Sides Of Fracture Research Articles

Analytical Investigation on the Shear Propagation Mechanism of Multi-Cracks in Brittle Tight Rocks under Compressive and Shear Loading Conditions

There is abundant shale oil in the ocean and on land. Due to the tight lithology of the reservoir, volume fracturing technology is needed to improve the oil and gas productivity. It is very important to study the expansion law of multiple natural fractures in rock masses and its influencing factors in the process of volume fracturing for the formation of fracture networks. Based on the theory of online elastic fracture mechanics, the calculation method of the stress intensity factor at the end of any I–II composite fracture is established by using effective shear stress and considering the influence of T-stress. The calculation model of the stress intensity factor of any fracture on the main fracture wall or the horizontal section of the main fracture wall is established according to the concrete stress conditions in the process of hydraulic fracturing. Based on the principle of stress superposition, the combined interference stress calculation model of fracture ends is established for the case of multiple penetrating cracks in infinite-plane rock masses. Based on the theory of shear failure and plane strain, a model of the initiation direction and condition of natural cracks on the horizontal section of the main fracture wall and both sides of the main fracture in brittle rock is established when there are many coaxial natural cracks under the action of remote site stress and water pressure on the fracture surface. According to the simulation results, on the main fracture wall, when σH > σv > σh or σH > σh > σv, when the crack angle (CA) is within a certain range and multiple natural cracks (MNC) exist, the required pressure for shear failure decreases. When the fracture angle exceeds a certain size, the required pressure increases. When there are MNC in the horizontal or perpendicular sections of the rock mass on both sides of the main fracture, the required net pressure for shear failure decreases within a certain CA range. When the CA exceeds a certain range, it increases or remains basically unchanged. On the whole, the presence of MNC reduces the net pressure for shear failure, which is conducive to the formation of fracture networks.

A Novel Technique for Reduction and Fixation of Severe Extracapsular Condylar Fracture.

Introducing a novel surgical technique that uses 2 screws and 3 titanium plates to reduce and fix an extracapsular condylar fracture. This technique has been used on 18 sides of extracapsular condylar fracture over the last 3 years in the Department of Oral and Cranio-Maxillofacial Science of Shanghai Ninth People's Hospital without severe complications in clinical practice. Applying this technique, the dislocated condylar segment can be reduced accurately and fixed efficiently.

Effectiveness of total elbow arthroplasty via olecranon osteotomy approach

To investigate the effectiveness of total elbow arthroplasty (TEA) via olecranon osteotomy approach. Between January 2011 and December 2021, 22 patients (25 sides) with elbow joint disease were treated with TEA via olecranon osteotomy approach. There were 9 males and 13 females with an average age of 52.0 years (range, 32-80 years). The disease involved unilateral elbow joint in 19 cases, including 12 cases on the left side and 7 cases on the right side, and 3 cases with bilateral elbow joints. There were 3 cases (3 sides) of osteoarthritis, 7 cases (9 sides) of rheumatoid arthritis, 6 cases (7 sides) of traumatic arthritis, 4 cases (4 sides) of distal humeral fracture, and 2 cases (2 sides) of elbow tuberculosis. The operation time, intraoperative blood loss, and postoperative complications were recorded. The Mayo Elbow Performance Score (MEPS) and range of motion (ROM) were used to evaluate the elbow joint function, and imaging was used to review the position of the prosthesis and the healing of the osteotomy. The operation time ranged from 53 to 120 minutes (mean, 90.6 minutes); intraoperative blood loss ranged from 10 to 200 mL (mean, 68.4 mL). All incisions healed by first intention. All patients were followed up 3.9-126.7 months, with a median time of 47.6 months. At last follow-up, the MEPS scores of 22 patients ranged from 72 to 100 (mean, 91.6); the elbow joint function was rated as excellent in 17 sides, good in 7 sides, and fair in 1 side, with an excellent and good rate of 96%. Elbow joint ROM was 98°-140° in flexion (mean, 119.7°), 5°-23° in extension (mean, 13.9°), 70°-90° in anterior rotation (mean, 83.3°), and 63°-90° in posterior rotation (mean, 79.4°). The follow-up time of 17 patients (20 sides) without fracture and joint stiffness before operation was 3.9-126.7 months, with a median time of 53.9 months; at last follow-up, the MEPS score and the elbow joint ROM were significantly better than those before operation ( P<0.05). The follow-up time of 5 patients (5 sides) with fracture and joint stiffness before operation was 12.0-124.2 months, with a median time of 40.1 months. At last follow-up, MEPS scores ranged from 89 to 100 (mean, 91.2), and elbow joint ROM restored. Two cases (2 sides) developed ulnar nerve symptoms after operation, and 1 case (1 side) suffered from periprosthetic fracture and periprosthetic infection after revision, and the elbow prosthesis was removed. The prosthesis survival rate was 96%. During follow-up, no prosthesis loosening occurred. The intraoperative visual field exposure of TEA via the olecranon osteotomy approach is sufficient, which can reduce the incidence of complications such as triceps weakness and ulnar nerve injury, effectively improve the function of the elbow joint, and obtain satisfactory effectiveness.

Numerical simulation of heat recovery potential of hot dry rock under alternate temperature loading

Alternate-temperature loading can cause cyclic thermal stress; therefore complex artificial fracture networks are formed in hot dry rock owing to thermal expansion and contraction under alternating thermal loading. In this study, the heat recovery potential of hot dry rock with a complex fracture network under alternating temperature loading was simulated numerically based on the hydrothermal coupling algorithm and compared with that of hot dry rock with a single fracture. The results show that the complex fractures formed under alternate thermal loading have better heat recovery performance than a single fracture, and the heat recovery performance of a complex fracture network is closely related to the intersection angle of fractures in the network. The temperature at the fracture outlet increases with an increase in the intersection angle between the branch fractures and the main fracture. At the angle of 30° between the branch fractures and main fracture, the average temperatures at the fracture outlet were 0.031% and 0.025% higher than those at the angles of 90° and 60°, respectively. Simultaneously with the water-injection, the temperature in the branch fractures gradually increased with an increase in the angle of the crossing fractures. When the angle between the branch and main fractures was 90°, the temperature fields on the two sides of the branch fracture were symmetrical. When the angle was 60° or 30°, the temperature fields on the two sides of the branch fracture were asymmetrical. The results of this study provide theoretical and technical support for the extraction of deep geothermal energy.

Associations between condylar fractures and external auditory canal fracture: A 7-year retrospective study

The study aimed to investigate whether the incidence rate of external auditory canal (EAC) fracture varies among different clinical types of condylar fracture. A retrospective cohort study was conducted in single hospital of China. Eligible patients diagnosed with mandibular condylar fractures were retrospectively reviewed. Among all patients with condylar fractures (318 cases and 437 sides), 45 cases and 59 sides (59/437 sides, 13.5%) were found with EAC fracture, including 17(17/38, 44.7%) sides of sagittal fracture of condyle (Type I), 21(21/59, 35.6%) sides of intracapsular condylar fracture (Type II), 8 (8/306, 2.6%) sides of condylar neck fracture (Type III), and 6 (6/34, 17.7%) sides of condylar base fracture (Type IV). Type III condylar fracture had a significant lower rate of EAC fracture than all other three types (all p<0.001). Type I condylar fracture had a higher rate of EAC fracture compared to Type IV (p=0.014). The incidence rates of EAC fracture in combined Type I+Type II group (38/97, 39.2%) was significantly higher than Type III (8/306,2.6%, p<0.001) and Type IV (6/34,17.7%, p=0.002). A total of 35 sides (27 patients) with combined fractures were followed up for 6 months after treatment, among whom 11 sides (7 patients) were operated for both fractures simultaneously. Neither EAC stenosis nor hearing loss was observed. Meanwhile, for 24 non-operated ears from 20 patients, all EACs showed different degrees of stenosis. In conclusion, oral and maxillofacial surgeons should pay more attention to EAC fracture combined with condylar fracture, especially for patients diagnosed with condylar head fracture. Maxillofacial fractures should be accompanied by early treatment of EAC fractures, in order to prevent EAC stenosis, hearing loss, and other complications.

Numerical Investigation of the Fracturing Effect Induced by Disturbing Stress of Hydrofracturing

Fracturing induced by disturbing stress of hydraulic fracturing is the frontier common core scientific problem of reservoir stimulation of coal bed methane and shale gas. The finite-discrete element method, numerical calculation method, is used to analyze the basic law of shear failure and tension failure of natural fractures induced by the disturbing stress of the hydraulic fracture. The simulation results show that when natural fractures and other weak structures exist on the front or both sides of hydraulic fracture, the shear stress acting on the surface of natural fracture will increase until the natural fracture failure, which is caused by the disturbing stress of hydraulic fracturing. The seepage area on the front and both sides of the hydraulic fracture did not extend to the natural fracture while the natural fracture failure occurred. It indicates that the shear failure of natural fractures is induced by the disturbing stress of hydraulic fracturing. When the hydraulic fracture propagates to the natural fracture, the hydraulic tension fracture and disturbed shear fractures are connected and penetrated. As the fluid pressure within the natural fracture surface increases, the hydraulic fracture will continue to propagate through the natural fracture. Meanwhile, due to the action of fluid pressure, a tensile stress concentration will occur at the tip of the natural fracture, which will induce the airfoil tension failure of the natural fracture. With the increase of the principal stress difference, the range of the disturbing stress area and the peak value of the disturbing stress at the front of the hydraulic fracture tip increase, as well as the shear stress acting on the natural fracture surface. During the process of hydraulic fracture approaching natural fracture, the disturbing stress is easier to induce shear failure of natural fracture. With the increase of the cohesive force of natural fracture, the ability of natural fractures to resist shear failure increases. As the hydraulic fracture approaches natural fractures, the disturbing stress is more difficult to induce shear failure of natural fracture. This study will help to reveal the formation mechanism of the fracture network during hydraulic fracturing in the natural fractures developed reservoir.

The investigation of fracture pattern effect on fluid transport and production prediction in M field

Due to the discontinuity and multi-scale of fracture porous media (FPM), fluid transport in the naturally fractured reservoir (NFR) is more complex than in the conventional reservoirs. Based on the embedded discrete fracture model (EDFM), the effect of fracture pattern (i.e. fracture orientation, intersection relationship, numbers and distribution) on fluid transport is investigated, and the paper also conducts research on pressure distribution and flow behavior. A series of fracture models are built to get a detailed analysis of fracture pattern influences. Results show that when the fracture orientation tends to parallel the main stream direction, the seepage flow through the fracture is more distinct and the pressure drop at two sides of fracture becomes larger. As the intersecting fracture cannot serve as part of main-stream channels, the intersection is almost invalid. In the multi-scale fracture model, the pressure drop in the large-scale fractures network is higher than in the small-scale fractures. Thus, the simulation results show that the fracture pattern has a significant impact on the seepage flow and pressure distribution. Also, this model is simulated for M field which has random natural fracture network to study the flow and transport characteristics in fractured porous media. The comprehensive simulation results the fracture patterns have impact effect on production.

BACKGROUND OF MODERN TECHNIQUES FOR LABORATORY DETERMINATION OF THE ELASTICITY MODULUS OF COHESIVE SOILS AND THEIR DESIGN CHARACTERISTICS IN THE ROAD STRUCTURE (Part 2)

According to the results of laboratory stamping tests, samples (d = 150mm; H=180mm) of bulk with soil compaction having a water saturation factor Sr≥0,85 in the range of values of fluidity index – 0,5≤lℓ≤0,25 , it is concluded that it is possible to determine practically every sample, their modulus of deformability (Епр; Ед), the calculated critical resistance – Ro of soil and its maximum relative deformation λmax. The loading of the samples is carried out by a step load with a proportional (1.3 times) increased pressure, such as at each stage. During the test, the sample is not unloaded but is subject to conditional destruction, that is, a disproportionate increase in the deposits of the die. The duration of each load is three minutes. The graphs of parabolic functions of the type λ=aσb are plotted in logarithmic coordinates in the form of two segments straight on both sides of the fracture. The parameter of the degree of parabola “b” serves for preliminary estimation of the index of deformability: for the modulus of elasticity – b≈1,0 ± 0,2; for the modulus of deformation – b≈2,0 ± 0,5; for the yield modulus – b≥3.0. The work gives a comparison with similar indicators of deformability of other building and structural materials. The elastic modulus (Епр) has only a soil that meets the conditions of the standard seal ρdmax&gt;ρdωρ і ω_o&lt;ωρ; the modulus of deformation (Ед) has a soil when 0&lt;lℓ&lt;0,5, and the modulus of fluidity (Ет) has only a soil lℓ≥0,5. Natural structured soils are characterized by a modulus of structural strength (Est) in the range 0&lt;lℓ&lt; 0, which is determined by compression tests. In order to reduce soil consumption and increase productivity, it is proposed to consider the task of determining soil deformability indices for the calculation of road clothing as a contact and therefore reduce the height of soil samples from 180 mm to 40 mm Keywords: soil, soil engineering structure, compacted soil, design condition, elastic modulus, critical design resistance, maximum relative deformation.

Power law relations in earthquakes from microscopic to macroscopic scales

Understanding the physics of earthquakes is a crucial step towards improving the prediction accuracy of earthquakes. Scale invariance or fractal features are often reported in earthquakes, such as the size distribution of earthquakes, the spatial distribution of hypocenters, and the frequency of aftershocks. Here we assess whether other key parameters and quantities involved in earthquakes also conform to the power law. By analyzing a large amount of data collected from the laboratory experiments and field monitoring of earthquakes, we find that the crack density on the two sides of small scale fracture or large scale fault decreases with increasing distance following the power law, and the crack number-crack length distribution is also scale invariant like natural faults. Besides, the earthquake b-value is found to decrease with increasing stress in a power law in the brittle regime of the Earth’s crust. The friction coefficient for dry fault and gouges or for partially saturated gouges decreases with the increasing effective normal stress in a power law. The stress dependency of b-value and friction coefficient is dictated by different mechanisms. Our findings will advance the understanding of earthquake physics, and will enable us to better model, predict and conduct hazard assessment of earthquakes.

The efficacy of telescopic intramedullary rod for treatment of femur fracture or deformity correction in children with osteogenesis imperfecta

Objective To evaluate the safety and efficacy of telescopic intramedullary rod for treatment of femur fracture or deformity correction in children with osteogenesis imperfecta, and to analysis the result of prevention recurrent fracture as well as the complication. Methods Data of patients who were treated by telescopic intramedullary rod for recurrent femur fracture or curved femoral deformity from March 2015 to December 2015 were prospectively analyzed. There were 39 boys and 26 girls. The average age of the patients was 9 years 2 months, ranging from 3 years 5 months to 13 years 4 month. All the patients had suffered from recurrent femur fractures leading to femoral deformity. The mean angulation angle was 58° (range, 30°-95°). Among 69 sides, there were 21 sides of new fracture and 48 sides of deformity. Sixty-one patients were operated at one side and the other 4 patients were treated bilaterally. According to the modified Sillence classification system, there were 5 cases of type I , 17 type III, 34 type IV, 3 type V, 2 type VI and 4 type XV. Results All the 65 patients were followed up for a mean period of 32 months (range, 15-43). The average healing time of the osteotomy site or fracture site of the femur was 8 weeks (range, 7-12). The patient was encouraged to begin weight bearing and walking when the X-ray film showed healing of the osteotomy or fracture site. By the latest follow up, 80% of the patients could stand and walk independently. The incidence of femur fracture decreased significantly to the level of 0.5±0.2/year, compared to 2.7±1.8/year before operation. All the parents of the children were satisfied with the result of deformity correction. The children’s self care and motion ability improved obviously after operation. During follow up, 6 patients suffered from recurrent fracture of the femur by various degree, 1 of them was treated by open reduction and telescopic rodding surgery, while the other 5 patients were treated conservatively because the fracture displaced or angulated minimally and 4 patients healed uneventfully while 1 patient need plate fixation to augment the axial stability. In 3 patients (1 type IV, 2 type Ⅲ) the intubator failed to elongate with the growth of the distal femoral epiphysis, and in 2 patients the obturator migrated proximally which needed to be re-fixed. Low toxic infections occurred in 2 patients (type VI) which were treated successfully by removal of the rod and antibiotics. Conclusion The telescopic intramedullary rod can maintain the correction of the femur deformity and improve the quality the bone, thus prevent the recurrent fracture of the femur in children with osteogenesis imperfecta effectively. Key words: Child; Osteogenesis imperfecta; Fractures, bone; Internal fixators; Fracture fixation, intramedullary

Influences of lateral, front-rear and rotational displacements on injury to sacral nerves in fractures of sacral zone II

Objective To retrospectively analyze the associations of injury to the sacral nerves with lateral, front-rear and rotational displacements in fractures of sacral zone Ⅱ. Methods The data of 62 patients with fracture of sacral zone Ⅱ who had been treated in our hospital between January 2005 through December 2008 were collected using the PACS system and case reports checking system. There were 44 sides of compressed fracture, 15 of which had combined nerve injury while 29 did not. There were 24 sides of separated fracture, 8 of which had combined nerve injury while 16 did not. The groups with and without combined nerve injury in both compressed and separated fractures were compared in terms of the compression or separation distances as well as front-rear and rotational displacements. Results In compressed fractures, the average compression distance in the group with nerve injury (7. 43 ±2. 98 mm) was significantly longer than that in the group without nerve injury (4. 40 ± 3. 02 mm) ( t = 0. 162, P = 0. 003). There were significantly more front-rear and rotational displacements in the nerve injury group than in the other group ( P < 0. 05). In separated fractures, the average separation distance in the group with nerve injury (8. 24 ± 5. 51 mm) was similar to that in the group without nerve injury (6. 91 ± 2. 78 mm) (t = 0. 792, P = 0. 437). No statistical difference was found between the 2 groups in the front-rear displacement (P = 0. 667) but there were significantly more rotational displacements in the nerve injury group than in the other group ( P = 0. 021) . Conclusions The compression distance is associated with neurological deficit in fractures of sacral zone II. The fractures combined with front-rear and rotational displacements are more likely associated with nerve injury. The separation distance in separated fractures is not associated with neural damage. The separated fractures combined with rotational dislocation are more likely combined with neural injury. Key words: Sacum; Fractures, bone; Nerve; Injury

Biomechanical comparison of two stabilization techniques for unstable sacral fractures

AimThe purpose of the study was to assess the stability provided by an ilio-iliac dorsal plate fixation technique using an AO narrow DCP on the pelvic brim in vertically and rotationally unstable type-C pelvic ring injuries. Materials and methodsWe examined 12 fresh cadaver pelvises in a single limb stance load. A type-C pelvic ring injury (a type I lateral sacral fracture in the classification of Denis with symphysis pubis rupture) was performed on the cadaver specimen and fixed with a four-hole narrow dynamic compression plate to stabilize the symphysis pubis rupture; the sacrum fracture was stabilized either anteriorly with two 3-hole reconstruction plates (“anterior plate osteosynthesis”) or with a posterior fixation using a 12-hole narrow DCP. A cyclic load of between 100 and 250N was applied to the fifth lumbar vertebra of the specimen. An extensometer was attached to both sides of the sacrum fracture to detect movements at the fracture site. ResultsWe were able to achieve usable measurements in nine specimens. Three measurements were performed on each specimen, and the movements recorded at the fracture gap in trans-sacral plate fixation were higher than or similar to those observed for anterior plate synthesis in 23 out of 27 cases. ConclusionDorsal ilio-iliac bridge plate fixation provides somewhat reduced stability compared to anterior plate fixation, but the difference is not significant.

Effect of a vertical fracture on horizontal unsaturated seepage flow

The movement of water flow in unsaturated fractured rock was investigated with the sandstone sample through experimental research and numerical simulation. The experimental results show that the arriving time of wetting front is delayed by the fracture, resulting in the increase of water saturation in the domain on the upstream side of the fracture, which will locally enhance water flow through the matrix. The numerical simulation with the finite volume method captures effectively these characteristics. The comparison between simulated and observed travel time and arriving time of wetting front shows that their difference are very small and the simulated results are in agreement with the observed results, which implies calibrated parameters are reliable and effective. Then according to the calibrated parameters, fractured models were established to examine how the change of large fractured aperture would affect the arriving time of wetting fronts, pressure heads and water saturation on the upstream and downstream sides of fracture.

Algorithmic Simulation of Flow in Rock Fractures

The two sides of a rock fracture are geometrically often very different. The difference or heterogeneity can be captured using aperture. This is also practically very significant because locally low or zero aperture in a rock fracture impedes flow. The aperture measurements of each of five paired rock blocks are discretely digitized (0–9). Each resulting weakly continuous two-dimensional matrix is then traversed by the nflow (new-flow) flow algorithm, once from each entry at one end to the other end. The paths are either incomplete and end surrounded by zeros or are completed at the other (exit) end. The numerical digit distribution is held constant from block to block. Fracture through-flow is defined as the average percentage of complete paths from one end to the other for that block. Fracture roughness is negatively correlated with fracture through-flow (r ~ −0.893). A rough fracture will only allow little flow compared with a smooth fracture with a smoother aperture distribution. Channeling of complete paths toward exit points is discussed for all blocks. Channeling is not related to roughness. A long complete sample path in a very rough fracture is shown. The distribution of numbers of complete paths is also investigated.

Evaluation of the Coverage Pattern on the Fracture Surface of Bi-Embrittled Cu Grain Boundaries by Means of Auger Electron Spectroscopy

In studying grain boundary segregation in Cu–Bi alloys by means of Auger electron spectroscopy samples must be broken in-situ. Consequently, the distribution of segregants on both sides of fracture path must be considered quantitatively. This question can be addressed by studying the influence of an adsorbed oxygen layer on the intensity of Auger peaks. This oxygen layer forms on the fracture surface when it is intentionally exposed to air. In this work, the values of Bi coverage have been measured both on the as-fractured Cu fracture surface and on the fracture exposed to air. The coverage values evaluated from the model of a crosstie-like pattern agree better with each other than those from the model of a continuous layer. Our study reveals that the Cu-Bi bond is weaker than the Bi-Bi bond.

Constraints for flow regimes on smooth fracture surfaces

In recent years, significant advances have been made in our understanding of the complex flow processes in individual fractures, aided by flow visualization experiments and conceptual modeling efforts. These advances have led to the recognition of several flow regimes in unsaturated individual fractures subjected to different initial and boundary conditions. For an idealized smooth fracture surface the most important regimes are film flow, rivulet flow, and sliding of droplets. The existence of such significantly dissimilar flow regimes has been a major hindrance in the development of self‐consistent conceptual models of flow for single fracture surfaces that encompass all the flow regimes. The objective of this study is to delineate the existence of the different flow regimes in individual fracture surfaces. For steady state flow conditions, we developed physical constraints on the different flow regimes that satisfy minimum energy configurations, which enabled us to segregate the wide range of fracture flux (volumetric flow rate per fracture width) into several flow regimes. These are, in increasing order of flow rate, flow of adsorbed films, flow of sliding drops, rivulet flow, stable film flow, and unstable (turbulent) film flow. The scope of this study is limited to wide‐aperture smooth fractures with the flow on the opposing sides of fracture being independent.

Segregation of Calcium to Magnesium Oxide Grain Boundaries

Grain boundary (GB) segregation has been measured in Ca-doped MgO by examining intergranular fracture surfaces with Auger electron spectroscopy. The measurements reveal several interesting features. The composition of any given GB on the fracture surface is almost uniform, except for small variations due to deviations from planarity. There is a strong anisotropy of GB composition, which can amount to as much as a factor of six between low and high segregation GB's. Finally, although the compositions of opposite sides of a GB fracture are uniform, there are sometimes significant differences between the two sides, in agreement with a recently formulated model of GB composition as a function of GB character.

Preliminary study of laminated, silt-rich debris bands: Matanuska Glacier, Alaska, U.S.A.

AbstractSeveral different types of laterally extensive debris bands occur along the western terminus region of the Matanuska Glacier, Alaska, U.S.A. An ice-bed process, which to our knowledge has not previously been recognized and described, forms the most common and most prominent type of debris band at Matanuska Glacier’s terminus. The debris bands are composed of one or several millimeter-thick laminations of silt-rich ice having much higher sediment content than that of the surrounding ice. Samples of these bands and their surrounding englacial ice have been analyzed for anthropogenic tritium (3H), oxygen-18 (δ18O), and deuterium (δD).We interpreted the laminated, silt-rich debris bands as basal fractures, along which silt-laden, glaciohydraulically supercooled and pressurized waters flowed, healing the fractures by ice growth. This process is analogous to the inward growth of hydrothermal quartz from the sides of an open fracture.