| 1. |
- Dahlin, Torleif, et al.
(författare)
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ASSERT - Kontroll av markstabilisering med resistivitetstomografi (ERT)
- 2023
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Ingår i: ; , s. 219-228
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Konferensbidrag (refereegranskat)abstract
- Soil stabilisation is becoming increasingly common for the development of areas withpoor bearing capacity. However, there is a need for better and volume-wide controlmethods for quality assurance. The control methods can be divided into two steps,where the first takes place in immediate connection to the mixing of binders to checkwhether the entire intended volume has been successfully treated, or whether thereare zones that need completion. The second step focuses on the strength of thestabilised volume and assumes that the binder has cured.The R&D project ASSERT focuses on quality control using electrical resistivitytomography (ERT). The idea is to use the method in immediate connection with themixing of binders to delineate the soil volume that has been treated with binders fromuntreated parts. ERT could then be used to quickly check the results of thestabilisation, so that supplementary measures can be taken in zones of insufficienttreatment while personnel and equipment are in place. Furthermore, there is potentialfor volume-wide quantification of strength growth via correlation between change inresistivity and change in strength during the curing process, but this would probablyneed to be done on a site specific basis.Testing and verification of the method takes place in different geomaterials in thelaboratory and in the field, including full-scale tests for different types ofstabilisations. Furthermore, method development and adaptation for the applicationare included, so that the method becomes sufficiently robust and fast to be usedroutinely in a sustainable manner. Field trials have been carried out by installingelectrodes in lime-cement columns and jet columns in direct connection to thestabilisation. Laboratory tests have so far been carried out for lime-cementstabilisation of clay and for stabilisation of dredged masses.
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| 2. |
- Dahlin, Torleif, et al.
(författare)
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Novel electrode design for non-destructive resistivity measurement on material in geotechnical standard sample cylinders
- 2023
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Ingår i: Procs. Near Surface Geoscience 2023.
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Konferensbidrag (refereegranskat)abstract
- We present a novel design of an electrode arrangement for measurement of the resistivity of soil samples contained in a sample cylinder used in standard geotechnical site investigations in Sweden. The objective is to make it possible to measure the resistivity of the same samples that are to be used for mechanical tests, without disturbing the samples in order to get unbiased mechanical test data. A design with four piece-of- pie shaped electrodes integrated in the lids in each end of the sample has been tested and evaluated. Temperature sensors are embedded in the electrode lids to allow temperature compensation of the measured data.Alternative electrode designs were modelled numerically with the finite element method (FEM) prior to the prototype manufacturing. Measurement tests with water filled sample cylinders show that stacking and reciprocal errors can be kept below 1% provided that suitable measurement settings and sequences are used. The geometrical factors depends on the distance between the electrodes in each end of the cylinder, i.e. varies with the length of the sample, and must be determined experimentally or via FEM modelling.
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| 3. |
- Olsson, Per-Ivar, et al.
(författare)
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Field-Scale Quality Control of Lime-Cement Pillar in Conductive Clay Using Electrical Resistivity Tomography
- 2019
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Ingår i: Proceedings of the 1st Conference on Geophysics for Infrastructure Planning, Monitoring and BIM. - : European Association of Geoscientists & Engineers.
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Konferensbidrag (refereegranskat)abstract
- Ground improvement with lime-cement pillars is becoming increasingly common in the Nordic countries for exploitation of areas with poor stability. However, there is no non-destructive method for quality control of the ground improvement. Significant changes in the electrical properties after mixing of the binders make electrical resistivity tomography (ERT) a potential method. In connection with lime-cement pillar trials for the Västlänken project in Gothenburg, Sweden, a series of different single borehole ERT measurements were performed. Three cases are compared in this paper: untreated ground, treated uncured ground and treated cured ground. The raw data pseudosections show a significant general drop in resistivity between the untreated and treated uncured data sets, while the curing process increase the resistivity significantly close to the borehole. Full 3D inversions have been carried out for all three cases. In model space the cured pillar is still causing a clear increase in resistivity around the borehole, while the decrease between the untreated and uncured case is less obvious than in data space. With the large contrast between the untreated and the treated uncured in data space it was expected to be visible in model space, improved inversion methods and settings could help resolve this.
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| 4. |
- Rejkjär, Simon, et al.
(författare)
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Determination of the resistivity distribution along underground pipes in urban contexts using galvanic and capacitive methods
- 2021
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Ingår i: Near Surface Geophysics. - : Wiley. - 1569-4445 .- 1873-0604. ; 19:1, s. 27-41
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Tidskriftsartikel (refereegranskat)abstract
- Renovation of water and central heating pipelines is a very costly and time-consuming process, so a way to prioritize the limited resources between different parts of the systems is very important. The risk for corrosion damage can be assessed from the resistivity of the ground, due to the processes facilitating the metal oxidation also affecting the resistivity, but galvanic resistivity mapping is time consuming and work-intensive in paved areas. To determine the resistivity in the vicinity of pipes two different resistivity methods were applied: electrical resistivity tomography, using galvanic coupling, and the logistically easier and rapid electrostatic measurements, using capacitive coupling. The two methods were tested in a series of experiments undertaken in the province of Scania in southern Sweden with the aim to acquire better knowledge about the electrical resistivity of the soil surrounding heating and water distribution pipes, in order to better assess the corrosivity of the environment. From the experiments it is shown that the electrical resistivity tomography and electrostatic methods mostly give comparable results for the shallow investigated depths in focus here, where differences might be caused by different sensitivities and noise characteristics. In the case of both methods, it is shown, with the help of modelling of the different expected ground models including the pipes, that the pipes only influence the data in cases of pipes of very large diameters or those buried at a very shallow depth, even without any protective surface coating. The missing influence of the pipes on the data makes the methods very applicable for knowing the resistivity of the soil surrounding the pipes and thus evaluation of corrosion risk.
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