Site Investigation

Soil exploration

__________ is a part of site investigation

Site Investigation

deals with determining in general, the suitability of the site for the proposed construction

Site Investigation

its objectives are:

The nature and sequence of strata

The ground water conditions at the site

The physical properties of soil and rock underlying the site

The mechanical properties such as strength of different soil or rock strata

Importance of Site Investigation

Minimize Damages

Saves on Cost

Determine Construction Costs

Increases Project Safety

Initial Information of Site Investigation

Type of Structure

Structure Characteristics

Starting Data

Construction Method

Estimated Construction Period

Soil condition (Geological, Geotechnical or Aerial Analysis)

Behavior of Existing Structures

Retaining Walls Failure

Settlement Failure

Sinkholes

Site Investigation - Failures

Site Reconnaissance

Preliminary Site Exploration

Detailed Site Exploration

Preparation of Report

Stages of Site Investigation

Site Reconnaissance

first stage of site investigation

researching the site to gain as much geological and historical information as possible

Preliminary Site Exploration

General Site Exploration

to obtain an approximate picture of sub-soil conditions at low cost.

Soil sample (experimental borings and shallow test pits)

Simple laboratory tests (moisture content test, density, unconfined compressive strength test, etc.)

Preliminary Site Exploration

Approximates values of soil's compressive strength.

Position of the groundwater table.

Depth and extent of soil strata.

Soil composition

Depth of hard stratum from ground level.

Engineering properties of soil ( disturbed sample)

Detailed Site Exploration

complex projects, major engineering works, heavy structures

field tests (in-situ vane shear test, plate load test, etc.)

laboratory tests (permeability tests, compressive strength test on undisturbed soil samples)

Preparation of Report

an example of this report is Boring Logs

Open Excavation (Test Pits)

Permits visual inspection of sub-surface conditions in natural state.

Max. depth limited to 18 -20 feet.

Especially useful for gravelly soil where boring boreholes may be difficult.

Sampling/testing done on exposed surfaces

Methods of Boring

Auger Borings

Power Auger

Wash Boring

Rotary Drilling

Percussion Drilling

Auger Borings

Simplest method of exploration and sampling.

Power driven or hand operated.

Max. depth 10 m.

Suitable in all soils above GWT but should not be used below GWT.

Hollow stem augers used for sampling or conducting Standard Penetration Tests.

Power Auger

used for boring to a depth of about 10 to 30 m.

set with a drill rig can be used to obtain samples from deeper strata.

can be used to drill a hole to 100 m depth.

Wash Boring

Casing is driven with a drop hammer

Soil is loosened and removed from the borehole using water or a drilling mud jetted under pressure

The water reaches the ground level where the soil in suspension is allowed to settle and mud is re-circulated.

Rotary Drilling

A heavy string of the drill rod is used for choking action

Suitable for drilling holes 10cm diameter 10cm, or more preferably 15 to 20cm in most of the rocks

depth of various strata can be detected by inspection of cuttings

Percussion Drilling

Done by alternatively lifting and dropping a heavy drilling bit that is attached to the lower end of the drilling which is attached to the cable

The strokes of bit varies according to the ground condition

45-100 cm in depth with rate of 35-60 drops/min.

It cannot detect thin strata

True

Dams:

Geological character and thickness of the strata

Channels

Materials

Induced seismicity, denudation of flora and fauna.

Resettlement of displaced people

Geological investigations

True

Tunnel:

Type and strength of the rock or soil

Presence of groundwater and its flow characteristics

Proximity of seismic activity

Potential for geological hazards

True

Tunnel:

Rock or soil type

Rocks mass quality

Geological structures

Groundwater

Seismicity

Slope stability

Environmental considerations

Dams, Tunnel, Buildings, Road Cut

Geologic Considerations in Construction of Dams, Tunnels, Buildings and Road Cutting