This preview shows page 1. Sign up to view the full content.
Unformatted text preview: cm 3.9 Miscellaneous
Apparatus - Datum bar of 5 m length with suitable
dial gauge attachments, pick axes, showel, trowel, spatula, spirit level and
4. TEST PROCEDURE
4.1 Two alternative test procedures may be followed. More accurate tests
are made with a 75-cm plate, and a load reaction arrangement, a loading
jack, a proving ring to measure the load and three dial gauges placed
diagonally apart about 10 mm from the rim to measure the vertical deflection. 4.2 Preparation of Test Area - K-value tests should be conducted on
representative area. Most soils exhibit a marked reduction in the modulus
of subgrade reaction with increase in moisture content, which cannot be
generalized. Conditions of moisture content, density, and type of material
all enter into the interpretation of test results to give a design value which
will represent the condition of equilibrium that ultimately will exist in the
Generally, subgrade is composed of either natural ground or
Preparation of an area for testing will depend on composifill-material.
tion of subgrade.
4.2.1 Preparation of Tut Area for flatural
Ground - Strip off an area
equal to twice the area of the bearing plate to the proposed elevation of
the subgrade surface.
In any case, it is necessary to remove the top
25 cm of the soil before testing. The effect of surcharge can be eliminated
by having supports of datum bar at least 1.25 m away from ‘the nearest
edge of bearing plates.
7 IS:9214- 1979 188.8.131.52 On fine grained soils the bearing plate, with its lower surface
oiled, shall be placed and rotated.
When the plate is removed the irregularities in the surface, being marked with oil shall be trimmed off.
process is repeated
until the plate is in contact with the soil over the
When the test is made on granular
shall be taken not to disturb the natural condition
of the subgrade while
the test site is being prepared.
Prior to placement
of 75 cm diameter
plate, the area should be cleared of loose material and levelled.
On gravely soils flat bearing surface can best be obtained
with plaster of paris, which should be levelled with the plate before the
plaster has set.
The K-value test should not be started until the plaster
has sufficiently hardened.
4.2.2 Prebaration of Filled-Up Area - In case the test is to be conducted
on subgrade composed of fill materials, a test embankment
of about 75 cm
should be constructed,
purposes the conditions of the moisture content and dry density of the test
arca should be those which are likely to exist when the subgrade ha
reached a state of relative equilibrium
to the construction
will be compacted
moisture content and specified density.
equipment is not available, approximate
may be obtained by hand
tamping in layers.
The test should be conducted keeping in view elimination of
bearing pressures of reaction frame and datum bar, as mentioned in 4.2.1.
The bearing plate with its lower surface oiled shall be placed on the
When the plate is removed all proud porprepared surface and rotated.
by oil marks shall be as levelled as possible.
is difficult due to presence of granular material, a layer of fine dry sand at
no place thicker than 5 mm may be laid and the plate seated properly.
- There are two methods for determination
modulus of subgrade reaction as given...
View Full Document
- Spring '13