Conclusions

Geophysical Methods for Road Construction and MaintenanceHedi Rasul1&2, Caroline Karlsson1, Imran A. Jamali1, Robert Earon1, Bo Olofsson1

References

Corresponding author: Hedi Rasul, E-mail (hedir@kth.se), Address: Teknikringen 76, 10044 Stockholm. Phone: +46 (0) 8790 7045.

MethodDescription of various geophysical methods which can effectively be used during the road planning, construction and maintenance phases are presented in Table 1. Suggested methods for different phases of road construction are based on state of the art and practical experience. Additionally electrical resistivity (ER) measurements were carried out at a road test site in Sweden using Wenner-Array setting (Fig. 3).

Benson, R. C., 2000. An overview of geophysical and non-destructive methods for characterization of roads and bridges., Use of Geophysical Methods in Construction, pp. 1-14

Lundmark, A. and Olofsson, B. 2007. Chloride deposition and distribution in soils along a deiced highway – Assessment using different methods of measurement. Water air soil pollution 182. Pp 173-185.

Olofsson, B. and Lundmark, A. 2009. Monitoring the impact of de-icing salt on roadside soils with time-lapse resistivity measurements. Environmental Geology 57. pp 217-229.

Reynolds, J., 2011. An introduction to applied and environmental geophysics., 2nd Ed, Oxford: Wiley Blackwell, p.695.

1. Department of Sustainable Development, Environmental Science and Engineering, Royal Institute of Technology KTH- Sweden

2. Faculty of Engineering, Koya University- Kurdistan

Study area-Monitoring at Testsite-E18The study area is located on the E18 highway between Västerås and Enköping, Sweden (Fig. 2). The site is a major highway which has electrical resistivity monitoring equipment installed under the roadway, along with other measurement instruments.

Table 1 Summary of optimized geophysical methods that can be used in road design and construction phases .

Phases Problem cases Geophysical methodsGravity Geo

MagneticSeismic GPR ER TDR EM

reflection refractionPlanning Stratigraphy     * *** *** **   *

Depth to bedrock      ** *** *** ***   **Density of bedrock ***  *  *     **  

Investigations in high level of noise

***              

GW level     *  ** *** *** ** ***Tunnelling *   * ** **   ** **   * Cavities underground ***    * ** **      

Construction Degree of compaction         ** ** * *Layer thickness      * ** ** * *

Surface crack and faults         *** **   **Underground defects       *  ** *   *Underground buried objects   **     *** *   *

Water content         *  *** *** ***Maintenance Underground pipes and cables   ***     *** * **

Thickness of road layers         *** *   *Monitoring pollutant spreading          * *** * ***

                   * Can be applied but not in many cases  ** Has been applied successfully in past  *** Often applicable, few limitations  

Results and Discussion

IntroductionThe use of geophysical methods in road planning is an effective way to identify the subsurface characteristics, such as groundwater levels, soil thickness and stratigraphy of geological formations. Moreover, these methods can also assist in assessing the level of pollution arising from the road before, during and after construction. Thus making it both time and cost effective as opposed to invasive tests, i.e drillings.

During the construction phase, ground penetrating radar (GPR) with combination of electric resistivity (ER) is effective for detecting water content and base course compaction. For post construction phase, ER and electromagnetic (EM) can effectively be used to monitor chemical changes in groundwater. During the maintenance phase, GPR has been proved effective and has been used in many applications, especially for detecting pipes and cables. However, during maintenance phase, ER can also be useful to detect pathways of pollutants and their varying concentrations.

Roads play an important role for the development of any country. Especially in Kurdistan which is a land-locked region that has been suffering from decades of war. For instance, only in southern Kurdistan 5.2 Billion US$ is planned to be invested in the construction of new roads by 2018 (Fig. 1). Therefore it is necessary to adopt some sustainable, economical, and environmentally friendly methods for construction of roads. While planning any road projects, hydrological and hydrogeological characteristics play an important role.For example, the presence of moisture in road layers affects the stability of the road and causes maintenance problems. Moisture is necessary for a well-functioning road but excessive moisture often causes problems; ultimately leading to road failure. Roads are also a major source of environmental pollution. Therefore, environmental monitoring programs are required to assess the level of pollution caused by roads. Geophysical methods can benefit these projects greatly during all phases.

Different geophysical methods can be utilized in different situations (Table 1). However, a combination of two or more methods at times can prove effective. It has been suggested that a fixed electrical resistivity array is quite suitable for monitoring contaminant transport (Fig. 3).Results from E18 site indicated that a hydraulic pathway was created during the construction of the roadway (Fig. 3). A constant infiltration of highly contaminated runoff through the road base material has caused environmental stress.

Figure.1 South-Kurdistan, poor road quality

Figure.2 Test site E18

Figure.3 2D-Resistivity model for highway E18 monitoring station at Sweden.

m0

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Resistivity in ohm.m