APPLICATION OF REMOTE SENSING TO MAPPING OF EXPANSIVE SOILS AND ROCKS IN OMAN
Anil K. Bagchi!, Amer A. Al Rawas?, Ali Al Barwani?
Associate Professor, Lecturer and Undergraduate Student, respectively.
Department of Civil Engineering, Sultan Qaboos University, P.O.Box 33, Al-Khod, 123, Sultanate of Oman
1,2,3
Commission VII, Working Group 6
KEY WORDS: Remote Sensing, Soil, Classification, Mapping, Multispectral.
ABSTRACT:
Presence of expansive soil increases cost and time for many civil engineering construction projects. Identification of
the expansive soils and rocks using remote sensing, which involves less ground visits, should be useful. This has
therefore been taken up as an ongoing research in the Civil Engineering Department of Sultan Qaboos University
using the facility available in the Remote Sensing Center. The Center is equipped with a PC based system, consisting
of a number of PC's, duly networked, and appropriate peripherals. The software in use is ERDAS.
A large scale geotechnical mapping program was carried out covering the entire country. The geotechnical
information including the subsurface soil profile and soil characteristics were collected from more than seventy towns.
A brief report on the ground situation is included.
The remote sensing phase of the investigation started with identification of a few training samples. Next job is to
develop a signature, a rather elaborate exercise in finding statistical parameters which can represent the training
samples. Identification of expansive soil is thereafter tried using the supervised classification technique, following the
maximum likelihood decision rule. Success and applicability of one or the other of the methods depend upon the
nature of the data structure, uniqueness of the signature, statistical distances between the signatures, nature of
information class being sought, spectral bands used etc. All these were kept in view and studied at appropriate places.
All the three groups of spectral bands - visual, infra-red and microwave- have been applied for the investigation.
The data source is restricted to the satellites JERS and Landsat TM. The final result of classification appears in the
form of a classified map.
1. INTRODUCTION depending upon the upward movement. As a
consequence of the structural damage evidenced, the
Expansive soils and rocks are those which undergo potential problems associated with the Omani expansive
volumetric changes upon wetting and drying. These soils and rocks have been recognised and preventive
materials swell when the moisture content is increased measures are being incorporated into new designs and
and shrink when the moisture content is decreased. The ^ construction works.
moisture change can be due to natural sources such as
rainfall or manmade sources such as surface irrigation, Studies in the possibility of applying remote sensing
broken water supply and sewers, and leakages from technique to identify and map the expansive soils and
swimming and feature pools. These materials cause rocks has therefore been undertaken in the remote
distress and damage to engineering structures founded sensing centre of Sultan Qaboos university of Oman. The
on them. It was reported that the annual cost of damage Center is equipped with a PC based system, consisting of
from expansive soils in the United States alone exceeds $ a number of PC’s, duly networked, and appropriate
10 billion, Steinberg (1992). peripherals. The software in use is ERDAS. It is an on-
going research and the present paper is a status report.
Oman has experienced a tremendous urban expansion in
the last two decades. This expansion was accompanied
by a sharp increase in water consumption which means 2. EXPANSIVE SOILS AND ROCKS IN OMAN
that considerable amounts of water are infiltrating into
the ground. Several structures have suffered from varieus The regional geology of northern Oman is dominated by
types of damage due to wetting of the foundation soil, the Oman mountains and is geologically distinct from
from water ingress into the ground. The structural cracks the rest of the Arabian Peninsula. The problems of
are observed in different types of structures such as ground heave experienced in Oman are predominantly
residential houses, garden walls, roads and open related to the presence of smectite clay minerals with
drainage channels. The pattern of cracks seems to vary
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996