Quality control of fine-grained embankments using penetration tests

Abstract

The compaction control of earth works is an essential task in geotechnical engineering. In order to build more sustainably and to reduce project costs, fine-grained materials are more often used for embankment construction nowadays. The quality control of compacted soil layers is usually defined in terms of deformation moduli obtained from static and dynamic plate load tests or based on the degree of compaction, which is generally related to the Proctor density. Penetration tests, such as cone penetration tests (CPT), seismic flat dilatometer tests (SDMT) or dynamic probings (medium heavy dynamic probings (DPM)), show a potential for assessing the compaction along vertical profiles but no standardized quality criteria have been elaborated yet. The present work investigates the effects of different water contents and degrees of soil stabilization on results of CPT, SDMT, DPM, plate load tests and Proctor tests for an 8 m high trial embankment, characterized by a clayey to silty material. CPT and DMT results were found to strongly correlate with deformation moduli of static and dynamic plate load tests, enabling the definition of new quality criteria for compaction control.

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Article
Quality control of fine-grained embankments using
penetration tests
Simon Oberhollenzer a,b, Laurin Hausera, Martin Ehalla, Roman Martea, Franz Tschuchnigga,and
Helmut F. Schweigera
aGraz University of Technology, Institute of Soil Mechanics, Foundation Engineering & Computational Geotechnics,
Rechbauerstraße 12, 8010 Graz, Austria; bNorwegian Geotechnical Institute, Sandakerveien 140, 0484 Oslo, Norway
Corresponding author: Simon Oberhollenzer (email: s.oberhollenzer@tugraz.at)
Abstract
The compaction control of earth works is an essential task in geotechnical engineering. In order to build more sustainably
and to reduce project costs, fine-grained materials are more often used for embankment construction nowadays. The quality
control of compacted soil layers is usually defined in terms of deformation moduli obtained from static and dynamic plate load
tests or based on the degree of compaction, which is generally related to the Proctor density. Penetration tests, such as cone
penetration tests (CPT), seismic flat dilatometer tests (SDMT) or dynamic probings (medium heavy dynamic probings (DPM)),
show a potential for assessing the compaction along vertical profiles but no standardized quality criteria have been elaborated
yet. The present work investigates the eects of dierent water contents and degrees of soil stabilization on results of CPT,
SDMT, DPM, plate load tests and Proctor tests for an 8 m high trial embankment, characterized by a clayey to silty material.
CPT and DMT results were found to strongly correlate with deformation moduli of static and dynamic plate load tests, enabling
the definition of new quality criteria for compaction control.
Key words: quality control, earth embankment, in-situ tests, cone penetration test, seismic flat dilatometer test
1. Introduction
Soil compaction and quality control of earth constructions
built in layers are required for a wide range of problems in
geotechnical engineering (e.g., road and railway construction
or sealing structures). As a consequence of compaction works,
the soil density increases, settlements are reduced and the
bearing capacity of the overall system increases. Therefore,
the structural safety and serviceability of embankments are
strongly related to the quality of compaction works (Adam et
al. 2009).
Static plate load tests (SLPT) and dynamic plate load tests
(DLPT) with the light falling weight device are widely used for
quality control in geotechnical engineering. Quality criteria
are usually defined based on static or dynamic deformation
moduli which characterize the quality of compaction for the
depth of influence. Alternatively, the quality of compaction in
fine-grained soils can be investigated by the determination of
the in situ density which is compared to the Proctor density.
If the required limit values for the respective tests are not
reached further compaction is required. Over the last years,
great experience has been gained in executing and interpret-
ing the latter tests. Especially load plate tests enable a quick
assessment of compaction on-site. However, results of plate
load and Proctor tests are only representative for a defined
depth of influence leading to a pointwise control during em-
bankment construction. Test results can be influenced by the
operator and the comparison of dierent testing techniques
is often not possible within projects since they are not exe-
cuted close-by or just one test is used due to time or economic
reasons.
On the other hand, penetration tests as the piezocone
penetration test (CPTu), seismic flat dilatometer test (SDMT)
and dynamic probing test (heavy dynamic probings (DPH)
and medium heavy dynamic probings (DPM)) enable a con-
tinuous characterization along profiles and are nowadays
widely used for soil classification, parameter identification
and quality control (Robertson and Campanella 1989;Mayne
2006;Robertson 2016;Schnaid 2009;Steiner and Togliani
2016). Especially vibro-compaction works are often evalu-
ated based on CPTu, SDMT or DPH where pre-defined min-
imum values——usually defined in terms of the measured
in situ measurements——must be reached after compaction
(Tschuchnigg et al. 2018;Massarsch and Fellenius 2019). Pen-
etration tests show a great potential in terms of the com-
paction control of earth embankments since (i) compaction
can be assessed along profiles, (ii) deeper situated layers can
investigated and (iii) the influence of the operator is de-
creased. So far, the potential of using CPTu, SDMT, DPH and
DPM for the compaction control of earth embankments has
not yet been investigated extensively. This may be related, on
Can. Geotech. J. 61: 469–484 (2024) | dx.doi.org/10.1139/cgj-2022-0055 469