| Author | Kanitthorn Adisornsupawat |
| Call Number | AIT Thesis no.GE-03-03 |
| Subject(s) | Imaging systems in geophysics
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. GE-03-03 |
| Abstract | Nowadays, near surface geophysics or shallow geophysics can be used as supplement
exploratory borehole data to reduce the site-characterization cost. Among geophysical
techniques, Electric Imaging (ED is a useful method that has proven its applicability in soil
contaminant monitoring, landslide and environmental engineering studies. The main
objective of this study is to review and assess applicability of electric imaging technique in
a developing country like Thailand and to promote application of this method in
geotechnical engineering.
At present, field resistivimeter have been rapidly improved. Most of the commercial
manufacturers produce to automatic recording system that is easily operated but costly. In
this study, a semi-automatic procedure with switching unit was developed to compromise
the advantage and disadvantage of manual and automatic instrument. The comparisons
between semi-automatic and automatic measurements are proved that the semi-automatic
setup could work very well and save the cost of investigation.
One application that electric imaging can be a useful tool is to detect a buried object or
structure which has resistivity contrast to surrounding medium. In this study, a2D EI was
applied for detection of a buried water pipe, which is made up of concrete, air and also has
water inside. The results obtained from this application show the location of buried pipe
that conform to the location of the pipe in the field. Another 2D EI application in this
study is to identify the thickness of a weathered granite layer in the hilly area. The inverse
analyses were taking into account the topographic effect and could indicate clearly the
boundary of a weathered granite layer.
The study has also dealt with application of a 3D EI survey. The full-scale field test at site
with a concrete pile was performed. The result indicated that highly resistive anomalies
can be related to the location of the pile and can use to confirm the presence of
underground pile. Then a 3D EI survey was employed in the real conditions at
Thammakaya temple where piles were installed for an ongoing construction project to
localize the underground pile. A design chart was developed for pile detection according
to which the ratio of depth to the top of pile to pile diameter (D/~) is less than 1.2.
A major part of this study is performance of a time-dependent EI monitoring to detect the
change in resistivity caused by the decrease of water content due to ground improvement
process at the New Bangkok International Airport (NBIA). The effects of inversion
parameters, such as the damping factor and flatness ratio have been studied in order to
evaluate the optimal parameters to process the field data. Result of forward modeling
revealed that an appropriate choice of inversion parameters was important, and that
required to adjusted for overcome the effect of high resistivity due to surcharge material.
According to the findings in the field condition, the values of resistivity can be associated
with water content decrease and undrained shear strength increase due to the process of
ground improvement.
It's expected that the results of this study could successfully provide a good introduction
of EI technique that can be well used in various applications in geotechnical engineering,
especially in Thailand. |
| Year | 2003 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. GE-03-03 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Pham Huy Giao; |
| Examination Committee(s) | Noppadol Phien-Wej;
Park, Kyung-Ho;
Borne, Frederic ; |
| Scholarship Donor(s) | Royal Thai Government; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2004 |