scholarly journals The role of mechanical stratigraphy on the refraction of strike-slip faults

2018 ◽  
Author(s):  
Mirko Carlini ◽  
Giulio Viola ◽  
Jussi Mattila ◽  
Luca Castellucci
Keyword(s):  
Grain Size ◽  
Failure Modes ◽  
Shear Failure ◽  
Shear Fracture ◽  
Process Zone ◽  
Regional Scale ◽  
Strike Slip ◽  
Fracture Planes ◽  
Evolutionary Scheme ◽  
Tensile Fractures

Abstract. Fault and fracture planes (FFP) that cut through multilayer sequences can be significantly refracted at layer-layer interfaces due to the different mechanical properties of the contiguous layers, such as shear strength, friction coefficient and grain size. Detailed studies of different but coexisting and broadly coeval failure modes (tensile, hybrid and shear) within multilayers deformed in extensional settings have led to infer relatively low confinement and differential stress as the boundary stress conditions at which FFP refraction occurs. Although indeed widely recognized and studied in extensional settings, the details of FFP nucleation, propagation and refraction through multilayers remain not completely understood, partly because of the common lack of geological structures documenting the incipient and intermediate stages of deformation. Here we present the results of a study on strongly refracted strike-slip FFP within the mechanically layered turbidites of the Marnoso Arenacea Formation (MAF) of the Italian Northern Apennines. The MAF is characterized by the alternation of sandstone (strong) and carbonate mudstone (weak) layers. The studied refracted FFP formed at the front of the regional-scale NE-verging Palazzuolo anticline and post-date almost any other observed structure except for a set of late extensional faults. The studied faults display coexistence of shear and hybrid (tensile-shear) failure modes and we suggest that they initially nucleated as shear fractures (mode III) within the weak layers and, only at a later stage, propagated as dilatant fractures (mode I-II) within the strong layers. The tensile fractures within the strong layers invariably contain blocky calcite infills, which are, on the other hand, almost completely absent along the shear fracture planes deforming the weak layers. Paleostress analysis was performed to constrain the NNE-SSW compressional stress field that produced the refracted FFP and to exclude the possibility that the present attitude of these structures may result from the rotation through time of faults with an initial orientation. Slip tendency analysis was also performed to infer the relative slip and dilation potentials of the observed structures. Mesoscopic analysis of preserved structures from the incipient and intermediate stages of development and evolution of the refracted FFP allowed us to build an evolutionary scheme wherein: a) Nucleation of refracted FFP occurs within weak layers; b) Refraction is primarily controlled by grain size and clay mineral content and variations thereof at layer-layer interfaces but also within individual layers; c) Propagation within strong layers occurs primarily by fluid-assisted development ahead of the FFP tip of a “process zone” defined by a network of hybrid and tensile fractures; d) The process zone causes the progressive weakening and fragmentation of the affected rock volume to eventually allow the FFP to propagate through the strong layers; e) Enhanced suitable conditions for the development of tensile and hybrid fractures can be also achieved thanks to the important role played by pressured fluids.

scholarly journals The role of mechanical stratigraphy on the refraction of strike-slip faults

Solid Earth ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 343-356 ◽  
Author(s):  
Mirko Carlini ◽  
Giulio Viola ◽  
Jussi Mattila ◽  
Luca Castellucci
Keyword(s):  
Grain Size ◽  
Failure Modes ◽  
Shear Failure ◽  
Shear Fracture ◽  
Process Zone ◽  
Regional Scale ◽  
Strike Slip ◽  
Fracture Planes ◽  
Evolutionary Scheme ◽  
Tensile Fractures

Abstract. Fault and fracture planes (FFPs) affecting multilayer sequences can be significantly refracted at layer–layer interfaces due to the different mechanical properties of the contiguous layers, such as shear strength, friction coefficient and grain size. Detailed studies of different but coexisting and broadly coeval failure modes (tensile, hybrid and shear) within multilayers deformed in extensional settings have led to infer relatively low confinement and differential stress as the boundary stress conditions at which FFP refraction occurs. Although indeed widely recognized and studied in extensional settings, the details of FFP nucleation, propagation and refraction through multilayers remain not completely understood, partly because of the common lack of geological structures documenting the incipient and intermediate stages of deformation. Here, we present a study on strongly refracted strike-slip FFPs within the mechanically layered turbidites of the Marnoso Arenacea Formation (MAF) of the Italian northern Apennines. The MAF is characterized by the alternation of sandstone (strong) and carbonate mudstone (weak) layers. The studied refracted FFPs formed at the front of the regional-scale NE-verging Palazzuolo anticline and post-date almost any other observed structure except for a set of late extensional faults. The studied faults document coexisting shear and hybrid (tensile–shear) failure modes and, at odds with existing models, we suggest that they initially nucleated as shear fractures (mode III) within the weak layers and, only at a later stage, propagated as dilatant fractures (modes I–II) within the strong layers. The tensile fractures within the strong layers invariably contain blocky calcite infills, which are, on the other hand, almost completely absent along the shear fracture planes deforming the weak layers. Paleostress analysis suggests that the refracted FFPs formed in a NNE–SSW compressional stress field and excludes the possibility that their present geometric attitude results from the rotation through time of faults with an initial different orientation. The relative slip and dilation potential of the observed structures was derived by slip and dilation tendency analysis. Mesoscopic analysis of preserved structures from the incipient and intermediate stages of development and evolution of the refracted FFPs allowed us to propose an evolutionary scheme wherein (a) nucleation of refracted FFPs occurs within weak layers; (b) refraction is primarily controlled by grain size and clay mineral content and variations thereof at layer–layer interfaces but also within individual layers; (c) propagation within strong layers occurs primarily by fluid-assisted development ahead of the FFP tip of a “process zone” defined by a network of hybrid and tensile fractures; (d) the process zone causes the progressive weakening and fragmentation of the affected rock volume to eventually allow the FFPs to propagate through the strong layers; (e) enhanced suitable conditions for the development of tensile and hybrid fractures can be also achieved thanks to the important role played by pressured fluids.

Influence of off-axis ply orientation on the axial compression behaviour of CFRP tubes

2016 ◽  
Vol 36 (6) ◽  
pp. 399-413
Author(s):  
Jie Tao ◽  
Feng Li ◽  
Qilin Zhao ◽  
Dongdong Zhang
Keyword(s):  
High Speed ◽  
Failure Modes ◽  
Shear Failure ◽  
Shear Fracture ◽  
Gauge Length ◽  
Compression Tests ◽  
Average Value ◽  
Compression Behaviour ◽  
Cfrp Tubes ◽  
Ply Orientation

This paper presents an experimental investigation of the compression behaviour of Carbon Fiber Reinforced Plastics (CFRP) tubes with different off-axis ply orientations. A series of compression tests with effective end-reinforcement were conducted on [04/±theta] CFRP tubes, with θ equal to either 0°, 30°, 45°, 60°, or 90°. Various failure progressions and fracture morphologies were measured using a high-speed camera and a scanning electron microscope. The failure modes and mechanisms of CFRP tubes with different stacking sequences were analysed in detail. The results indicate that the off-axis ply orientation greatly influences the compression behaviour. The adopted end-reinforcement ensures that nearly all of the CFRP tubes fail within the gauge length. When θ < 45°, the tubes exhibit various failure modes, and the scatter of strength is large. However, when θ ≥ 45°, the sole failure mode is a shear fracture of the inner 0° layers, and their scatter of strength is minor. A new shear failure mechanism is instrumented: the shear fracture direction changes from inclining along the circumferential direction to inclining along the radial direction when θ varies from 45° to 90°. The failure strength and off-axis ply orientation display a complex non-linear relationship. When θ = 60°, the compression strength becomes maximum at an average value of 602 MPa, and the scatter of strength is 2.71%.

Machine learning-based failure mode identification of RCSPSW

2021 ◽  
Author(s):  
Dongqi Jiang ◽  
Shanquan Liu ◽  
Tao Chen ◽  
Gang Bi
Keyword(s):  
Machine Learning ◽  
Failure Mode ◽  
Failure Modes ◽  
Shear Failure ◽  
Tall Buildings ◽  
Shear Walls ◽  
Superior Performance ◽  
Ann Model ◽  
Mode Recognition ◽  
Wide Range

<p>Reinforced concrete – steel plate composite shear walls (RCSPSW) have attracted great interests in the construction of tall buildings. From the perspective of life-cycle maintenance, the failure mode recognition is critical in determining the post-earthquake recovery strategies. This paper presents a comprehensive study on a wide range of existing experimental tests and develops a unique library of 17 parameters that affects RCSPSW’s failure modes. A total of 127 specimens are compiled and three types of failure modes are considered: flexure, shear and flexure-shear failure modes. Various machine learning (ML) techniques such as decision trees, random forests (RF), <i>K</i>-nearest neighbours and artificial neural network (ANN) are adopted to identify the failure mode of RCSPSW. RF and ANN algorithm show superior performance as compared to other ML approaches. In Particular, ANN model with one hidden layer and 10 neurons is sufficient for failure mode recognition of RCSPSW.</p>

Study on Failure of Rock Mass around Deep Tunnel

2011 ◽  
Vol 99-100 ◽  
pp. 370-374 ◽  
Author(s):  
Yue Hong Qian ◽  
Ting Ting Cheng ◽  
Xiang Ming Cao ◽  
Chun Ming Song
Keyword(s):  
Rock Mass ◽  
Stress Field ◽  
Failure Modes ◽  
Shear Failure ◽  
Simple Function ◽  
Tensile Failure ◽  
Deep Tunnel ◽  
Main Mode

During excavating the problem of unloading is a dynamic one essentially. Assuming the unloading ruled by a simple function and based on the Hamilton principal, the distribution of the stress field nearby the tunnel is obtained. The characteristics of the failure nearby the tunnel are analyzed considering the shear failure and tensile failure. The results show that the main mode of the shear failure, intact and tensile failure occurs from the tunnel. The characteristic of the shear failure, intact and tensile failure are one of the likely failure modes.

Shear Failure Analysis of Concrete Beams Reinforced with Newly Developed GFRP Stirrups

2006 ◽  
Vol 324-325 ◽  
pp. 995-998
Author(s):  
Cheol Woo Park ◽  
Jong Sung Sim
Keyword(s):  
Failure Modes ◽  
Shear Failure ◽  
Concrete Beams ◽  
Fiber Reinforced Polymer ◽  
Experimental Program ◽  
Shear Stresses ◽  
Fiber Reinforced ◽  
Shear Span ◽  
Reinforced Polymer ◽  
A New Technique

Even though the application of fiber reinforced polymer (FRP) as a concrete reinforcement becomes more common with various advantages, one of the inherent shortcomings may include its brittleness and on-site fabrication and handling. Therefore, the shape of FRP products has been limited only to a straight bar or sheet type. This study suggests a new technique to use glass fiber reinforced polymer (GFRP) bars for the shear reinforcement in concrete beams, and investigates its applicability. The developed GFRP stirrup was used in the concrete instead of ordinary steel stirrups. The experimental program herein evaluates the effectiveness of the GFRP stirrups with respect to different shear reinforcing ratios under three different shear span-to-depth testing schemes. At the same shear reinforcing ratio, the ultimate loads of the beams were similar regardless the shear reinforcing materials. Once a major crack occurs in concrete, however, the failure modes seemed to be relatively brittle with GFRP stirrups. From the measured strains on the surface of concrete, the shear stresses sustained by the stirrups were calculated and the efficiency of the GFRP stirrups was shown to be 91% to 106% depending on the shear span-to-depth ratio.

scholarly journals Behavior of the T-Shaped Concrete-Filled Steel Tubular Columns after Elevated Temperature

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Xianglong Liu ◽  
Jicheng Zhang ◽  
Hailin Lu ◽  
Ning Guan ◽  
Jiahao Xiao ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Bearing Capacity ◽  
Failure Modes ◽  
Shear Failure ◽  
Element Model ◽  
Ultimate Bearing Capacity ◽  
Steel Tubes ◽  
Tubular Columns ◽  
Short Columns ◽  
Experimental Values

The mechanical properties of T-shaped concrete-filled steel tubular (TCFST) short columns under axial compression after elevated temperature are investigated in this paper. A total of 30 TCFST short columns with different temperature (T), steel ratio (α), and duration of heating (t) were tested. The TCFST column was directly fabricated by welding two rectangular steel tubes together. The study mainly investigated the failure modes, the ultimate bearing capacity, the load-displacement, and the load-strain performance of the TCFST short columns. Experimental results indicate that the rectangular steel tubes of the TCFST column have deformation consistency, and the failure mode consists of local crack, drum damage, and shear failure. Additionally, the influence of high temperature on the residual bearing capacity of the TCFST is significant, e.g., a higher temperature can downgrade the ultimate bearing capacity. Finally, a finite element model (FEM) is developed to simulate the performance of the TCFST short columns under elevated temperature, and the results agree with experimental values well. Overall, this investigation can provide some guidance for future studies on damage assessment and reinforcement of the TCFST columns.

scholarly journals Failure Characteristics and Mechanism of Multiface Slopes under Earthquake Load Based on PFC Method

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tao Yang ◽  
Yunkang Rao ◽  
Huailin Chen ◽  
Bing Yang ◽  
Jiangrong Hou ◽  
...  
Keyword(s):  
Moisture Content ◽  
Failure Mechanism ◽  
Failure Modes ◽  
Shear Failure ◽  
Shaking Table ◽  
Tensile Failure ◽  
Particle Flow Code ◽  
Shear Cracks ◽  
Local Shear ◽  
Shear Slip

Understanding the failure mechanism and failure modes of multiface slopes in the Wenchuan earthquake can provide a scientific guideline for the slope seismic design. In this paper, the two-dimensional particle flow code (PFC2D) and shaking table tests are used to study the failure mechanism of multiface slopes. The results show that the failure modes of slopes with different moisture content are different under seismic loads. The failure modes of slopes with the moisture content of 5%, 8%, and 12% are shattering-shallow slip, tension-shear slip, and shattering-collapse slip, respectively. The failure mechanism of slopes with different water content is different. In the initial stage of vibration, the slope with 5% moisture content produces tensile cracks on the upper surface of the slope; local shear slip occurs at the foot of the slope and develops rapidly; however, a tensile failure finally occurs. In the slope with 8% moisture content, local shear cracks first develop and then are connected into the slip plane, leading to the formation of the unstable slope. A fracture network first forms in the slope with 12% moisture content under the shear action; uneven dislocation then occurs in the slope during vibration; the whole instability failure finally occurs. In the case of low moisture content, the tensile crack plays a leading role in the failure of the slope. But the influence of shear failure becomes greater with the increase of the moisture content.

Failure analysis of three-dimensional braided composite tubes under torsional load: Experimental study

2017 ◽  
Vol 36 (12) ◽  
pp. 878-888 ◽  
Author(s):  
Xiaopei Wang ◽  
Deng’an Cai ◽  
Chao Li ◽  
Fangzhou Lu ◽  
Yu Wang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Failure Modes ◽  
Shear Failure ◽  
Three Dimensional ◽  
Damage Mechanism ◽  
Test Device ◽  
Composite Tubes ◽  
Torsional Strength ◽  
Braided Composite ◽  
Torsional Load

An experimental study on the effects of braided processes on the torsional strength, torsional modulus and failure modes of the three-dimensional braided composite tubes are presented. Based on the movement of carries, the yarn traces of three-dimensional braided composite tubes are analyzed systematically. Four different three-dimensional braided composite tubes are formed by resin transfer molding, and a number of torsional tests are performed respectively using a special test device. It is found that the torsional strength of three-dimensional five-directional braided composite tubes is higher than others, while the torsional modulus of three-dimensional multi-layer wrapping braided composite tubes is the highest. Furthermore, the damage behaviors of 3D braided composite tubes are significantly influenced by braiding process. One focus is to evaluate the damage mechanism of three-dimensional braided composite tubes by cutting the specimens and using scanning electron microscopy. Under torsional load, three-dimensional five-directional braided composite tubes and three-dimensional surface-core five-directional braided composite tubes are fractured in compression and shear failure, while three-dimensional multi-layer wrapping braided composite tubes and three-dimensional seven-directional braided composite tubes are split open in tensile and shear failure.

Fractures in Granite: Results from United Downs Deep Geothermal well UD-1

2021 ◽  
Author(s):  
Mark W. Fellgett ◽  
Richard Haslam
Keyword(s):  
Power Generation ◽  
Stress Field ◽  
Fault Zone ◽  
Regional Scale ◽  
Complex Nature ◽  
Fracture Density ◽  
Production Well ◽  
Borehole Breakouts ◽  
Tensile Fractures ◽  
Geothermal Power

&lt;p&gt;The geothermal potential of the granites of SW England has long been known. The first significant exploration of the resource was in the Carnmenellis Granite under the &amp;#8216;Hot Dry Rock (HDR) Project&amp;#8217; during the 80&amp;#8217;s and early 90&amp;#8217;s. Following completion of the HDR project there was little further exploration in the area for geothermal power generation. Recently however, development of the United Downs Deep Geothermal Power (UDDGP) project marks a significant leap forward, and this aims to be the first commercial project to explore deep geothermal power generation in SW England.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The UDDGP project targets the Porthtowan Fault zone, a regional scale NW to NNW striking strike-slip fault that is inferred to transect the NE margin of the Carnmenellis Granite. Two directional wells were drilled to intersect this fault zone, maximising the surface area of the fault exposed. A production well with a measured depth of 5275 m true vertical depth of 5054 m and an injection well vertically above the production well at a measured depth of 2393 m and a true vertical depth of 2214 m. A full suite of geophysical wireline logs were collected for the production well, including borehole image logs from 900 mMD to 5160 mMD (900 - 4097mTVD).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Interpretation of the borehole imaging across the 4260 m identified a total of 12031 discontinuities. The features were classified using a simple schema and provide new insights into the complex nature of faulting and fracturing within the Granite. Stress field indicators including Borehole Breakouts and Drilling Induced Tensile Fractures (DIFs) were also interpreted.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The orientations of the borehole breakouts and DIFs are consistent and are comparable to previous measurements in the region and the regional stress field, indicating the direction of maximum compression is, approximately horizontal trending towards 320&amp;#176;.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The data show variable fracture density along the imaged section of the well with the maximum density tentatively associated with discreet fault zones. At least 3 fracture sets are identified with the largest concentration of fractures approximately parallel to inferred Porthtowan Fault Zone, suggesting UD-1 intersected the target fault zone. Key fracture attributes are explored and discussed including orientation, spacing, intensity, and spatial correlation.&lt;/p&gt;

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