Markradar- och resistivitetsmätningar : undersökningar utav korrosionsförhöjande markegenskaper kring fjärrvärmeledningar i Ängelholm

Sammanfattning: District heating pipes at two localities in Ängelholm have been investigated with two geophysical methods; ground penetrating radar (GPR) and resistivity measurements (ERT, Electrical Resistivity Tomography). District heating pipes are constantly exposed to the influence of external- and internal forces. As a result the pipes degrade over time, and leakage can eventually occur. Management owners have expressed a wish that techniques should be developed for easier management of the grid (DH- and sewerage pipes). A three-year Vinnova project was therefore launched in late 2015, with the aim to implement and evaluate five different methods. In this study one of these methods is evaluated, which is to correlate the two geophysical survey methods; ground penetrating radar and resistivity measurements. The rationale of this study has been to mainly examine soil conditions in areas around the pipes and to detect soil transitions zones since these constitute potential differences in the ground, which can lead to corrosion. These conditions may pose an increased risk of damage to the pipes. Ground penetrating radar is a method which provides information whether or not objects in the ground can act as a reflector. If the electromagnetic pulse is suppressed, the area can for example contain clay rich soils. Correlated with resistivity measurements these areas should obtain lower resistivity, since clay rich soils exhibit low resistance. The results of the geophysical surveys have been correlated. From the interpretation, it is clear that the soil transitions are housed in the two premises, where a soil transition in each locality could be detected. The conclusion is that this method has good potential to detect soil transitions in relative large scale. Excavations of the premises will be made at a later stage in the Vinnova project, which will provide a kind of "hindsight" of the pipes condition.