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DEPARTMENT OF INFRASTRUCTURE ENGINEERING
CVEN90050 Geotechnical Engineering
Assessment 3 – Part 1: Unconsolidated-Undrained Triaxial Test (this document)
Part 2: Design project (see LMS)
Introduction. In engineering practice, components of a structure are designed to tolerate tension,
compression or shear forces. The shear strength of a soil mass is the internal resistance per unit area that
the soil mass can offer to resist failure and sliding along any potential failure plane inside it. It is essential
to understand the nature of shearing resistance in order to analyse soil stability problems, such as bearing
capacity, slope stability, and lateral pressure on earth-retaining structures. The shear strength parameters of
soil can be determined through a variety of geotechnical investigations including laboratory and/or in situ
testing. The focus of this part of the assessment is on shear strength of soils, stress conditions in ground and
obtaining soil strength parameters through UU triaxial test.
Task: A pile foundation is proposed to carry the weight of a bridge passing through a swampy area of soft
saturated normally consolidated clay overlaying a layer of seemingly medium/stiff clay (Figure 1). The
water table was measured a depth of 4 m. The characteristics of the top soft clay layer is known for
engineers; there are given in the figure for your information. The characteristics of the bottom clay are not
known. The characteristics of this soil have to be determined in a lab, so that the pile foundation can be
designed. For characterization of the bottom clay, an undisturbed sample from the depth of 8 m obtained
from the field investigation has been delivered to the Geotechnical laboratory of The University of
Melbourne. In this laboratory assignment, you are asked to conduct an Unconsolidated-Undrained Triaxial
Test (UU test) on the obtained specimen of this normally consolidated clay layer (“Bottom clay”) to
determine its strength parameters.
Figure 1. Profile of proposed pile
Bottom clay
