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- Harmankaya, Utku, et al.
(författare)
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Locating scatterers while drilling using seismic noise due to TBM
- 2018
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Ingår i: Journal of Applied Geophysics. - : Elsevier BV. - 0926-9851 .- 1879-1859. ; 152, s. 86-99
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Tidskriftsartikel (refereegranskat)abstract
- Unexpected geological structures can cause safety and economic risks during underground excavation. Therefore, predicting possible geological threats while drilling a tunnel is important for operational safety and for preventing expensive standstills. Subsurface information for tunneling is provided by exploratory wells and by surface geological and geophysical investigations, which are limited by location and resolution, respectively. For detailed information about the structures ahead of the tunnel face, geophysical methods are applied during the tunnel-drilling activity.We present a method inspired by seismic interferometry and ambient-noise correlation that can be used for detecting scatterers, such as boulders and cavities, ahead of a tunnel while drilling. A similar method has been proposed for active-source seismic data and validated using laboratory and field data. Here, we propose to utilize the seismic noise generated by a Tunnel Boring Machine (TBM), and recorded at the surface. We explain our method at the hand of data from finite-difference modelling of noise-source wave propagation in a medium where scatterers are present. Using the modelled noise records, we apply cross-correlation to obtain correlation gathers. After isolating the scattered arrivals in these gathers, we cross-correlate again and invert for the correlated traveltime to locate scatterers. We show the potential of the method for locating the scatterers while drilling using noise records due to TBM.
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- Harmankaya, Utku, et al.
(författare)
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Modelling 3D elastodynamic wave scattering due to density and Lame parameter contrasts of near-surface scatterers
- 2022
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Ingår i: Near Surface Geophysics. - : John Wiley & Sons. - 1569-4445 .- 1873-0604. ; 20:3, s. 292-314
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Tidskriftsartikel (refereegranskat)abstract
- Investigating the near-surface structure of the Earth through geophysical methods is a crucial aspect in many areas of study in geotechnical engineering, environmental science and exploration. Among several geophysical methods, seismic-based ones are widely used for characterizing near-surface features that are distinguished by contrasts in elastic parameters. In this paper, we model 3D elastodynamic wave propagation and scattering using a method based on domain-type integral representation with Born approximation. We calculate the scattered wavefield by considering the first-order perturbations in density and Lame parameter contrasts of scatterers. Contrasts in Lame parameters can be useful for determining the material properties of subsurface structures in cases of weak contrasts in velocities accompanying considerable Lame parameter variations. We examine the effects of each parameter contrast on a series of models involving a subsurface scatterer. We also compare the seismograms obtained from our method with those from a 3D finite-difference wavefield modelling program, where we observe good agreement between the modelling results. Sensitivity of the wavefield to the perturbation in each model parameter is also examined by calculating and analysing the Frechet derivatives. In general, the method discussed here can provide a solid foundation for prospective imaging studies involving density and Lame parameters simultaneously.
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- Ivandic, Monika, et al.
(författare)
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Subsurface seismic imaging with a hammer drilling source at an exploration drilling test center in Örebro, Sweden
- 2022
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Ingår i: Advances in Geosciences. - : European Geosciences Union (EGU). - 1680-7340 .- 1680-7359. ; 56, s. 163-169
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Tidskriftsartikel (refereegranskat)abstract
- Seismic imaging while drilling (SWD) technology offers possibilities of imaging ahead of the drill-bit, which could be useful for determining when to go from hammer drilling to core drilling. Also, seismic images of the surrounding rock can improve geological models which could be then used to guide drilling programs.An SWD field test was carried out in August 2020 at an exploration drilling test site in Örebro, Sweden, with the aim to determine if the signals from hammer drilling can be used for seismic imaging around the drill-bit in a hard-rock environment where the strong drill-rig noise interference is one of the main challenges. The test site had previously been investigated with various geophysical methods, geological mapping and diamond core drilling, and it therefore represented an ideal location to perform this feasibility study.After data pre-processing and cross-correlation with the trace from the geophone closest to the rig, the shot-gathers were vertically stacked over the length of a drill pipe to achieve further signal improvement. A comparison with the active seismic data shows reasonable agreement, in spite of the fact that the noise level is significant even after careful processing. However, the lack of clear reflections in the active seismic data, indicating no detectable changes in the bedrock lithology in the near surface, hinders the full assessment of the seismic signal generated with hammer drilling at this site.
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- Ivandic, Monika, et al.
(författare)
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Subsurface seismic imaging with a hammer drilling source at an exploration drilling test center in Örebro, Sweden
- 2021
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Ingår i: EGU General Assembly 2021. - : Copernicus GmbH.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- <p>Seismic imaging while drilling technology offers possibilities of imaging ahead of the drill-bit, which could be useful for determining when to go from hammer drilling to core drilling. Moreover, seismic images of the surrounding rock can improve geological models which could be then used to guide drilling programs.</p><p>A seismic imaging while drilling field test was carried out in August 2020 at the I-EDDA Test Center next to the Epiroc factory in &#214;rebro, which is an outcome of the EIT Raw Materials funded project &#8220;Innovative Exploration Drilling and Data Acquisition (I-EDDA)&#8221;. The purpose of the test presented here was to determine if the signals from hammer drilling can be used for seismic imaging around the drill-bit. The I-EDDA test site has been extensively investigated with geophysical investigations, geological mapping and diamond core drilling, and it therefore represents an ideal location to perform the proposed feasibility study.</p><p>The data were recorded along a west-east oriented line consisting of 45 active 1C vertical geophones with a spacing of about 2 m and the rig located approximately in the middle of the profile. A reference signal, which is usually recorded by the pilot sensor fixed to the top of the drill string to be used to convert geophone recordings to impulsive-like seismic data, was not available. The passive recordings on the surface were thus correlated with the trace from the geophone closest to the rig.</p><p>After data pre-processing and cross-correlation, the shot-gathers were vertically stacked over the length of a drill pipe to achieve further signal improvement. A comparison with the results of a modelling study shows certain agreement. However, it has to be noted that the velocity model obtained from earlier studies and used to generate the synthetic data set here is rather a simple one and the noise level in the real data set is still significant, in spite of careful processing. Besides the strong contamination by the rig noise, more typical for data with smaller offsets, the mono-frequency waveform footprints present in the cross-correlograms, which have been observed in similar experiments where a trace from the nearest geophone was used to approximate the bit signal, could also play a role. The recent results from the active seismic studies conducted at the site have not detected any clear reflections within the bedrock, which further hinders the quality assessment of the seismic signal.</p><p>&#160;</p><p>&#160;</p><p>This work was partly supported by VINNOVA with the project 2019-04832 titled Integrated Smart Test environment for the mining industry - SMIG. We gratefully acknowledge this financial support.</p>
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