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An evaluation of seismic flat dilatometer and lateral stress seismic piezocone

The flat dilatometer (DMT) and piezocone penetration (CPTU) tests are likely to be among the most
widely used in situ testing methods for soil characterization and indirect determination of geotechnical
design parameters such as: strength, stiffness, permeability and compressibility. The flat dilatometer has
proved to be a reliable, robust and adaptable tool, and the data obtained with this instrument is very
repeatable, and easy to reduce and process. Furthermore, the addition of a seismic module to the standard
flat dilatometer (SDMT) to measure the shear wave velocity (Vs) significantly complements the set of
data typically obtained with a standard DMT test. Nonetheless, the experience in interpreting the
combination between Vs and DMT data is fairly limited due to the recent introduction of the SDMT for
commercial applications. Additionally, the estimation of the coefficient of earth pressure at rest (K₀) has
been the most important application of the DMT since its introduction. However, a potential weakness of
the DMT is that the derivation of K₀ is based upon empirical correlations developed some time ago and
neither improvement work nor upgrade of these approaches has been performed in the last 10 years.
Throughout the years several additional sensors have been developed in order to supplement the data
collected with the CPTU test. Among the wide variety of sensor developed, the lateral stress module
mounted behind a piezocone represents a promising tool for estimation of in situ lateral stress conditions
from the interpretation of lateral stress penetration data. However, the popularity of the so called lateral
stress cone has declined over the years due to constraints in both the instrumentation and the
interpretation of measured data. Also, the application of this instrument remains limited to specific soils
conditions and specific projects. However, the valuable experience gained throughout the years in the
development and application of several lateral stress cones in combination with developments in
electronics and understanding of soil behaviour allow the improvement of this type of technology.
This thesis presents the results of a comprehensive laboratory and field testing programs performed by the
author at several research sites located in the Lower Mainland of BC, undertaken in order to assess the
performance of the seismic flat dilatometer and lateral stress seismic piezocone (LSSCPTU), built and
develop at UBC. Firstly, the analysis of field measurements with the SDMT collected at several sites have
demonstrated the potential for an improved soil characterization through the combination of DMT
parameters and the small strain shear modulus (G₀). Additionally the usefulness of the DMT-C closing
pressure for soil identification is shown. On the basis of several relationships identified from this data, a
new soil type behaviour system based upon SDMT measurements is proposed. Furthermore, empirical
correlations based upon fairly large and updated databases have been developed to estimate K₀ and Vs
values from DMT parameters.
Date05 1900
CreatorsRivera Cruz, Ivan
PublisherUniversity of British Columbia
Source SetsLibrary and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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