Download - Soil Test and Surveys
The sieve analysis is the process used to
det. the particle sizes for gravels and for
coarse and fine sands. A sample of the
materials is thoroughly dried and then
shaken through a series of sieves ranging
from coarse to fine and the amount on
each sieve is weighed and recorded.
The AASHTO standard sieve sizes for soil
aggregate are as follows:
_________________________________________Sieve Designation
in inches 2 1 ½ 1 ¾ 3/8 4 10 40 200
_________________________________________By Number Opening
in Millimeter 50 37.5 25.0 19.0 9.50 4.75 2.00 .425 .075
_________________________________________
Materials that are finer than the no. 200 sieve (.075 mm) is not
feasible for determining the particles size.
The AASHTO Designation T 89 on LIQUID
LIMIT
– signifies the percentage of moisture
at which the sample changes by
decreasing the water from liquid to a
plastic state.
The Plastic Limit
- AASHTO Designation T-90 signifies the
percentage of moisture wherein the
sample changes with lowering wetness
from a plastic to semi-solid condition.
The Plastic Index
- AASHTO Designation T-90 is defined
as the numerical difference between its
liquid limit and its plastic limit. It is also
referred to as a percentage of dry
weight.
Shrinkage Test (AASHTO Designation T-92)
-the test measures the changes in
volume and weight that occur as a party
mixture of soil (except sieve no. 40) and
the water.
Hand Feel Test
-experienced soil engineers employ the
“ hand-feel” test to approximately predict
the plasticity index of the soils. These test
may include:
1. Thread toughness at a moisture contentapproximating the plastic limit.
2. The air dried strength
3. Dilatancy
Sand Equivalent Test
(AASHTO Designation T-176)
-the sand equivalent is the ratiobetween the height of the sandcolumn(lab. experiment test) and thecombined height of the sand and theexpanded saturated clay which areexpressed in percentage.
- the density of soil or weight per cubic foot varieswith the peculiarities of the soil itself, the moisturecontent, and the compactive device, plus themethod of their use:
1. The Specific Gravity of the Soil Particles themselves -which may vary from 2.0 to 3.3 but usually is between 2.5and 2.8.
2. The particle size of the distribution of the soil – a masscomposed entirely of spheres of one size in the densestpossible condition will contain 75% solid and 25% voids.The smaller the sphere in the mass the higher thepercentage of the solid, hence, particle size distributionmay greatly affect density.
3. The grain shapes of soils particles – sharp angular willresist shifting from a loose to a compacted state.. Flakyparticles in soil will decrease its density because they aredifficult to compact.
Test for density maybe divided into two
classes:1. Laboratory test to set a standard for density.
2. Field test to measure the density of soil in place in
the road way
Laboratory test maybe subdivided into
three, according to the basis of
compaction procedure.1. Static test
2. Dynamic or Impact test
3. Tamping –foot or kneading-compaction test.
Static test
- to determine the maximum density oflaboratory samples a sample of about 5000 gramsof soil containing a specified percentage of wateris placed in a cylinder mold 6” (15cm.) in adiameter and 8” (20cm.) in height.
The dynamic or Impact test
- samples of soil each containing a designatedpercentage of water are compacted in layers intomolds of specifies sizes.
Tamping foot or Kneading compact test
- material is fed into a rotating mold and iscompacted by several repetitive loads appliedthrough a tamping shoe shaped like a sector of acircle.
Soil test to determine the strength of soil
are divided into:
1. Test for load carrying capacity for foundation and
rate and amount of consolidation in soils that
support the foundation. This is applicable to
bridge foundation
2. Test to measure the supporting power of disturbed
soils as compacted under standard procedures.
The California Bearing Ratio Method(CBR)
- combines a load deformation test performed
in the laboratory with an empirical design chart to
determine the thickness of pavement base and
other layers.
The HVEEM Stabilometer Method
- this method measures the horizontal pressure
developed in a short cylindrical sample loaded
vertical on its end.
Stabilometer Test
- after the expansion test is completed, the
specimen is enclosed in a flexible sleeve and
placed in the stabilometer. Vertical pressure is
applied slowly at a speed of 0.05 in./min. until it
reaches 160 psi. The developed horizontal pressure
is reduced to 5 psi using the displacement pump.
Then the turns of the displacement , pump needed
to bring the horizontal pressure to 100 psi are
determined, this displacement procedure is
intended to measure the penetration of the flexible
diagram into intersection of the sample.
The resistance Value R of the soil iscomputed by the formula:
R = 100 – 100 / ( 2.5𝑷𝒗
𝑷𝒉− 𝟏 + 𝟏)
Where:
R = Resistance Value
Pv = Vertical pressure (160 psi)
D = Turns Displacement reading
Ph = Horizontal pressure in psi at Pv of 160 psi
The resistance value of a fluid where Ph = Pv willbe 0. The R value of an infinitely rigid solid (Ph = 0)will equal 100.
Triaxial Design Method
- This method is adopted by some agencies forcompression tests (see AASHTO desig. T 234) theopen system triaxial test, lateral pressure is heldconstant by releasing from the container asincreased load causes the sample to expandlaterally.
Nuclear Devices Test
- recently, nuclear devices for determining in-place densities and moisture contents are used.The principle of the measurement by nuclearinstrument is relatively simple. Gauge reading areeasily converted to density and prevent moistureusing calibration curves or microprocessors. Theportable devices are of either the transmission orbackscatter types.
Soil Surveys
A. A preliminary soil investigation is an integral part
of highways reconnaissance and preliminary
location survey.
B. In fixing the position of the road the following has
to be considered:
1. Soil conditions
2. Directness of route
3. Topography
4. Right of way
5. Neighborhood disruption
6. Environmental consideration
The early phase of the soil survey is the collection ofinformation such as:
1. Identification of soil types from geological andagricultural soil maps, aerial photographs andother sources.
2. Investigation of ground water conditions.
3. Examination of existing roadways cuts and otherexcavation.
4. Review of the design and construction procedures
5. Present condition of roads that traverse the area.
6. Soil exploration along the right of way using augerboring and test pile.
7. Sampling should be at frequent enough intervalsto fix the boundaries of each soil types.
8. Test holes should extend to a significant depthbelow the sub grade elevation with arecommended minimum depth of 1.50 meters.
9. A complete and systematic record shall be madefor each hole.
10. The location , the nature of the ground, origin ofparent material, landform and agricultural soilname should be recorded.
11. Each soil layer is described according to itsthickness texture structure, organic, relationcontent and of cementation.
12. The depth of seepage zones of the free watertable and bedrock are also recorded.
13. The soil profile along the roadway centerlineshowing location or test holes range of soil profilecharacteristic for each district soil type is plotted.
Most highway agencies make a detailed study
along with the first survey such as:
1. The vertical and horizontal location of the
proposed construction.
2. Location and evaluation of suitable borrow and
construction materials.
3. Need for and type or sub grade or embankment
foundation treatment and drainage.
4. Need for special excavation and dewatering
techniques.
5. Development of detailed subsurface investigation
for specific structure.
6. Investigation of slope stability in both outs and
embankment.
7. Selection of roadway pavement type of section.