JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003 GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP. LOA; RITES/AP/KUPPAM/2018/14700 DT 29-10-2018. Report No 1 03-12-2018 : , Page 1 of 100 Geotechnical Investigation Report Mobile: 9343330089, 9341372399 ,7353737711,7353737900, [email protected], [email protected]REGD.OFFICE:- # 30/1.AMBA BHAVANI TEMPLE STREET ATTURLAYOUT, YELAHANKA, BANGALORE 560 064 ADMIN OFFICE:-155/6, 2ND MAIN ROAD, 2 ND CROSS, MATHRU LAYOUT, YELAHANKA NEW TOWN, BANGALORE 560 065.
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Geotechnical Investigation Report Mobile: 9343330089 ...€¦ · Report No 1 03-12-2018 : , Page 11 of 100 Method of conducting Standard Penetration Test SPT. Standard Penetration
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JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
LOA; RITES/AP/KUPPAM/2018/14700 DT 29-10-2018. Report No 1 03-12-2018 : ,
JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
LOA; RITES/AP/KUPPAM/2018/14700 DT 29-10-2018. Report No 1 03-12-2018 : ,
Page 5 of 100
JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
LOA; RITES/AP/KUPPAM/2018/14700 DT 29-10-2018. Report No 1 03-12-2018 : ,
Page 6 of 100
FIELD WORK
BORE DEPTH & WATER TABLE BORE BORE HOLE BORE GROUND WATER LEVEL HOLE DIA DEPTH IN THE BORE HOLE No cms mts mts BH-1 15 6.0 NILL BH-2 15 6.0 NILL BH-3 15 6.0 NILL BH-4 15 6.0 NILL BH-5 15 6.0 NILL BH-6 15 6.0 NILL BH-7 15 6.0 NILL BH-8 15 6.0 NILL
C B R GROUND WATER LEVEL 1 NILL 2 NILL 3 NILL 4 NILL 5 NILL 6 NILL 7 NILL 8 NILL
PLATE LOAD TEST GROUND WATER LEVEL 1 NILL
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BORE HOLES
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NO DESCRIPTION NO. OF PAGES. PAGE NO 1 FIELD INVESTIGATION & SPT 10 9—19 2 FIELD BORE LOG 8 20—28 3 SOIL CLASSIFICATION 7 29—36 4 DENSITY & OVER BURDEN PRESSURE 3 37—40 5 SBC FOR EACH BORE HOLE 3 41—44 6 RECOMMENDATION 0 45 7 SBC CALCULATIONS 2 46—48 8 LAB TEST 8 49—57
JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
LOA; RITES/AP/KUPPAM/2018/14700 DT 29-10-2018. Report No 1 03-12-2018 : ,
Page 9 of 100
DRILLING RIG
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Field Investigation
Bore holes Explorations:
The most common method used to obtain soil details directly is to drill a borehole.
To estimate the engineering properties, plasticity etc.
Standard Penetration Tests,
150mm auger boring was carried out manually method.
1 Field test ;- Standard Penetration Test.:- SPT.
The Standard Penetration Tests aims to determine the SPT N value, which gives an
indication of the soil stiffness and can be empirically related to many engineering
properties.
Purpose of Standard Penetration Test :- SPT.
The main purpose of the test is to provide an indication of the relative density of
granular deposits, such as sands and gravels from which it is virtually impossible
to obtain undisturbed samples.
The great merit of the test and the main reason for its widespread use is that it is
simple and inexpensive.
In conditions where the quality of the undisturbed sample is suspect, e.g. very silty
or very sandy clays, or hard clays, it is often advantageous to alternate the
sampling with standard penetration tests to check the strength.
The usefulness of SPT results depends on the soil type, with fine-grained sands
giving the most useful results, with coarser sands and silty sands giving reasonably
useful results,
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Method of conducting Standard Penetration Test SPT.
Standard Penetration test was conducted in accordance to IS 2131 using a
standard split spoon sampler (51mm OD & 38 mm ID & length of 650 mm)
driven by 63.50 kg drop weight tripping automatically with a free fall of 750 mm.
The number of hammer blows required to drive 150mm of the sample is counted.
The sampler is further driven by 150mm and the number of blows recorded.
Like wise the sampler is once again further driven by 150mm and the number of
blows recorded. The number of blows recorded for the first 150mm is disregarded.
The number of blows recorded for the last two 150mm intervals are added to give
the standard penetration resistance Value ‘N’.
S P T Refusal & ‘N’ Correction
Refusal means when the sampler penetrates less than 2.5 cm under 50 blows.
Soil Samples were collected in LD 300 mg covers of standard size also labeled and
packed before sending to laboratory.
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Disturbed Samples: - DS
Disturbed soil samples were taken at every 1.5m interval and at significant change of
stratum.
Disturbed samples were be placed without delay in LD 300 mg covers of standard
size of 0.4kg also labeled and packed before sending to laboratory.
5.2 Undisturbed Samples: - UDS
Undisturbed soil samples were taken in clay soils stratum only.
Sealing and Labelling of Samples
Immediately after taking disturbed sample all samples were clearly labelled indicating
job number, borehole number, sample number, date of sampling, brief description of
sample, type of sample, elevation of sample etc.
Transporting and Storing of Samples
The samples were transported to laboratory for testing.
Sample bags containing disturbed soil samples were not exposed to direct sun and
were be kept in a shade covered with wet gunny bags.
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DRILLING IN ROCK
Drilling was carried out by core double tube core barrel fitted with a diamond bit of Nx
size is fixed to a hallow drilling rod. As the drilling rod is rotated, the bit advances in such
a manner that maximum core is recovered and cuts an annular hole around and intact
core. The core is then removed from its bottom and is retained by a core lifter and brought
to the ground surface. Water is pumped continually into the drilling rod and keep the
drilling bit cool and to carry the disintegrated material to the ground surface. Coring runs
were to a maximum length of 1.50m. The cores were removed from the drill hole
immediately. The returning drill water were kept constantly under observation and its
character, such as, its clarity or its turbidity, its colour, etc. were be recorded. For each
run, Core Recovery and Rock Quality Designation (RQD) were noted carefully,
immediately after cores are taken out of the barrel. Each and every core piece was serially
and sequentially numbered from top downwards as soon as the core pieces are removed
from the core barrel. The serial number was painted with good quality enamel paint. All
core pieces were placed in core boxes in serial order in correct sequence from top
downwards. Core boxes were be made according specifications laid down in IS: 4078.
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DRILLING IN ROCK
Rock Quality Designation : RQD
The sum total of lengths of cores of the length 10cms and longer recovered from the
drilling, expressed as percentage of the total length of the hole drilled .
Rock Mass Rating
The geo-mechanics classification system provides Rock Mass Rating (RMR) values for
Different rocks. The RMR Value depends on the quality and it may vary from 0 to 100. The
RMR is derived from 5 universal parameters (Goodman 1980)
Strength of rock. Drill core quality. Joint spacing
Joint characteristics Ground water conditions.
D. Weathering classification
I Grade Fresh Rock
II Grade Slightly weathered Rock
III Grade Moderately weathered Rock IV Grade Highly weathered Rock
V Grade Completely weathered Rock
VI Grade Residual soil
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Bearing capacity concept
A strip footing of width B gradually compresses the foundation soil underneath due to the
vertical load from superstructure. Let qf be the final load at which the foundation soil
experiences failure due to the mobilization of plastic equilibrium. The foundation soil fails
along the composite failure surface and the region is divided in to five zones, Zone 1 which
is elastic, two numbers of Zone 2 which are the zones of radial shear and two zones of Zone
3 which are the zones of linear shear. Considering horizontal force equilibrium and
incorporating empirical relation, the equation for ultimate bearing capacity is obtained as
follows.
Ultimate bearing capacity, BNDNcNq qcf 5.0
If the ground is subjected to additional surcharge load q, then
BNNqDcNq qcf 5.0)(
Net ultimate bearing capacity, DBNDNcNq qcn 5.0
BNNDcNq qcn 5.0)1(
Safe bearing capacity, DF
BNNDcNq qcs 15.0)1(
Here, F = Factor of safety (usually 3)
c = cohesion γ = unit weight of soil D = Depth of foundation
q = Surcharge at the ground level B = Width of foundation
Nc, Nq, Nγ = Bearing Capacity factors
Aa
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Bearing capacity factors in zones of local, mixed and general shear conditions. Local Shear Failure Mixed Zone General Shear Failure
Φ < 28o 28o< ϕ < 36o Φ > 36o
Nc1, Nq
1, Nγ1 Nc
m, Nqm, Nγ
m Nc, Nq, Nγ
Effect of Water Table fluctuation The basic theory of bearing capacity is derived by assuming the water table to be at great
depth below and not interfering with the foundation. However, the presence of water
table at foundation depth affects the strength of soil. Further, the unit weight of soil to be
considered in the presence of water table is submerged density and not dry density.
Hence, the reduction coefficients RW1 and RW2 are used in second and third terms of
bearing capacity equation to consider the effects of water table Density of soil :
In geotechnical engineering, one deals with several densities such as dry density, bulk
density, saturated density and submerged density. There will always be a doubt in the
students mind as to which density to use in a particular case. In case of Bearing capacity
problems, the following methodology may be adopted.
1. Always use dry density as it does not change with season and it is always
smaller than bulk or saturated density.
Aa
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Factors influencing Bearing Capacity
Bearing capacity of soil depends on many factors. The following are some important ones. 1. Type of soil
2. Unit weight of soil 3. Surcharge load 4. Depth of foundation 5. Mode of failure 6. Size of footing
7. Shape of footing 8. Depth of water table 9. Eccentricity in footing load 10. Inclination of footing load 11. Inclination of ground. 12. Size of footing.
LAB TESTS :- Particle size analysis
Sieve Analysis
Sieve analysis for coarser fractions has been done by dry sieving, while wet sieving method
has been followed for soil fractions with appreciable amount of clay. Sieving has been done
using a sieve shaker by passing through the following IS sieves.
4.75mm, 2.36 mm, 1.70 mm, 1.40 mm, 1.00 mm, 600 microns, 425 microns, 100 microns and 75 microns.
Liquid Limit
Testing is done as per IS: 2720 (Part 5) 1985. About 200 gm of soil sample passing through
425 micron IS sieve is mixed thoroughly with distilled water on the flat glass to form a
uniform paste. The paste generally has a consistency that will require 30 to 35 drops of the
cup to cause the required closure of standard groove. The ready mix soil is placed in the
Casagrande cup in such a way to form a depth of 1 cm at the centre of the cup and then
central groove of 12 mm is made using standard grooving tool. The cup is fitted and dropped
by turning the crank at the rate of 2 revolutions per second until the two halves of the soil
close. The number of drops required to make the groove close for the length of 12 mm is
recorded.
A portion of the sample is then taken out for water content determination and the water
content corresponding to 25 blows represents the liquid limit.
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Plastic Limit
About 15gms of oven dried soil passing through 425 microns sieve is mixed with sufficient
quantity of water such that the soil mass becomes plastic enough to be easily shaped into a
ball. A portion of this ball is rolled on a glass plate with the palm of the hand into a thread of
uniform dia of 3 mm. The water content represents the plastic limit.
Natural Moisture Content (NMC)
A moisture cup is loosely filled with soil and weighed with lid. It is then kept in oven with lid
removed and maintained at temperature of the oven at 1100 C for 24 hours. The lid of the
container is replaced and the dry weight found out. The percentage of water content shall be
calculated using the formula.
W= W2-W3 x 100 W3-W1
Where W2= weight of container with wet soil, in g.W3= weight of container with dry soil, in g
W1= weight of container with lid, in g, W= moisture content (%)
Bulk and Dry Density
Test procedure shall be as per IS: 2720 (Part-7) – 1987.
The unit weight of soil in g/cc is its weight per unit volume. Soil is filled in container and its
weight determined. Knowing the volume of container, the ratio of weight to volume
represents bulk density. The soil is then oven dried and weighed and dry density yd(g/cc) is
computed using formula.
yd = yb /(1+W),Where, yb = bulk density in g/cc
W= natural moisture content in %. Aa
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Specific Gravity Test procedure shall be as per IS: 2720 (Part 3/ Section 1) – 1987 for fine-grained soils. The
specific gravity of soil solids can be defined as the weight of given volume of soil particles to
the weight of equal volume of distilled water. This term is used in relating weight of soil to its
volume. Specific gravity is found out using standard specific gravity bottle of 50 ml capacity
by weighing empty bottle (w1), bottle+ dry soil (w2), bottle + dry soil + water (w3), bottle +
water (w4)
Specific gravity of soil = (w2-w1) / ((w2-w1) – (w3 – w4))
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TABLE—A DRILLING & SPT LOG IS:1892 & IS:2131 Bore Hole : 1 Water Level -NILL Refusal : 50 blows exceeds 15cms Bore dia 150/100 mm M Penetration cms cms cms
GROUND WATER TABLE NOT ENCOUNTERED WITH IN THE DEPTH OF INVESTIGATION.
Foundation recommendation: - SHALLOW FOUNDATION. CONCLUSION: - THE SOIL IS OF COURSED GRAINED SOIL UP TO 3.0 MTS DEPTH FOLLOWED BY COMPLETELY WEATHERED ROCK.
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TYPICAL CALCULATION
BEARING CAPACITY OF SOIL
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CALCULATION OF SAFE BEARING CAPACITY OF SOIL. Calculation based on shear for a square footing of 1.0m x 1.0m.
IS 6403 BH Bore Hole No. Ø Value= Degrees. 2/3 Ø Value= Degrees. C cohesion of the soil = kN/m2 .γb Density of soil= kN/m3 q. Effective over burden pressure = kN/m2 RL Ground Level= m FL Foundation Level= m Df Depth Of Footing= m Dw Depth Of Water Table m
BORE HOLE From DEPTH To DEPTH SPT DRY DENSITY
No mts mts N kN/m^3 BH-1 0.00 1.10 27 15.20
BORE HOLE DEPTH DRY DENSITY
FOOTING WIDTH COHESION ANGLE
OVER BURDEN PRESSURE
No METER KN/M^3 METER KN/M^2 Ø kN/m^2 BH-1 1.50 15.4 1.0 0.00 35.1 23.06
Bearing capacity factors: - (Ref.Table-1, page-8 of IS: 6403-1981)
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C B R
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General
The CBR test was originally developed by O.J. Porter for the California
Highway Department during the 1920s.
It is a load-deformation test performed in the laboratory or the field, whose
results are then used with an empirical design chart to determine the
thickness of flexible pavement, base, and other layers for a given vehicle
loading.
Though the test originated in California, the California Department of
Transportation and most other highway agencies have since abandoned the
CBR method of pavement design. In the 1940s, the US Army Corps of
Engineers (USACE) adopted the CBR method of design for flexible airfield
pavements.
The USACE and USAF design practice for surfaced and unsurfaced airfields is
still based upon CBR today (US Army, 2001; US Army and USAF, 1994).
The CBR determination may be performed either in the laboratory, typically
with a recomputed sample, or in the field. Because of typical logistics and
time constraints with the laboratory test, the field CBR is more typically used
by the military for design of contingency roads and airfields.
The thickness of different elements comprising a pavement is determined by
CBR values.
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The CBR test is a small scale penetration test in which a cylindrical plunger of
3 in2 (5 cm in dia) cross-section is penetrated into a soil mass (i.e., sub-grade
material) at the rate of 0.05 in. per minute (1.25 mm/minute).
Observations are taken between the penetrations resistances (called the test
load) versus the penetration of plunger. The penetration resistance of the
plunger into a standard sample of crushed stone for the corresponding
penetration is called standard load. The California bearing ratio, abbreviated
as CBR is defined as the ratio of the test load to the standard load, expressed
as percentage for a given penetration of the plunger
CBR = (Test load/Standard load)×100 In most cases, CBR decreases as the penetration increases. The ratio at 2.5
mm penetration is used as the CBR. In some case, the ratio at 5 mm may be
greater than that at 2.5 mm. If this occurs, the ratio at 5 mm should be used. The CBR is a measure of resistance of a material to penetration of standard
plunger under controlled density and moisture conditions. The test
procedure should be strictly adhered if high degree of reproducibility is
desired. The CBR test may be conducted in re-moulded or undisturbed
specimen in the laboratory. The test is simple and has been extensively
investigated for field correlations of flexible pavement thickness
requirement.
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Test Procedure
The CBR test is carried out on a compacted soil in a CBR mould 150 mm in
diameter and 175 mm in height, provided with detachable collar of 50 mm
and a detachable perforated base plate. A displacer disc, 50 mm deep to be
kept in the mould during the specimen preparation, enables a specimen of
125 mm deep to be obtained. The moulding dry density and water content
should be the same as would be maintained during field compaction. To
simulate worst moisture condition of the field, the specimens are kept
submerged in water for about 4 days before testing. Generally, CBR values of
both soaked as well as unsoaked samples are determined. Both during
soaking and penetration test, the specimen is covered with equal surcharge
weights to simulate the effect of overlying pavement or the particular layer
under construction. Each surcharge slotted weight, 147 mm in diameter with
a central whole 53 mm in diameter and weighing 2.5 kg is considered
approximately equivalent to 6.5 cm of construction. A minimum of two
surcharge weights (i.e. 5kg surcharge load) is placed on the specimen. Load is
applied on the penetration piston so that the penetration is approximately
1.25mm/min. The load readings are recorded at penetrations, 0, 0.5, 1, 1.5, 2,
2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 8, 9, 10, 11, 12, and 12.5mm. The maximum
load and penetration is recorded if it occurs for a penetration of less than
12.5 mm.
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The table gives the standard loads adopted for different penetrations for the
Standard material with a CBR value of 100%. Standard Load Used In California Bearing Ratio Test Penetration of plunger(mm) Standard load (kg)
2.5 1370 5.0 2055 7.5 2630 10.0 3180 12.5 3600
Scope of Work The present scope of work for this project is to ascertain the CBR value under
different soaking time conditions and to study the influence of moisture
content developed in the samples under varying soaking.
1) To collect a particular soil sample and determine its basic physical
property such as LL,PL,PI and grain size distribution
2) To study the soil under modified proctor compaction and determine the
MDD and OMC for the soil sample
3) To carry out CBR Test for sample soaked in different times
4) To obtain moisture content for varying degree of soaking
5) To study the influence of soaking on Subgrade strength
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General
The experimental work comprises in the following parts.
1. Determination of index property
• Liquid limit by liquid limit device
• Plastic limit
• Plastic Index
2. Particle size distribution
3. Estimation of maximum dry density and optimum moisture content by
modified proctor test
4. Calculation of CBR strength
(i) Moulding the soil sample into standard moulds keeping its moisture
content and dry density exactly same as its optimum moisture content and
proctor density respectively.
(ii) Determination of CBR strength of the respective soil samples in moulds
using the CBR instrument.
(iii) Soil sample is tested for its CBR strength after being soaked in water for
1 day, 2 days, 3 days and 4 days. Unsoaked CBR is also determined for each
sample. Brief steps involved
Particle size distribution
The Standard grain size analysis test determines the relative proportions of
different grain sizes as they are distributed among certain size ranges.
JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
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Liquid Limit Test
This test is done to determine the liquid limit of soil as per IS: 2720 (Part 5) –
1985. The liquid limit of fine-grained soil is the water content at which soil
behaves practically like a liquid, but has small shear strength. Its flow closes
the groove in just 25 blows in Casagrande’s liquid limit device.
Plastic Limit Test
Plastic limit is defined as minimum water content at which soil remains in
plastic state. The plasticity index is defined as the numerical difference
between its Liquid limit and Plastic limit
JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
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ABSTRACT
Design of the various pavement layers is very much dependent on the
strength of the Subgrade soil over which they are going to be laid.
Subgrade strength is mostly expressed in terms of CBR (California Bearing
stronger Subgrade goes well with thinner pavement layers. The pavement
and the Subgrade mutually must sustain the traffic volume. The Indian
Road Congress (IRC) encodes the exact design strategies of the pavement
layers based upon the Subgrade strength which is primarily dependant on
CBR value for a laboratory or field sample soaked for four days. The
Subgrade is always subjected to change in its moisture content due to
rainfall, capillary action, overflow or rise of water table. For an engineer,
it’s important to understand the change of Subgrade strength due to
variation of moisture content. This project is an attempt to understand the
strength of Subgrade in terms of CBR values subjected to different days of
soaking and the corresponding variation in moisture content. It is
observed that the CBR decreases and the moisture content increases for
high degree of soaking
JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
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Subgrade
Subgrade can be defined as a compacted layer, generally of naturally
occurring local soil, assumed to be 300 mm in thickness, just beneath the
pavement crust, providing a suitable foundation for the pavement. The
Subgrade in embankment is compacted in two layers, usually to a higher
standard than the lower part of the embankment The Subgrade, whether in
cutting or in embankment, should be well compacted to utilize its full
strength and to economize on the overall pavement thickness. The current
MORTH Specifications require that the Subgrade should be compacted to
100% MDD achieved by the Modified Proctor Test (IS 2720-Part 7).
JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
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Subgrade Soil Soil is a gathering or deposit of earth material, derived naturally from
the breakdown of rocks or decay of undergrowth that can be excavated
readily with power equipment in the field or disintegrated by gentle
reflex means in the laboratory. The supporting soil below pavement
and its special under course is called sub grade. Without interruption
soil beneath the pavement is called natural sub grade. Compacted sub
grade is the soil compacted by inhibited movement of heavy
compactors.
Desirable Property of Subgrade Soil The advantageous properties of sub grade soil as a highway material are • Stability • Incompressibility • Permanency of strength • Minimum changes in volume and stability under adverse conditions of Weather and ground water • Superior drainage, and • Ease of compaction
JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
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Methods for determining Subgrade strength for designing new roads For the pavement design of new roads the sub grade strength needs to be
evaluated in terms of CBR value. Based on soil classification tests and the table given in IRC: SP: 72-2007
Which gives typical design CBR values for soil samples Compacted to proctor density at optimum moisture content and soaked Under water for 4 days.
Typical CBR values DESCRIPTION OF
SOIL SUBGRADE SOIL
CLASSIFICATION AS PER IS
TYPICAL SOAKED
CBR VALUE IN (%)
Highly plastic clays CH, MH 2-3 Silty clays
and sandy clays
ML, MI CL, CI 4-5
Clayey sands and
Silty sands SC, SM 6-10
Typical CBR values CBR VALUE SUBGRADE STRENGTH 3% or less Poor 3% - 5% normal 5% - 15% good
JOINT GENERAL MANAGER.AIRPORTS. RITES LTD. 144,SECTOR 44, GURGAON 122003
GEO TECHNICAL INVESTIGATION FOR DEVELOPMENT ADMINISTRATIVE AIR STRIP AT KUPPAM, CHITTOOR DISTRICT. AP.
LOA; RITES/AP/KUPPAM/2018/14700 DT 29-10-2018. Report No 1 03-12-2018 : ,