SOIL NAILING FULL SEMINAR REPORT AND PPT
1.INTRODUCTION
Soil
nailing is a procedure to reinforce and strengthen ground adjacent to an excavation
by installing closely spaced steel bars called nails, as construction proceeds
from top down. It is an effective and economical method of constructing
retaining wall for excavation support, support of hill cuts, bridge abutments
and highways. This process is effectively in cohesive soil, brocken rock, shale
or fixed face conditions.
Soil
nail technology was first used in France to build a permanent retaining wall
cut in soft rock. The project
undertaken in 1961, was the first where steel nails were used to reinforce a
retaining wall. The first soil nail wall to use modern soil nailing techniques was build near Versailles in 1972.
The technique included installing high density,
grouted soil nails into 160-ft-high wall and facing it with
reinforced concrete. Germany was the next country to
investigate soil nailing. From 1975-1981 the University of Karlsruhe and the
construction company Baur collaborated to establish a research program. This
program conducted full scale testing of experimental walls with different
configurations and developed analysis procedures for use in design. The United
States first used soil nailing in 1976 for the support of a 13.7 m deep
foundation excavation in dense silty sands. Soil nailing was implemented in the
expansion of The Good Samaritan Hospital in Portland, Oregon. This retaining
system was produced in approximately half the time at about 85% of the cost of
conventional retaining systems
Soil nail walls can be used for
a variety of soil types and conditions. The most favorable conditions for soil
nailing are as follows: The soil should be able to stand unsupported one to two
meters high for a minimum of two days when cut vertical or nearly vertical.
Also all soil nails within a cross section should be located above the
groundwater table. If the soil nails are not located above the groundwater
table, the groundwater should not negatively affect the face of the excavation,
the bond between the ground and the soil nail itself. Based upon these
favorable conditions for soil nailing stiff to hard fine-grained soils which
include stiff to hard clays, clayey silts, silty clays, sandy clays, and sandy
silts are preferred soils. Sand and gravels which are
dense to very dense soils with
some apparent cohesion also work well for soil nailing. Weathered rock is also
acceptable as long as the rock is weathered evenly throughout(meaning no
weakness planes). Finally, glacial soils work well for soil nailing].
A list of unfavorable or difficult soil conditions for soil nailing can include
dry, poorly graded cohesion-less soils, soils with a high groundwater table,
soils with cobbles and boulders, soft to very soft fine-grained soils, highly
corrosive soils, weathered rock with unfavorable weakness planes, and loess.
Other difficult conditions include prolonged exposure to freezing temperatures,
a climate that has a repeated freeze-and-thaw cycle, and granular soils that
are very looses.
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