​ SECTION:

Republic of the Philippines

SORSOGON STATE UNIVERSITY 2B
College of Engineering and Architecture
Bibingcahan Baribag, Sorsogon City DATE SUBMITTED:
Tel. No.: (056) 211 0178

GEOLOGY FOR CIVIL ENGR'S

(A.Y. 2024-2025)

List of Members Group Number:

Ebuenga, Febie Rae

Lignes, Adrian
9
Malaca, Ronnel A.
Malana, San Rafael
Nicolita,Cedrick S.

GEOLOGICAL AND GEOPHYSICAL INVESTIGATION IN CIVIL ENGINEERING

Introduction
Site investigations and geological methods are essential components of any engineering or
construction project. These processes involve collecting, analyzing, and interpreting data about a site’s
physical, environmental, and geological characteristics to determine its suitability for development. Through a
combination of desk studies, physical inspections, sampling, and laboratory testing, site investigations aim to
provide a comprehensive understanding of subsurface conditions. In parallel, geological and geophysical
methods—ranging from field surveys to advanced remote sensing and electromagnetic techniques—play a
vital role in exploring and mapping underground formations, resources, and potential hazards. Together, these
methodologies form the foundation for safe, efficient, and informed project planning and decision-making.

SITE INVESTIGATIONS
​ Site investigations is a process that involves gathering detailed information about the physical and
environmental characteristics of a specific location to assess its suitability for construction, development, or
other engineering projects.

Stages in Site Investigation

1.​ Desk Study - it gathers the background information about the site before any physical investigation
begins.
2.​ Site Reconnaissance - it performs an initial physical inspection of the site to observe surface
conditions.
 3.​ Site Exploration and Sampling - it investigates the subsurface conditions through sampling and
testing.
4.​ Field Test / In Site Test - use non-invasive methods to explore the subsurface further.
5.​ Laboratory testing - analyze the samples collected from the site to understand their physical and
engineering properties.
6.​ Report Writing - present the findings of the investigation in a comprehensive report.

GEOLOGICAL METHODS
Geology is the study of the Earth, including its materials and how it changes over time. Geologists use
different methods to learn about the Earth’s structure, resources, and history. These methods include field
surveys, laboratory testing, remote sensing, and geophysical techniques.
Types of Methods
1.​ Field Survey - this are a hands-on method where​ geologists go directly to sites to study the Earth's
surface. They examine rock formations, soil types, and land structures to gather data.
Key Activities:
●​ Map/Mapping: Draw maps to show the location of different rock layers.
●​ Collect Samples: Take rocks and soil samples to study them later.
●​ Study Layers: Look at layers of rock to learn about the Earth’s history.

2.​ Laboratory Testing - after collecting samples, geologists analyze them in a lab. Common tests include:
●​ Microscopic Study: Looking at rocks through a microscope to see what minerals they contain.
●​ Chemical Tests: Using machines to check the chemical makeup of the samples.
●​ Dating Rocks: Measuring the age of rocks to understand when they were formed.

3.​ Geophysical Methods - it involves studying the Earth’s physical properties, such as its magnetic field
or how it responds to waves. Some common methods are:
●​ Seismic Waves: Sending waves into the Earth to learn about its inside.
●​ Magnetic and Gravity Tests: Measuring changes in the Earth's magnetic field and gravity to find
minerals and other resources.
●​ Electrical Measurements: Using electricity to study the ground and find water or
minerals.

4.​ Remote Sensing - it involves using satellites or airplanes to take pictures of the Earth from above. It
helps geologists in identifying rock types and land features, monitoring large areas for changes like
earthquakes or volcanoes, and for studying places that are hard to reach.
EXPLORATION TECHNIQUES
Exploration techniques encompass various methods used to find and assess resources, including
geological mapping, geophysical surveys (like seismic, magnetic, and gravity), geochemical sampling, and
drilling, all aimed at understanding subsurface structures and potential deposit.

●​ Geophysical Surveys - these are non-destructive methods that use ground-based physical sensing
techniques to create detailed images or maps of an area, revealing subsurface information about
geological structures, materials, and potential anomalies without extensive excavation.

●​ Geological Mapping - Geological mapping is the process of a geologist physically going out into the
field and recording geological information from the rocks that outcrop at the surface. Information the
geologist looks for will include: boundaries between different rock types and structures e.g. fault-lines
and evidence of the rocks undergoing deformation

●​ Desktop Surveys - an office based investigation of existing records such as different maps,
photographs, historical sources, archaeological records and documents.

●​ Geochemical Surveys - in exploration techniques involve systematically collecting and analyzing

samples of natural materials (like soil, rock, sediments, water, and vegetation) to identify anomalies in
chemical composition, which can indicate the presence of mineral or petroleum deposits.

GEOPHYSICAL METHODS
Geophysical methods are techniques that measure physical fields at the Earth's surface to gather
information about subsurface formations and geological structures, providing both quantitative and qualitative
data.

●​ Electrical Resistivity Methods - The electrical resistivity method is a geophysical technique that
measures the ability of electrical current to flow through the subsurface, revealing information about
subsurface materials and structures by analyzing the resistance to current flow.

Types of Electrical Resistivity Methods

●​ Vertical Electrical Sounding (VES - a geophysical method that measures variations in apparent
resistivity with depth, used to characterize subsurface geological formations and identify potential
aquifers.
●​ Electrical Profiling - a geophysical survey method that maps subsurface resistivity variations along a
line or "profile" by moving an electrode array along a survey line while maintaining fixed electrode
spacing.
●​ Electrical Imaging - it is basically the combination of two electric resistivity methods. A
non-destructive method for subsurface investigation. In this method the electrical current is injected into
the earth through a pair of current electrodes and the potential difference is measured between a pair
of potential electrodes.
●​ Gravity Geophysical Methods - The gravity method is a non-invasive, non-destructive remote sensing
method that is relatively inexpensive. Subsurface geology is studied using gravity surveying, which
uses changes in Earth's gravitational field caused by differences in density between subsurface rocks.
The notion of a causative body, which is a rock unit with a different density than its surroundings, is an
underlying concept.

●​ Microgravity Profiling Method - a passive technique that involves measuring relative shifts in the
Earth's gravitational field with extreme precision. A gravity meter, which consists of a highly sensitive
temperature stabilized spring balance, is used to take measurements. Since differences in the density
of materials inside the subsurface cause subtle changes in gravity, the method can be used to
effectively identify voids or submerged features like underground storage tanks.

●​ Electromagnetic Methods - refers to methods that employ the theory of electromagnetic induction to
excite electrical currents in the ground using a low frequency time-varying magnetic field as a source.
These methods are sensitive to the electrical conductivity of the subsurface.

Types of Electromagnetic Methods

1.​ Frequency Domain EM - it relies on electromagnetic waves induced on the surface to produce
electrical currents in subsurface conductors. In geophysics, the terms "Frequency-domain EM (FDEM)"
and "EM induction" refer to geophysical investigation methods based on the principles of induction as
defined by Faraday's Law. As such, the EM induction umbrella covers all methods that involve
measuring voltages induced in the earth when exposed to a varying magnetic field, either time- or
frequency-domain.
2.​ Time Domain EM - a non-intrusive geophysical approach for collecting subsurface
resistivity-conductivity data is the time domain electromagnetic method. Time domain electromagnetic
method is a useful tool for mapping changes in rock or soil, such as clayey layers that limit groundwater
flow, conductive leachate in groundwater, and seepage in earthen embankments.
3.​ Ground Penetrating Radar - it works by sending beams of ultra-high frequency radio waves down into
the ground through a transducer. The ground penetrating radar antenna is dragged along the ground by
hand or by a vehicle or ATV. Various buried objects or distinct interactions between different earth
materials represent the transmitted energy. The reflected waves are then received by the antenna and
 stored in the digital control unit. The signal is amplified after the control unit detects the reflections
against the two-way travel time in nanoseconds. The digital control unit plots the output signal voltage
peaks as different color bands on the ground penetrating radar profile.

●​ Radiometric Methods - the radiometric, or gamma-ray spectrometric method, is a geophysical method

for estimating potassium, uranium, and thorium concentrations by calculating the gamma-rays that
these elements' radioactive isotopes emit during radioactive decay. By measuring gamma radiation
above the ground from low-flying aircraft or helicopters, airborne gamma-ray spectrometric surveys
estimate radioelement concentrations at the Earth's surface.

●​ Seismic Methods - it assesses the response of seismic (sound) waves that enter the earth and then
refract or bounce off subsurface soil and rock boundaries. A sledgehammer strikes a metal plate on the
ground, a larger weight.

Conclusion
Through site investigations and the use of various geological and geophysical methods are critical for
the successful planning and execution of construction and exploration projects. Each stage, from initial desktop
research to advanced geophysical surveys, contributes valuable data that helps in understanding the
subsurface environment. Whether assessing soil conditions, identifying mineral deposits, or detecting
subsurface voids, these techniques ensure that engineers and geologists can make informed choices that
enhance safety, reduce risks, and optimize resource management. As technology continues to advance, the
integration of these methods will only grow more precise and impactful in shaping the future of infrastructure
and resource exploration.

References
●​ Surface Geophysical Methods | US EPA.(2025, January 24). US EPA.
https://www.epa.gov/environmental-geophysics/surface-geophysical-methods
●​ https://youtube.com/playlist?list=PLZScDy-0gb-UHK6hCwgwfYpA9AwmAfm9n&si=kLB68GCSd
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