ABSTRACT
THE EFFECT OF GROUP BEHAVIOR ON THE PULL-OUT
CAPACITY OF SOIL NAILS IN HIGH PLASTIC CLAY
Ak& / #56256 / & / #56533 / & / #56256 / & / #56570 / , Ebru
Ph. D., Department of Civil Engineering
Supervisor : Assoc. Prof. Dr. B. Sad& / #56256 / & / #56533 / k Bak& / #56256 / & / #56533 / r
Co-Supervisor : Asst. Prof. Dr. M. Tolga Y& / #56256 / & / #56533 / lmaz
September 2009, 161 pages
Soil nailing technique is widely used in stabilizing roadway and tunnel portal
cut excavations. The key parameter in the design of soil nail systems is the
pull-out capacity. The pull-out capacity of the soil nails can be estimated
from the studies involving similar soil conditions or can be estimated from
the empirical formulas. Field verification tests are performed before the
construction stage in order to confirm the parameter chosen in the design of
soil nailing system. It is reported in the literature that, the pull-out resistance
of a soil nail in sand should be reduced for the nails installed closer than a
specific minimum distance, whereas no such requirement have been
discussed for nail groups in clays.
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In this study, the pull-out resistance of nails in high plastic clay are tested to
investigate the influence of nail spacing in group applications. The laboratory
set-up for the pull-out tests is composed of an aluminum model box (300mm
(w) x 300mm (h) x 500 mm (l)), soil sample, reinforcements, pull-out device,
overburden pressure applicator and monitoring device. A series of pull-out
tests has been carried out on single nails and group of nails with spacings 2
and 6 times the diameter of a nail in order to observe the group effect on the
pullout capacity of the nails. The nails are located into their positions during
the placement of clay into the box.
Within the limitations of this study, it is observed that, there is a reduction in
the pull-out capacity of the central nail in 2Ø / spaced group. The pull-out
capacity of the central nail in nail group with 6Ø / spacing, is not affected from
the neighboring nails. In all tests, the plots of pull-out load on nail versus nail
displacement show that, the peak value of load is followed by a sharp
reduction. The peak pull-out load is mobilized at first few millimeters of the
nail displacements.
A 3D finite element program is used for numerical analyses of the
experiments. The measured pull-out capacity of the soil nails are compared
by the results of simulated forces obtained from these analyses. By and
large, the agreement between the tests and the numerical analyses is
observed to be satisfactory. The details of the numerical models are briefly
presented in order to give insight into numerical modeling of soil nails in real
applications.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/3/12611066/index.pdf |
| Date | 01 September 2009 |
| Creators | Akis, Ebru |
| Contributors | Bakir, Sadik Bahadir |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | Access forbidden for 1 year |
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