ORCID Profile
0000-0001-9787-7164
Current Organisation
Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences
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Publisher: Elsevier BV
Date: 11-2019
Publisher: American Geophysical Union (AGU)
Date: 09-12-2022
DOI: 10.1029/2022GL101212
Abstract: The influence of elevated temperature on injection‐induced fault slip is poorly constrained. In this study, at steady‐state elevated temperatures, triaxial shear‐flow experiments on a sawcut fault in granite were conducted to simulate injection‐induced slip of a critically stressed fault. Our results suggest that an elevated temperature favors a more uniform fluid pressure distribution over the fault surface mainly by reducing water viscosity. At temperatures above ambient, a larger perturbation force from the injected fluid is required to reactivate the fault primarily because of the enhanced thermally activated fault healing processes, resulting in a faster fault slip rate upon failure. This study may partially explain the causal link between higher reservoir temperature and higher maximum magnitude of injection‐induced earthquakes in geothermal systems, and the observation that larger magnitude seismic events concentrate near the deeper part of the reservoir, where temperature is higher.
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 11-2022
Publisher: Elsevier BV
Date: 03-2016
Publisher: Elsevier BV
Date: 09-2020
Publisher: Hindawi Limited
Date: 2014
DOI: 10.1155/2014/987020
Abstract: The vulnerability assessment model, composed by 11 vulnerability factors, is established with the introduction of the concept of “vulnerability” into the assessment of tunnel support system. Analytic hierarchy process is utilized to ide these 11 factors into human attributes and natural attributes, and define the weight of these factors for the model. The “vulnerability” applied io the assessment of the tunnel support system model is reached. The vulnerability assessment model was used for evaluating and modifying the haulage tunnel #3207 of Bo-fang mine panel #2. The results decreased the vulnerability of the tunnel support system and demonstrated acceptable effects. Furthermore, the results show that the impact of human attributes on tunnel support systems is dramatic under the condition that natural attributes are permanent, and the “vulnerability” is exactly a notable factor to manifest the transformation during this process. The results also indicate that optimizing human attributes can attenuate vulnerability in tunnel support systems. As a result, enhancement of stability of tunnel support systems can be achieved.
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-4204
Abstract: & & In this study, we conducted injection-driven shear tests on a sawcut fault in granite s les using a triaxial deformation apparatus. The granite s les were drilled from Odenwald basement rocks in Germany. The sawcut fault, inclined 30& #176 to the s le axis, was ground using sandpaper with a particle size of 201 & em& & #181 & /em& m. Two boreholes (nominal diameter 1.8 mm) were drilled near the short edge of each s le half to allow direct fluid access to the fault surface. Eight strain gauges, and eight pairs of acoustic emission (AE) sensors attached on the s le surface were used to monitor the deformation, local strain and AE events.& & & & & During the experiments, we first measured the peak shear strength of the faulted s le by advancing the axial piston at a constant rate of 1 & em& & #181 & /em& m/s under 36 MPa confining pressure and 1 MPa pore pressure. We then adjusted the shear stress to be 90% of the peak shear strength. Subsequently, the piston was fixed, and the first injection-driven shear test was initiated by injecting distilled water from the bottom borehole at a rate of 0.2 mL/min. We observed three full cycles of fast slip events until the injection pressure was increased up to approximately 18 MPa. We then reduced the pore pressure to the initial 1 MPa and the axial force was removed, followed by the second injection-driven shear test conducted at a higher injection rate of 0.8 mL/min using the same procedure as in the first test. We also observed three episodes of fast slip events until the injection pressure was increased to about 20 MPa. Fluid pressures were monitored continuously at the top and bottom boreholes. We employed a COMSOL model to obtain the time-dependent fluid pressure distribution along the sawcut fault during fluid injection.& & & & For slow fluid injection, we find that the fault surface near the center experiences slight normal dilation and gradual shear stress release prior to the fast slip event. In contrast, for high-rate fluid injection, the same fault patch exhibits normal compaction and shear stress increase preceding fast slip. In both cases, significant normal dilation and abrupt shear stress drops were observed near the fault center during fast slip events. The distinct evolution of local fault deformation and stress are likely attributed to the distribution of slow slipping patches, as signified by the fluid pressure distribution and Mohr-Coulomb failure envelope. At slow injection rate, slow precursory slip may have occurred on the entire fault, initiating a fast slip event. In contrast, at higher rates, slow slip may have been localized around the injection port, resulting in local stress concentration beyond the slow slipping patch. Our results demonstrate that the evolution of local fault deformation and stress can be erse in different fault patches, depending on the relative location to the fluid pressurized zone and the resulting slow slipping patch. This suggests that the strongly heterogeneous fault deformation should be considered when analyzing the precursors to injection-induced fault reactivation.& &
Publisher: Springer Science and Business Media LLC
Date: 30-03-2021
Publisher: Elsevier BV
Date: 12-2021
Publisher: Authorea, Inc.
Date: 08-07-2023
Publisher: Frontiers Media SA
Date: 29-08-2022
Publisher: Publicaciones DYNA
Date: 2015
DOI: 10.6036/7580
Publisher: Springer Science and Business Media LLC
Date: 29-03-2021
Publisher: Wiley
Date: 28-09-2023
DOI: 10.1002/DUG2.12053
Publisher: Elsevier BV
Date: 02-2019
Publisher: Elsevier BV
Date: 07-2020
Publisher: American Geophysical Union (AGU)
Date: 09-12-2022
DOI: 10.1029/2022GL100418
Abstract: We conducted fluid injection experiments on cylindrical low‐permeability granite s les with a critically stressed sawcut fault at local injection rates of 0.2 and 0.8 mL/min and confining pressures of 31 and 61 MPa. A local array of six strain gauges attached close to the faults allows us to estimate the nucleation length of each injection‐induced dynamic slip event (i.e., laboratory earthquake). We find nucleation lengths decrease from approximately 90% to % of the fault length with higher injection rate and increased effective normal stress. Injection‐induced laboratory earthquakes with smaller nucleation lengths show generally higher peak slip rates and larger fault slip displacements, signifying an intensified seismic hazard. Our results also indicate that initially stable fault patches may be reactivated to slip seismically by increasing injection rates. This study systematically demonstrates that higher injection rates constitute dynamic loading, which increase the seismic hazard by shrinking the earthquake nucleation length.
Publisher: Elsevier BV
Date: 03-2022
Publisher: Elsevier BV
Date: 10-2021
Publisher: Hindawi Limited
Date: 16-12-2018
DOI: 10.1155/2018/3031714
Abstract: The shield-roof interaction as mining proceeds in longwall panels remains unclear, hindering the further increase of longwall productivity. To uncover the mechanisms of shield-roof interaction, using our self-developed Status of Shield and Roof IntelliSense (SSRI) system, we investigated the effects of idle time, retreating rate, setting pressure, yielding, and shearer’s cutting, as well as neighboring shields’ advance on the spatial-temporal evolution of leg pressure and leg closure of shields. Our results show that the shield-roof interaction is not only dependent on the shield capacity, but also collectively determined by the time-related factors, the geological condition, the setting pressure, yielding characteristics, and mining method. Understanding the shield-roof interaction in longwall panels enables us to apply the SSRI system for ground control in longwall coal mines. Early warning of severe roof weighting can be achieved by establishing a warning model based on the decision tree algorithm. Apart from this, we can also assess the working condition of yield valve and diagnose fluid leakage of shield cylinder using the SSRI system. Finally, we propose the research prospects on shield-roof interaction in longwall panels to achieve a more reasonable determination of shield capacity, prediction of roof fall and coal wall spalling, and self-adaptive control of the shield.
Publisher: Elsevier BV
Date: 10-2019
Publisher: Springer Science and Business Media LLC
Date: 17-03-2023
Publisher: Springer Science and Business Media LLC
Date: 12-02-2022
DOI: 10.1007/S00603-022-02797-9
Abstract: • A novel numerical approach has been proposed to retrieve the hydraulic transmissivity of elliptical rock fractures in triaxial shear-flow experiments. • The accuracy of different methods for estimation of hydraulic transmissivity of elliptical rock fractures has been evaluated and discussed. • The numerical approach and electrical analogy are recommended for accurate evaluation of hydraulic transmissivity of elliptical rock fractures.
Publisher: Elsevier BV
Date: 10-2022
Publisher: Springer Science and Business Media LLC
Date: 19-08-2020
Publisher: Elsevier BV
Date: 06-2020
Publisher: Elsevier BV
Date: 09-2020
Publisher: Oxford University Press (OUP)
Date: 21-10-2022
DOI: 10.1093/GJI/GGAC416
Abstract: Fault zones often serve as the major fluid pathways in a variety of geo-energy systems, such as deep geothermal systems. However, injection-induced instability of faults can sometimes lead to large-magnitude earthquakes. Cyclic injection has thus been proposed as an alternative injection protocol to better manage and mitigate the associated seismic risks. The risks of injection-induced seismicity depend primarily on the extent and magnitude of the fluid pressure perturbation. When fluid is injected into a fault zone, the local fault permeability will be enhanced, which in turn promotes the migration of fluid along the fault. This nonlinear process is further complicated during cyclic injection via alternating the injection pressure. In this study, both numerical and analytical modelling are conducted to investigate cyclic fluid injection into a fault zone with pressure sensitive permeability, in which the local fault permeability changes as a function of the local effective stress. The match with laboratory-scale experimental and field-scale analytical results of cyclic fluid injection verifies the accuracy of the numerical model. The parametric study reveals that the injection pressure attenuation, quantified by the litude ratio and phase shift, is enhanced by a lower initial fault permeability, a smaller stress sensitivity coefficient and a shorter period of pressure cycle (i.e. a higher frequency). Besides, the litude of the pressure cycle has a negligible effect on the injection pressure attenuation. We also discuss the implications of our results for the less amenable far-field seismic hazard and post shut-in seismicity.
Publisher: American Geophysical Union (AGU)
Date: 20-09-2023
DOI: 10.1029/2023GL104662
Location: Germany
No related grants have been discovered for Yinlin Ji.