This document discusses various topics related to geotechnical engineering challenges and ground improvement methods. It begins by describing the different types of parent rock and elements that make up the earth's crust. It then discusses mechanical and chemical weathering processes, different types of soils formed from weathered parent rock, and problematic soil types. Various ground conditions that can cause difficulties are presented, along with examples. The document concludes by describing different methods for classifying and improving ground conditions, such as compaction grouting, deep soil mixing, and soil nailing.

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2. Thanks to
Sigma Institute of Engineering, and
IGS – Baroda Chapter
Good Afternoon

3. Dr. D.L.SHAH
Consulting Geotechnical Engineer
dr_dlshah@yahoo.com
Geotechnical Challenges and
Ground Improvement Methods

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5. Parent Rock
~ formed by one of these three different rock type
igneous sedimentary metamorphic
formed by cooling of
molten magma (lava)
formed by gradual
deposition, and in layers
formed by alteration
of igneous &
sedimentary rocks by
pressure/temperature
e.g., limestone, shale
e.g., marble
e.g., granite

6. Elements of Earth
12500 km dia
8-35 km crust
% by weight in crust
O = 49.2
Si = 25.7
Al = 7.5
Fe = 4.7
Ca = 3.4
Na = 2.6
K = 2.4
Mg = 1.9
other = 2.6
82.4%
Geotechnical engineers are interested mainly in the top 100 metres of
the earth crust. As you can see from the table, 82% of the elements are
oxygen, silicon and aluminium.

7. Mechanical Weathering
• Unloading – removal of overlying material
• Frost Action – up to 280kg/cm2
• Organism Growth – growth inside of joints causes wedging effect
• Abrasion - friction
– Wind
– Water
Decomposition of rock through chemical bonding
Examples include:
Hydration (combining with water)
Oxidation
Carbonation (saturation with carbon dioxide)
Chemical Weathering

8. Soil Formation
Parent Rock
Residual soil Transported soil
~ in situ weathering (by
physical & chemical
agents) of parent rock
~ weathered and
transported far away
by wind, water and ice.

9. Residual Soils
Formed by in situ weathering of parent rock
Transported Soils
 wind “Aeolian”
sea (salt water) “Marine”
lake (fresh water) “Lacustrine”
river “Alluvial”
ice “Glacial”
Transported by: Special name:

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11. Grain Size Distribution - Gravel
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12. Grain Size Distribution - Sand
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13. Grain Size Distribution - Clay
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14. Effect of Water on Soil
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15. PROBLEMATIC SOILS
Certain soils present problems to civil engineering developments
due to the specific conditions in which these soils occur.
These soils are known as problem soils and the following soil
types have been identified:
•Collapsible soils causing damage due to differential settlement.
•Expansive clays, causing damage due to continual heave and
shrinkage.
•Soft clays causing damage due to compressibility.
•Dispersive soils causing damage due to erosion of colloidal
particles.
•Pedogenic materials causing problems due to variable
conditions.
•Slope instability causing problems due to variable conditions.

16. SOME EXAMPLES OF DIFFICULT GROUND CONDITIONS
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Loose soils
Unstable dune sands
Soft Clays, under-
consolidated deposits
Filled-up ground
Mine tailings, flyash
Water Seepage
Liquefaction during
earthquakes / vibration
Deep excavations in built-
up areas
Unstable hill slopes
Soil Hillocks
Landslides
Soft rocks, Fractured
rocks
Shear zones
Tunnels, solution cavities,
voids in rock
Artesian conditions
Erosion, floods, scour, etc

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22. Colloidal coatings which adhere to individual soil grains provide
intergranular bonds and thus an apparent strength to the soil at
low moisture content, but this apparent strength diminishes when
the moisture content increases.

23. Driveway Drop 8”
due to Collapse
of Collapsible soil

24. STABILITY OF VERTICAL CLIFF OF
SHERGARH HILL
Shergarh hill adjacent to Right bank approach
road has been cut almost vertically and the
rock strata of hill is fractured and weaken.
There is a possibility of falling of loose
material on approach road.

25. Malin Village, Pune. 30 July, 2014.

27. Liquefaction failure
Kawagishi-cho apartment suffered
from bearing capacity failure
secondary to sand liquefaction in
1964, Nigata Earthquake.

28. Environmental Issues

29. Untreated Effluent from
Vatva Factory Blaken the
Khari River near Lali Village
Children from Village near
Nandesari Learn their Lesson in
Colour from the Water they Drink

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Some unsung heroes of Civil Engineering…
… buried right under your feet.
foundations soil
exploration
tunneling

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?
Need good knowledge
of the soil conditions
proposed structure
Problem Soils
e.g., reactive clays, soft
soils, sink holes, etc.

32. Site Investigation
Site investigation plays an important role in the early days of most civil
engineering projects. The idea is to obtain adequate information about
the soil conditions at the site, at minimal cost.

33. In clay layers…
collect undisturbed clay
samples in thin walled
sampler
(e.g. shelby tube)
Clay
bore hole Consolidation,
triaxial tests in lab

34. Classification of ground modification
techniques
• Mechanical modification
• Hydraulic modification
• Physical and chemical modification
• Modification by inclusion and
confinement
• Combination of the above

35. Chemical Modification
Deep Soil Mixing Jet Grouting Injection Grouting
Reinforcement

36. Ground Improvement Methods
Ground
Improvement
Densification
Vibro
Compaction
Dynamic
Compaction
Blast
Densification
Compaction
Grouting
Consolidation
PVD +
Surcharge
Vacuum
Consolidation
(Vibro
Replacement)
Chemical
Modification
Deep Soil
Mixing
Jet Grouting
Injection
Grouting
Reinforcement
Vibro
Replacement
Geosynthetic
Reinforcement
Rigid
Inclusions
(Compaction
Grouting)
Others
Removal &
Replacement
Thermal
Electrical

37. Liquefaction
One of the most dramatic causes of damage of structures during
earthquakes has been the development of liquefaction in saturated
cohesion-less deposits. These deposits have tendency to densify
when subjected to earthquake loading. However, when saturated, the
tendency to densify causes the excess pore water pressure to
increase. This, in turn, results in the effective stress of soil to
decrease. As a consequence, the cohesion-less deposit will lose a
substantial strength and a subsequent reduction in soil volume until
the excess pore water pressure has a chance to dissipate. The
phenomenon of pore pressure build-up following with the loss of soil
strength is known as liquefaction (Committee on Earthquake
Engineering, 1985).

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41. Dynamic
compaction.ppt
Dynamic
Compaction

42. Burgan Cape Terminals (Pty) Ltd. Capetown, South Africa.

43. Burgan Cape Terminals (Pty) Ltd. Capetown, South Africa.

45. Vibroflotation is a
technique for in situ
densification of thick
layers of loose granular
soil deposits. It was
developed in Germany in
the 1930s.
• Vibro Compaction.flv

47. Stone Columns
• Stone columns technique is similar to vibro-compaction. The
difference is in the backfill that is used. Stone columns generally
use gravel or crushed stone as backfill. Thus, the name of stone
column. In general, stone columns can be installed in two ways:
dry or wet method (Munfakh, et al., 1987; Hayward Baker, 1996).
• In the dry method, compressed air is used to assist the advance of
the vibrator. The stone is fed by pipes directly to the nose of the
vibrator (bottom feed technique). Little soil is extracted during the
installation. Stone columns installed using dry method are
referred to as vibro-displacement stone columns.

49. Top feed vibro replacement method

50. DETAILS OF THE STOCK PILE
• Each of the iron ore stock pile has a triangular
cross section with a maximum crest height of 20 m
and base with exceeding 50m. The unit weight of
the iron ore is taken as 28kN/m3. The average load
intensity over the area is expected to be 300 kPa.
• Between the stock piles there is separate foundation
for rails to operate stacker and reclaimer. For
operational reasons these foundations have stringent
settlement requirements and it is therefore necessary
to support them on pile foundation.

51. Typical cross section

57. Factor of Safety for DSP-3, without ground improvement

64. SSNNL - Canal

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70. Soil Nailing

71. Ahmedabad

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Expansive soil stabilization