8/9/2019 CPT General Httpwww.fes.Co.ukdownloadsCPT General.pdf

1/2

More information available at WWW.FES.CO.UK 

Fugro Engineering Services Limited

Fugro House

Hithercroft Road, Wallingford

Oxfordshire, OX10 9RB

tel. +44 1491 820 400, fax +44 1491 820 499

e-mail: wallingford@fes.co.uk 

 Armstrong House

Unit 43, Number One Industrial Estate, Medomsley Road

Consett Co. Durham DH8 6TW

tel. +44 1207 581120, fax +44 1207 581609

e-mail: consett@fes.co.uk

© Fugro 2011

Cone Penetration Tests  Cone Penetration Tests 

Providing geotechnical data, geo - environmental data and unexploded ordnance clearance both onshore and offshore.

Introduction

The objective of all site investigations is to obtain data whi ch

will adequately quantify the variability of the geotechnical

properties of the site. Sufficient data is required to assess

the impact of soil variability within a time frame such that

it can be allowed for within the geotechnical design and/ 

or construction. Cone Penetrometer Testing (CPT) provides

 you w ith a rapid and cost effective means by which this

objective can be achieved.

CPT units can be mobilised as road-going vehicle types or as avariety of narrow chassis and crawler undercarriages, ideally suited

to traversing soft, water-logged terrain or entering sites with limited

access. Fugro’s development of CPT applications has a number of

advantages that combine well with boring, sampling and standard

penetration tests :

• Identifies soil stratigraphy in terms of general soil behavior

and, to lesser degree, soil type.

• Provides a continuous (although indirect) record of ground

conditions, avoiding the ground disturbance associated with

boring and sampling.

• Data may be used in long established semi-empiri cal design

methods, for example, analysis of foundation bearing capacity,

foundation settlement, pile carrying capacity and liquefaction

potential.

• Routinely, ground engineering properti es (cu, Ø, Eoed , E’ and

Dr) may be derived from the data, the accuracy of assessment

increasing when a piezo-cone is deployed.

• Piezo -cones (CPTU) can also be used to assess hydrostatic

head, consolidation and permeability characteristics.

• Yields thousands or tens of thousands of data points that can

be digitally stored and transferred in real time.

• Cost-effective method employing rapid probing rates to

accredited test procedures.

CPT generates high value data and adapts readily to the

environmental sensitivities of many investigations in favourable

types of material, generally excluding bedrock, very dense granular

fill and strata containing cobbles and boulders.

 A cone about to be pushed in the ground.

.

Tracked crawler rig.

World – wide support

Wherever you are in the world FUGRO is at hand to be your local

specialist for geotechnical, survey and instrumentation services.

Our unrivalled geographical spread means that we have local

specialists who will fully understand the technology, logistics

and project management requirements of your work. Our 8,000

employees are distributed through 260 offices worldwide.

By using our regional staff, supplemented where necessary by

specialists drawn from our international centres of expertise, we

can provide the optimal mix of resources to support your projects.

Guide for Estimating Soil Type and Characteristics using Cone Penetration Testing

FRICTION RATIO (%)

Cone resistance

(qc) (MPa)

Compaction of

Fine Sand

SPT

(N)

Relative

Density Dr (%)

 Angle of internal

Fiction (degrees)

8/9/2019 CPT General Httpwww.fes.Co.ukdownloadsCPT General.pdf

2/2

Cone Penetration Tests

• The Seismic Cone Penetration Test

(SCPT) is a reliable, cost effective

technique to determine the insitu

seismic wave velocity.

• Seismic wave velocities give an

indication of ground characteristics

such as low strain shear modulus

and Poisson’s ratio.

• Data from the cone penetrometer is

used in delineating the strata changes

identified by the seismic results.

 The CPT cone is used as an adapter for

two different geoenvironmental screening

methods to detect contaminants present

in the subsurface.

• Rapid Optical Screening Tool

(ROST) Screening of hydro carbon

derived contamination in soil and

groundwater.

• Membrane Interface Prob (MIP) Direct

measurement of organic compounds

and chlorination hydrocarbons in the

soil.

Detailed lithological information of the

subsurface soil available from the CPT

cone.

Interpretation of CPT results can be

enhanced by the use of site specic

correlations. Such correlations are

obtained by performing laboratory

tests on soil samples obtained from the

location of the CPT tests.

Soil samples can be obtained using

CPT equipment and proprietary

samplers such as the Mostap 35/65.

• Soil samples of up to 1.5m in

length and either 35mm or 65mm

diameter can be obtained, depend-ent upon depth and soil conditions

encountered.

• “Magcone”- Magnetometer (triaxial)

mounted in a piezocone.

• Deployed from CPT rigs.

• As fast as standa rd CPT.

• Up to 3m diameter of detection gives

multiple pile clearance.

• Used to clear piles, CPT & BH

locations.

• Penetrates most pile mats and fill.

Soil SamplingDynamic Properties

Geoenvironmental Cones

• The piezocone incorporates a porous

element in the shoulder of the cone.

 An internal pressure transducer measures

the transient porewater pressure

variations during cone penetration.

• Rapid dissipation of porewater pressure

is indicative of permeable strata and

features, whilst excess porewater

pressures are indicative of clays. Features

as thin as 1 cm can be detected.

• Pore pressure dissipation with time

provides data from which estimates of

the coefficient of consolidation of the soil

can be derived. This data can be used to

estimate soil permeability.

• Porewater pressure data can be used to

estimate over consolidation ratio in clays.

• Fugro Cone Pres suremeter (CPM)

provides a reliable measurement of

the insitu strength and load deforma-

tion behaviour of the soil.

• Results from cone pressuremeter

tests can be used to derive para-

meters such as:

  - undrained shear strength

  - shear modulus

  - effective horizontal stress

  - relative density

• Data from the cone penetrometer can

be used to ensure that the pressure-

meter is positioned within the zone of

soil interest.

Insitu strength can be de-termined from

the results of cone penetrometer tests

and/or insitu vane tests using the Geonor

vane deployed from a CPT rig.

where:

qc  = measured cone resistance

Su = undrained shear strength

Nk  = cone factor

σv1 = effective overbur den pressure

Nq = bearing capacity factorrelated

to friction angle φ1

 T = measured rota tional torque

Insitu Strength

Soil DeformationHydraulic Behaviour

• Detailed characterisation of soil types

• On-site determination of strata variations

• UKAS accredited testing procedures

• Continuous real-time data

• Accurate depth control

• Slope indicator

• High production rates (>100m/day)

• Up to 20 tonne thrust capacity

Soil Type & Stratification

UXO Combined Magnetometer and Piezocone

for UXO detection with geotechnical properties

Body waves

Push rods

Geophonearray

Friction sleeve

PorepressuresensorCone

BeamHammer

 Trigger

Seismograph

CPT recordingunit Thrust machine

x

yz

Standardconerod

Pushhead

CDMtubing

Controlsystem

Conerodadaptor

Pressuremetermodule

Conepenetrometer