Author:
Adamo Nasrat,Al-Ansari Nadhir,Sissakian Varoujan,Laue Jan,Knutsson Sven
Abstract
The use of geophysical methods in dam sites investigations and safety monitory has
proved their good value and versatility in many earthfill dam sites as early as the
1920s. In the following years great development has occurred in the methods,
application procedures and tools used. They may be considered today as good ways
for carrying out observation tasks on existing dams in non-intrusive and much faster
and cheaper ways than the traditional geotechnical methods. It is possible using
them to discover anomalies in the dam body or its foundation at an early stage and
allowing quick intervention repair works. These methods seek to register and
present variations in the basic geotechnical material properties in dams such as; bulk
density, moisture content, elasticity, mechanical properties of rocks, electrical
resistivity and mineralogy and magnetic properties and so forth. Such variations can
indicate increasing seepage flow, progression in cracks’ sizes, formation of voids,
caverns and other instability manifestations. Depending on how any investigation
is carried out and the targeted anomaly, there is now selection of these methods such
as: Electromagnetic Profiling (EM), Electrical Resistivity Tomography (ERT), SelfPotential (SP), Ground Penetration Radar (GPR), variety of Seismic Methods (SM)
which can be applied using such equipment as in Seismic refraction, Seismic
Reflection, Multi Analysis of Rayleigh surface waves (MASW) instruments, or
using Refraction Micrometer (ReMi), macro-gravity method, and Cross-Hole
Seismic Tomography. In addition, Temperature Measurements and other less used
methods can be used like Microgravity measurement, Magnetic Profiling and Radio Magnetotelluric methods. An attempt is made here to cover the details of these
methods, their advantages and limitations and to prove their usefulness in many dam
sites all over the world. One observed issue is their adaptability to embankment
dams more than to concrete dams and their popularity for checking seepage related
problems and material changes within dam bodies and their foundations such as
formation of voids and sinkholes.
Publisher
Scientific Press International Limited