Soil Investigation for Building Foundation

Stages Involved In Soil Investigation for Building Foundation ?

• Planning the details and sequence of operations
• Collection of soil samples from the field
• Conducting all field tests for determining the strength and compressibility characteristics of the soil
• Study of ground water level conditions and collection of water samples for chemical analysis
• Geophysical exploration
• Laboratory Testing of all samples of soil, rock, and water
• Preparation of drawings and charts (Grain Size Distribution, Stress –Strain curve, etc.)
• Analysis of the test results
• Preparation of report

Phase of Soil Investigation

• Type of soil,
• Size of structure , and
• Nature , Importance of the Structure
• The Engineer’s familiarities with the site
• Indian Standards & Building Codes
• The Customer Requirement
• Topographical Condition –Terrain

PHASE – I DESK STUDY

It involves collection of available information such as

• A site plan
• Type, size, and importance of the structure
• Loading conditions
• Previous geotechnical reports
• Maps
  1. Topographical maps,
  2. Aerial photographs,
  3. Still photographs,
  4. Satellite images, and
  5. Geologic maps

Geographical Information System (GIS)
An integration of software, hardware, and digital data

• Capture,
• Manage,
• Analyse and
• Display
  Spatial information can be used to view, share’ understand’ question, interpret, and visualize data. in ways that reveal relationships, patterns, and trends.

Google Earth
can be used to view,

• Satellite imagery,
• Maps,
• Terrain, and
• 3D structures

PHASE – II PRILIMINARY RECONNAISSANCE / EXPLORATION

Field Observations

Inspection of the site is must at reconnaissance stage as it gives better appreciation of site and overcomes some of
the obvious mistakes.

While performing site inspection some of the important points which are to be observed are:
i . Slope failures
ii. Evidence of seepage
iii. Check outcrops or open cuts
iv. Check surface material
v. Problem with existing structures
vi. Shrinkage cracks
vii. Environmental contamination especially in industrial areas.
viii. Interviewing/feedback from residents

PHASE – III DETAILED SOIL EXPLORATION

The objectives of a detailed soils exploration are:

• To determine the geological structure, which should include the thickness, sequence, and extent of the soil strata.
• To determine the groundwater conditions.
• To obtain disturbed and undisturbed samples for laboratory tests.
• To conduct in situ tests.

Detailed Geotechnical Investigation

• Detailed geotechnical investigation involves determination of shear strength, compressibility, density,
• natural moisture content and permeability of different types of soil.
• Investigation is carried out before finalizing any drawing for foundation of structures whether it is
  building, bridge or even railway formation.
• In geotechnical investigation primarily field testing is performed with collection of disturbed and
  undisturbed soil samples for detailed laboratory testing.
• Field and laboratory testing for SOIL index as well as engineering properties of soils helps in
  identification, classification as well as assessment of strength/bearing capacity and settlement patterns.
• The detailed investigation involves boring programme and sampling to determine these properties.
  Field tests which may be performed are in-situ vane shear tests and plate load tests.

PHASE – IV LABORATORY TESTING

1. To classify the soils.
2. To determine

• Soil strength,
• Stress – strain response
• Permeability,
• Compatibility, and
• Settlement parameters.

PHASE – V WRITE A REPORT

• The report must contain a clear description of the soil at the site ,
• Method of exploration,
• Soil stratigraphy,
• In situ and laboratory test methods and results
• The location of the groundwater.