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AXIAL PILE RESISTANCE FOR INTERMEDIATE SOILS

Development of Cone Penetration Test Method

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AXIAL PILE RESISTANCE FOR INTERMEDIATE SOILS

Development of Cone Penetration Test Method

Rechten: Alle rechten voorbehouden

Samenvatting

In the geotechnical field there are soils which in terms of behaviour, behave neither fully drained or
fully undrained (intermediate soils). In these soils, drained/undrained behaviour mainly depends on
both loading conditions and foundation dimensions, which makes the determination of the soil
behaviour, and therefore, also the axial pile capacity predictions more difficult.
The purpose of this study is to set up a CPT-based soil layer interpretation based on the soil
behaviour type index (Ic), with the focus on intermediate soils and to examine if a CPT-based axial pile
capacity method, can improve axial pile capacity predictions. Hence, the main question is formulated:
to what extent can the estimation of soil behaviour improve based on the Ic, to obtain more accurate
axial pile capacity predictions?
For the correlation between axial pile capacity and the Ic, a soil layer interpretation is set. This
interpretation is based on the Ic and the initial pore pressure dissipation. In principle, sand exhibits a
drained behaviour and clay an undrained one. Intermediate soils can behave either drained or
undrained and are mostly classified as silts.
Various sites are selected, where CPT and sample data are available. The selected sites contain
layers of sand, clay and silt. The derived data from the CPTs are used to determine the percentages
of pore pressure dissipation and the soil behaviour type indices. Based on these two parameters, a
soil layer interpretation is defined for the three main soil types: sand, clay and silt. The interpretation is
based on the normalized Ic.
The Ic varies between 1.31 and 3.60. Low indices indicate sand and high indices indicate clay. Both
sand and clay Ic boundaries are defined. These boundaries are defined based on a normal distribution
with an excess of 10%. The Ic for sand (drained) is defined at 2.16 and for clay (undrained) it is
defined at 2.54. Soils between these two indices are assumed to be intermediate soils, which can
either behave drained or undrained.
This study shows the possibility to define a soil layer interpretation based on the Ic. Normal distribution
of the soil behaviour type indices per soil type seems an accurate method to define boundaries for the
Ic. Laboratory tests and dissipation behaviour confirm these results. The boundaries are defined for a
36 mm cone with a penetration rate of 2 cm/s, and have therefore limited direct applicability. A scale
factor, considering dimensions and penetration rate is required to derive boundaries applicable to pile
capacity. The proposed interpretation must be treated with care due to limited data.
A pile load test site is selected in order to verify whether the estimation of axial pile capacity in
intermediate soils can be improved. Axial pile capacity assessments were performed following various
CPT-based methods and based on the original soil layer interpretation two soil layer models are
defined: one with intermediate soils modelled as frictional soils and one with intermediate soils
modelled as cohesive soils. Axial pile capacity is calculated for both soil layer models. The results are
compared with the measured axial pile capacity from the pile load test.

Toon meer
OrganisatieAvans Hogeschool
OpleidingCiviele Techniek-Den Bosch
PartnersFUGRO ENGINEERS B.V.
Datum2014-06-12
TypeBachelorscriptie
TaalEngels

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