Parametric Study of Anchored Diaphragm Wall For Deep Excavations Using Plaxis 2D
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Date
2020-11
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Addis Ababa University
Abstract
There is a growing need for the construction of underground structures beneath
buildings because of the scarcity of available space in Addis Ababa either for parking or
other purposes. Because of that there is a need for deep excavations during
construction of the structures, which shall minimize the ground movement caused by
the structures to remain within the allowable limits. It’s the geotechnical engineer’s
responsibility to properly study the soil-structure interaction and soil behavior to design
a support structure which satisfies this requirement in addition to providing a safe
working space.
There are many ways to support deep excavations; among which diaphragm walls and
contiguous piles are the most popular ones in Addis Ababa. There is a need to study
the effect of different parameters prior to the construction for a safer design. Previous
studies on anchored diaphragm walls show that the effect of excavation depth, depth of
embedment, soil type, strut spacing, and stiffness of the anchored diaphragm wall but
no consideration is given for the geometric properties of the ground anchor used.
Therefore, this research presents a study of anchored diaphragm walls using Plaxis 2D
for deep foundation support in dry excavation by performing parametric study on the
anchor orientation, anchor length and the grout (geo-grid) length to compare their
influence on the stability of the diaphragm wall.
Available literatures on diaphragm wall had been carefully studied followed by a
numerical analysis using Plaxis 2D on the representative base models. The comparison
of the effect of the parameters are carried out by analyzing the result of the maximum
horizontal displacement, vertical displacement, and bending moments induced in the
diaphragm wall using FEM.
The results of the parametric studies showed that increasing the anchor orientation
more than 25ᴼ isn’t advisable unless the site situation inhibited the installation. It was
found out that free anchor length beyond the assumed wage slip surface should be a
minimum of 1 meter for a safe anchorage. Beyond the assumed wage slip surface, for
the same length of anchorage, it was found out that longer free anchor length and
shorter grout result in a better anchorage than a short free anchor length with longer
grout for both expansive and red silty clay soil.
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Keywords
Plaxis 2D, Anchored Diaphragm Wall, Deep Excavations