Oulu University Press, 2006. — 125 р.The synopsis of this work begins with a presentation of the theory and basic principles of GPR
techniques. Special attention is given to the dielectric properties and seasonal changes of unbound
road materials and subgrade soils. The synopsis also presents different kinds of GPR hardware
systems as well as recommendations and experiences from different data collection, processing and
interpretation techniques. Special attention is given to a method whereby GPR data is integrated with
other road survey data and then analysed using a number of structural diagnostic methods. Finally,
the synopsis provides an overview of of the various GPR applications on roads and streets, bridges,
railways and airports.
The laboratory test results presented in this work show that the relationship between dielectric
value and increasing water content is not linear or exponential but more likely a series of logarithmic
functions. Laboratory results also showed that dielectric dispersion, which can be related to poorly
performing subgrade soils and road aggregates, takes place mainly in loosely bound adsorption water
and capillary water layer. As such these moisture sensitive problem materials can also be identified
during the dry summer seasons when they are stiff. Dielectric value and electrical conductivity can
also be related to other technical properties of road materials and subgrade soils such as frost
susceptibility, shear strength, plastic limit, compaction degree and voids content. Laboratory tests and
field data collected using the Percostation technique also demonstrate that a knowledge of seasonal
changes and thermodynamics is very important in understanding and modelling the mechanical
behaviour of road structures. Finally, laboratory and field tests indicate that colloids have an
important role in the failure mechanism of the road materials.
This research demonstrates that the GPR technique not only gives valuable structural information
on the different types of structures and subgrade soils but it provides a wide range of information of
the electrical properties of the materials under survey which can be further related to their mechanical
performance. The best information will be gained if GPR data is analysed together with other non
destructive testing data collected form the roads, railways and airports.Contents
Introduction
GPR principles and pulse propagation
Dielectric properties and seasonal changes of unbound road materials and
subgrade soils
GPR hardware and accessories
GPR data collection
Data processing and interpretation
Integrated GPR data analysis with other road survey data
GPR applications on roads and streets
Bridges
Railways
Airfields
Conclusions
