scholarly journals Comparison of DFN Modelled Microfracture Systems with Petrophysical Data in Excavation Damaged Zone

2021 ◽  
Vol 11 (7) ◽  
pp. 2899
Author(s):  
Risto Kiuru ◽  
Dorka Király ◽  
Gergely Dabi ◽  
Lars Jacobsson
Keyword(s):  
Geophysical Methods ◽  
Fracture Network ◽  
Rock Types ◽  
Excavation Damaged Zone ◽  
Macro Scale ◽  
Damaged Zone ◽  
Discrete Fracture ◽  
Disturbed Layer ◽  
The Difference ◽  
Excavation Damage

Physical and petrographic properties of drill core specimens were determined as a part of investigations into excavation damage in the dedicated study area in the ONKALO® research facility in Olkiluoto, Western Finland. Microfractures in 16 specimens from two drillholes were analysed and used as a basis for fractal geometry-based discrete fracture network (DFN) modelling. It was concluded that the difference in resistivity between pegmatoid granite (PGR) and veined gneiss (VGN) specimens of similar porosity was likely due to differences in the types of microfractures. This hypothesis was confirmed from microfracture analysis and simulation: fractures in gneiss were short and mostly in one preferred orientation, whereas the fractures in granite were longer and had two preferred orientations. This may be due to microstructure differences of the rock types or could suggests that gneiss and granite may suffer different types of excavation damage. No dependencies on depth from the excavated surface were observed in the geometric parameters of the microfractures. This suggests that the excavation damaged zone cannot be identified based on the changes in the parameters of the microfracture networks, and that the disturbed layer observed by geophysical methods may be caused by macro-scale fractures.

Excavation Damage Zone in the Experimental Deposition Holes at Äspö and Comparison to Existing Data

2003 ◽  
Vol 807 ◽  
Author(s):  
Jorma Autio ◽  
Hanna Malmlund ◽  
Thomas Hjerpe ◽  
Maarit Kelokaski ◽  
Marja Siitari-Kauppi
Keyword(s):  
Hard Rock ◽  
Damage Zone ◽  
High Level Waste ◽  
Excavation Damaged Zone ◽  
Damaged Zone ◽  
Crushed Zone ◽  
High Level ◽  
Excavation Damage ◽  
The Impact ◽  
Clear Increase

ABSTRACTDisposal in deep, stable bedrock is currently one concept for isolating high-level wastes from the environment. Repository for high-level waste in rock excavated using different drilling techniques is surrounded by an excavation damaged zone (EDZ) which properties have been changed. The micro fracturing of samples taken from the experimental deposition holes in the underground Hard Rock Laboratory at Äspö were investigated by the 14C polymethylmetha-crylate (14C-PMMA) method and scanning electron microscopy (SEM) to evaluate the impact of EDZ on migration. The porosity of the damaged rock zone is clearly higher than the porosity of undisturbed rock. The thickness of the crushed zone with significantly higher porosity is a few millimetres and the average depth of the damaged zone (i.e. a clear increase in porosity found) is from 5 to 20 mm from the hole wall. The apertures of the inter- and intragranular fractures in the crushed zone varied from 5 to 30 μm according to SEM examination. Earlier results of porosity, diffusivity and permeability measurements in granites were compiled and the results of the porosity values of Äspö diorite were compared to the porosity values measured in other types of granites. The results were compiled in permeability-diffusivity-porosity space and were found to form a plane that could be used to estimate the range of diffusivity and permeability of the Äspö diorite.

scholarly journals Discrete Fracture Network Modelling in Triassic–Jurassic Carbonates of NW Lurestan, Zagros Fold-and-Thrust Belt, Iran

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 496
Author(s):  
Luigi Massaro ◽  
Amerigo Corradetti ◽  
Francesco d’Assisi Tramparulo ◽  
Stefano Vitale ◽  
Ernesto Paolo Prinzi ◽  
...  
Keyword(s):  
Large Scale ◽  
Line Drawing ◽  
Fracture Network ◽  
Poor Quality ◽  
Discrete Fracture Network ◽  
Network Modelling ◽  
Multi Scale ◽  
Fracture Systems ◽  
Macro Scale ◽  
Discrete Fracture

In this study, discrete fracture network (DFN) modelling was performed for Triassic–Jurassic analogue reservoir units of the NW Lurestan region, Iran. The modelling was elaborated following a multi-scale statistical sampling of the fracture systems characterising the analysed succession. The multi-scale approach was performed at two different observation scales. At the macro-scale, a digital outcrop analysis was carried out by means of a digital line-drawing based on camera-acquired images, focussing on the distribution of major throughgoing fractures; at the meso-scale, the scan line method was applied to investigate the background fractures of the examined formations. The gathered data were statistically analysed in order to estimate the laws governing the statistical distribution of some key fracture set attributes, namely, spacing, aperture, and height. The collected dataset was used for the DFN modelling, allowing the evaluation of the relative connectivity of the fracture systems and, therefore, defining the architecture and the geometries within the fracture network. The performed fracture modelling, confirmed, once again, the crucial impact that large-scale throughgoing fractures have on the decompartmentalization of a reservoir and on the related fluid flow migration processes. The derived petrophysical properties distribution showed in the models, defined the Kurra Chine Fm. and, especially, the Sehkaniyan Fm. as good-quality reservoir units, whereas the Sarki Fm was considered a poor-quality reservoir unit.

scholarly journals The Numerical Simulation of Hard Rocks for Tunnelling Purposes at Great Depths: A Comparison between the Hybrid FDEM Method and Continuous Techniques

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Nicholas Vlachopoulos ◽  
Ioannis Vazaios
Keyword(s):  
Numerical Models ◽  
Fracture Initiation ◽  
Fracture Network ◽  
Complex Nature ◽  
Underground Opening ◽  
Hard Rocks ◽  
Excavation Damaged Zone ◽  
Damaged Zone ◽  
Stress Changes ◽  
Element Method

Tunnelling processes lead to stress changes surrounding an underground opening resulting in the disturbance and potential damage of the surrounding ground. Especially, when it comes to hard rocks at great depths, the rockmass is more likely to respond in a brittle manner during the excavation. Continuum numerical modelling and discontinuum techniques have been employed in order to capture the complex nature of fracture initiation and propagation at low-confinement conditions surrounding an underground opening. In the present study, the hybrid finite-discrete element method (FDEM) is used and compared to techniques using the finite element method (FEM), in order to investigate the efficiency of these methods in simulating brittle fracturing. The numerical models are calibrated based on data and observations from the Underground Research Laboratory (URL) Test Tunnel, located in Manitoba, Canada. Following the comparison of these models, additional analyses are performed by integrating discrete fracture network (DFN) geometries in order to examine the effect of the explicit simulation of joints in brittle rockmasses. The results show that in both cases, the FDEM method is more capable of capturing the highly damaged zone (HDZ) and the excavation damaged zone (EDZ) compared to results of continuum numerical techniques in such excavations.

Identifikasi Potensi Air Tanah untuk Kebutuhan Penyediaan Air Bersih dengan Metode Geolistrik: Studi Kasus di Kawasan Geostech, Puspiptek Serpong

2020 ◽  
Vol 21 (2) ◽  
pp. 204-212
Author(s):  
Heru Sri Naryanto ◽  
Puspa Khaerani ◽  
Syakira Trisnafiah ◽  
Achmad Fakhrus Shomim ◽  
Wisyanto Wisyanto ◽  
...  
Keyword(s):  
Geophysical Methods ◽  
Groundwater Potential ◽  
Clean Water ◽  
Rock Types ◽  
Groundwater Aquifers ◽  
Groundwater Aquifer ◽  
Groundwater Origin ◽  
Laboratory Facility ◽  
Potential Groundwater ◽  
Lower Depth

ABSTRACTGeostech Building, as an office and laboratory facility, requires a source of clean water from groundwater related to the limited supply of clean water from the PDAM. Due to the needs of freshwater from groundwater origin, data and information are needed regarding the potential groundwater in the area, including aquifer configuration, depth, and groundwater potential. The presence of groundwater is not distributed through every area, and it's related to the geological and geohydrological conditions. One of the geophysical methods that can describe subsurface is 2D geoelectric methods. This method can distinguish and analyze rock types, geological structures, groundwater aquifers, and other important information based on the characteristics of the electricity of rocks by looking at the value of the type of resistance. In this measurement, the Wenner Alpha configuration has been used, where the arrangement of A-B current electrodes and M-N potential electrodes have constant spacing. From the measurement results, it can be interpreted that there is a low resistivity layer containing porous groundwater as an aquifer. Based on regional geological data, it has been estimated that this layer is in the form of sandy tuff (0-1.5 ohm-m). The exploitation of groundwater with drilling is expected to reach the aquifer's upper layer at depth, starting from 11.5-13 meters. The groundwater aquifer thickness cannot be ascertained because of the penetration of the lower depth of 2D geoelectric measurements truncated by the constraint of a maximum stretch of cable. The upper layer of the aquifer contains a turned layer of fine tufa and medium tuff, which is impermeable, coarse tuff, and mixed soil with varying thickness at the upper layer.Keywords: 2D geoelectric, aquifer, potential groundwater, Geostech  ABSTRAKGedung Geostech sebagai sarana perkantoran dan laboratorium memerlukan sumber air bersih dari air tanah terkait dengan terbatasnya suplai air bersih dari PDAM. Kebutuhan air bersih berasal dari air tanah, maka diperlukan data dan informasi mengenai kondisi potensi air tanah di kawasan tersebut termasuk konfigurasi akuifer, kedalaman, dan potensi air tanahnya. Keberadaan air tanah tidaklah merata untuk setiap tempat dan sangat terkait dengan kondisi geologi dan geohidrologinya. Salah satu metode geofisika yang dapat memberikan gambaran kondisi bawah permukaan adalah dengan metode geolistrik 2D. Metode ini dapat membedakan dan menganalisis jenis batuan, struktur geologi, akuifer air tanah, dan informasi penting lainnya berdasarkan sifat kelistrikan batuan dengan melihat nilai tahanan jenisnya. Dalam pengukuran ini digunakan konfigurasi Wenner Alpha, dimana susunan elektroda arus A dan B dan elektroda potensial M dan N mempunyai spasi yang konstan. Dari hasil pengukuran dapat diinterpretasikan adanya lapisan dengan resistivitas rendah yang mengandung air tanah dan bersifat porous sebagai akuifer. Berdasarkan data geologi regional diperkirakan lapisan ini berupa tuf pasiran (0-1,5 ohm-m). Pengambilan air tanah dengan pemboran diperkirakan akan mengenai batas atas lapisan akuifer pada kedalaman 11,5-13 meter. Ketebalan akuifer air tanah tidak bisa dihitung karena penetrasi kedalaman pengukuran geolistrik 2D terbatasi oleh bentangan elektroda di permukaan. Lapisan di atas akuifer merupakan lapisan selang-seling tuf halus dan tuf sedang yang kedap air, tuf kasar, dan pada bagian paling atas merupakan tanah urugan dengan ketebalan bervariasi.Kata kunci: Geolistrik 2D, akuifer, potensi air tanah, Geostech  

scholarly journals Characterization of a Shallow Coastal Aquifer in the Framework of a Subsurface Storage and Soil Aquifer Treatment Project Using Electrical Resistivity Tomography (Port de la Selva, Spain)

2021 ◽  
Vol 11 (6) ◽  
pp. 2448
Author(s):  
Alex Sendrós ◽  
Aritz Urruela ◽  
Mahjoub Himi ◽  
Carlos Alonso ◽  
Raúl Lovera ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Water Reuse ◽  
Electrical Resistivity Tomography ◽  
Groundwater Modeling ◽  
Geophysical Methods ◽  
Soil Aquifer Treatment ◽  
Modeling Tools ◽  
Resistivity Tomography ◽  
Implicit Modeling ◽  
The Difference

Water percolation through infiltration ponds is creating significant synergies for the broad adoption of water reuse as an additional non-conventional water supply. Despite the apparent simplicity of the soil aquifer treatment (SAT) approaches, the complexity of site-specific hydrogeological conditions and the processes occurring at various scales require an exhaustive understanding of the system’s response. The non-saturated zone and underlying aquifers cannot be considered as a black box, nor accept its characterization from few boreholes not well distributed over the area to be investigated. Electrical resistivity tomography (ERT) is a non-invasive technology, highly responsive to geological heterogeneities that has demonstrated useful to provide the detailed subsurface information required for groundwater modeling. The relationships between the electrical resistivity of the alluvial sediments and the bedrock and the difference in salinity of groundwater highlight the potential of geophysical methods over other more costly subsurface exploration techniques. The results of our research show that ERT coupled with implicit modeling tools provides information that can significantly help to identify aquifer geometry and characterize the saltwater intrusion of shallow alluvial aquifers. The proposed approaches could improve the reliability of groundwater models and the commitment of stakeholders to the benefits of SAT procedures.

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