1. Birla Vishvakarma Mahavidyalaya Gujarat Technological University
Subject: SOIL MECHANICS
( )
Prepared by:
Name
Enrollment number
KACHCHHI JATEENKUMAR M.
KOTWAL KRUNALKUMAR H.
Guided By: Prof. B. R. DALWADI

2. SOIL INVESTIGATION

3. BROAD OBJECTIVES Subsurface conditions Subsurface soil profile
To get specific, reliable & adequate information about:-
Subsurface conditions
Subsurface soil profile
Ground water (hydro-static/hydro-dynamic) conditions
Geological information
Past history
To assess feasibility and suitability of type of foundation (shallow/deep)
To generate adequate and reliable information regarding soil profile and soil parameters for design and execution purpose
To evaluate parameters for constrains in activities, considering safety and security

4. SOIL INVESTIGATION To recognize, to be familiar of the site
PHASES OF SOIL EXPLORATION:
RECONNAISSANCE SURVEY:
To recognize, to be familiar of the site
To collect general details regarding site from published literatures such as journals, reports, geological maps, soil survey maps etc.
To visit the site for getting idea about the terrain and its geological features.
To talk with local people, to study existing structures with similar site conditions etc.
(sites with BC soil)

5. Few samples can be collected for laboratory testing.
2. PRELIMINARY EXPLORATION:
Few bore holes may be drilled to observe the soil types and their depths.
Few samples can be collected for laboratory testing.
It depends on nature of structure and site.(Narmada dam site)
3. DETAILED EXPLORATION:
Drilling large no. of bore holes, collection of disturbed and undisturbed samples for lab. Testing.
It depends on nature of structure and site.
SUMMARY:
Purpose of soil exploration:-
To find the sequence, extent and location of the subsurface strata.
To determine engineering properties of the strata.
To determine ground water conditions.

6. TYPES OF SOIL SAMPLES little or no disturbance to the soil structure
UNDISTURBED SAMPLES:-
little or no disturbance to the soil structure
natural structure and properties will be preserved
useful for important laboratory tests like shear test, consolidation test etc.
DISTURBED SAMPLES:-
NON-REPRESENTATIVE SAMPLES:
mixture of soils from different layers/levels
complete disturbance to soil structure and properties
can not be used for any test
2 REPRESENTATIVE SAMPLES:
disturbance to soil structure
water content may or may not be changed
no change in mineral constituents
suitable for classification and identification tests

7. FIELD METHODS OF EXPLORATION
1. OPEN EXCAVATIONS: to prepare trial pits, trenches upto required depth
ADVANTAGES:- -simple method, involves manual operations
-direct examination of soil strata
-easy collection of disturbed and undisturbed
samples
-useful for preliminary exploration for shallow
foundations only.
DISADVANTAGES:-economical for shallow footings only.
-upto about 3.0m depth otherwise cost
increases with depth

8. details along vertical / horizontal / inclined line
2. BORING / DRILLING METHODS:
drilling of bore holes
details along vertical / horizontal / inclined line
different boring methods based on soil types
samples can be collected from greater depths e.g. 30m / 40m depths
useful for both preliminary and detailed exploration
time consuming and costly

9. (1) AUGER BORING:
bore hole is drilled / advanced by pushing and twisting / rotating an auger
post hole type auger / helical auger
may be manually operated ( upto 12-15m) or power driven auger (upto 15-30m)
rate of progress according slow / fast
extensively used for subsurface exploration of highways, airfields, railways
simple, light and inexpensive equipment
disturbed bur representative samples, for collecting undisturbed sample the bottom of the BH should be cleaned carefully
generally useful for cohesive soils, for cohesionless soils, bailer (a heavy metallic cylinder with flap valve at bottom) is used
GWT can be determined
Casing pipes generally not required i.e. uncased BH
(2) WASH BORING:
Boring / drilling is advanced (i) partly by chopping and twisting of a light drill bit and (ii) partly by jetting with water which is pumped through a hollow drill bit and drill rod
Casing pipes are required
Samples :highly disturbed and non representative
Before collection of UDS, careful cleaning of BHY is required
Suitable for all common soils which do not contain stones and boulders
Not suitable for very hard and cemented soils or rocks

10. Auger boring Power drills
Boring tools
Auger boring Power drills

11. Wash Boring

12. (3) PERCUSSION DRILLING:
Boring is advanced by alternatively raising and dropping a heavy drill bit (also called as a churn bit)- churning action
Small quantity of water is added during boring
After sufficient churning, bit is lifted and slurry removed by using bailer or sand pump
Samples :highly disturbed and non representative
Casing is generally required except rock
Oldest method
Applicable to all soils and rock
Best suited for coarse gravel deposits, boulderly soils and very hard soils
(4) ROTARY DRILLING:
BH is advanced by rapid rotation of the drilling bit which cuts, chips and grinds the material into small particles
Water or drilling mud is pumped through drilling rods and bit
Light, portable or heavy drilling rig required.
Very fast method in all soils and rocks, Suitable for all soils and rocks
Not well suited for deposits with very coarse gravels, numerous stones and boulders and badly fissured rocks
Samples :highly disturbed and non representative
Except soft soils, BH is uncased

13. To measure resistance to penetration of a rod, cone or sampler etc.
3. SUBSURFACE SOUNDINGS / PROBING METHODS :
Can be considered as soil exploration methods as well as field tests (why?)
To measure resistance to penetration of a rod, cone or sampler etc.
Empirical correlations between soil properties ( E, Poisson’s ratio, bearing capacity, settlement etc.) and resistance offered gives idea about soil type, extent etc.
Direct observation of soil type & collection of sample may or may not be.
e.g. SPT, DCPT, SCPT

14. SPT

15. (i) electrical receptivity methods
4. GEOPHYSICAL METHODS:
based on the measurement of change in the physical characteristics of mineral and fluids e.g. resistance to electrical current, magnetic fields, elastic waves, density etc. give idea about soil strata
Previously developed and extensively used for finding oil and minerals by companies like ONGC, useful upto greater depths.
(i) electrical receptivity methods
(ii) seismic refraction/reflection methods

16. [A] ELECTRICAL RESISTIVITY METHODS Wenner’s Method :

17. [A] ELECTRICAL RESISTIVITY METHODS: Wenner’s Method :
(i) ELECTRICAL PROFILING : idea parallel to the ground i.e. in linear / longitudinal direction
keep electrodes at constant spacing and move along a line
change in curve indicates change in soil profile
Distance ‘a’ ρ
Depth ‘a’
(ii) ELECTRICAL SOUNDING :
idea in vertical direction i.e. wrt the depth, spacing ‘a’ should be successively increased

18. ADVANTAGES of GEOPHYSICAL METHODS :
compared to borings, large area or projects of great linear extent can be explored more rapidly and economically e.g. sites for dams and reservoirs, large group of buildings, factory site, tunnels, highways, airfields, etc.
subsurface irregularities can be detected easily which can be missed by drilling ( because these methods cover areas, zones)
simple, quick, economic covering large area and great depth
well suited for reconnaissance survey
DISADVANTAGES:
no collection of samples and hence no exact ideas about soil properties
materials can not be identified definitely

19. THANK YOU….