Soil Investigation

Foundtest Drilling Site Investigation Works

Site Investigation (S.I.) Overview

Site Investigation—commonly known as Soil Investigation in Malaysia—is essential for all construction projects. It involves drilling boreholes into the ground to gather information about the physical properties of the soil and rock at a site. This data is crucial for designing earthworks and foundations for proposed structures and can also aid in diagnosing and repairing issues related to subsurface conditions affecting existing structures.

Subsurface Exploration Methods

To understand soil conditions below ground, subsurface exploration methods are used. These methods involve observing soils, collecting samples, and determining their physical properties through techniques such as test pits, boring, and in situ tests.

Test Pits

  • Method: Excavated manually with shovels or by machine up to a depth of 4.5 meters.
  • Purpose: Collect soil samples and observe soil conditions.
  • Applications: Best suited for low-rise developments that do not require deep foundations.

Borehole (Deep Soil Boring)

  • Technique: The most commonly used method is Rotary Wash Boring.
  • Capabilities: Drilling rigs can reach depths of up to 100 meters, depending on site conditions.
  • Sampling Tools:
    • Disturbed Samples: Collected using tools like the Split Spoon Sampler (SPT).
    • Undisturbed Samples: Obtained with Piston Samplers, Thin-Wall Tubes, and Mazier Samplers.
  • Rock Sampling: When encountering rock layers, coring methods are used to extract rock samples.

In Situ Tests

Common in situ tests conducted during soil investigations include:

  • Mackintosh Probe Test
  • Standard Penetration Test (SPT)
  • Vane Shear Test
  • Dynamic Cone Penetration Test (DCP)
  • Cone Penetration Test (CPT)

Reporting

All findings from site investigations are compiled into a Factual Geotechnical Report. This report includes:

  • Bore Logs with soil descriptions and in situ test results
  • Laboratory Test Results

This comprehensive data provides critical insights for engineers to design safe, stable foundations and address potential geotechnical challenges effectively.

Here are some detailed description of few typical terms and techniques which is commonly used in Site Investigation works:

Rotary Wash Soil Boring

Rotary Wash Soil Boring

Rotary Wash Boring is one of the most common method used to drill a borehole during Site Investigation work.  Drilling Fluid (Usually water) is used to flush off soils to create borehole in ground with steel casing which is rotated by the Drilling Machine. The purpose of drilling a borehole is to allow for access into deep ground to carry out other in-situ test, sampling and installation of monitoring instrument at designated depth. This method is capable of drilling up to approximately 80-100m depth depending on ground condition.

JKR / Mackintosh Probe Test is a quick and economical way to estimate the Bearing Capacity of Soil layer by co-relating the cone penetration resistance to the bearing capacity. It can goes up to a maximum depth of 15 m and is recommended only for shallow foundation.  This method is not able to collect any soil or rock samples and unable to report on type of soil as well.  Its also not suitable for rocky areas.

For more details of JKR/Mackintosh Probe Test, Please refer this page.

Hand Auger drilling is carried out by using hand held auger which is manually drilled into ground to obtain soil samples.  The drilled depth is very limited (usually less than 5m) due to the limitation of human power.  This method would only being considered under special circumstances, such as drilling fluid is not permitted, or borehole location is inaccessible to drilling machines, etc.  It doesn’t gives any soil resistance value, and also unsuitable in sandy or high water table area, because the open auger hole will tend to collapse.

A test pit is carried out by excavating the ground to the designated depth (not more than 5m deep) to observe the soil profile underneath and collect bulk samples.

Standard Penetration Test (SPT)

Standard Penetration Test (SPT)

Standard Penetration Test (SPT) is one of the most common field test to determine the driving resistance in soil strata.  This method is done in accordance to BS 1377:1990, “Determination of the penetration resistance using a split barrel sampler and a self tripping hammer of approved design”.  The result is presented as SPT-N value which indicates blow count per 300mm penetration.

SPT equipment consist of a 63.5kg hammer, hammer fall guide, anvil, automatic hammer release system and a split barrel sampler.  The SPT is carried out by repeatedly driving the split barrel sampler into the ground at the desired depth level (usually at 1.5m interval) using the automatic hammer release system that would free fall the 63.5kg hammer with a drop height of 0.76m.  Number of blow counts to achieve a penetration of 75mm into ground is recorded.  The same procedure is repeated for 6 times for a total of 450mm penetration.

The first 2 layer of 75mm penetration each is considered as seating drive and not counted in reporting the SPT-N value.  The total number of blow counts within the final 300mm penetration (separately recorded for every 75mm penetration) would be taken as the SPT-N value.

The Soil samples recovered from the split barrel were preserved as disturbed samples for subsequent testing in laboratory.

Rock & Soil Sampling is one of the most important scope in Site Investigation work.  It provides an in-depth understanding on type of the material and its characteristic behavior in substrata.

Soil Samples can be obtained using various techniques depending on soil condition and can be classified into Disturbed (D) or Undisturbed (UD) samples.  Disturb samples is usually collected by using SPT split barrel while Undisturbed samples can be extracted using Block Sampler Box, UD Tube, Piston Sampler & Mazier Sampler.  The samples collected would be used as specimen in laboratory test later for various classification, strength, consolidation and chemical content test.

Rock Samples can be extracted from deep ground using Diamond Core Bit with Core Barrel.  The Core Recovery Ratio (CRR) and Rock Quality Designation (RQD) would be reported for each core run.

Disturb Soil Sampling

Disturb Soil Sampling

Core Sample

Core Sample

Rock & Cavity Probing is carried out to determine the exact depth of bed rock and existence of cavity.  This information is very useful during the piling stage and it could have huge impact on the cost and design of piling foundation, especially when a development is carried out on a limestone area.  Cavity Grouting could be carried out for area where cavities is encountered.

Geotechnical Laboratory

Geotechnical Laboratory

Being a One Stop Geotechnical Soil Investigation contractor, Foundtest Drilling  also provides laboratory testing services as well.  All construction materials, soil samples (disturb & undisturbed) and rock samples collected on site can be further tested in our associate labs according to the client or design engineer’s requirement.

LABORATORY SOIL TESTS BS1377 : 1990
MOISTURE CONTENT Part 2, Method 3.2
ATTERBERG LIMITS ( LL, PL, PI ) Part 2, Method 4 & 5
LINEAR SHRINKAGE LIMITS Part 2, Method 6.5
BULK DENSITY Part 2, Method 7.2
SPECIFIC GRAVITY ( PARTICLE DENSITY ) Part 2, Method 8
PARTICLE SIZE DISTRIBUTION – COARSE GRAINED. Part 2, Method 9.2 & 9.3
PARTICLE SIZE DISTRIBUTION – FINE GRAINED. Part 2, Method 9.5
UNCONFINED COMPRESSION TEST ( UCT ) Part 7, Method 7.2
38mm diameter, 1 specimen
50mm diameter, 1 specimen
70mm diameter, 1 specimen
UU TRIAXIAL COMPRESSION TEST WITHOUT P.W.P. Part 7, Method 8
38mm diameter
50mm diameter
70mm diameter
CU TRIAXIAL COMPRESSION TEST WITH P.W.P. Part 8, Method 7
38mm diameter
50mm diameter
70mm diameter
CD TRIAXIAL COMPRESSION TEST WITH P.W.P. & VOL. Part 8, Method 8
38mm diameter
50mm diameter
70mm diameter
ONE DIMENSIONAL CONSOLIDATION TEST Part 5, Method 3
e vs log pressure, Mv & Cv, t90 graphs
e vs log pressure, Mv & Cv, t50 & t90 and c-alpha
LABORATORY PERMEABILITY TEST
Falling Head Permeameter ( k>E-04 m/s ) [ KH Head, Vol.2 – 10.7.2 ]
CHEMICAL TESTS ON SOIL / WATER
pH value Part 3, Method 9
Total / soluble sulphate Part 3, Method 5
Chloride content Part 3, Method 7
Organic matter Part 3, Method 8
Total dissolved solids Part 3, Method 9
Salinity Test Part 3, Method 10
DIRECT SHEAR STRENGTH ( 60 x 60mm samples ) Part 7, Method 4
Soaked – Consolidated Drained ( 3 specimen )
ROCK TEST
Unconfined compressive strength [ ASTM D2938-79 ]
UCT with Young’s Modulus & Poisson’s Ratio [ ASTM D3148-80 ]
Point Load Strength [ Broch, E & Franklin, JA ]

Inclinometer: To monitor horizontal movement of soil layer to prevent any soil erosion and other construction problems.  Inclinometer track would be installed in the borehole along the required depth and reading would be taking periodically to ensure the soil stability.

Standpipe Piezometer: To monitor ground water table or water pressure for foundation design or other research purpose.