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FHWA CPT workshop
Practical Experiences using the CPT--
September 2015 - Indianapolis, IN--
Gerald Verbeek
1
The disclaimers
• I’m Dutch
• I’m a Conehead
But I will try not to be biased2
Practical Experiences using the CPT
3
Theory Equipment Mindset
The Theory
4
The same theory is used around the world to interpret CPT results
The Equipment
5
The same equipment is used around the world to obtain CPT results
whether for electrical CPT (ASTM D5778)
The Equipment
6
Or mechanical CPT (ASTM D3441)
7
The Mindset
8
The Mindset - US
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The Mindset - US
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The Mindset - US
11
Vs.
The Mindset – Aspect 1
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The Mindset – Aspect 1
Vs.
Feeling is believing…..or is it?
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The Mindset – Aspect 1
Soil Classification according to CUR(Center for Civil Engineering Project Execution Research and Regulations)
The Mindset – Aspect 2
Vs.
Trust …..but verify?
15
The Mindset – Aspect 2
In 2014 ADSC and DFI developed the workshop“Bored Piles / Drilled Shafts Best Practices: Design, Construction, Contracting Methods”
5 aspects were reviewed from a North American perspective and from a European perspective:
DesignConstructionContracting MethodsInnovations and technologiesQuality Control
16
The Mindset – Aspect 2
Typical findings regarding foundation testing:Germany It is possible to calculate the piles bearing capacity based on empirical data. Therefore, there is generally no load test on piles.
SpainIt is very unusual to do a Load Test on a drilled shaft.
The NetherlandsIt is very unusual to do a load test on a drilled shaft (“maybe for 1 % of the projects one or two piles may be tested”).
Or maybe just trust
The Mindset – The Netherlands• CPT: “It has always been there”
17
1932 -1934Pieter Barentsen develops the first internationally recognized cone model for Cone Penetration Testing (CPT). All testing and production was performed at GMF Gouda.The Dutch Cone was born and also the first patent in CPT history, applied in 1934 and granted in 1938 to Goudsche Machinefabriek and Pieter Barentsen. GMF Gouda became the first manufacturer of CPT equipment on an industrial scale.
1959GMF Gouda introduces the first hydraulic pushing rigs for 10 ton and later also 20 ton capacity setting a new standard for efficient CPT soundings.
1965H.K.S. Begemann improved the Dutch cone and added an extra sliding shaft for measuring the sleeve friction, resulting in the Friction Jacket Cone, also known as Begemann Cone.
1971After a period of testing, failing and improving the electric cone penetrometers with strain gauged measuring bodies become more reliable and popular.
18One of the first CPT devices (around 1940)
The Mindset – The Netherlands“It has always been there”
1950 kN hand operated CPT device
The Mindset – The Netherlands“It has always been there”
2050 kN hand operated CPT device
The Mindset – The Netherlands“It has always been there”
21Hand operated 50 kN pusher installed on old army truck
The Mindset – The Netherlands“It has always been there”
22Manual pusher inside a truck
The Mindset – The Netherlands“It has always been there”
The Mindset – The Netherlands• there is only 1 university in The Netherlands
where you can get an MSc in Civil Engineering
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The Mindset – The Netherlands
“Under Ground”
Manual geotechnical soil investigation
The Mindset – The Netherlands
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18 pages – CPT10 pages – boreholes6 pages – other soil investigations
The Mindset – The Netherlands
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Manual geotechnical soil investigationTOTAL 34 pages
18 pages – CPT10 pages – boreholes6 pages – other soil investigations
Geotechnical Engineering Circular 5TOTAL 42 pages
8 pages – CPT17 pages – boreholes17 pages – other soil investigations
Vs.
.
The next slides are taken from presentations by a premier Dutch geotechnical consulting company.
They show how CPT is marketed by Dutch firms within The Netherlands and abroad.
The Mindset – The Netherlands
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.
For site investigations CPT’s are usually carried out in combination with a few boreholes for soil sampling. Next to an almost continuous profile is speed another advantage. Per unit 200 to 300 meter of soil profile can be collected per day.
The Mindset – The Netherlands
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CPT data are used for soil stratigraphy and soil classification , and correlations can also provide information regarding:
State characteristics soil unit weight, overconsolidation ratio, in-situ horizontal stressStrength characteristicsundrained shear strength, sensitivity, effective stress strength parametersDeformation characteristicsconstrainted modulus, undrained Young’s Modulus, small strain shear modulus.Consolidation and flow characteristicsconsolidation and permeability coefficients
The Mindset – The Netherlands
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CPT’s used for geotechnical profiles
The Mindset – The Netherlands
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An alternative approach is to apply the in situ test results directly to engineering problems as :
• Determination of pile bearing capacities and load settlement response
• Bearing capacities for shallow foundations• Quality control for ground improvement• Evaluation of the potential for soil liquefaction
The Mindset – The Netherlands
31
What mostly happens
Some examples of geophysical measurements that can be carried out using CPT equipment:Magnetic measurements : to determine the length of (sheet) piles, soil anchors and the presence of unexploded ordnance;Seismic measurements : to determine the potential of liquefaction and elastic soil parameters for dynamic loading;Conductivity measurements : to assist in the interpretation of (airborne) electromagnetic and geo-electric measurements and to determine the fresh- salt water interface in groundwater. Presently used e.g. in a European project aimed at predicting effects of climate change to coastal areas.
The Mindset – The Netherlands
32
Magnetic measurements
The effect of a piece of steel reinforcement steel measured at different distancesshowing the vertical, horizontal and derivative component of the magnetic field
The Mindset – The Netherlands
Conductivity measurements
Standard CPT graph - soil classification - conductivity - chloride mg/l
The Mindset – The Netherlands
• Comprehensive coverage using the Dutch Eurocode 7 standards and guidelines for accurate design of vertically loaded bearing piles and tension piles and shallow foundations with both horizontal and vertical loading.
• Easy soil data definition by importing CPT data, which can be done in several formats, including the Geotechnical Exchange Format (GEF). The automatic CPT interpretation tool provides soil-type dependent suggestions for all applicable parameters.
The Mindset – The Netherlands
Work in progress
Questionable
Eurocode 7 applies to geotechnical aspects of the design of buildings and civil engineering works.• part 1 covers the general basis for the
geotechnical aspects of the design of buildings and civil engineering works, assessment of geotechnical data, use of ground improvement, ground reinforcement, dewatering and fill. It also includes calculation rules for spread foundations, piles, retaining structures, embankments and slopes.
• part 2 covers requirements for the execution, interpretation and use of results of laboratory tests to assist in the geotechnical design of structures.
It is the national standard in 33 European countries since 2010.
The Mindset – Europe
The Mindset – Europe
CEN member states
The Mindset – Europe
CEN member states
The Mindset – Europe
Cone penetration tests are extensively used in soil mechanics to determine the layer structure and the bearing capacity of the subsoil. Data from the cone penetration test is stored digitally and supplied to the client in the format they request. The result is a large variety of formats which makes mutual exchange problematic and hinders durable storage of penetration test data. The standard Geotechncial Exchange Format brings an end to this confusing situation.
The Mindset – The Netherlands
In summary:• CPT is known to every civil engineer• CPT is the test method of choice for soil
investigations• CPT is generally accepted as a reliable method for
soil investigations (clients – contractors – consultants – regulatory agencies)
• The CPT results are generally accepted as direct inputs for the design of any foundation type.
The Mindset – The Netherlands
It is just what you do
Thank you!
Questions?
42
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