this slide is related to geotechnical engineering a subject of civil engineering .

1. (CIVIL ENGINEERING DEPARTMENT )
(GEOTECHNICAL ENGINEERING 2)
METHODS OF SUB-SURFACE EXPLORATION,
METHODS OF BORING, NUMBER , LOCATION
AND DEPTH OF BORING.
PRESENTED BY PRAJAKTA LADE
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2.  Sub – surface Exploration
 Nessecity of Sub- surface Exploration
 Methods of sub- surface Exploration
 Types of Boring
 Number , Location and Depth of Boring
CONTENT
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3.  The surface and subsurface investigation or
site exploration is carried out to collect the
information about physical properties and
characteristics of the subsoil material as well
as the details of other geological features of
the site area.
SUB-SURFACE INVESTIGATION
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4.  1. Selection of the type and the depth of foundation suitable for a given
structure.
 2. Evaluation of the load-bearing capacity of the foundation.
 3. Estimation of the probable settlement of a structure.
 4. Determination of potential foundation problems (for example, expansive
soil, collapsible soil, sanitary landfill, and so on).
 5. Establishment of ground water table
.
 6. Prediction of lateral earth pressure for structures like retaining walls,
sheet pile bulkheads, and braced cuts.
 7. Establishment of construction methods for changing subsoil conditions
NECESSITY OF SUB-SURFACE EXPLORATION FOR
FOUNDATION.
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5.  The various methods of soil exploration may be grouped as follows.
 1. OPEN EXCAVATIONS.
 2. METHODS OF BORING
 3. SURFACE SOUNDINGS.
 4. GEOPHYSICAL METHODS.
METHOD OF SUBSURFACE EXPLORATION.
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6. 6

7.  This method for subsurface exploration is adopted to inspect
the substrata . open excavation for soil exploration can be done by
two ways.
 PITS

 Shallow pits called trial pits
 Long shallow pits called trenches
 PROBING.
 DRIFT AND SHAFTS
OPEN EXCAVATION
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8.  TRIAL PITS
 The depth is limited to 4-5m only.
 The in-situ conditions are examined visually
 It is easy to obtain disturbed and undisturbed samples
Block samples can be cut by hand tools and tube samples can be taken from the bottom of the pit.
Walls of the test pit indicate four layers (1) Clayey silt (2) Sandy silt (3) Clean sand (4) Sandy gravel

 Pits upto 1m not require lateral support , if pits are depper and below ground water table , they require the lateral
supprts like bracing and sheeting system .
 TRENCHES
 Long shallow pits called trenches
 In case of dipper pits called trenches , ventilation is neccesary to avoid unhygenic conditions if water is encountered
in trench it should be propely disposeed.
 On slopping ground trenches are more suitable than pits
 Trenches and trial pits excavation can be done mehanically OR Manually.
PITS
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9. PITS
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10.  This method is suitable for soft soils such as clay , gravel and sand.
 In this method , a steel bar of 25 to 40mm diameter having a pointed end is
driven in the ground until a hard strata is met . The bar is allowed to fall
vertically under its own weight or it is driven by drop hammer .
 The bar is drawn out at some interval , so that the rough idea of the nature
of strata is obtained from the soil sticking to the sides of the bar.
 The experienced persons can be engaged in the execution of the driving
operation . Fig. shows various types of probing stones:
PROBING
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11. PROBING
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12.  Drifts are horrizontal tunnels made in the hill-stone to determine the nature and
structure of the geological formation .
 IS 4453-1980 reccomends th at a drifts should have the minimum clear diemenssion of
1.5m width and 2.0 m height in hard rock. ,
 If soft rock, an arch roof is more advantageous than fiat roof.
SHAFTS
 Shafts are the large size vertical hole in the geological formation .
 These may be rectangular or circular in section .
 The minimum width of a rectangular shaft is 2.4 m and for a circular shaft , the
minimum diameter is 2.4 m .
DRIFTS
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13. DRIFT SHAFT
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14.  THE VERTICAL BORE HOLE IS DRILLED IN THE GROUND TO GET THE
IMFORMATION ABOUT THE SUB-SOIL STRATA IS CALLED BORING.
 Depending upon the type of soil and the purpose of boring , the following
methods are used for drilling the holes.

 The various boring methods adopted for soil exploration are as follows :
 Auger boring
 Wash borin
 Percussion boring
 Rotary drilling (core boring or core drilling)
METHODS OF BORING
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15.  This type of augers are commonly used for clayey
or sandy soils or soft soils .
 It can be operated manually or mechanically . The
hand operated augers are used up to 6 m depth and
the mechanically operated augers are used for
greater depth up to 15 m .
 The auger is vertically driven into the ground by
rotating its handle and is pressed down during the
process of rotation .
 At every 30 cm depth of penetration , the auger is
drawn out and the samples of soils are collected
separately for testing ..
AUGER BORING
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16. Power Driven Augers
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17.  A casing of about 2 to 3m is driven with a drop hammer.
A hollow drill rod with chopping bit is inserted inside the
casing at its lower end .
 Water is pumped down the hollow drill rod , which is
called a wash pipe. As a result water comes as a strong
jet through a small opening of a chopping bit as a result
a hole is drilled by a combination of chopping and jetting
action .
.
 The water in wash pipe leaves the hole along with the
loose soil, and reach the ground with soil.
 The sample collected give some idea about thE change in stata which obtained by
the reaction of chopping bit as the hole is drilled change in
colour of wash water also suggest change in strata.
 Mainly wash boring is used for drilling holes in the ground
ones the hole is drilled a sampler is inserted to obtain soil samples for labortary
testing.
WASH BORING
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18. WASH BORING OR MUD ROTARY (SOIL)
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19.  It is very fast method of advancing hole in rock , but also used in soils.
The hole is drilled by rotating a drilling tool, (cutting bit or a coring bit) is
attached to the lower end of hollow drilling rods
 At the top of drill rod , drill head is provided it comprises of a rotary mechanisum
and drilling rod is rotated, the cutting bit shears off chips of the material
penetrated either soil or rock.
 The drilling fluid cools and lubricates the drilling tool and carries the loose debris
to the surface .
 Drilling bit is replaced by sampler when sampler is required to be taken.
 when rotary drilling is done to drill soil then it is ROTARY DRILLING.
 When rotary drilling is done to drill rock then it is a CORE DRILLING .
ROTARY DRILLING (CORE DRILLING)
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20. ROTARY DRILLING OR CORE DRILLING (ROCK)
Tricone Drill Bit
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21. ROTARY DRILLING
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22.  This method is used for rocks and soils having boulders ; which are
broken up by repeated blows from a bit or chisel in vertical hole in
ground the material gets pulverised .
 Thus , the pulverised material is converted into slurry by pouring water
in the bore and this slurry is bailed out at regular interval using sand
pump and dried for testing.
 For drilling tube wells also and for boring holes in glacier hills ,
percussion drilling is used .
Because of the heavy blows of the chisael , the material at
the is in disturb state we get disturb sample .
PERCUSSION DRILLING.
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23. P
PERCUSSION DRILLING
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24.  The degree of variation of the sub-surface data in the horizontal and
vertical direction decides the depth of exploration required at a
perticular site .
 THE SIGNIFICANT DEPTH IS DEPEND UPON-
 TYPE OF STRUCTURE
 WEIGHT OF STRUCTURE
 SIZE OF STRUCTURE
 SHAPE OF STRUCTURE
 DIPOSITION OF LOADED AREAS
 SOIL PROFILE AND ITS PROPERTIES
DEPTH OF BORING
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25. SR NO TYPE OF CONSTRUCTION
OR FOUNDATION
DEPTH OF BORING
1. FOR SQUARE FOOTING 1.5B = D
2 FOR STRIP FOOTING 3B = D
3. FOR PILE FOUNDATION D= 1.5 times the width of pile
group
4. IN CASE OF FRICTION PILE D= 1.5 times the width of pile
group measured from lower
3rd point .
5. FOR GRAVITY DAM D = 2H of Dam
6. IN CASE OF ROAD FILL D = 2m below ground surface
DEPTH OF BORING
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26. 7. FOR MULTISTORIE BUILDING
DEPTH OF BORING
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27. DEPTH OF BORING
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28. THANK YOU
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