Validation of Coupled FDM-DEM Approach on the Soil-Raft Foundation Interaction Subjected to Normal Faulting

2021 ◽  
Author(s):  
Fang Ru-Ya ◽  
Lin Cheng-Han ◽  
Lin Ming-Lang
Keyword(s):  
Active Fault ◽  
Ground Deformation ◽  
Numerical Models ◽  
Hanging Wall ◽  
Normal Fault ◽  
Small Scale ◽  
Foot Wall ◽  
Normal Faulting ◽  
Raft Foundation ◽  
Overburden Soil

<p>Recent earthquake events have shown that besides the strong ground motions, the coseismic faulting often caused substantial ground deformation and destructions of near-fault structures. In Taiwan, many high-rise buildings with raft foundation are close to the active fault due to the dense population. The Shanchiao Fault, which is a famous active fault, is the potentially dangerous normal fault to the capital of Taiwan (Taipei). This study aims to use coupled FDM-DEM approach for parametrically analyzing the soil-raft foundation interaction subjected to normal faulting. The coupled FDM-DEM approach includes two numerical frameworks: the DEM-based model to capture the deformation behavior of overburden soil, and the FDM-based model to investigate the responses of raft foundation. The analytical approach was first verified by three  benchmark cases and theoretical solutions. After the verification, a series of small-scale sandbox model was used to validate the performance of the coupled FDM-DEM model in simulating deformation behaviors of overburden soil and structure elements. The full-scale numerical models were then built to understand the effects of relative location between the fault tip and foundation in the normal fault-soil-raft foundation behavior. Preliminary results show that the raft foundation located above the fault tip suffered to greater displacement, rotation, and inclination due to the intense deformation of the triangular shear zone in the overburden soil. The raft foundation also exhibited distortion during faulting. Based on the results, we suggest different adaptive strategies for the raft foundation located on foot wall and hanging wall if the buildings are necessary to be constructed within the active fault zone. It is the first time that the coupled FDM-DEM approach has been carefully validated and applied to study the normal fault-soil-raft foundation problems. The novel numerical framework is expected to contribute to design aids in future practical engineering.</p><p><strong>Keywords</strong>: Coupled FDM-DEM approach; normal faulting; ground deformation; soil-foundation interaction; raft foundation.</p>

scholarly journals Numerical Investigation of Factors Influencing Oil and Gas Lifelines Behavior due to Normal Faulting Geo-Hazard

2015 ◽  
Vol 10 (Special-Issue1) ◽  
pp. 806-813
Author(s):  
Reza Khaksar ◽  
Majid Moradi
Keyword(s):  
Oil And Gas ◽  
Hanging Wall ◽  
Small Scale ◽  
Foot Wall ◽  
Buried Pipeline ◽  
Normal Faulting ◽  
Geotechnical Centrifuge ◽  
Centrifuge Model ◽  
Factors Influencing ◽  
Centrifuge Model Tests

In this study, some factors influencing the response of buried oil and gas lifelines subjected to normal faulting are investigated. Due to such phenomenon, the stress, strain and displacement are induced in pipeline. Finite element code of Abaqus has been employed to model pipe and its surrounding soil considering material nonlinearities, soil-pipe interaction and foot wall and hanging wall interface. The numerical model has been calibrated through some small scale geotechnical centrifuge model tests and based on such calibrated model, some factors influencing the response of buried pipeline has been investigated.

Imaging Poro-Elastic Effects induced by a Normal Fault Aseismic-to-Seismic Dislocation in Shales

2020 ◽  
Author(s):  
Yves Guglielmi ◽  
Jens Birkholzer ◽  
Jonathan Ajo-Franklin ◽  
Christophe Nussbaum ◽  
Frederic Cappa ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Fault Zone ◽  
Hanging Wall ◽  
Three Dimensional ◽  
Normal Fault ◽  
Fault Reactivation ◽  
Foot Wall ◽  
Fault Activation ◽  
Strain Monitoring ◽  
Receiver Array

<p>Understanding fault reactivation as a result of subsurface fluid injection in shales is critical in geologic CO<sub>2</sub> sequestration and in assessing the performance of radioactive waste repositories in shale formations. Since 2015, two semi-controlled fault activation projects, called FS and FS-B, have been conducted in a fault zone intersecting a claystone formation at 300 m depth in the Mont Terri Underground Research Laboratory (Switzerland). In 2015, the FS project involved injection into 5 borehole intervals set at different locations within the fault zone. Detailed pressure and strain monitoring showed that injected fluids can only penetrate the fault when it is at or above the Coulomb failure criterion, highlighting complex mixed opening and slipping activation modes. Rupture modes were strongly driven by the structural complexity of the thick fault. An overall normal fault activation was observed. One key parameter affecting the reactivation behavior is the way the fault’s initial very low permeability dynamically increases at rupture. Such complexity may also explain a complex interplay between aseismic and seismic activation periods. Intact rock pore pressure variations were observed in a large volume around the rupture patch, producing pore pressure drops of ~4 10<sup>-4</sup> MPa up to 20 m away from the ruptured fault patch. Fully coupled three-dimensional numerical analyses indicated that the observed pressure signals are in good accordance with a poro-elastic stress transfer triggered by the fault dislocation.</p><p> </p><p>In 2019, the FS-B experiment started in the same fault, this time activating a larger fault zone volume of about 100 m extent near (and partially including) the initial FS testbed. In addition to the monitoring methods employed in the earlier experiment, FS-B features time-lapse geophysical imaging of long-term fluid flow and rupture processes. Five inclined holes were drilled parallel to the Main Fault dip at a distance of about 2-to-5m from the fault core “boundary”, with three boreholes drilled in the hanging wall and two boreholes drilled in the foot wall. An active seismic source-receiver array deployed in these five inclined boreholes allows tracking the variations of p- and s-wave velocities during fault leakage associated with rupture, post-rupture and eventually self-sealing behavior. The geophysical measurements are complemented by local three-dimensional displacements and pore pressures measurements distributed in three vertical boreholes drilled across the fault zone. DSS, DTS and DAS optical fibers cemented behind casing allow for the distributed strain monitoring in all the boreholes. Twelve acoustic emission sensors are cemented in two boreholes set across the fault zone and close to the injection borehole. Preliminary results from the new FS-B fault activation experiment will be discussed.</p>

Analytical approach for estimating ground deformation profile induced by normal faulting in undrained clay

2013 ◽  
Vol 50 (4) ◽  
pp. 413-422 ◽  
Author(s):  
Q.P. Cai ◽  
Charles W.W. Ng
Keyword(s):  
Ground Deformation ◽  
Error Function ◽  
Hanging Wall ◽  
Numerical Data ◽  
Theoretical Models ◽  
Failure Surface ◽  
Vertical Displacement ◽  
Normal Faulting ◽  
Soil Thickness ◽  
Undrained Shear

Although theoretical models have been developed to predict the location of the failure surface in soil induced by bedrock faulting, no analytical tool is available to estimate subsurface ground deformation. In this paper, a newly developed semi-empirical approach is introduced and developed for calculating surface and subsurface deformations induced by normal faulting in undrained clay. Based on observations from centrifuge model tests, the ground deformation mechanisms are identified by three regions; namely, a stationary zone, a shearing zone, and a rigid body zone. By using an error function to represent vertical displacement continuously, the ground deformation profile can be described quantitatively. It is revealed that the ground deformation profile depends on vertical displacement of the bedrock hanging wall, soil thickness, dip angle of the bedrock fault plane, and a shape parameter that is a function of the undrained shear modulus normalized by the undrained shear strength. Validation and consistent agreement are obtained between calculated ground deformation profiles and other independent centrifuge test results and reported numerical data.

scholarly journals Instrumental and field observations for the determination of the seismogenic structure of the 7 September 1999 Athens earthquake

2001 ◽  
Vol 34 (4) ◽  
pp. 1457 ◽  
Author(s):  
Γ. Α. ΠΑΠΑΔΟΠΟΥΛΟΣ ◽  
Α. ΓΚΑΝΑΣ ◽  
Σ. ΠΑΥΛΙΔΗΣ
Keyword(s):  
Main Shock ◽  
Hanging Wall ◽  
Strong Motion ◽  
Small Scale ◽  
Foot Wall ◽  
Seismogenic Structure ◽  
Rock Falls ◽  
Field Evidence ◽  
Athens Earthquake ◽  
Fili Fault

The earthquake of 7 Sept. 1999 (Ms= 5.9) that struck the metropolitan area of Athens, occurred only at a distance of '18 NW from the historical center of the city and has been the most destructive shock in modern history of Greece. Therefore, it is of great importance to identify the seismogenic structure. Focal mechanisms of the main shock as well as the lateral and vertical distributions of the aftershocks , determined by several institutes, are consistent in that the main shock was associated with a normal faulting striking WNE-ESE and dipping SW. The only geological faults known in the area to have the geometrical characteristics that are compatible with the seismographic results are the fault of Thriassion Pedion and the Fili fault. We support that the Fili fault, striking 110° - 150° Ν at an observable length of 8-10 Km, has been very probably the seismogenic structure of the Athens earthquake because ( i) it proved to be an active fault as revealed by the striations we observed on several segments of the fault mirror, ( ii) the meizoseismal region as well as the most important ground failures, like local small-scale landslides and rock-falls, all are located on the hanging-wall domain and very close to the surface trace of the fault as it is theoretically expected (e.g. Oglesby et al., 2000), ( iii) we observed a possibly co-seismic displacement by 3-6 cm of the SW (hanging-wall) segment towards SW . On the contrary, the fault of Thriassion Pedion is recognizable in satellite images but in the field it is evident only as a series of alluvium cones which is an evidence of a possibly inactive structure. Moreover, the meizoseismal area and the ground failures observed in association with the Athens earthquake are located in its foot-wall, that is in the domain where strong motion should not expected to occur. In addition, if that fault was the seismogenic one then the earthquake focus would fit the fault geometry only if it was shifted at least 15 km southwestwards. The last possibility that the Athens earthquake was associated with a blind fault is not supported by any kind of instrumental or field evidence.

Faulting, doming and basin formation during orogenic arcuation – the case of the Shkoder-Peja Normal Fault System (northern Albania and Kosovo)

2021 ◽  
Author(s):  
Marc U. Grund ◽  
Mark R. Handy ◽  
Jörg Giese ◽  
Jan Pleuger ◽  
Lorenzo Gemignani ◽  
...  
Keyword(s):  
Hanging Wall ◽  
Normal Fault ◽  
Sedimentary Basins ◽  
Vertical Displacement ◽  
Ductile Deformation ◽  
Fault System ◽  
Normal Faulting ◽  
Two Phase ◽  
Brittle Faulting ◽  
Topographic Constraints

<p>The junction between the Dinarides and the Hellenides coincides with an orogenic bend characterized by a complex system of faults, domes and sedimentary basins. The major structure at this junction is the Shkoder-Peja Normal Fault (SPNF) system, which trends oblique to the orogen and is segmented along strike, with ductile-to-brittle branches in its southwestern and central parts that border two domes in its footwall: (1) the Cukali Dome (RSCM peak-T 190-280°C), a doubly-plunging upright antiform deforming Dinaric nappes, including the Krasta-Cukali nappe with its Middle Triassic to Early Eocene sediments; (2) the newly discovered Decani Dome (RSCM peak-T 320-460°C) delimited to the E by the ~1500 m wide Decani Shear Zone (DSZ) that exposes Paleozoic to Mesozoic strata of the East Bosnian Durmitor nappe (EBD). In the northeasternmost segment, the strike of the SPNF system changes from roughly orogen-perpendicular to orogen-parallel. There, the SPNF system has brittle branches- most notably the Dukagjini Fault (DF) that forms the northwestern limit of the Western Kosovo Basin (WKB).</p><p>The westernmost ductile-brittle SPNF segment strikes along the southern limb of the Cukali Dome with an increasing vertical offset from 0 m near Shkoder eastwards to >1000 m at the eastern extent of the dome (near Fierza) where normal faulting cuts the nappe contact between the High Karst and Krasta-Cukali unit. The central segment north of the Tropoja Basin, with several smaller branches changing in strike, has a vertical throw of at least 1500 meters based on topographic constraints. Even further to the northeast, the SPNF system includes the moderately E-dipping DSZ juxtaposing the EBD in its footwall against mèlange of the West Vardar unit in its hanging wall, where offset is difficult to determine. 3 km eastwards, in the hanging wall to the DSZ, the brittle DF accommodates another 1000 m of vertical displacement as constrained by maximum depth of sediments of the WKB.</p><p>Ductile deformation along the Cukali and Decani Domes occurred sometime between the end of Dinaric thrusting and the formation of the WKB. Brittle faulting partly reactivates ductile segments, but also creates new branches (DF) within the hanging wall of the ductile DSZ. These were active during mid-Miocene to Pliocene times as constrained by syn-tectonic sediments in the WKB. We interpret the SPNF system as a two-phase composite extensional structure with normal faulting that migrated from its older trace along the ductile DSZ to the brittle DF as indicated by cross-cutting relations. The Decani Dome, with higher metamorphic temperature conditions than the Cukali Dome, may reflect the south-westernmost extent of late Paleogene extension in the Dinarides. It may be related to other core complexes and possibly to limited subduction rollback beneath the Dinarides (Matenco and Radivojevi, 2012). Extension from mid-Miocene time onwards was probably related to Hellenic CW rotation during Neogene orogenic arcuation, possibly triggered by enhanced rollback beneath the Hellenides (Handy et al., 2019).</p><p>Handy, M.R.,et al. 2019: Tectonics, v. 38, p. 2803–2828, doi:10.1029/2019TC005524.</p><p>Matenco, L.,& Radivojevi, D. 2012: Tectonics, v. 31, p. 1–31, doi:10.1029/2012TC003206.</p>

The Kozani-Grevena (Greece) earthquake of 13 May 1995 revisited from a detailed seismological study

1997 ◽  
Vol 87 (2) ◽  
pp. 463-473
Author(s):  
D. Hatzfeld ◽  
V. Karakostas ◽  
M. Ziazia ◽  
G. Selvaggi ◽  
S. Leborgne ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Active Fault ◽  
Fault Plane ◽  
Ground Surface ◽  
Strong Motion ◽  
Normal Fault ◽  
Normal Faulting ◽  
Waveform Modeling ◽  
Epicentral Region ◽  
Better Than

Abstract The Kozani earthquake (Ms = 6.6) of 13 May 1995 is the strongest event of the decade in Greece and occurred in a region of low seismic activity. Using regional data and the strong-motion record at the Kozani station, we relocate the mainshock at 40.183° N and 21.660° E, beneath the Vourinos massif at a depth of 14.2 km. We also compute a focal mechanism by body-waveform modeling at teleseismic distance, which confirms a normal mechanism. The most likely plane strikes 240° ± 1° N and dips 40° ± 1° N with a centroid depth of 11 ± 1 km. Modeling of the strong-motion record at Kozani confirms that nucleation started at the eastern termination of the bottom of the fault. Six days after the mainshock, we installed a network of 40 portable seismological stations for one week around the epicentral region. Several thousand aftershocks were recorded, among which we locate 622 with a precision better than 1 km. We compute 181 focal mechanisms that mostly show normal faulting. The aftershock seismicity is restricted between 5 and 15 km depth and defines a plane dipping north at an angle of about 35°, consistent with the mainshock mechanism. Seismic activity with the same pattern of normal fault mechanisms is also seen on an antithetic fault connected to the main one at 12 km depth, which cuts the ground surface north of the Vourinos ophiolite massif in the Siatista valley. These results suggest two possibilities for the active fault plane; either it is the Deskati fault that is flat and dips with a constant angle, and therefore the surface breaks are secondary features, or, more likely, it is the Paleohori fault that is new, of listric shape, and located ahead of the Deskati fault, which was not active during the earthquake.

scholarly journals On the mechanical behaviour of a low angle normal fault: the Altotiberina fault (Northern Apennines, Italy) system case study

2016 ◽  
Author(s):  
Luigi Vadacca ◽  
Emanuele Casarotti ◽  
Lauro Chiaraluce ◽  
Massimo Cocco
Keyword(s):  
Mechanical Behaviour ◽  
Numerical Models ◽  
Hanging Wall ◽  
Normal Fault ◽  
Active Role ◽  
Northern Apennines ◽  
Fault System ◽  
Tectonically Active ◽  
Main Fault ◽  
Microseismic Activity

Abstract. Geological and seismological observations have been used to parameterize 2D numerical models to simulate the interseismic deformation of a complex extensional fault system located in the Northern Apennines (Italy). The geological system is dominated by the presence of the Altotiberina fault (ATF), a large (60 km along strike) low-angle normal fault 20° dipping in the brittle crust (0–15 km). The ATF is currently interested by a high and constant rate of microseismic activity and no moderate-to-large magnitude earthquakes have been associated to it for the past 1000 years. Modelling results have been compared with GPS data in order to understand the mechanical behaviour of this fault and a suite of minor syn- and antithetic normal fault segments located in the main fault hanging-wall. The results of the simulations demonstrate the active role played by the Altotiberina fault in accommodating the on going tectonic extension in this sector of the chain. The GPS velocity profile constructed through the fault system cannot be explained without including the ATF's contribution to deformation, indicating that this fault although misoriented has to be considered tectonically active and with a creeping behaviour below 5 km of depth. The low angle normal fault also shows a high degree of tectonic coupling with its main antithetic fault (the Gubbio fault) suggesting that creeping along the ATF may control the observed strain localization and the pattern of microseismic activity.

scholarly journals Analysis and Monitoring of Small-Scale Rock Fracture Zone Deformation and Shaft Failure in a Metal Mine

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Rong Lu ◽  
Fengshan Ma ◽  
Jie Zhao ◽  
Jianbo Wang ◽  
Guilin Li ◽  
...  
Keyword(s):  
Fracture Zone ◽  
Rock Fracture ◽  
Hanging Wall ◽  
Wall Rock ◽  
Ground Movement ◽  
Small Scale ◽  
Foot Wall ◽  
Fracture Zones ◽  
Metal Mine ◽  
Deep Fracture

Rock fracture zones were distributed in a metal mine, and their deformation was always neglected because they are available on a small scale. However, the deformation of the small-scale fracture zone may lead to serious consequences, such as underground building and structure failure. Combined with the ground movement and surface fissure monitoring, the deformation of several fracture zones was analyzed by field monitoring, experimental test, and numerical simulation. The results showed that fracture deformation promoted the surface fissure movement. The horizontal movement of the foot wall rock of the fracture was found to be larger than the hanging wall rock. Deep mining engineering resulted in the squeezing of the shallow fracture, and the shallow fracture deformed more severely than the deep fracture. In the study area, fracture zone displacements were estimated according to a numerical model. The deformation and stress comparison of the shallow fracture zone and the deep fracture zone provided the characteristic of the broken structure in the field investigation.

scholarly journals Numerical simulation study of mining process of upper and lower walls of normal and reverse faults

2021 ◽  
Vol 2083 (3) ◽  
pp. 032071
Author(s):  
Bian Zhuang
Keyword(s):  
Coal Seam ◽  
Numerical Models ◽  
Hanging Wall ◽  
Coal Pillar ◽  
Normal Fault ◽  
Reverse Fault ◽  
Coal Seams ◽  
Working Face ◽  
Geological Conditions ◽  
Mining Coal

Abstract Mining coal seams near faults are prone to various mine disasters, and different mining sequences have different effects on coal seam disasters. Under this background, the numerical models of normal fault hanging wall, normal faultfoot wall, reverse fault hanging wall and reverse fault footwall under the same geological conditions are established. It is found that the stress concentration of coal pillar is the largest in the mining process of hanging wall of normal fault and footwall of reverse fault, and the possibility of inducing coal pillar rockburst is the largest. Affected by the fault, the coal pillar abutment stress between the working face and the fault shows an upward trend. When mining the coal seam near the fault, various methods such as hydraulic fracturing should be adopted to reduce the coal pillar abutment stress and reduce the risk of mine disasters.

scholarly journals The Effectiveness of Ensemble-Neural Network Techniques to Predict Peak Uplift Resistance of Buried Pipes in Reinforced Sand

2021 ◽  
Vol 11 (3) ◽  
pp. 908
Author(s):  
Jie Zeng ◽  
Panagiotis G. Asteris ◽  
Anna P. Mamou ◽  
Ahmed Salih Mohammed ◽  
Emmanuil A. Golias ◽  
...  
Keyword(s):  
Neural Network ◽  
Numerical Models ◽  
Correlation Coefficients ◽  
Network Models ◽  
Small Scale ◽  
Offshore Platforms ◽  
Neural Network Models ◽  
Buried Pipes ◽  
Ensemble Techniques ◽  
Uplift Resistance

Buried pipes are extensively used for oil transportation from offshore platforms. Under unfavorable loading combinations, the pipe’s uplift resistance may be exceeded, which may result in excessive deformations and significant disruptions. This paper presents findings from a series of small-scale tests performed on pipes buried in geogrid-reinforced sands, with the measured peak uplift resistance being used to calibrate advanced numerical models employing neural networks. Multilayer perceptron (MLP) and Radial Basis Function (RBF) primary structure types have been used to train two neural network models, which were then further developed using bagging and boosting ensemble techniques. Correlation coefficients in excess of 0.954 between the measured and predicted peak uplift resistance have been achieved. The results show that the design of pipelines can be significantly improved using the proposed novel, reliable and robust soft computing models.

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