The document outlines the soil exploration process, which involves identifying soil layers, analyzing physical properties, and assessing conditions for foundation design. Various methods, such as pits, boring, and geophysical techniques, are employed depending on depth and soil characteristics. The purpose of soil exploration is to inform the selection of foundation type, evaluate bearing capacity, estimate settlement, and identify potential issues like expansive soils.

1. Soil Exploration/ Sub-surface Exploration
Prepared by: Er. Utkarsha Bhetuwal
Structural Engineer

2. Soil Exploration
Process of:
• Identifying layers of soil deposits
• Pointing out physical properties of soil (unit
weight, angle of internal friction, cohesion,
etc)
for gathering data used in design of foundation

3. Soil Exploration
• Sampling of soil for laboratory test
• Testing in site (in situ test)

4. Purpose of the soil exploration
Done to gather data for design of footing:
• Selecting type and depth of foundation
• Evaluating bearing capacity of the foundation
• Estimating probable settlement of structure
• Determining the location of ground water table
• Finding out potential foundation problems (eg.
Expansive soil, collapsible soil, etc)

5. Depth required for exploration
Depends upon:
• Degree of variation of soil
• Load from the structure
• Characteristics of soil

6. Methods of soil explorations
• Pits and Trenches
• Boring
• Rotary Drilling
• Core cutting
• Geophysical Methods

7. Pits and Trenches
• Excavated to inspect strata of soil
• Must be sufficiently wide to provide working
space

8. Pits and Trenches
• For depth
– Up to 3m, lateral support is not required
– > 3m, lateral support is required
• For depth > 6m, boring and
drilling are feasible

9. Boring and Drilling
• Done when depth of exploration is large
• Types
– Auger Boring
– Wash Boring
– Rotary Drill
– Percussion Drill

10. Auger Boring
• Types :
– Hand Auger (for 3m to 6m depth)
– Mechanical Auger (for > 6m depth)

11. Auger Boring
• The bore hole is advanced by:
– Turning the auger and
– Applying thrust in downwards direction
• Auger Boring is used for depths < 12m

12. Wash Boring
• First, casing is driven
• Casing has chopping bit
at bottom
• Hollow drill rod is
inserted in the casing
• Water is pumped down
the hollow drill rod
• Hole is advanced by chopping and jetting action

13. Wash Boring
• Suitable for soft soils
• Not suitable for stiff soils and hard rock

14. Rotary Drill
• Drilling bits are used
• Drilling bits rotate rapidly that advance the
hole
• Used for clay, sand and rocks

15. Percussion Drill
• Used for making holes in rocks, boulder and other
hard strata
• It contains heavy chisel
• The chisel is raised
and dropped so that
the rock is pulverized
• Pulverized materials
are removed
through pumping
by water

16. Core Drill
• Used for drilling holes and
obtaining rock cores (samples)
• Core barrel is attached
to drilling rod
• Coring bit
(made up of diamond,
carbide, tungsten)
is attached at bottom
• Hole is advanced
by rotating the drill

17. Geophysical Exploration
• Indirect method
• Eg: Seismic refraction survey, Resistivity
survey
• Less time consuming
• Less expensive than conventional exploration
• But interpretation of results is difficult