DIRECT PENETRATION
INTRODUCTION
Direct Penetration, also known as Direct Investigation Method, is a more detailed
description of underground conditions at specific locations that obtains information by
physically sampling or testing soil, rock, and groundwater (Villegas, 2021).
With this method, the soil samples are taken from the site undergoes field test or
laboratory tests, then the groundwater table were determined (Villegas, 2021) whereas
groundwater table is the upper limit or the surface of the groundwater (Trenchlesspedia,
2021).
There type of Direct Penetration called as:
1. Standard Penetration Test (SPT)
2. Cone penetration Test (CPT)
.
STANDARD PENETRATION TEST (SPT)
A well-established and simple procedure created in the United States around 1925,
since then, it has experienced improvements in terms of testing methodology and
equipment. Different regions of the world use different testing methods. It was crucial to
standardize SPT in order to make it easier to compare the findings of various investigations,
despite being disturbed, representative soil samples were acquired. (El-Reedy, 2017)
According to Mahajan from Civiconcepts, the two major purposes of the SPT are:
● To evaluate the penetration resistance of the soil at different depths, which is
used for geotechnical design.
● To identify the kind and character of the soil at various depths.
According to Mishra from The Constructor, there are tools for Standard Penetration
Test:
1. Standard Split Spoon Sampler
2. Drop Hammer weighing 63.5kg
3. Guiding Rod
4. Drilling Rig
5. Driving Head (Anvil)
Photo retrieved from
https://theconstructor.org/geotechnical/standard-penetration-test-procedure-precautions-advantages/4657/
There are two corrections applied to standard penetration test values which are:
1. The Dilatancy Correction in saturated fine sands and silts, due to their limited
permeability, silty and fine sands soils cannot release pore pressure when dynamic
loads are applied to them in saturated state (Suryakanta, 2013).
2. The Overburden Pressure Correction, the overload pressure affects the soil’s
resistance to penetrate. In-situ soil will respond to SPT better at greater depths due
to higher overburden pressure than at shallower depths due to the same soil
(Suryakanta, 2013).
CONE PENETRATION TEST (CPT)
The CPT is used to identify the geotechnical engineer properties of the soil
delineating soil stratigraphy. The CPT is the one to collect the important information from
SPT and provide the important business factors like design foundation for the structures and
subsurface soils.
● HOW DOES THE CPT WORKS?
The steel cone has a electronic measuring system that will record tip resistance and
the sleeve friction. When the cond push into the ground, the soil will respond with a differing
degrees of resistance. The resistance will be recorded with the help of the sensors in the tip.
CPT can provide the information onsite that is quick and more accurate and the results from
the onsite can benefit and improve your business productivity leading for more efficient
business process.
Photo retrieved from:
https://www.researchgate.net/figure/Cone-Penetration-Test-CPT-a-Test-overview-b-Output-example-after-17_fig1
_340012844
CORE BORING
Core boring is used by many civil engineers for digging activities, research mineral
resources in the subsoil, and to analyze the ground. The core is an extracted sample of rock
or ice that is shaped as a cylinder. By obtaining these cores, it gives more information on
change in climate in the past.
Photo retrieved from:
https://cdn11.bigcommerce.com/s-uxd1f/images/stencil/1280x1280/products/304/733/Core_Bore_CB515_Core_
Drill_In_Action__84321.1524751488.png?c=2
6 DIFFERENT BORING METHODS FOR SOIL EXPLORATION
1. DISPLACEMENT BORING
Combination of sampling method and boring operations. Closed bottom
sampler, slit cup, or piston type is forced in to the ground up to the desired depth.
Then the sampler is detached from soil below it, by rotating the piston, & finally the
piston is released or withdrawn. The sampler is then again forced further down &
sample is taken. After withdrawal of sampler & removal of sample from sampler, the
sampler is kept in closed condition & again used for another depth.
Photo retrieved from:
https://junttan.com/wp-content/uploads/2015/11/displacement_bored_pile.jpg
2. WASH BORING
It is a popular method due to the use of limited equipment. The advantage of
this is the use of inexpensive and easily portable handling and drilling equipment.
Photo retrieved from:
https://i0.wp.com/civilblog.org/wp-content/uploads/2015/09/Wash-Boring.jpg?w=547&ssl=1
3. AUGER BORING
This method is fast and economical, using simple, light, flexible and
inexpensive instruments for large to small holes. It is very suitable for soft to stiff
cohesive soils and also can be used to determine ground water table.
Photo retrieved from:
https://i0.wp.com/civilblog.org/wp-content/uploads/2015/09/Augers.jpg?resize=219%2C300&ssl=1
4. ROTARY DRILLING
Rotary drilling method of boring is useful in case of highly resistant strata. It is
related to finding out the rock strata and also to access the quality of rocks from
cracks, fissures and joints. It can conveniently be used in sands and silts also. This
method is suitable for boring holes of diameter 10cm, or more preferably 15 to20cm
in most of the rocks. It is uneconomical for holes less than 10cm diameter. The depth
of various strata can be detected by inspection of cuttings.
Photo retrieved from:
https://i0.wp.com/civilblog.org/wp-content/uploads/2015/09/Rotary-Drilling-System.jpg?w=552&ssl=1
5. PERCUSSION DRILLING
In case of hard soils or soft rock, auger boring or wash boring cannot be
employed. For such strata, percussion drilling is usually adopted. One main
disadvantage of this process is that the material at the bottom of the hole is disturbed
by heavy blows of the chisel and hence it is not possible to get good quality
undisturbed samples. It cannot detect thin strata as well.
Photo retrieved from:
https://i0.wp.com/civilblog.org/wp-content/uploads/2015/09/Percussion-Drilling.jpg?w=395&ssl=1
6. CONTINUOUS SAMPLING
The sampling operation advances the borehole and the boring is
accomplished entirely by taking samples continuously. The casing is used to prevent
the caving in soils. It provides more reliable and detail information on soil condition
than the other methods. Therefore it is used extensively in detailed and special
foundation exploration for important structures.
LOGGING OF CORES
A core is a cylindrical piece of rock that has been sampled from the interval by a core
barrel and transported to the surface for inspection and analysis, and logging is the term
used to describe all drill hole data collecting (Pramoda, 2017).
Ghart (2019) defines core logging as the systematic recording and measurement of
as much data as is possible or necessary to ascertain the lithology (rock types), mineralogy,
potential geological history, structure, and alteration zones through a small piece of
cylindrical rock that has been drilled out of a potential mineral deposit.
In addition, according to Haldar (2013), "core logging" is the geological analysis and
documentation of drill cores.
Geotechnical core logging is a practice that requires appropriate knowledge of
industry-standard geotechnical core logging techniques. It provides data and parameters
necessary for rock mass classification and should be conducted so that the data can be
easily applied to all industry standard classification systems. The data allows engineers to
better assess the probable ground reaction and stability in response to mining and apply
geotechnical designs to surface and underground excavations. By using standardized
logging techniques, the data recorded from drill core can be readily used by multiple
stakeholders (owners, contractors and consultants). It also provides a means to ensure data
is recorded consistently between multiple personnel and/or core logging campaigns.
Using people without sufficient experience, expertise, and understanding of
geotechnical parameters can lead to the collection of poor-quality geotechnical data. This
may result in misleading characterization and classification of a rock mass domain. The key
is finding the balance, such as, sufficient support to ensure safety and uninterrupted
operations, without excessive cost and obstruction of mining activities. When conducted
properly, geotechnical core logging and interpretation of the results produced in the
preliminary or early phases of a project can have a major impact on project design and
development further down the line.
REFERENCES
● Villegas (2021). Direct Penetration Method. [vid] Retrieved from
https://www.youtube.com/watch?v=_JNstqSF8Ks
● Trenchlesspedia (2021). Groundwater Table. [web] Retrieved from
https://www.trenchlesspedia.com/definition/2776/groundwater-table
● Science Direct (n.d.). Standard penetration test [Web]. Retrieved from
https://www.sciencedirect.com/topics/engineering/standard-penetration-test
● Mishra, G. (2020, April 13). Standard penetration test (spt)-procedure,precautions,
advantages [Web]. Retrieved from
https://theconstructor.org/geotechnical/standard-penetration-test-procedure-precautio
ns-advantages/4657/
● Suryakanta (2013, May 23). Correction applied to SPT value [Web]. Retrieved from
https://civilblog.org/2013/05/13/correction-applied-to-spt-value/
● Mahajan, B. (2022, April 27). SPT test: Standard penetration test: Soil Penetration
test: Standard penetration test procedure: SPT test report [Web]. Retrieved from
https://civiconcepts.com/blog/spt-test#Standard_Penetration_Test_Lab_Manual
● Vertex Team (2020, April 21). "Cone Penetration Test (CPT) Overview 101" [Web].
Retrieved from https://www.vertekcpt.com/cone-penetration-test-cpt-101/
● Piazzale, M. (2005). Studying of Climate. Retrieved from
https://www.eniscuola.net/en/argomento/climate-change/studying-the-climate/core-bo
ring/#:~:text=Core%20boring%20is%20a%20sampling,is%20known%20as%20a%20
core
● Pramoda, J. (2017, May 24). Drilling and core logging. [Web]. Retrieved from
https://www.slideshare.net/pramodgpramod/drilling-and-core-logging
● Ghart (2019, February 17). THE BASICS OF LOGGING CORE FOR
EXPLORATION. [Web]. Retrieved from
https://canadamines.ca/basics-of-logging-core-samples-for-mineral-exploration/
● Haldar (2013). Mineral Exploration. [PDF]. Retrieved from
https://doi.org/10.1016/B978-0-12-416005-7.00007-6
● RockEng (n.d.). “Geotechnical Core Logging – Having the Right People is Vital.”
[Web] Retrieved from
https://rockeng.ca/events-news/geotechnical-core-logging-having-the-right-people-is-
vital/
● Choundhury, D. (2015, September 5). 6 Different Methods of Boring Used for Soil
Exploration. Retrieved from
https://civilblog.org/2015/09/05/6-different-methods-of-boring-used-for-soil-exploratio
n/
