Lecture 8: Geologic Investigations

Question 1

aims to foresee problems that may

arise and figure out possible ways to address them.

Answer 1

Site investigation

Question 2

Data needed for Site investigation

Answer 2

• Soil and rock underlying the site (kinds, properties, probable issues)
• Groundwater level
• Extent of weathering
• Hazards (landslide, earthquake, etc.)

Question 3

3 General Phases of Site Investigation

Answer 3

• Desk Study
• Preliminary Reconaissance
• Site Exploration

Question 4

Aims to gather and study all available literature and data related to the site

Answer 4

Desk Study

Question 5

maps that show the geology of an area including data related to the rock units and distribution in the area, geologic structures, age relationships of the rocks, as well as cross section view of the map.

Answer 5

GEOLOGIC MAPS

Question 6

shows mainly the elevation data
related to the map. It uses contour lines to show which areas are at the same altitude/elevation and thus allows for visualization of flat areas vs slope areas and how steep slopes are.

Answer 6

TOPOGRAPHICAL MAPS

Question 7

show data and distribution of soil in an area.

Answer 7

Soil Maps

Question 8

shows the site’s susceptibility to various

hazards like earthquake or liquefaction

Answer 8

Hazard Maps

Question 9

based on the expected structure, one can estimate how much load will be transferred to the ground

Answer 9

POSSIBLE LOADS

Question 10

certain important structures have stricter rules in design and construction

Answer 10

IMPORTANCE

Question 11

some structures can have deformation like settlement of floor while some like factories that require precision (due to machine connections to each other) may have more stringent design considerations related to deformations.

Answer 11

TOLERANCE TO DEFORMATION

Question 12

The amount of effort put into desk study must be based on several factors. What are these factors

Answer 12

• Project complexity
• Project extent/size
• Site conditions (possible issues based on material on site)

Question 13

desk study should provide you with a list of_____________

This ensures efficiency.

Answer 13

what data is still

needed and what exploration tests will be needed to get them.

Question 14

In 2D Topographic maps, if a slope is steep, you will see _____ as it increases its height
quite quickly

Answer 14

closer lines

Question 15

A _________usually covers very large

areas. Provides a bigger picture of the site

Answer 15

geologic map

Question 16

USGS maps, they range from scales of ______ to _________

Answer 16

1:20,000 to 1:2,500,000

Question 17

Limitation of Geologic Maps

Answer 17

Does not necessarily have quantitative properties that we want to know about our site.

Question 18

Geologic Mapping

Answer 18

Scientific process to map geologic features in the area concerned and create maps of it.

Question 19

Process of Geologic Mapping

Answer 19

• The first step is the traditional field visit where a geologist walks around and takes FIELD NOTES which will then be used to make geologic maps.
• These data can be supplemented by aerial images and remote sensing and other technologies.

Question 20

Map of SURFACE GEOLOGY

Answer 20

shows data about material

occurring at ground surface including alluvium, mud, and other materials.

Question 21

it shows materials that have been “drifted”

and covers the more solid units underneath

Answer 21

Drift Edition

Question 22

Map with no drift shown (like looking at ground if drift material are removed), only the SOLID geology underneath

Answer 22

Solid Edition

Question 23

SUBSURFACE GEOLOGY MAPS

Answer 23

ISOCHORE MAPS
ISOPACHYTE MAPS
HORIZONTAL PLANE MAPS
STRUCTURAL CONTOUR MAPS
GEOPHYSICAL MAPS

Question 24

ISOCHORE MAPS

Answer 24

Isochore maps show the vertical thickness of geologic units using isochore lines (lines that join points with same vertical thickness)

Question 25

ISOPACHYTE MAPS

Answer 25

Uses isopachyte lines that join points of same
stratigraphical thickness rather than vertical thickness. This is more complicated and more used by geologists than engineers.

Question 26

HORIZONTAL PLANE MAPS

Answer 26

maps the geology at some horizontal plane

below the surface. Visualize chopping off certain thickness from the surface and mapping what you see afterwards.

Question 27

STRUCTURAL CONTOUR MAPS

Answer 27

maps structural surfaces (faults,

unconformities) and the contours is based on the dip value of the surface being illustrated.

Question 28

GEOPHYSICAL MAPS

Answer 28

maps from geophysical methods (discussed later on)

showing information based on the data gathered from whichever geophysical method was used

Question 29

Key information you must understand from the geologic maps

Answer 29

AGE OF UNITS, STRUCTURAL RELATIONSHIP OF UNITS, make 3d maps by making geologic maps at different levels and stacking them, geological sections

Question 30

shows the relative ages of strata in a map and is usually found at the margin of the map

Answer 30

STRATIGRAPHIC COLUMN

Question 31

TECHNOLOGY FOR MAPPING

Answer 31

• GIS
• GPS
• Remote Sensing
• Aerial Images

Question 32

Technology that allows easier management of spatial data. Used for data capturing, storing, retrieving, editing, analyzing, comparing, and displaying.

Answer 32

Geographic Information System

Question 33

Other data that can be used in GIS

Answer 33

remote sensing, aerial

images, and other maps from geophysical methods (gravimetric maps, aeromagnetometry maps, etc.).

Question 34

GLOBAL POSITIONING SYSTEM

Answer 34

• Allows determination of precise location.
• This gives geologists the ability to assign a structure/unit of
importance to a coordinate easily

Question 35

Uses aircraft or satellites to measure reflected and

emitted radiation to monitor physical characteristics of an area or structures in an area.

Answer 35

REMOTE SENSING

Question 36

The data measured from Remote Sensing can

take the form of __________

Answer 36

1 acoustic waves

2 other electromagnetic spectrum waves

Question 37

Two main Systems used in Remote Sensing

Answer 37

1. Infrared Lin Scan

2. Side Looking Airborne Radar

Question 38

uses emitted electromagnetic

radiation related to temperature of objects.

Answer 38

Infrared Lin Scan

Question 39

Pulses of energy are shot from an aircraft, bounces off the ground, and is received by the aircraft again. This allows creation of photographs from
recorded data. One of its advantages is that it is not affected by cloud cover.

Answer 39

Side Looking Airborne Radar

Question 40

The images from remote sensing can:

Answer 40

• Help in study of landforms, their characteristics, which may
provide information as to what comprises them.
• For places with limited maps, it can be useful in creation of
other maps related to the terrain or geology, among others.

Question 41

reflects lasers to create ground elevation maps

Answer 41

Light Detecting and Ranging System

Question 42

Applications of Remote Sensing in Civil Engineering

Answer 42

• Water resources studies and modelling
• Disaster risk management related research for natural
calamities
• Environmental observation
• Urban monitoring and studies

Question 43

• Image usefulness depends on its quality as well as what can be shown in the photograph, can be used with a stereoscope to make a 3D
ground surface model, which can then be used to make topographic
maps.

Answer 43

Aerial Images

Question 44

Its done to supplement the desk study and give a better

report.

Answer 44

PRELIMINARY RECONAISSANCE

Question 45

site inspection or walkover

survey

Answer 45

PRELIMINARY RECONAISSANCE

Question 46

A report is made summarizing all details related to the project and site, the possible issues (and solutions), as well as future work suggestions to further determine feasibility of project or rule-out possible issues and data to be used for design phase.

Answer 46

PRE-SITE EXPLORATION REPORT