Dislocation Displacement Research Articles

Study of the failure characteristics and mechanical response of railway tunnel under oblique-slip fault displacement

When a tunnel intersects an active fault, the dislocation of the fault often leads to failures such as lining fractures and structural deformations, severely threatening the safe operation of the tunnel. To investigate the fracture characteristics and mechanical responses of tunnels under oblique-slip fault conditions, a large-scale indoor model test with a geometric similarity ratio of 1:35 was conducted. This study was based on a railway tunnel in Western China that crosses an oblique-slip active fault. Additionally, a three-dimensional model of the tunnel-surrounding rock-fault fracture zone interaction was established using ABAQUS finite element analysis software. The purpose of this study is to clarify the structural cracking characteristics, deformation modes, strain trends, changes in bending moment and shear force of tunnels under fault displacement, as well as the contact force between tunnels and surrounding rocks, and further reveal the differences in the impact of oblique-slip faults and other types of faults on tunnels. The results indicate that under oblique-slip fault dislocation, the tunnel experiences shear failure at the fault fracture zone manifested as shear diagonal cracks. Tensile bending failures, characterized by bending circumferential cracks, occur at the hanging wall and footwall. At the fault fracture zone, the strain, contact pressure, bending moment, and shear force of the tunnel undergo drastic changes and peak values appear. The tunnel exhibits distinct three-dimensional failure characteristics, including horizontal bending, axial stretching and twisting, and vertical shearing. The damage zone of the tunnel extends approximately 2D (where D is the tunnel diameter) from both the hanging wall and footwall towards the fault fracture zone, with the severity of damage increasing closer to the fault fracture zone. The damage process of the tunnel under increasing fault dislocation displacement can be divided into three stages: initial intact stage, onset of damage stage, and complete failure stage. When the strike-slip dislocation reaches 20.7 mm (corresponding to an actual displacement of 724.5 mm), structural damage accumulates to its limit, leading to large-scale failure of the tunnel. Compared to purely strike-slip faults, the tunnel is more prone to damage and exhibits a larger range of structural failure under oblique-slip fault dislocation. These findings provide scientific and rational data support and reference for disaster prevention and mitigation design of tunnels.

Magnetooptical Faraday and Kerr effects in nanosized BiYIG/GGG structures

AnnotationMagnetooptical Faraday and Kerr effects are studied in the nanosized BiY2Fe5O12 films within the spectral region of 1.3 eV<E<4.5 eV and magnetic fields of up to 10 kOe. It is shown that the thin-films BiY2Fe5O12 with the thicknesses ranging from 5 to 51 nm obtained by magnetron sputtering on the single-crystalline Gd3Ga5O12 substrates have high magneto-optical quality. The specific Faraday rotation for the nanosized Bi0.5Y1.5Fe5O12-δ films reaches about 140000 deg/cm close to that for bulk BiY2Fe5O12. Meanwhile, the polar Kerr effect reaches about 30 min within the range of 1.6 eV–4.1 eV at the magnetic fields above 2 kOe.It is shown that the strong paramagnetic contribution of Gd3Ga5O12 substrates significantly affects the Faraday and Kerr effect for the films. The defining of magnetooptical parameters and Verdet constant for the Gd3Ga5O12 substrate permitted to separate the substrate contribution and reveal peculiarities of spectral dependences of both Faraday and Kerr effects for magnetic films of various thicknesses. The estimated critical thickness of the film-substrate interface region is as large as 35 lattice constants of BiY2Fe5O12. It is shown that the magnetooptical effects for the thin films with the thickness above the critical one correspond to those for bulk BiY2Fe5O12. For samples with the smallest thicknesses of the film (5 nm) the contributions from magnetically dead and magnetically passive layers lead to a drastic reduction in the observable Faraday and Kerr effects with a dominating contribution from the substrate. The high density of displacement dislocations at the film-substrate interface leads to the decrease the magnetooptical quality of the nanosized films.

Fractures of the lateral condyle of the humerus in children : High risk of secondary dislocation with conservative treatment

Fractures of the lateral condyle of the humerus in children are articular fractures with difficult diagnostics due to the incompletely ossified elbow joint. The aim of this study was to evaluate the method of treatment at initial presentation and to analyze the frequency of subsequent displacement during follow-up. Retrospective analysis of the frequency of primary fracture dislocation and subsequent displacement of fractures of the lateral condyle of the humerus in children under 16years of age between 2004 and 2021. Conventional radiographs in two planes at the time of the accident and in the follow-up after 5-7days were evaluated. Atotal of 285 fractures of the lateral condyle of the humerus were evaluated. The average age was 5.3years. Of the fractures 109 (38.3%) were directly surgically treated in cases of primary displacement and 176 fractures (61.7%) were not primarily displaced and were initially treated conservatively. During follow-up, subsequent displacement was evident in 46fractures (26.1%). Atotal of 130 fractures (45.6%) were treated conservatively and 155 fractures (54.4%) were treated surgically using open joint visualization and screw osteosynthesis or K‑wire osteosynthesis. Fractures of the lateral condyle of the humerus occur more frequently in acertain age group and require targeted radiological diagnostics. Nondisplaced fractures can be treated conservatively but essential radiological follow-up shows ahigh number of subsequent displacements, so that open surgical stabilization is often necessary.

Dislocations in nonlocal simplified strain gradient elasticity: Eringen meets Aifantis

The nonlocal strain gradient elasticity theory is used to address mechanical problems at small scales where size effects and regularization cannot be neglected. In this work, dislocations are investigated in the framework of nonlocal simplified first strain gradient elasticity. It is shown that nonlocal simplified strain gradient elasticity is the unification of the theories of Eringen’s nonlocal elasticity of Helmholtz type and simplified first strain gradient elasticity. Nonlocal simplified strain gradient elasticity contains two characteristic lengths, namely the characteristic length of nonlocal elasticity of Helmholtz type and the characteristic length of simplified first strain gradient elasticity. The advantage of nonlocal simplified first strain gradient elasticity is that the displacement, elastic distortion, plastic distortion, total stress, Cauchy stress and double stress fields of screw and edge dislocations which are calculated here are nonsingular and finite everywhere. Moreover, the Peach-Koehler force of two screw dislocations and two edge dislocations is derived and it is shown that the Peach-Koehler force is also nonsingular. Numerical examples for all dislocation fields of screw and edge dislocations in aluminum are given.

Effectiveness of injured vertebra fixation with inclined-long pedicle screws combined with interbody fusion for thoracolumbar fracture dislocation with disc injury

To investigate the effectiveness of injured vertebra fixation with inclined-long pedicle screws combined with interbody fusion for thoracolumbar fracture dislocation with disc injury. Between January 2017 and June 2022, 28 patients with thoracolumbar fracture dislocation with disc injury were underwent posterior depression, the injured vertebra fixation with inclined-long pedicle screws, and interbody fusion. There were 22 males and 6 females, with a mean age of 41.4 years (range, 22-58 years). The causes of injury included falling from height in 18 cases, traffic accident in 5 cases, and bruise in 5 cases. Fracture segment included 1 case of T 11, 7 cases of T 12, 9 cases of L 1, and 11 cases of L 2. According to the American Spinal Injury Association (ASIA) scale, the spinal injuries were graded as grade A in 4 cases, grade B in 2 cases, grade C in 11 cases, and grade D in 11 cases. Preoperative spinal canal encroachment ratio was 17.7%-75.3% (mean, 44.0%); the thoracolumbar injury classification and severity score (TLICS) ranged from 9 to 10 (mean, 9.9). Seventeen patients were associated with other injuries. The time from injury to operation ranged from 1 to 4 days (mean, 2.3 days). The perioperative indicators (operation time, intraoperative blood loss, and the occurrence of complications), clinical evaluation indicators [visual analogue scale (VAS) score and Oswestry Disability Index (ODI)], radiologic evaluation indicators [anterior vertebral height ratio (AVHR), kyphosis Cobb angle (KCA), intervertebral space height (ISH), vertebral wedge angle (VWA), displacement angle (DA), and percent fracture dislocation displacement (PFDD)], neurological function, and interbody fusion were recorded. The operation time was 110-159 minutes (mean, 130.2 minutes). The intraoperative blood loss was 200-510 mL (mean, 354.3 mL). All incisions healed by first intention, and no surgical complications such as wound infection or hematoma occurred. All patients were followed up 12-15 months (mean, 12.7 months). The chest and lumbar pain significantly relieved, VAS scores and ODI after operation were significantly lower than those before operation, and further decreased with the extension of postoperative time, with significant differences ( P<0.05). At last follow-up, the ASIA classification of neurological function of the patients was grade A in 3 cases, grade B in 1 case, grade C in 1 case, grade D in 10 cases, and grade E in 13 cases, which was significantly different from preoperative one ( Z=-4.772, P<0.001). Imaging review showed that AVHR, KCA, ISH, VWA, DA, and PFDD significantly improved at 1 week, 3 months and last follow-up ( P<0.05). There was no significant difference between different time points after operation ( P>0.05). At last follow-up, according to the modified Brantigan score, all patients achieved good intervertebral bone fusion, including 22 complete fusion and 6 good intervertebral fusion with a few clear lines. No complications such as internal fixation failure or kyphosis occurred during follow-up. The injured vertebra fixation with inclined-long pedicle screws combined with interbody fusion is an effective treatment for thoracolumbar fracture dislocation with disc injury, which can correct the fracture dislocation, release the nerve compression, restore the injured vertebral height, and reconstruct spinal stabilization.

Response of prefabricated-polyurethane reinforced ballasted track to dislocation in tunnels through active fault zone

ABSTRACT The dislocation of the active fault zone may cause some threat to the track structures passing through it, in order to investigate the response of prefabricated-polyurethane reinforced ballasted track and CRTS III slab track to different forms of fault and to compare their adaptability in fault zone, a finite element model of the track-tunnel-surrounding rock system and a dynamic model of vehicle-track system were integrated together in this study. Based on the models, the changes of track geometry of the two track structures were studied, the mechanical behaviour of track components was revealed, and the effect of irregularity caused by fault dislocation on vehicle dynamic response was studied. Results show that the components of CRTS III slab track are damaged at a smaller dislocation displacement than those of prefabricated-polyurethane reinforced ballasted track. With the increase of the train speed and dislocation displacement, the derailment coefficient and wheel load reduction rate also increase. The safe speed limits for travelling under different types of fault and different dislocation displacements are obtained, which can provide reference for similar engineering applications.

Influence of advanced engineering measures on displacement and stress field of surrounding rock in tunnels crossing active strike-slip faults

Based on significant improvements in engineering materials, three advanced engineering measures have been proposed—super anchor cables, high-strength concrete anti-fault caverns, and grouting modification using high-strength concrete-to resist fault dislocation in the surrounding rock near tunnels crossing active strike-slip faults. Moreover, single- or multiple-joint advanced engineering measures form the local rock mass-anti-fault (LRAF) method. A numerical method was used to investigate the influence of LRAF methods on the stress and displacement fields of the surrounding rock, and the anti-fault effect was evaluated. Finally, the mechanism of action of the anchor cable was verified using a three-dimensional numerical model. The numerical results indicated that the anchor cable and grouting modification reduced the displacement gradient of the local surrounding rock near the tunnels crossing fault. Furthermore, anchor cable and grouting modifications changed the stress field of the rock mass in the modified area. The tensile stress field of the rock mass in the modified anchor cable area was converted into a compressive stress field. The stress field in the modified grouting area changed from shear stress in the fault slip direction to tensile stress in the axial tunnel direction. The anti-fault cavern resisted the dislocation displacement and reduced the maximum dislocation magnitude, displacement gradient, and shear stress. Among the three advanced engineering measures, the anchor cable was the core of the three advanced engineering measures. An anchor cable, combined with other LRAF measures, can form an artificial safety island at the cross-fault position of the rock mass to protect the tunnel. The research results provide a new supporting idea for the surrounding rock of tunnels crossing active strike-slip faults.

Anatomic and Biomechanical Study of the Forearm Interosseous Membrane, Distal Oblique Bundle, and Triangular Fibrocartilage Complex: Role in Galeazzi Fracture Dislocation

The purpose of this study was to measure distal radioulnar joint (DRUJ) dislocation and radioulnar displacement associated with sequential sectioning of the different bands of the interosseous membrane and triangular fibrocartilage complex in the simulation of a Galeazzi fracture dislocation. Twelve fresh-frozen cadaver forearms were dissected. We examined the anatomy and function of the forearm interosseous membrane. Each forearm was then mounted onto a biomechanical wrist and forearm device. In the control group, radial osteotomy was performed and the degree of DRUJ displacement with progressive loads was measured. In addition to radial osteotomy, in group 1, the central band (CB) was sectioned; in group 2, the CB, distal membranous portion of the interosseous membrane, and distal oblique bundle were sectioned; and in group 3, the CB, distal membranous portion of the interosseous membrane, distal oblique bundle, and triangular fibrocartilage complex were sectioned. The radioulnar displacement (mm) at 25 N, 50 N, and 75 N was recorded. In group 1, applying progressive loads resulted in an average DRUJ displacement of 4.3, 5.9, and 7.9 mm, respectively. In group 2, the displacement was 5.2, 5.7, and 6.9 mm, respectively. In group 3, the displacement was 6.2, 8.1, and 9.9 mm, respectively. Our study showed a correlation between increase in the load applied to the same injury and the degree of displacement (P= .001). In group 3, the degree of DRUJ displacement was statistically increased compared to the other groups (P= .04). Migration of the radius under loads implies disruption of both the CB and triangular fibrocartilage complex. The distal oblique bundle by itself does not seem to have a relevant role in radioulnar displacement at the DRUJ. This study provides insights into the interosseous membrane and stability of the DRUJ, which can contribute to a better understanding of Galeazzi fracture-dislocations.

Development of a non-Gaussian copula Bayesian network for safety assessment of metro tunnel maintenance

The operation and maintenance of metro systems play a crucial role in urban development, with a focus on ensuring the serviceability and safety of metro tunnels. Accurate evaluation of the condition of these tunnel states requires investigating the complex interaction of multiple factors that impact their safety state. This study developed a hybrid model that integrates pair copula constructions (PCCs) and Bayesian networks (BN) to assess the safety state of metro tunnels, considering complex dependencies among these factors. First, key performance indicators (KPIs) were selected to assess tunnel safety, based on six failure modes. Then, an improved copula-based PC algorithm was employed to learn the non-Gaussian bayesian network model, which eliminated the normality assumption in the marginal densities of the KPIs. Finally, a combination of forward reasoning and GM(1,1) was utilized to predict the safety state of the metro tunnel in time series, facilitating the formulation of effective operation and maintenance plans. Furthermore, the proposed approach was applied to a real case study of the Wuhan metro system to demonstrate its effectiveness and applicability. The results highlighted the significant influence of some KPIs, such as convergence deformation, dislocation displacement, and stripping area, on metro tunnel safety. These KPIs emerged as key factors requiring focused attention in the operation and maintenance of metro tunnels.

Study on the mechanism of tunnel catastrophe in Xigeda formation considering the interbed effect

The Xigeda formation, widely distributed in southwestern China, is a special semi-diagenetic rock with horizontal bedding，which is mudding in water. In order to study the failure law, catastrophe characteristics and catastrophe mechanism of the interbed type to the surrounding rock and structure of Xigeda formation tunnel, this paper, by means of field investigation, indoor test, numerical simulation, field monitoring and theoretical research, relying on more than ten Xigeda formation tunnels in the Chengdu-Kunming double track railway, analyzes the apparent failure characteristics and catastrophe mechanism of the surrounding rock of Xigeda formation tunnels with different interbed types. The results show that: the catastrophe characteristics of Xigeda formation tunnel have certain water content sensitive area and influence area division of interbed type. The water content of Xigeda formation is 25% - 30% of the catastrophic critical region of Xigeda formation tunnel. In this critical region, the vault of the overlying Xigeda formation tunnel is prone to large deformation, the invert of the underlying Xigeda formation tunnel is prone to large uplift deformation, and the side wall and tunnel face of interlayer Xigeda formation tunnel are prone to large extrusion deformation; when the water content of Xigeda formation is 30%, it becomes a weak layer, and under the effect of interbed, the rock and soil of Xigeda formation are prone to large deformation, resulting in catastrophes by extruding the tunnel structure; based on the analysis of chemical effect, physical effect and mechanical effect, the structural components of interbed rock chemically react with water, leading to weakening of the strength and causing catastrophic effects. The catastrophic effect is similar to that of simply supported beam in the strong and weak regions of the interbed, while the weakening effect of the interlayer structural plane leads to the opening of the interlayer fracture plane of the tunnel surrounding rock and the large interlayer dislocation displacement, which forces the shear failure of the supporting structure. The research results of this paper can provide theoretical guidance for the Sichuan-Tibet railway to be constructed.

Experimental study on forced response characteristics and anti-dislocation performance of articulated tunnel structure under dislocation action of normal fault

The stick–slip dislocation of normal faults will produce large permanent displacement. The tunnel lining structure crossing active normal faults is easily affected by fault dislocation. It is necessary to study the mechanical behavior of tunnel lining structure under fault dislocation. Therefore, taking the subway tunnel of Urumqi Rail Transit Line 1 crossing the Jiujiawan fault project as an example, based on the optimal mix ratio determined by the indoor similar material ratio test, the self-designed large-scale active fault dislocation simulation loading system is used to carry out the stick–slip dislocation model test of normal fault with 60° dip angle. The mechanical behavior difference between the conventional tunnel structure and the flexible articulated tunnel structure is compared and analyzed, and the cracking range, damage characteristics and failure mode of the tunnel lining structure are defined. The results show that: (1) The failure modes of the conventional tunnel structure and the flexible articulated tunnel structure are basically the same, including the large eccentric failure of the inverted arch and the wall foot, and the compression shear failure at the fault plane, which are longitudinal cracks and oblique cracks respectively. In addition, there are longitudinal cracks in the inner side of the invert and the lateral side of the wall foot, but few circumferential cracks. (2) Because the flexible articulated structure increases the overall longitudinal flexibility of the tunnel, the flexible joints between segments can share part of the fault dislocation displacement, so the deformation range, failure degree and number of cracks of the articulated tunnel structure are significantly reduced compared with the conventional tunnel structure, and the anti-dislocation performance is better. (3) Considering the influence of fault dislocation on tunnel structure, the loose area and empty area should be investigated and repaired in the rapid repair and reinforcement of post-disaster tunnel. At the same time, the case study ideas and test methods in this paper can provide some reference value and guidance for other similar tunnel engineering studies in the future.

The seismic damage mechanism of Daliang tunnel by fault dislocation during the 2022 Menyuan Ms6.9 earthquake based on unidirectional velocity pulse input

Fault dislocation may cause severe damage to tunnel structures. A representative example is the severe damage of the Daliang Tunnel caused by the dislocation of the Lenglongling Fault in the 2022 Menyuan, Qinghai, China, Ms6.9 earthquake. The relative displacement on both sides of the fault during an earthquake is often assumed to be a quasi-static dislocation load, ignoring the dynamic effect. In this study, the dislocation load was considered as a unidirectional harmonic velocity pulse and the damage mechanism of the Daliang tunnel was studied. First, the background of this earthquake and the damage of Daliang tunnel is introduced. The characteristics of surface displacement in this earthquake are analyzed by finite fault model and Okada dislocation theory model, and the dislocation vector of Daliang tunnel is calculated. On this basis, a fault-tunnel FEM nonlinear dynamic model is established, in which unidirectional velocity pulse is used as input of dislocation displacement to consider the dynamic effect of fault dislocation. The study found that the Daliang tunnel was located in one of the regions with the largest dislocation displacement in this earthquake, and the tunnel structure was damaged as a result. The analysis of FEM model reveals that when a unidirectional velocity pulse is used as the load, the tunnel damage is consistent with reality, and the conventional method using the quasi-static dislocation as the load only reflects the dislocation effect of the fault displacement and ignores the impact effect. When the dislocation displacement is certain, the duration of the unidirectional velocity pulse is an important parameter; the shorter the duration, the greater the amplitude of unidirectional velocity pulse, resulting in more serious tunnel damage. The tunnel’s failure mechanism near the fault can be divided into dislocation failure and impact failure. The dislocation failure is manifested by non-uniform dislocation displacement along the longitudinal direction of tunnel, which is mainly related to the amount of dislocation. The impact failure is manifested by crushing and invert uplift of the lining in cross-section, and it is related to the pulse duration.

Вивчення малоамплітудної тектоніки вугільних родовищ геофізичними методами

An analysis was made as to the usage of geological-geophysical methods for studying of low-amplitude tectonic dislocations in coal-enclosing massifs. As a result of geophysical researches conducted at coal fields, mine fields and mine workings of the Lviv-Volyn Coal Basin, the methods of field observations by means of natural electromagnetic and electric fields were worked and their results were processed for prediction and diagnostics of tectonic dislocations with a break of continuity and zones of unstressed state. To raise the efficiency of the methods of electromagnetic fields it is recommended to carry out measurements at wide frequency range (from 5 to 50 hz) with orientation of the antenna according to the world sides (azimuthal surveying) and at narrow frequency range (5; 12.5; 17 khz) with the southern orientation of the antenna (frequency sensing). According to azimuthal surveying one can calculate the vector of maximum intensity of electromagnetic radiation. It was ascertained that over distinctive dislocation one can observe the variation in the direction and absolute value of vectors. Displacement of the anomaly of electromagnetic radiation intensity at different frequency range by profile indicates the direction of dipping of the area of displacement of dislocations with a break of continuity. The method of natural electromagnetic impulse field of the Earth fixes both the dislocations, distinguishes by geological-geophysical methods before, and new low-amplitude dislocations and stressed zones.Tectonic dislocations, that are displayed only in Paleozoic deposits, are distinguished by contrast anomalies of electromagnetic radiation in electromagnetic field, but dislocations with a break of continuity that cut the Mesozoic thickness and in most cases are accompanied by zones of rock fracturing in the Cretaceous deposits: by wide destructive anomalies. Plots over worked-out lavas with stressed deformational state are characterized by strongly differential abnormal values of the intensity of natural impulse electromagnetic field of the Earth. The method of natural electric field allows us to detect zones with water-bearing fracturing rocks in the upper part of the geological section. Methods of natural impulse electromagnetic field of the Earth and natural electric field may be used both independently and in the complex with other geophysical methods for detection and tracing of tectonic dislocations and dynamically-unstressed zones. Thus, the optimum apparatus-methodical complex for detection and diagnostics of low-amplitude dislocations with a break of continuity of coal-enclosing series by electromagnetic methods (NIEMF, NEF) was formed and effective methods of field observations, processinf and interpretation of data were developed.

Numerical Assessment of the Structural Damage of a Composite Lining Water Conveyance Tunnel Subjected to Reverse Fault Conditions

In this paper, the structural responses and failure characteristics of a new type of water conveyance tunnel lining structure subjected to reverse fault conditions were numerically investigated by considering multiple loads and interaction separation modes between different structural layers. This study proposes a new evaluation standard for the safety level of the damage state of the composite lining water conveyance tunnel. It also discusses the influences of fault dislocation displacement (Δf), dip angle (β), and the mechanical properties of the surrounding rock in the fault fracture zone on the water conveyance tunnel response and damage. The results indicate that the buckling failure of the steel tube under axial compression is the dominant failure mode of the composite lining structure. With increasing fault dislocation displacement, the axial compressive strain and circumferential shear strain of the composite lining are most severely damaged on the sliding plane. With decreasing fault dip angle, the axial compressive strain of the composite lining weakens, while the bending and shear strains increase. The increase in rock stiffness in the fault fracture zone reduces the damage scope but increases the composite lining structural damage severity. Overall, the numerical results of this study provide a better understanding of the failure mode and damage process of composite lining water conveyance tunnels under reverse fault conditions; therefore, this study can serve as a reference for composite lining structure disaster assessments.

192. Can we predict a complete spinal cord injury based on fracture dislocation displacement?

<h3>BACKGROUND CONTEXT</h3> The AO Spine Subaxial and Thoracolumbar Injury Classifications denote "Type C" fractures as dislocation-translation type injuries. These injuries are often grossly unstable due severe ligamentous compromise, which place patients at high risk for spinal cord injury (SCI). While prior research has investigated the role of early surgical decompression on neurologic outcomes, the relationship between the amount of vertebral column displacement and preoperative neurologic injury and postoperative neurologic recovery has been poorly documented. <h3>PURPOSE</h3> The purpose of this study is to 1) identify if preoperative vertebral column displacement (in millimeters) is predictive of a complete SCI (defined as ASIA A) prior to fracture fixation and 2) identify if the preoperative or postoperative vertebral column displacement is predictive of no postoperative neurologic improvement (ie, no improvement in ASIA score) following fixation. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>PATIENT SAMPLE</h3> All patients with cervical or thoracolumbar Type C injuries between 2006-2021 were identified from a prospectively collected database. Only patients who underwent operative intervention were included. <h3>OUTCOME MEASURES</h3> Neurologic injury and/or recovery based on the ASIA Impairment Scale. <h3>METHODS</h3> Patient demographics, surgical characteristics and clinical outcomes were collected. Preoperative and postoperative CT scans or MRI were utilized to measure the fracture-dislocation translation (in millimeters [mm]) prior to and following surgical fixation. Receiver operating characteristic (ROC) curves were generated to predict the probability of a SCI prior to reduction and fixation based on the preoperative fracture-dislocation displacement with optimal cutoffs identified using Youden's index. A second ROC curve was generated to predict the probability of having no postoperative neurologic recovery following reduction and fixation. Alpha was set at P<0.05. <h3>RESULTS</h3> A total of 67 patients were included. The cohort was predominantly male (80.6%) with a mean age of 42.9 + 18.8 years. The majority of the injuries involved cervical vertebrae (n=45; 67.2%). The mean preoperative vertebral column displacement was 10 + 10 mm, and the mean postoperative vertebral column displacement was 1.87 + 2.08 mm. A majority of patients (n=61, 91.0%) underwent neurologic decompression within 24 hours following admission. Of the 67 patients, 42 (62.7%) were determined to have a complete SCI (ASIA A) upon admission; two patients experienced neurologic deterioration following surgery and 7 patients experienced some degree of neurologic recovery. ROC analysis identified 6.10 mm (AUC: 0.771, CI: 0.650-0.892) of preoperative vertebral column displacement as an optimal cutoff, predictive of a complete SCI. ROC analysis also identified 6.70 mm (AUC: 0.654, CI: 0.421-0.887) of preoperative vertebral column displacement and 5.40 mm (AUC: 0.427, CI: 0.214-0.639) of postoperative vertebral column displacement as optimal cutoff values predictive of no postoperative neurologic recovery following fixation. <h3>CONCLUSIONS</h3> The distance of vertebral column translation in subaxial cervical and thoracolumbar AO Spine Type C injuries is highly predictive of a complete SCI. However, the amount of preoperative fracture-dislocation translation is only mildly predictive of neurologic recovery. The remaining postoperative fracture-dislocation displacement had no predictive effect on neurologic recovery. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Reduced strain gradient elasticity model with two characteristic lengths: fundamentals and application to straight dislocations

In this paper, the reduced strain gradient elasticity model with two characteristic lengths is proposed and presented. The reduced strain gradient elasticity model is a particular case of Mindlin’s first strain gradient elasticity theory with a reduced number of material parameters and is a generalization of the simplified first strain gradient elasticity model to include two different characteristic length scale parameters. The two characteristic lengths have the physical meaning of longitudinal and transverse length scales. The reduced strain gradient elasticity model is used to study screw and edge dislocations and to derive analytical solutions of the dislocation fields. The displacement, elastic distortion, plastic distortion and Cauchy stress fields of screw and edge dislocations are non-singular, finite and smooth. The dislocation fields of a screw dislocation depend on one characteristic length, whereas the dislocation fields of an edge dislocation depend on up to two characteristic lengths. For the numerical analysis of the dislocation fields, the material parameters including the characteristic lengths have been used, computed from a second nearest neighbor modified embedded-atom method (2NN MEAM) potential for aluminum.

Seismic Responses and Damage Mechanisms of Deep-Buried Underground Powerhouse in Layered Rock Mass

Layered rock mass generally has adverse effects on the seismic stability of deep-buried underground powerhouses. Aiming at the complexity of seismic wave field in deep-buried underground powerhouses, the obliquely input methods of P and SV waves considering the incident direction and multi-incident surfaces are constructed in this study, respectively. It can convert the seismic wave input problem into the problem of solving equivalent nodal force acting on the artificial boundaries. Based on the characteristics of dynamic interaction between interlayers in layered rock mass, an explicit dynamic contact force method considering the seismic deterioration effect and bond-slip characteristics of interface is also presented to simulate various contact states such as bond, separation, and sliding. The combined application of the above methods to analyze the seismic response of underground powerhouse at Azad Pattan hydropower station shows that they could accurately simulate the seismic damage evolution process of deep-buried underground powerhouses in layered rock mass. The numerical results indicate that the obliquely incident seismic waves contribute to a larger seismic reaction of underground powerhouses, which largely lies in the amplitudes of the displacement and stress fluctuations. After considering the dynamic contact, the obvious seismic deterioration effect and interlaminar dislocation displacement occur between soft and hard rock, and the sidewalls suffer more severe deterioration degree than the top arch. The seismic damage area of lining structure is mainly distributed in the place where the soft rock strata pass through and the upper structure with larger free surface. Additionally, two major damage modes of underground powerhouses in layered rock mass, namely, damage due to structural deformation and interlaminar dislocation, are derived from the numerical results and can be reasonably explained by the corresponding damage mechanisms.

Mechanical Properties and Damage Characteristics of Coal Samples under Water Immersion Pressure

Abstract Uniaxial compression tests were conducted on four groups of coal samples under dry condition and 0, 3, and 5 MPa water immersion pressure using acoustic emission, scanning electron microscopy, and a digital scattered spot deformation monitoring system to investigate the mechanical properties and damage characteristics of coal samples under the action of water pressure. The results showed that as the water immersion pressure increased, the water–rock interaction intensified and aggravated the internal damage of the samples. The uniaxial compressive strength, elastic modulus, and peak strain decreased by 71.4%, 43.3%, and 34.74%, respectively. The deformation localized zone of the samples first appeared at the original crack in the deformation and failure process. As the water immersion pressure increased, the coal sample deformation localization zone appeared earlier, the displacement dislocation momentum of the deformation localization zone increased, and the deformation failure gradually increased, furthermore, the samples transitioned from brittle to plastic failure, and their failure mode changed from tensile to tensile–shear hybrid failure. The acoustic emission activity of the samples corresponds to their failure processes. The initial compaction stage of the samples was prolonged as the water immersion pressure increased. In the stage before the peak point, the plastic damage to the samples caused a gradual increase in the intensity and frequency of the acoustic emission signal, and multiple sudden increase points appeared. After the peak point, the active degree of the acoustic emission decreased, and the signal changed from “single tremors” to “swarm tremors” type fluctuation. The water immersion pressure promoted the water–rock interaction in the samples, the water flow continuously eroded the samples, and many water marks appeared on the fracture surface. The average porosity of the fracture surface increased, and the defect size of the coal samples increased.

Prelom vrata talusa - pregled kliničkih karakteristika i metoda lečenja

The talus transfers the weight of the whole body onto the foot and is therefore an important factor of stability and posture. The prerequisite for successful treatment of talus neck fractures is knowledge of anatomy, understanding of the mechanisms that lead to fractures of the talus neck, knowledge of the potential complications of all treatment methods, as well as knowledge of indications for surgical treatment. About 55% of the talus surface is covered with articular cartilage, and displaced fractures lead to the destabilization of several joints. Since fractures are caused by high energy trauma, the result can easily be comminution and/or dislocation (displacement). Fractures of the talus neck can occur as an isolated injury, as well as part of polytrauma (falls from height, traffic accidents). The X-ray is the basic diagnostic tool for making an accurate diagnosis, in case of suspect talus fracture. Multi-slice computerized tomography is the most useful method for studying fracture patterns and is indispensable in planning surgical treatment. The Hawkins classification of talus neck fractures, from 1970, has remained in use to this day, while recommended treatment methods vary depending on the type of fracture. The main goal of treatment is anatomical reduction. The anatomical characteristics of the talus, the particular blood supply, as well as the "high energy" mechanism of fracture, pose a challenge for clinical evaluation and optimal treatment of talus fractures. This paper highlights the necessity of the knowledge of surgical techniques for the selection of an adequate method of treatment, in order to prevent unwanted consequences for the patient, which in the case of suboptimal treatment can be severe.

Morphology of fibrous structures formed in the course of superplastic deformation of the 01420T alloy with the original bimodal grain structure

The morphology of the fibrous structures formed in the working parts of the 01420T alloy samples with the initial bimodal grain structure, deformed to fracture under optimal conditions of superplastic deformation at a temperature Т = 520°С and flow stress σ = 4,5 MPa is investigated. The maximum elongation of specimens deformed to failure δ is 670%. It has been suggested that the specific type of fibrous structures found in the specimens of the investigated alloy 01420T probably depends on the volume of the metastable liquid-solid phase, which was concentrated in the form of inclusions at some grain boundaries and made a viscous flow during superplastic deformation, its shear viscosity , the characteristics of its surface tension, the degree of dynamic oxidation of the melt, and the kinetics of the development of this process. The final view of the fibers and their shape, likely, depends not only on the nature of the viscous flow of the liquid-solid material, but also on the process of its crystallization during the cooling of the specimen in air to room temperature after mechanical tests. It was found that in view, all fibrous structures found in the working parts of the specimens can be conditionally divided into the following: cylindrical fibers; tapered fibers; cylindrical fibers on which there is a thickening or one or more drop-like formations; ribbon-like fibers; fibers that look like stalactites or stalagmites. The reasons for the formation of cracks on ribbon-like fibers are considered. It is assumed that they were formed as a result of relaxation of internal stresses, which were not fully minimized in the course of recrystallization, which was carried out when the sample was cooled. The reasons for the formation of droplets on the fibers are considered. It has been suggested that fibrous structures similar to stalactites and stalagmites were formed from a viscous material, which, in the course of superplastic deformation, as a result of crystallization, occured in local microvolumes of fibers, gradually turned from liquid-solid to solid-liquid. This led to the fact that in the crystallized microvolume of this fiber, the viscous homogeneous flow of the material probably turned into a localized flow, which is characteristic of the plastic flow carried out as a result of displacement of dislocations in the solid phase, and leads to the formation of stalagmitic fibers.