Background:Tibial stress fracture(TSF)is an overuse running injury with a long recovery period.While many running studies refer to biomechanical risk factors for TSF,only a few have compared biomechanics in runners wi...Background:Tibial stress fracture(TSF)is an overuse running injury with a long recovery period.While many running studies refer to biomechanical risk factors for TSF,only a few have compared biomechanics in runners with TSF to controls.The aim of this systematic review and meta-analysis was to evaluate biomechanics in runners with TSF compared to controls.Methods:Electronic databases PubMed,Web of Science,SPORTDiscus,Scopus,Cochrane,and CINAHL were searched.Risk of bias was assessed and meta-analysis conducted for variables reported in 3 or more studies.Results:The search retrieved 359 unique records,but only the 14 that compared runners with TSF to controls were included in the review.Most studies were retrospective,2 were prospective,and most had a small sample size(5-30 per group).Many variables were not significantly different between groups.Meta-analysis of peak impact,active,and braking ground reaction forces found no significant differences between groups.Individual studies found larger tibial peak anterior tensile stress,peak posterior compressive stress,peak axial acceleration,peak rearfoot eversion,and hip adduction in the TSF group.Conclusion:Meta-analysis indicated that discrete ground reaction force variables were not statistically significantly different in runners with TSF compared to controls.In individual included studies,many biomechanical variables were not statistically significantly different between groups.However,many were reported by only a single study,and sample sizes were small.We encourage additional studies with larger sample sizes of runners with TSF and controls and adequate statistical power to confirm or refute these findings.展开更多
BACKGROUND Femoral and tibial stress injuries are commonly found in long distance running athletes.Stress fractures have rarely been reported in athletes performing high intensity interval training(HIIT)exercise.The o...BACKGROUND Femoral and tibial stress injuries are commonly found in long distance running athletes.Stress fractures have rarely been reported in athletes performing high intensity interval training(HIIT)exercise.The objective of this study was to report a case of a patient who presented with medial tibial stress syndrome and femoral neck stress fracture after performing HIIT exercises.CASE SUMMARY A 26 year old female presented with bilateral medial tibial pain.She had been performing HIIT exercise for 45 min,five times weekly,for a seven month period.Her tibial pain was gradual in onset,and was now severe and worse on exercise,despite six weeks of rest.Magnetic resonance imaging(MRI)revealed bilateral medial tibial stress syndrome.As she was taking norethisterone for birth control,a dual energy X-ray absorbitometry scan was performed which demonstrated normal bone mineral density of her lumbar spine and femoral neck.She was managed conservatively with analgesia and physiotherapy,but continued to exercise against medical advice.She presented again six months later with severe right hip pain.MRI of her right hip demonstrated an incomplete stress fracture of her subtrochanteric region.Her symptoms resolved with strict rest and physiotherapy.CONCLUSION HIIT may cause stress injury of the tibia and femur in young individuals.展开更多
BACKGROUND Stress fractures of the femoral neck are not common in clinical practice,and simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur are even more rare.We introduce a ca...BACKGROUND Stress fractures of the femoral neck are not common in clinical practice,and simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur are even more rare.We introduce a case of this type of fracture that was treated in our department,analyze the causes,and review similar stress fractures reported in the literature to provide references for the diagnosis and treatment of such conditions.CASE SUMMARY A 62-year-old female,with a free medical history,was admitted to the hospital mainly due to pain in the right hip and worsening pain in the right thigh.The patient had no obvious history of trauma.X-ray and computed tomography showed fracture of the femoral neck and proximal femur.The patient had undergone surgery 1 year prior to address a fracture of the left proximal femur that had occurred in a traffic accident.Our first consideration was stress fracture of the femoral neck;however,simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur were seen.The femoral neck stress fracture was a tension fracture,with obvious displacement and varus deformity of the hip.Considering that the patient was an elderly female,we performed total hip arthroplasty.Follow-up X-rays showed that the stress fracture of the proximal femur had mostly healed after 3 mo.CONCLUSION Muscle fatigue and hip varus deformity provide an anatomical basis for the occurrence of femoral neck stress fractures.展开更多
BACKGROUND Individuals’interest in sports activities has been increasing,contributing to more stress fracture occurrences in uncommon locations on the skeleton.In this study,several cases of stress fractures in atypi...BACKGROUND Individuals’interest in sports activities has been increasing,contributing to more stress fracture occurrences in uncommon locations on the skeleton.In this study,several cases of stress fractures in atypical locations are presented,and the possibility of combining diagnostic methods to make accurate and quick diagnoses is explored.Additionally,different causes of stress fractures,as well as various modalities of treatment,are highlighted.Other potential factors of stress fractures were identified by a literature review.CASE SUMMARY Six cases of stress fractures in the calcaneus,intermediate cuneiform bone,sacrum,tibia(bilateral),navicular bone and femoral neck are presented,with different types of diagnostic imaging and treatments.All of the cases were associated with an aspect of mobility because all of the patients were physically active in various sport disciplines.CONCLUSION The type of therapeutic procedure selected should depend on the specific clinical case,i.e.,the patient’s condition and level of physical activity.展开更多
BACKGROUND Femoral neck stress fractures(FNSFs)are commonly found in long-distance running athletes.For FNSFs,early diagnosis and proper treatment are important.The objective of this study was to report FNSFs that occ...BACKGROUND Femoral neck stress fractures(FNSFs)are commonly found in long-distance running athletes.For FNSFs,early diagnosis and proper treatment are important.The objective of this study was to report FNSFs that occurred after excessive exercise using trampoline in middle-aged women.CASE SUMMARY The patient was a 43-year-old woman who exercised jumping on a trampoline for 6 wk for 1-3 h a day to diet.Exercise includes repeated flexion-extension of the hip joint.The patient was admitted to the hospital due to sudden bilateral groin pain that occurred suddenly during a trampoline exercise.Hip magnetic resonance imaging(MRI)revealed bilateral FNSFs.After 2 wk of follow-up with conservative treatment,the pain slightly decreased.However,it did not disappear completely.It was determined that it was difficult to control symptoms only by conservation treatment.Thus,closed reduction and internal fixation using a cannulated screw were performed for the more painful left hip joint.After operation,the pain was improved.Walking using crutches was possible.Followup MRI showed that the right femoral head signal was decreased compared to the left femoral head signal.Therefore,nonsteroidal anti-inflammatory drug and conservative treatment were provided.CONCLUSION In middle-aged people,excessive trampoline exercise can repeat hip flexion and extension for a short period of time,leading to FNSFs.展开更多
Stress fractures in sport are becoming increasing more common,comprising up to 10%of all of sporting injuries.Around 90%of such injuries are located in the lower limb.This articles aims to define the optimal managemen...Stress fractures in sport are becoming increasing more common,comprising up to 10%of all of sporting injuries.Around 90%of such injuries are located in the lower limb.This articles aims to define the optimal management of lower limb stress fractures in the athlete,with a view to maximise return rates and minimise return times to sport.Treatment planning of this condition is specific to the location of the injury.However,there remains a clear division of stress fractures by"high"and"low"risk."Low risk"stress fractures are those with a low probability of fracture propagation,delayed union,or non-union,and so can be managed reliably with rest and exercise limitation.These include stress fractures of the PosteroMedial Tibial Diaphysis,Metatarsal Shafts,Distal Fibula,Medial Femoral Neck,Femoral Shaft and Calcaneus."High risk"stress fractures,in contrast,have increased rates of fracture propagation,displacement,delayed and non-union,and so require immediate cessation of activity,with orthopaedic referral,to assess the need for surgical intervention.These include stress fractures of the Anterior Tibial Diaphysis,Fifth Metatarsal Base,Medial Malleolus,Lateral Femoral Neck,Tarsal Navicular and Great Toe Sesamoids.In order to establish the optimal methods for managing these injuries,we present and review the current evidence which guides the treatment of stress fractures in athletes.From this,we note an increased role for surgical management of certain high risk stress fractures to improve return times and rates to sport.Following this,key recommendations are provided for the management of the common stress fracture types seen in the athlete.Five case reports are also presented to illustrate the application of sportfocussed lower limb stress fracture treatment in the clinical setting.展开更多
BACKGROUND Femoral neck stress fractures are rarely encountered among young adults and are often associated with either repetitive excessive loading or underlying bone pathology.Preliminary research has indicated huma...BACKGROUND Femoral neck stress fractures are rarely encountered among young adults and are often associated with either repetitive excessive loading or underlying bone pathology.Preliminary research has indicated human immunodeficiency virus(HIV)/antiretroviral therapy(ART)as predisposing agents to osteopenia and osteoporosis related complications.We report a case of HIV/ART induced insufficiency fracture in a resource limited setting in Central India.Our aim is to increase awareness and promote screening of HIV/ART related osteopenia and osteoporosis in order to prevent catastrophic orthopaedic complications.CASE SUMMARY A 35-year-old HIV positive male presented with a stress fracture of left femoral neck.The patient was on ART and reported no comorbidities.He went on to be successfully managed surgically.However,during work-up osteopenia of the contralateral proximal femur was recognised using Singh’s Index.Six months post-op the patient presented with right-sided femoral-neck stress fracture.At this stage the patient was nonconcordant with ART and denied surgical fixation.CONCLUSION In the absence of co-morbidities,several mechanisms of HIV/antiretroviral therapy may have played a role in predisposing our patient towards such a presentation.We recommend routine screening all HIV-infected patients for osteopenia,especially in younger individuals.In low resource settings and district hospitals,pelvis radiograph&Singh’s index can be used for screening.展开更多
AIM: To determine if rabbit models can be used to quantify the mechanical behaviour involved in tibial stress fracture(TSF) development.METHODS: Fresh rabbit tibiae were loaded under compression using a specifically-d...AIM: To determine if rabbit models can be used to quantify the mechanical behaviour involved in tibial stress fracture(TSF) development.METHODS: Fresh rabbit tibiae were loaded under compression using a specifically-designed test apparatus. Weights were incrementally added up to a load of 30 kg and the mechanical behaviour of the tibia was analysed using tests for buckling, bone strain and hysteresis. Structural mechanics equations were subsequently employed to verify that the results were within the range of values predicted by theory. A finite element(FE) model was developed using cross-sectional computer tomography(CT) images scanned from one of the rabbit bones, and a static load of 6 kg(1.5 times the rabbit's body weight) was applied to represent running. The model was validated using the experimental strain gauge data, then geometric and elemental convergence tests were performed in order to find the minimum number of cross-sectional scans and elements respectively required for convergence. The analysis was then performed using both the model and the experimental results to investigate the mechanical behaviour of the rabbit tibia under compressive load and to examine crack initiation.RESULTS: The experimental tests showed that un der a compressive load of up to 12 kg, the rabbit tibia demonstrates linear behaviour with little hysteresis Up to 30 kg, the bone does not fail by elastic buckling however, there are low levels of tensile stress which predominately occur at and adjacent to the anterio border of the tibial midshaft: this suggests that fatigue failure occurs in these regions, since bone under cycli loading initially fails in tension. The FE model predic tions were consistent with both mechanics theory and the strain gauge results. The model was highly sensi tive to small changes in the position of the applied load due to the high slenderness ratio of the rabbit s tibia. The modelling technique used in the curren study could have applications in the development o human FE models of bone, where, unlike rabbit tibia the model would be relatively insensitive to very sma changes in load position. However, the rabbit mode itself is less beneficial as a tool to understand the me chanical behaviour of TSFs in humans due to the sma size of the rabbit bone and the limitations of human scale CT scanning equipment.CONCLUSION: The current modelling technique could be used to develop human FE models. However, the rabbit model itself has significant limitations in under standing human TSF mechanics.展开更多
AIM To determine the location of medial tibial plateau stress fractures and its relationship with tibial plateau morphology using magnetic resonance imaging(MRI).METHODS A retrospective review of patients with a diagn...AIM To determine the location of medial tibial plateau stress fractures and its relationship with tibial plateau morphology using magnetic resonance imaging(MRI).METHODS A retrospective review of patients with a diagnosis of stress fracture of the medial tibial plateau was performed for a 5-year period. Fourteen patients [three female and 11 male, with an average age of 36.4 years(range, 15-50 years)], who underwent knee MRI, were included. The appearance of the tibial plateau stress fracture and the geometry of the tibial plateau were reviewed and measured on MRI.RESULTS Thirteen of 14 stress fractures were linear, and one of them stellated on MRI images. The location of fractures was classified into three types. Three fractures were located anteromedially(AM type), six posteromedially(PM type), and five posteriorly(P type) at the medial tibial plateau. In addition, tibial posterior slope at the medial tibial plateau tended to be larger when the fracture was located more posteriorly on MRI.CONCLUSION We found that MRI showed three different localizations of medial tibial plateau stress fractures, which were associated with tibial posterior slope at the medial tibial plateau.展开更多
AIM:To analyze stress fractures in athletes based on experience from our sports medicine clinic.METHODS:We investigated the association between stress fractures and age,sex,sports level,sports activity,and skeletal si...AIM:To analyze stress fractures in athletes based on experience from our sports medicine clinic.METHODS:We investigated the association between stress fractures and age,sex,sports level,sports activity,and skeletal site in athletes seen at our sports medicine clinic between September 1991 and April 2009.Stress fractures of the pars interarticularis were excluded from this analysis.RESULTS:During this period(18 years and 8 mo),14276 patients(9215 males and 5061 females)consulted our clinic because of sports-related injuries,and 263 patients(1.8%)[171 males(1.9%)and 92 females(1.8%)]sustained stress fractures.The average age of the patients with stress fractures was 20.2 years(range 10-46 years);112 patients(42.6%)were 15-19 years of age and 90(34.2%)were 20-24 years of age.Altogether,90 patients(34.2%)were active at a high recreational level and 173(65.8%)at a competitive level.The highest proportion of stress fractures was seen in basketball athletes(21.3%),followed by baseball(13.7%),track and field(11.4%),rowing(9.5%),soccer(8.4%),aerobics(5.3%),and classical ballet(4.9%).The most common sites of stress fractures in these patients were the tibia(44.1%),followed by the rib(14.1%),metatarsal bone(12.9%),ulnar olecranon(8.7%)and pelvis(8.4%).The sites of the stress fractures varied from sport to sport.The ulnar olecranon was the most common stress fracture site in baseball players,and the rib was the most common in rowers.Basketball and classical ballet athletes predominantly sustained stress fractures of the tibia and metatarsal bone.Track and field and soccer athletes predominantly sustained stress fractures of the tibia and pubic bone.Aerobics athletes predominantly sustained stress fractures of the tibia.Middle and long distance female runners who sustained multiple stress fractures had the female athlete triad.CONCLUSION:The results of this analysis showed that stress fractures were seen in high-level young athletes,with similar proportions for males and females,and that particular sports were associated with specific sites for stress fractures.Middle and long distance female runners who suffered from multiple stress fractures had the female athlete triad.展开更多
Stress fracture（SF）in military recruits in China was investigated using<sup>99m</sup>Tc-MDP bone scintigraphy in a randomized sample of 432 injured who wereclinically screened from 1060 recruits during b...Stress fracture（SF）in military recruits in China was investigated using<sup>99m</sup>Tc-MDP bone scintigraphy in a randomized sample of 432 injured who wereclinically screened from 1060 recruits during basic training.The relationship between SFand training intensity was discussed.It was shown that the total incidence was 32.5%.There were two peaks during 9 training-weeks:one was in the 2nd week,and the otherin the 7th.Infantry soldiers had a more intensive training and,therefore a higher inci-dence than in artillery and service troops.Although SF was found in most ofweight-bearing bones,tibia was most commonly fractured（67%）.The findings suggestthat SF is a major training-related injury in military recruits and improperly strengthenedtraining can increase the incidence.展开更多
Stress fractures of the tibia are commonly seen in young athletes or military recruits due to repetitive micro trauma. These are rare in elderly patients. Osteoarthritis knee with varus deformity leading to stress fra...Stress fractures of the tibia are commonly seen in young athletes or military recruits due to repetitive micro trauma. These are rare in elderly patients. Osteoarthritis knee with varus deformity leading to stress fracture is rare but has been reported in literature. Stress fracture in osteoarthritis more commonly occurs in upper third tibia. We report a patient who had stress fractures of distal tibial shaft secondary to advanced osteoarthritis of knee with varus deformity.展开更多
Purpose: The objective of this research is to investigate whether bioimpedance is useful to indicate a shank’s physical condition during training. Methods: Bioimpedance was applied to monitor the condition of 8 rabb...Purpose: The objective of this research is to investigate whether bioimpedance is useful to indicate a shank’s physical condition during training. Methods: Bioimpedance was applied to monitor the condition of 8 rabbits’ shanks in 3 weeks, during which the rabbits were trained for regular excessive jump daily. Nine tibias in 16 developed stress fracture after the 3-week training. Results: According to the analysis of the bioimpedance data, we found that changing pattern of bioimpedance properties of shanks which were more liable to suffer from SF was different from that of shanks which were not during training. Conclusions: This suggests that bioimpedance may be used to monitor the physical condition of a limb, imply its liability to develop stress fracture, and indicate stress fracture during training.展开更多
Background: Stress fractures are fatigue-induced, very small cracks in the bone caused by repetitive application of force and most often seen in the weight-bearing bones of the lower extremities of athletes or militar...Background: Stress fractures are fatigue-induced, very small cracks in the bone caused by repetitive application of force and most often seen in the weight-bearing bones of the lower extremities of athletes or military recruits. Case Report: A 47-year-old postmenopausal and heavy smoker woman complained of localized sensitivity on the distal-anterior and medial surfaces of both tibiae, which had been ongoing for 1 month. She moved to a flat at 5th-floor without an elevator a year ago. Bilateral stress fractures were diagnosed by radiographs and confirmed by Magnetic Resonance Imaging (MRI). She was suggested to restrict activities and to use crutches until the symptoms subsided. Bilateral ankle joint pneumatic brace with full heel support was applied. The patient was followed one year after diagnosis. At the 2-month follow-up examination, the patient was pain free and planning to move to a new house. Conclusions: Several risk factors have been defined in the pathogenesis of stress fracture. In the present case, the acute phase had passed and diagnosis could be made from the direct radiographs. Although extremely rarely seen, tibia distal stress fracture should be kept in mind in the differential diagnosis of patients with the relevant risk factors who present with tibia distal localized pain.展开更多
To gain insight into the flow mechanisms and stress sensitivity for fractured-vuggy reservoirs,several core models with different structural characteristics were designed and fabricated to investigate the impact of ef...To gain insight into the flow mechanisms and stress sensitivity for fractured-vuggy reservoirs,several core models with different structural characteristics were designed and fabricated to investigate the impact of effective stress on permeability for carbonate fractured-vuggy rocks(CFVR).It shows that the permeability performance curves under different pore and confining pressures(i.e.altered stress conditions)for the fractured core models and the vuggy core models have similar change patterns.The ranges of permeability variation are significantly wider at high pore pressures,indicating that permeability reduction is the most significant during the early stage of development for fractured-vuggy reservoirs.Since each obtained effective stress coefficient for permeability(ESCP)varies with the changes in confining pressure and pore pressure,the effective stresses for permeability of four representative CFVR show obvious nonlinear characteristics,and the variation ranges of ESCP are all between 0 and 1.Meanwhile,a comprehensive ESCP mathematical model considering triple media,including matrix pores,fractures,and dissolved vugs,was proposed.It is proved theoretically that the ESCP of CFVR generally varies between 0 and 1.Additionally,the regression results showed that the power model ranked highest among the four empirical models mainly applied in stress sensitivity characterization,followed by the logarithmic model,exponential model,and binomial model.The concept of“permeability decline rate”was introduced to better evaluate the stress sensitivity performance for CFVR,in which the one-fracture rock is the strongest,followed by the fracture-vug rock and two-horizontalfracture rock;the through-hole rock is the weakest.In general,this study provides a theoretical basis to guide the design of development and adjustment programs for carbonate fractured-vuggy reservoirs.展开更多
This work applies stress tensors inversions and quantification of fracture patterns along the Mesa de Los Santos, in the Eastern Cordillera of Colombia, to better understand the potential fluid flow. It thus contribut...This work applies stress tensors inversions and quantification of fracture patterns along the Mesa de Los Santos, in the Eastern Cordillera of Colombia, to better understand the potential fluid flow. It thus contributes to the conceptual hydrogeological model. The area was subdivided into three blocks, separated by the NW Potreros and the Los Santos faults, having minor inner faults of different orientations. This separation facilitates the analysis of the fractures measured in the field, which in general show high dip angles and a conjugate geometry in the northern block, tension fractures(Mode I) in the central block, and a random distribution in the southwestern block. WinTensor treatment of slickensides yielded a maximum horizontal stress(SHmax) of 111o, which coincides with the WNW-ESE tensor observed from the conjugate and tension joints. We then used Frac Pa Q to generate interpolation maps of fracture intensity and density. The maps show the highest values in the central block and the lowest in the northern block,where the precipitation is higher, causing intensive rock weathering and homogenization of the fracture planes. Although the highest values of connectivity by line are found to the south of the mesa, we suggest the possibility of greater flow from the recharge zone(NE) along bedding planes and open NW-SE fractures.展开更多
Grouting is a widely used approach to reinforce broken surrounding rock mass during the construction of underground tunnels in fault fracture zones,and its reinforcement effectiveness is highly affected by geostress.I...Grouting is a widely used approach to reinforce broken surrounding rock mass during the construction of underground tunnels in fault fracture zones,and its reinforcement effectiveness is highly affected by geostress.In this study,a numerical manifold method(NMM)based simulator has been developed to examine the impact of geostress conditions on grouting reinforcement during tunnel excavation.To develop this simulator,a detection technique for identifying slurry migration channels and an improved fluid-solid coupling(FeS)framework,which considers the influence of fracture properties and geostress states,is developed and incorporated into a zero-thickness cohesive element(ZE)based NMM(Co-NMM)for simulating tunnel excavation.Additionally,to simulate coagulation of injected slurry,a bonding repair algorithm is further proposed based on the ZE model.To verify the accuracy of the proposed simulator,a series of simulations about slurry migration in single fractures and fracture networks are numerically reproduced,and the results align well with analytical and laboratory test results.Furthermore,these numerical results show that neglecting the influence of geostress condition can lead to a serious over-estimation of slurry migration range and reinforcement effectiveness.After validations,a series of simulations about tunnel grouting reinforcement and tunnel excavation in fault fracture zones with varying fracture densities under different geostress conditions are conducted.Based on these simula-tions,the influence of geostress conditions and the optimization of grouting schemes are discussed.展开更多
Tectonic stress fields are the key drivers of tectonic events and the evolution of regional structures.The tectonic stress field evolution of the Tanlu fault zone in Shandong Province,located in the east of the North ...Tectonic stress fields are the key drivers of tectonic events and the evolution of regional structures.The tectonic stress field evolution of the Tanlu fault zone in Shandong Province,located in the east of the North China Craton(NCC),may have preserved records of the NCC’s tectonic history.Borehole television survey and hydraulic fracturing were conducted to analyze the paleo and present tectonic stress fields.Three groups of tensile fractures were identified via borehole television,their azimuths being NNW-SSE,NW-SE and NE-SW,representing multiple stages of tectonic events.Hydraulic fracturing data indicates that the study region is experiencing NEE-SWW-oriented compression and nearly-N-Soriented extension,in accordance with strike-slip and compression.Since the Cretaceous,the orientation of the extensional stress has evolved counterclockwise and sequentially from nearly-NW-SE-oriented to NE-SW-oriented and even nearly N-S-oriented,the stress state having transitioned from strike-slip-extension to strike-slip-compression,in association with the rotating and oblique subduction of the Pacific Plate beneath the NCC,with the participation of the Indian Plate.展开更多
Through high-precision engraving,self-affine sandstone joint surfaces with various joint roughness coefficients(JRC=3.21e12.16)were replicated and the shear sliding tests under unloading normal stress were conducted r...Through high-precision engraving,self-affine sandstone joint surfaces with various joint roughness coefficients(JRC=3.21e12.16)were replicated and the shear sliding tests under unloading normal stress were conducted regarding various initial normal stresses(1e7 MPa)and numbers of shearing cycles(1 e5).The peak shear stress of fractures decreased with shear cycles due to progressively smooth surface morphologies,while increased with both JRC and initial normal stress and could be verified using the nonlinear Barton-Bandis failure criterion.The joint friction angle of fractures exponentially increased by 62.22%e64.87%with JRC while decreased by 22.1%e24.85%with shearing cycles.After unloading normal stress,the sliding initiation time of fractures increased with both JRC and initial normal stress due to more tortuous fracture morphologies and enhanced shearing resistance capacity.The surface resistance index(SRI)of fractures decreased by 4.35%e32.02%with increasing shearing cycles due to a more significant reduction of sliding initiation shear stress than that for sliding initiation normal stress,but increased by a factor of 0.41e1.64 with JRC.After sliding initiation,the shear displacement of fractures showed an increase in power function.By defining a sliding rate threshold of 5105 m/s,transition from“quasi-static”to“dynamic”sliding of fractures was identified,and the increase of sliding acceleration steepened with JRC while slowed down with shearing cycles.The normal displacement experienced a slight increase before shear sliding due to deformation recovery as the unloading stress was unloaded,and then enhanced shear dilation after sliding initiation due to climbing effects of surface asperities.Dilation was positively related to the shear sliding velocity of fractures.Wear characteristics of the fracture surfaces after shearing failure were evaluated using binary calculation,indicating an increasing shear area ratio by 45.24%e91.02%with normal stress.展开更多
The frictional rupture mechanisms of rock discontinuities considering the dynamic load disturbance still remain unclear.This paper investigates the transitional behaviors of slip events happened on a planar granite fr...The frictional rupture mechanisms of rock discontinuities considering the dynamic load disturbance still remain unclear.This paper investigates the transitional behaviors of slip events happened on a planar granite fracture under cyclic normal stress with diferent oscillation amplitudes.The experimental results show that the activations of fast slips always correlate with unloading of normal stress.Besides,the intensive normal stress oscillation can weaken the shear strength which is recoverable when the normal stress return to constant.The rupture patterns are quantifed by stress drop,slip length and slip velocity.With the efect of small oscillation amplitudes,the slip events show chaotic shapes,compared to the regular and predictable style under constant normal stress.When the amplitude is large enough,the big and small slip events emerge alternately,showing a compound slip style.Large amplitude of the cyclic normal stress also widens the interval diferences of the slip events.This work provides experimental supports for a convincible link between the dynamic stress disturbance and the slip behavior of rock fractures.展开更多
文摘Background:Tibial stress fracture(TSF)is an overuse running injury with a long recovery period.While many running studies refer to biomechanical risk factors for TSF,only a few have compared biomechanics in runners with TSF to controls.The aim of this systematic review and meta-analysis was to evaluate biomechanics in runners with TSF compared to controls.Methods:Electronic databases PubMed,Web of Science,SPORTDiscus,Scopus,Cochrane,and CINAHL were searched.Risk of bias was assessed and meta-analysis conducted for variables reported in 3 or more studies.Results:The search retrieved 359 unique records,but only the 14 that compared runners with TSF to controls were included in the review.Most studies were retrospective,2 were prospective,and most had a small sample size(5-30 per group).Many variables were not significantly different between groups.Meta-analysis of peak impact,active,and braking ground reaction forces found no significant differences between groups.Individual studies found larger tibial peak anterior tensile stress,peak posterior compressive stress,peak axial acceleration,peak rearfoot eversion,and hip adduction in the TSF group.Conclusion:Meta-analysis indicated that discrete ground reaction force variables were not statistically significantly different in runners with TSF compared to controls.In individual included studies,many biomechanical variables were not statistically significantly different between groups.However,many were reported by only a single study,and sample sizes were small.We encourage additional studies with larger sample sizes of runners with TSF and controls and adequate statistical power to confirm or refute these findings.
文摘BACKGROUND Femoral and tibial stress injuries are commonly found in long distance running athletes.Stress fractures have rarely been reported in athletes performing high intensity interval training(HIIT)exercise.The objective of this study was to report a case of a patient who presented with medial tibial stress syndrome and femoral neck stress fracture after performing HIIT exercises.CASE SUMMARY A 26 year old female presented with bilateral medial tibial pain.She had been performing HIIT exercise for 45 min,five times weekly,for a seven month period.Her tibial pain was gradual in onset,and was now severe and worse on exercise,despite six weeks of rest.Magnetic resonance imaging(MRI)revealed bilateral medial tibial stress syndrome.As she was taking norethisterone for birth control,a dual energy X-ray absorbitometry scan was performed which demonstrated normal bone mineral density of her lumbar spine and femoral neck.She was managed conservatively with analgesia and physiotherapy,but continued to exercise against medical advice.She presented again six months later with severe right hip pain.MRI of her right hip demonstrated an incomplete stress fracture of her subtrochanteric region.Her symptoms resolved with strict rest and physiotherapy.CONCLUSION HIIT may cause stress injury of the tibia and femur in young individuals.
基金Supported by Suzhou Gusu Health Talent Program Training Program,No.GSWS2020121。
文摘BACKGROUND Stress fractures of the femoral neck are not common in clinical practice,and simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur are even more rare.We introduce a case of this type of fracture that was treated in our department,analyze the causes,and review similar stress fractures reported in the literature to provide references for the diagnosis and treatment of such conditions.CASE SUMMARY A 62-year-old female,with a free medical history,was admitted to the hospital mainly due to pain in the right hip and worsening pain in the right thigh.The patient had no obvious history of trauma.X-ray and computed tomography showed fracture of the femoral neck and proximal femur.The patient had undergone surgery 1 year prior to address a fracture of the left proximal femur that had occurred in a traffic accident.Our first consideration was stress fracture of the femoral neck;however,simultaneous stress fractures of the femoral neck and proximal femur of the unilateral femur were seen.The femoral neck stress fracture was a tension fracture,with obvious displacement and varus deformity of the hip.Considering that the patient was an elderly female,we performed total hip arthroplasty.Follow-up X-rays showed that the stress fracture of the proximal femur had mostly healed after 3 mo.CONCLUSION Muscle fatigue and hip varus deformity provide an anatomical basis for the occurrence of femoral neck stress fractures.
文摘BACKGROUND Individuals’interest in sports activities has been increasing,contributing to more stress fracture occurrences in uncommon locations on the skeleton.In this study,several cases of stress fractures in atypical locations are presented,and the possibility of combining diagnostic methods to make accurate and quick diagnoses is explored.Additionally,different causes of stress fractures,as well as various modalities of treatment,are highlighted.Other potential factors of stress fractures were identified by a literature review.CASE SUMMARY Six cases of stress fractures in the calcaneus,intermediate cuneiform bone,sacrum,tibia(bilateral),navicular bone and femoral neck are presented,with different types of diagnostic imaging and treatments.All of the cases were associated with an aspect of mobility because all of the patients were physically active in various sport disciplines.CONCLUSION The type of therapeutic procedure selected should depend on the specific clinical case,i.e.,the patient’s condition and level of physical activity.
文摘BACKGROUND Femoral neck stress fractures(FNSFs)are commonly found in long-distance running athletes.For FNSFs,early diagnosis and proper treatment are important.The objective of this study was to report FNSFs that occurred after excessive exercise using trampoline in middle-aged women.CASE SUMMARY The patient was a 43-year-old woman who exercised jumping on a trampoline for 6 wk for 1-3 h a day to diet.Exercise includes repeated flexion-extension of the hip joint.The patient was admitted to the hospital due to sudden bilateral groin pain that occurred suddenly during a trampoline exercise.Hip magnetic resonance imaging(MRI)revealed bilateral FNSFs.After 2 wk of follow-up with conservative treatment,the pain slightly decreased.However,it did not disappear completely.It was determined that it was difficult to control symptoms only by conservation treatment.Thus,closed reduction and internal fixation using a cannulated screw were performed for the more painful left hip joint.After operation,the pain was improved.Walking using crutches was possible.Followup MRI showed that the right femoral head signal was decreased compared to the left femoral head signal.Therefore,nonsteroidal anti-inflammatory drug and conservative treatment were provided.CONCLUSION In middle-aged people,excessive trampoline exercise can repeat hip flexion and extension for a short period of time,leading to FNSFs.
文摘Stress fractures in sport are becoming increasing more common,comprising up to 10%of all of sporting injuries.Around 90%of such injuries are located in the lower limb.This articles aims to define the optimal management of lower limb stress fractures in the athlete,with a view to maximise return rates and minimise return times to sport.Treatment planning of this condition is specific to the location of the injury.However,there remains a clear division of stress fractures by"high"and"low"risk."Low risk"stress fractures are those with a low probability of fracture propagation,delayed union,or non-union,and so can be managed reliably with rest and exercise limitation.These include stress fractures of the PosteroMedial Tibial Diaphysis,Metatarsal Shafts,Distal Fibula,Medial Femoral Neck,Femoral Shaft and Calcaneus."High risk"stress fractures,in contrast,have increased rates of fracture propagation,displacement,delayed and non-union,and so require immediate cessation of activity,with orthopaedic referral,to assess the need for surgical intervention.These include stress fractures of the Anterior Tibial Diaphysis,Fifth Metatarsal Base,Medial Malleolus,Lateral Femoral Neck,Tarsal Navicular and Great Toe Sesamoids.In order to establish the optimal methods for managing these injuries,we present and review the current evidence which guides the treatment of stress fractures in athletes.From this,we note an increased role for surgical management of certain high risk stress fractures to improve return times and rates to sport.Following this,key recommendations are provided for the management of the common stress fracture types seen in the athlete.Five case reports are also presented to illustrate the application of sportfocussed lower limb stress fracture treatment in the clinical setting.
文摘BACKGROUND Femoral neck stress fractures are rarely encountered among young adults and are often associated with either repetitive excessive loading or underlying bone pathology.Preliminary research has indicated human immunodeficiency virus(HIV)/antiretroviral therapy(ART)as predisposing agents to osteopenia and osteoporosis related complications.We report a case of HIV/ART induced insufficiency fracture in a resource limited setting in Central India.Our aim is to increase awareness and promote screening of HIV/ART related osteopenia and osteoporosis in order to prevent catastrophic orthopaedic complications.CASE SUMMARY A 35-year-old HIV positive male presented with a stress fracture of left femoral neck.The patient was on ART and reported no comorbidities.He went on to be successfully managed surgically.However,during work-up osteopenia of the contralateral proximal femur was recognised using Singh’s Index.Six months post-op the patient presented with right-sided femoral-neck stress fracture.At this stage the patient was nonconcordant with ART and denied surgical fixation.CONCLUSION In the absence of co-morbidities,several mechanisms of HIV/antiretroviral therapy may have played a role in predisposing our patient towards such a presentation.We recommend routine screening all HIV-infected patients for osteopenia,especially in younger individuals.In low resource settings and district hospitals,pelvis radiograph&Singh’s index can be used for screening.
文摘AIM: To determine if rabbit models can be used to quantify the mechanical behaviour involved in tibial stress fracture(TSF) development.METHODS: Fresh rabbit tibiae were loaded under compression using a specifically-designed test apparatus. Weights were incrementally added up to a load of 30 kg and the mechanical behaviour of the tibia was analysed using tests for buckling, bone strain and hysteresis. Structural mechanics equations were subsequently employed to verify that the results were within the range of values predicted by theory. A finite element(FE) model was developed using cross-sectional computer tomography(CT) images scanned from one of the rabbit bones, and a static load of 6 kg(1.5 times the rabbit's body weight) was applied to represent running. The model was validated using the experimental strain gauge data, then geometric and elemental convergence tests were performed in order to find the minimum number of cross-sectional scans and elements respectively required for convergence. The analysis was then performed using both the model and the experimental results to investigate the mechanical behaviour of the rabbit tibia under compressive load and to examine crack initiation.RESULTS: The experimental tests showed that un der a compressive load of up to 12 kg, the rabbit tibia demonstrates linear behaviour with little hysteresis Up to 30 kg, the bone does not fail by elastic buckling however, there are low levels of tensile stress which predominately occur at and adjacent to the anterio border of the tibial midshaft: this suggests that fatigue failure occurs in these regions, since bone under cycli loading initially fails in tension. The FE model predic tions were consistent with both mechanics theory and the strain gauge results. The model was highly sensi tive to small changes in the position of the applied load due to the high slenderness ratio of the rabbit s tibia. The modelling technique used in the curren study could have applications in the development o human FE models of bone, where, unlike rabbit tibia the model would be relatively insensitive to very sma changes in load position. However, the rabbit mode itself is less beneficial as a tool to understand the me chanical behaviour of TSFs in humans due to the sma size of the rabbit bone and the limitations of human scale CT scanning equipment.CONCLUSION: The current modelling technique could be used to develop human FE models. However, the rabbit model itself has significant limitations in under standing human TSF mechanics.
文摘AIM To determine the location of medial tibial plateau stress fractures and its relationship with tibial plateau morphology using magnetic resonance imaging(MRI).METHODS A retrospective review of patients with a diagnosis of stress fracture of the medial tibial plateau was performed for a 5-year period. Fourteen patients [three female and 11 male, with an average age of 36.4 years(range, 15-50 years)], who underwent knee MRI, were included. The appearance of the tibial plateau stress fracture and the geometry of the tibial plateau were reviewed and measured on MRI.RESULTS Thirteen of 14 stress fractures were linear, and one of them stellated on MRI images. The location of fractures was classified into three types. Three fractures were located anteromedially(AM type), six posteromedially(PM type), and five posteriorly(P type) at the medial tibial plateau. In addition, tibial posterior slope at the medial tibial plateau tended to be larger when the fracture was located more posteriorly on MRI.CONCLUSION We found that MRI showed three different localizations of medial tibial plateau stress fractures, which were associated with tibial posterior slope at the medial tibial plateau.
文摘AIM:To analyze stress fractures in athletes based on experience from our sports medicine clinic.METHODS:We investigated the association between stress fractures and age,sex,sports level,sports activity,and skeletal site in athletes seen at our sports medicine clinic between September 1991 and April 2009.Stress fractures of the pars interarticularis were excluded from this analysis.RESULTS:During this period(18 years and 8 mo),14276 patients(9215 males and 5061 females)consulted our clinic because of sports-related injuries,and 263 patients(1.8%)[171 males(1.9%)and 92 females(1.8%)]sustained stress fractures.The average age of the patients with stress fractures was 20.2 years(range 10-46 years);112 patients(42.6%)were 15-19 years of age and 90(34.2%)were 20-24 years of age.Altogether,90 patients(34.2%)were active at a high recreational level and 173(65.8%)at a competitive level.The highest proportion of stress fractures was seen in basketball athletes(21.3%),followed by baseball(13.7%),track and field(11.4%),rowing(9.5%),soccer(8.4%),aerobics(5.3%),and classical ballet(4.9%).The most common sites of stress fractures in these patients were the tibia(44.1%),followed by the rib(14.1%),metatarsal bone(12.9%),ulnar olecranon(8.7%)and pelvis(8.4%).The sites of the stress fractures varied from sport to sport.The ulnar olecranon was the most common stress fracture site in baseball players,and the rib was the most common in rowers.Basketball and classical ballet athletes predominantly sustained stress fractures of the tibia and metatarsal bone.Track and field and soccer athletes predominantly sustained stress fractures of the tibia and pubic bone.Aerobics athletes predominantly sustained stress fractures of the tibia.Middle and long distance female runners who sustained multiple stress fractures had the female athlete triad.CONCLUSION:The results of this analysis showed that stress fractures were seen in high-level young athletes,with similar proportions for males and females,and that particular sports were associated with specific sites for stress fractures.Middle and long distance female runners who suffered from multiple stress fractures had the female athlete triad.
文摘Stress fracture（SF）in military recruits in China was investigated using<sup>99m</sup>Tc-MDP bone scintigraphy in a randomized sample of 432 injured who wereclinically screened from 1060 recruits during basic training.The relationship between SFand training intensity was discussed.It was shown that the total incidence was 32.5%.There were two peaks during 9 training-weeks:one was in the 2nd week,and the otherin the 7th.Infantry soldiers had a more intensive training and,therefore a higher inci-dence than in artillery and service troops.Although SF was found in most ofweight-bearing bones,tibia was most commonly fractured（67%）.The findings suggestthat SF is a major training-related injury in military recruits and improperly strengthenedtraining can increase the incidence.
文摘Stress fractures of the tibia are commonly seen in young athletes or military recruits due to repetitive micro trauma. These are rare in elderly patients. Osteoarthritis knee with varus deformity leading to stress fracture is rare but has been reported in literature. Stress fracture in osteoarthritis more commonly occurs in upper third tibia. We report a patient who had stress fractures of distal tibial shaft secondary to advanced osteoarthritis of knee with varus deformity.
文摘Purpose: The objective of this research is to investigate whether bioimpedance is useful to indicate a shank’s physical condition during training. Methods: Bioimpedance was applied to monitor the condition of 8 rabbits’ shanks in 3 weeks, during which the rabbits were trained for regular excessive jump daily. Nine tibias in 16 developed stress fracture after the 3-week training. Results: According to the analysis of the bioimpedance data, we found that changing pattern of bioimpedance properties of shanks which were more liable to suffer from SF was different from that of shanks which were not during training. Conclusions: This suggests that bioimpedance may be used to monitor the physical condition of a limb, imply its liability to develop stress fracture, and indicate stress fracture during training.
文摘Background: Stress fractures are fatigue-induced, very small cracks in the bone caused by repetitive application of force and most often seen in the weight-bearing bones of the lower extremities of athletes or military recruits. Case Report: A 47-year-old postmenopausal and heavy smoker woman complained of localized sensitivity on the distal-anterior and medial surfaces of both tibiae, which had been ongoing for 1 month. She moved to a flat at 5th-floor without an elevator a year ago. Bilateral stress fractures were diagnosed by radiographs and confirmed by Magnetic Resonance Imaging (MRI). She was suggested to restrict activities and to use crutches until the symptoms subsided. Bilateral ankle joint pneumatic brace with full heel support was applied. The patient was followed one year after diagnosis. At the 2-month follow-up examination, the patient was pain free and planning to move to a new house. Conclusions: Several risk factors have been defined in the pathogenesis of stress fracture. In the present case, the acute phase had passed and diagnosis could be made from the direct radiographs. Although extremely rarely seen, tibia distal stress fracture should be kept in mind in the differential diagnosis of patients with the relevant risk factors who present with tibia distal localized pain.
基金This work was supported by the Joint Fund of NSFC for Enterprise Innovation and Development(Grant No.U19B6003-02-06)the National Natural Science Foundation of China(Grant No.51974331)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20200525)The authors would like to sincerely acknowledge these funding programs for their financial support.Particularly,the support provided by the China Scholarship Council(CSC)during a visit of Ke Sun(File No.202106440065)to the University of Alberta is also sincerely acknowledged.
文摘To gain insight into the flow mechanisms and stress sensitivity for fractured-vuggy reservoirs,several core models with different structural characteristics were designed and fabricated to investigate the impact of effective stress on permeability for carbonate fractured-vuggy rocks(CFVR).It shows that the permeability performance curves under different pore and confining pressures(i.e.altered stress conditions)for the fractured core models and the vuggy core models have similar change patterns.The ranges of permeability variation are significantly wider at high pore pressures,indicating that permeability reduction is the most significant during the early stage of development for fractured-vuggy reservoirs.Since each obtained effective stress coefficient for permeability(ESCP)varies with the changes in confining pressure and pore pressure,the effective stresses for permeability of four representative CFVR show obvious nonlinear characteristics,and the variation ranges of ESCP are all between 0 and 1.Meanwhile,a comprehensive ESCP mathematical model considering triple media,including matrix pores,fractures,and dissolved vugs,was proposed.It is proved theoretically that the ESCP of CFVR generally varies between 0 and 1.Additionally,the regression results showed that the power model ranked highest among the four empirical models mainly applied in stress sensitivity characterization,followed by the logarithmic model,exponential model,and binomial model.The concept of“permeability decline rate”was introduced to better evaluate the stress sensitivity performance for CFVR,in which the one-fracture rock is the strongest,followed by the fracture-vug rock and two-horizontalfracture rock;the through-hole rock is the weakest.In general,this study provides a theoretical basis to guide the design of development and adjustment programs for carbonate fractured-vuggy reservoirs.
基金the financial backing provided by the Universidad Industrial de Santander through project 2534 “Estudio Integral del Agua en la Mesa de Los Santos”。
文摘This work applies stress tensors inversions and quantification of fracture patterns along the Mesa de Los Santos, in the Eastern Cordillera of Colombia, to better understand the potential fluid flow. It thus contributes to the conceptual hydrogeological model. The area was subdivided into three blocks, separated by the NW Potreros and the Los Santos faults, having minor inner faults of different orientations. This separation facilitates the analysis of the fractures measured in the field, which in general show high dip angles and a conjugate geometry in the northern block, tension fractures(Mode I) in the central block, and a random distribution in the southwestern block. WinTensor treatment of slickensides yielded a maximum horizontal stress(SHmax) of 111o, which coincides with the WNW-ESE tensor observed from the conjugate and tension joints. We then used Frac Pa Q to generate interpolation maps of fracture intensity and density. The maps show the highest values in the central block and the lowest in the northern block,where the precipitation is higher, causing intensive rock weathering and homogenization of the fracture planes. Although the highest values of connectivity by line are found to the south of the mesa, we suggest the possibility of greater flow from the recharge zone(NE) along bedding planes and open NW-SE fractures.
基金This work was supported by the Guangdong Basic and Applied Basic Research Foundation(Grant No.2021A1515110304)the Na-tional Natural Science Foundation of China(Grant Nos.42077246 and 52278412).
文摘Grouting is a widely used approach to reinforce broken surrounding rock mass during the construction of underground tunnels in fault fracture zones,and its reinforcement effectiveness is highly affected by geostress.In this study,a numerical manifold method(NMM)based simulator has been developed to examine the impact of geostress conditions on grouting reinforcement during tunnel excavation.To develop this simulator,a detection technique for identifying slurry migration channels and an improved fluid-solid coupling(FeS)framework,which considers the influence of fracture properties and geostress states,is developed and incorporated into a zero-thickness cohesive element(ZE)based NMM(Co-NMM)for simulating tunnel excavation.Additionally,to simulate coagulation of injected slurry,a bonding repair algorithm is further proposed based on the ZE model.To verify the accuracy of the proposed simulator,a series of simulations about slurry migration in single fractures and fracture networks are numerically reproduced,and the results align well with analytical and laboratory test results.Furthermore,these numerical results show that neglecting the influence of geostress condition can lead to a serious over-estimation of slurry migration range and reinforcement effectiveness.After validations,a series of simulations about tunnel grouting reinforcement and tunnel excavation in fault fracture zones with varying fracture densities under different geostress conditions are conducted.Based on these simula-tions,the influence of geostress conditions and the optimization of grouting schemes are discussed.
基金supported by the National Natural Science Foundation of China(Grant No.41574088)the Key Program of Chinese Central Government for Basic Scientific Research Operations in Commonwealth Research Institutes(Grant No.ZDJ2019-16)。
文摘Tectonic stress fields are the key drivers of tectonic events and the evolution of regional structures.The tectonic stress field evolution of the Tanlu fault zone in Shandong Province,located in the east of the North China Craton(NCC),may have preserved records of the NCC’s tectonic history.Borehole television survey and hydraulic fracturing were conducted to analyze the paleo and present tectonic stress fields.Three groups of tensile fractures were identified via borehole television,their azimuths being NNW-SSE,NW-SE and NE-SW,representing multiple stages of tectonic events.Hydraulic fracturing data indicates that the study region is experiencing NEE-SWW-oriented compression and nearly-N-Soriented extension,in accordance with strike-slip and compression.Since the Cretaceous,the orientation of the extensional stress has evolved counterclockwise and sequentially from nearly-NW-SE-oriented to NE-SW-oriented and even nearly N-S-oriented,the stress state having transitioned from strike-slip-extension to strike-slip-compression,in association with the rotating and oblique subduction of the Pacific Plate beneath the NCC,with the participation of the Indian Plate.
基金support from the National Natural Science Foundation of China(Grant Nos.52174092 and 52104125)the Fundamental Research Funds for the Central Universities,China(Grant No.2022YCPY0202)is gratefully acknowledged.
文摘Through high-precision engraving,self-affine sandstone joint surfaces with various joint roughness coefficients(JRC=3.21e12.16)were replicated and the shear sliding tests under unloading normal stress were conducted regarding various initial normal stresses(1e7 MPa)and numbers of shearing cycles(1 e5).The peak shear stress of fractures decreased with shear cycles due to progressively smooth surface morphologies,while increased with both JRC and initial normal stress and could be verified using the nonlinear Barton-Bandis failure criterion.The joint friction angle of fractures exponentially increased by 62.22%e64.87%with JRC while decreased by 22.1%e24.85%with shearing cycles.After unloading normal stress,the sliding initiation time of fractures increased with both JRC and initial normal stress due to more tortuous fracture morphologies and enhanced shearing resistance capacity.The surface resistance index(SRI)of fractures decreased by 4.35%e32.02%with increasing shearing cycles due to a more significant reduction of sliding initiation shear stress than that for sliding initiation normal stress,but increased by a factor of 0.41e1.64 with JRC.After sliding initiation,the shear displacement of fractures showed an increase in power function.By defining a sliding rate threshold of 5105 m/s,transition from“quasi-static”to“dynamic”sliding of fractures was identified,and the increase of sliding acceleration steepened with JRC while slowed down with shearing cycles.The normal displacement experienced a slight increase before shear sliding due to deformation recovery as the unloading stress was unloaded,and then enhanced shear dilation after sliding initiation due to climbing effects of surface asperities.Dilation was positively related to the shear sliding velocity of fractures.Wear characteristics of the fracture surfaces after shearing failure were evaluated using binary calculation,indicating an increasing shear area ratio by 45.24%e91.02%with normal stress.
基金supported by Fundamental Research Funds for the Central Universities(22dfx06)Natural Science Foundation of Guangdong Province-Joint Program for Ofshore Wind Power(2022A1515240009).
文摘The frictional rupture mechanisms of rock discontinuities considering the dynamic load disturbance still remain unclear.This paper investigates the transitional behaviors of slip events happened on a planar granite fracture under cyclic normal stress with diferent oscillation amplitudes.The experimental results show that the activations of fast slips always correlate with unloading of normal stress.Besides,the intensive normal stress oscillation can weaken the shear strength which is recoverable when the normal stress return to constant.The rupture patterns are quantifed by stress drop,slip length and slip velocity.With the efect of small oscillation amplitudes,the slip events show chaotic shapes,compared to the regular and predictable style under constant normal stress.When the amplitude is large enough,the big and small slip events emerge alternately,showing a compound slip style.Large amplitude of the cyclic normal stress also widens the interval diferences of the slip events.This work provides experimental supports for a convincible link between the dynamic stress disturbance and the slip behavior of rock fractures.
