clips / End Record CPT
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Data Presentation
The CPT factual log normally presented in a plate with the measured:
Cone resistance (qc) Sleeve friction (fs) Pore pressure (u) (Optional) Soil Classification
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Figure 8-1.1 CPT Log before and after processing
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Figure 8-1.2 CPT Log with Soil Behavior Classification
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Figure 8-1.3 CPT Log with Soil Behavior Classification with Derived Soil Parameters
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Figure 8-1.4 Combined CPT Log
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Creating ASCII File
American Standard Code for Information Interchange ASCII
ASCII File ASCII File of Plate
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Figure 9-1.1 Creating ASCII file
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Figure 9-1.1 Creating ASCII file of Plate Data
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CPT Data Interpretation
Soil Behavior Classification Bearing Capacity Calculation Liquefaction Analysis (LiquefyPro) Soil Parameter Interpretation
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Figure 10-1.1 Soil Behavior Type (Roberston 1990)
Friction Ratio, Fr (%)Gravely SAND 0 0.50SAND 0.50 1.00Fine silty SAND 1.00 1.50Sany SILT / silty SAND 1.50 2.50CLAYS 3.00 9.00
Soil Behavior Classification
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CPT Bearing Capacity Calculation
Valid only in cohesionless soil:
Bearing Pressure = qc / 40 (Footing of 1.0m width) (Indicative)
For larger width, check settlement if its 25mm or less
S = BC x B / 2qc
Where:
S - SettlementBC - Bearing CapacityB - Foundation width
Reminder:
DONT apply unless you have several meters of sand below footing level with consistent qc.
Reduce the obtained value by 30% if you want to apply for STRIP of the same width.Use only for 1.0m, 1.50m and up to 3.0m.
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Figure 11-1.1 Combined CPT logs used for interpretation
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Liquefaction Analysis using LiquefyPro using CPT Data
ASCII File Excel File Text Format
Export to LiquefyPro
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Derived Soil Design Parameter Based on CPT Data
Relative Density - Dr Undrained Shear Strength - Cu Over Consolidation Ratio - OCR
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Figure 12-1 CPT log with derived design parameters
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Figure 11-1.2 Assigning layer properties
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Figure 11-1.3 Soil Classification
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The only way to learn how to process
CPT is
PRACTICE.
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Thank You
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