Foot Arch Research Articles

A Novel Model Based on CNN-ViT Fusion and Ensemble Learning for the Automatic Detection of Pes Planus.

Background: Pes planus, commonly known as flatfoot, is a condition in which the medial arch of the foot is abnormally low or absent, leading to the inner part of the foot having less curvature than normal. Symptom recognition and errors in diagnosis are problems encountered in daily practice. Therefore, it is important to improve how a diagnosis is made. With the availability of large datasets, deep neural networks have shown promising capabilities in recognizing foot structures and accurately identifying pes planus. Methods: In this study, we developed a novel fusion model by combining the Vgg16 convolutional neural network (CNN) model with the vision transformer ViT-B/16 to enhance the detection of pes planus. This fusion model leverages the strengths of both the CNN and ViT architectures, resulting in improved performance compared to that in reports in the literature. Additionally, ensemble learning techniques were employed to ensure the robustness of the model. Results: Through a 10-fold cross-validation, the model demonstrated high sensitivity, specificity, and F1 score values of 97.4%, 96.4%, and 96.8%, respectively. These results highlight the effectiveness of the proposed model in quickly and accurately diagnosing pes planus, making it suitable for deployment in clinics or healthcare centers. Conclusions: By facilitating early diagnosis, the model can contribute to the better management of treatment processes, ultimately leading to an improved quality of life for patients.

Comparison of anthropometric measurements related to the medial longitudinal arch of feet between non-dancers and Bharatnatyam dancers- an observational study

BackgroundBharatnatyam is an Indian classical dance form that involves rhythmic barefoot tapping at varying speeds. The intense impact forces generated during this dance can result in biochemical alterations in the feet, potentially causing injuries to ligaments, tendons, and fascia. This can lead to changes in the structure of the foot over time. Therefore, this study was conducted to compare anthropometric measurements related to the medial longitudinal arch of the foot in non-dancer, mid-stage, and last stage Bharatnatyam dancers. MethodsThe study was conducted on 192 participants. They were divided into three groups: 1) Non dancers 2) Mid-stage Bharatnatyam dancers, and 3) Last-stage Bharatnatyam dancers. Each group consisted of 64 participants each. Various measurements were taken on both the right and left foot using a wooden platform, foot image, and footprint. Later the results were analyzed statistically. ResultsOn comparing the parameters in non-dancers and mid-stage Bharatnatyam dancers it was found that all the parameters were found to be significant except right and left arch index. On comparing the parameters of mid-stage and last-stage Bharatnatyam dancers, it was found that none of the parameters showed significant value. On comparing the non-dancers and last-stage Bharatnatyam dancers, it was found that except right and left arch index all the parameters were found to be significant. ConclusionFrom the results of the present study, it can be concluded that there were significant changes in the arches of the foot between the non-dancers and mid-stage and last-stage Bharatnatyam dancers.

Characterization of stability and support force of loess caves in northwest China

Numerous manually excavated loess caves are present within a cultural relic protection zone in the northwestern region of China. The collapse of these caves frequently leads to the cracking, tilting, and even collapse of ancient buildings above, posing a severe threat to the safety of cultural architectural relics. Investigating the stability and characteristics of deformation and failure in loess caves is essential for effectively reinforcing and protecting cultural relics. A two-dimensional model of a loess underground cavern was developed using OptumG2. The stability and modes of deformation and failure in the underground cavern were analyzed through the augmentation of soil gravity and the strength reduction method. This analysis determined the cavern's safety factor, force, deformation and damage mode, and the plastic zone's progression. Numerical simulations analyzed the force characteristics of the support structure under different stress release ratios. The findings revealed that, with the implementation of an anchor rod concrete lining support scheme, the most probable failure mode is a shear failure, initiating at the arch foot. The ground's stress release rate does not influence the safety factor of the cavern but rather the material, design, and strength of the support structure. However, the magnitude of the internal forces acting on the supporting structure by the soil in the cavern is related to the degree of ground stress release. When applied during significant stress release, support structures may experience reduced internal forces, albeit with more substantial stratum displacement; opting for an appropriate stress release when applying support structures is crucial for achieving optimal stratum displacement and lining internal forces.

Free Fibular Osteocutaneous Flap Combined With Simultaneous Tendon Reconstruction for Midfoot Restoration After Myoepithelial Carcinoma Resection.

Myoepithelial carcinomas of soft tissue are rare, and most are malignant. The optimal treatment is surgical excision. The arches of the foot are a composite structure responsible for weight bearing and pressure distribution, so it is a vast challenge in reconstruction. We report a case of reconstruction of the midfoot with a free fibular bone flap and tendon graft. We review the literature to compare various options in foot reconstructions and sort out the outcomes of different bone flaps. The free fibula osteocutaneous flap is the superior choice for midfoot reconstruction owing to its sufficient length, strength, flexible skin paddles, easy-to-withstand osteotomy, and simultaneous tendon graft harvesting.

Predicting Blast-Induced Damage and Dynamic Response of Drill-and-Blast Tunnel Using Three-Dimensional Finite Element Analysis

The significance of predicting the dynamic response and damage of an existing concrete tunnel during underground blasting has increased owing to the close proximity between the newly built and existing tunnels. Peak particle velocity (PPV) is a commonly used criterion in the assessment of blast-induced structural damage. However, such structural damage is also associated with the frequency content of the blast wave. Nevertheless, the recommended threshold PPVs, which are based on empirical criteria, predict conservative estimations. Using stringent and regulated blasting methods often results in project delays and escalates the total project expenditure. In this paper, a three-dimensional finite element model of an underground tunnel has been developed in LS-DYNA to analyze damage to the concrete tunnels under blast loading. A suite of analyses was performed to examine the potential damage induced in the underground tunnel. A lower frequency load was found to have a greater potential for producing damage compared with a high frequency blast load. The results showed that the location of the cracking within the tunnel, such as the arch foot or tunnel wall, was also influenced by the frequency of the blast wave. The maximum allowable PPV for the concrete tunnel was determined for a range of frequencies based on predicted free field PPV and additional factors of safety of 1.2 and 1.5 were established, depending on the safety needs and importance of the tunnel construction. Thus, our findings provide useful information for improving the evaluation of tunnel damage and guaranteeing the safety of underground tunnels.

High Medial Longitudinal Arch of the Foot and Latent Trigger Points in Lower Limb Muscles.

Background: The objective was to evaluate the prevalence of latent trigger points (LTrPs) in lower limb muscles in participants with a high medial longitudinal arch (MLA) of the foot compared to controls. Methods: Participants with a navicular drop test of 4-9 mm were included in the control group; the high MLA group included navicular drop test values of ≤4 mm. The presence of LTrPs was assessed by palpation techniques. The muscles evaluated were medial gastrocnemius (LTrP1), lateral gastrocnemius (LTrP2), soleus (LTrP1), peroneus longus, peroneus brevis, tibialis anterior, extensor digitorum longus, flexor digitorum longus, rectus femoris, vastus medialis (LTrP1 and LTrP2), and the vastus lateralis of the quadriceps (LTrP1 and LTrP2). Results: Thirty-seven participants with high MLA and thirty-seven controls were included in the study. Twenty-nine (78.4%) participants in the high MLA group had at least 1 LTrP, compared to twenty-three (62.2%) in the control group. No statistical difference (p < 0.05) was found in the total number of LTrPs between groups (4.46 ± 3.78 vs. 3.24 ± 3.85). There were more participants (p < 0.05) with LTrPs in the tibialis anterior, extensor digitorum longus, and vastus lateralis (LTrP1 and LTrP2) in the high MLA group than in the control group. Conclusion: Although no differences were found in the number of total LTrPs between groups, the prevalence was statistically significantly higher in the tibialis anterior, extensor digitorum longus, and vastus lateralis of the participants with high MLA of the foot.

Assessment of correctness of foot shape and correlations with anthropometric indicators and the centre of body gravity in preschool children

Introduction and objective: Preschool and early school age plays an important role in shaping the foot and posture in children. The aims of the study were to assess the correctness of foot shape in preschool children and to determine possible correlations with age, gender, waist-to-height ratio (WHtR) and body mass index (BMI), and the centre of body gravity. Materials and methods: A study of feet and anthropometric parameters was carried out in children aged 4–6 years. Foot examination was performed using a podoscope and a strain gauge platform, while body weight was assessed using a Tanita device. Body weight, height, Clarke’s angle, centre of gravity, and WHtR were analysed. Results: There were no statistically significant differences in the value of the Clarke’s angle between the left and right feet in both girls and boys, regardless of the age group. The BMI did not correlate statistically with the results of the Clarke’s angle measurements, both for all the subjects and taking into account their age. The BMI value was statistically significantly correlated with the centre of body gravity due to the correct WHtR. Conclusions: The study confirmed that the longitudinal arch of the foot shows no clear sexual dimorphism. The BMI and Clarke’s angle were not dependent on each other in the study group. The study showed no changes in the centre of body gravity in relation to the children’s body shape.

Effect of orthopedic insoles on lower limb motion kinematics and kinetics in adults with flat foot: a systematic review.

Flatfoot is characterized by the collapse of the medial longitudinal arch, eversion of the rearfoot and abduction of the loaded forefoot. Orthopedic insoles are the frequently recommended treatment to support the arch of the foot, adjust the structure of the foot, reduce pain, improve stability and new techniques have been applied to the design of orthopedic insoles in recent years. However, the effectiveness of orthopedic insoles in different motions is still debated from the perspective of biomechanics. Therefore, this study aimed to explore the impact of orthopedic insoles on the kinematics and kinetics of lower limb motion, and to verify effectiveness and propose possible future research directions. We conducted a literature search across three databases employing Boolean operations and filtered results based on eligibility criteria. A total of 671 relevant literature were searched in this review, and 19 literature meeting the requirements were finally included. The results showed that: 1) orthopedic insoles were effective when patients walk, run and jump from the perspective of biomechanics; 2) orthopedic insoles had different result on the change of ankle sagittal angle, moment and peak pressure in the metatarsal region; 3) Whether the effect of insoles, which uses new techniques such as different 3D printed technologies and adds various accessories, can be further improved remains to be further studied; 4) Follow-up studies can pay more attention to the differences between diverse populations, increase the breadth of running and jumping and other movements research and long-term intervention.

Effect of forefoot transverse arch stiffness on foot biomechanical response--based on finite element method.

The plantar vault, comprising the transverse and longitudinal arches of the human foot, is essential for impact absorption, elastic energy storage, and propulsion. Recent research underscores the importance of the transverse arch, contributing over 40% to midfoot stiffness. This study aimed to quantify biomechanical responses in the ankle-foot complex by varying the stiffness of the deep metatarsal transverse ligament (DTML). Using CT image reconstruction, we constructed a complex three-dimensional finite element model of the foot and ankle joint complex, accounting for geometric complexity and nonlinear characteristics. The focus of our study was to evaluate the effect of different forefoot transverse arch stiffness, that is, different Young's modulus values of DTML (from 135MPa to 405MPa), on different biomechanical aspects of the foot and ankle complex. Notably, we analyzed their effects on plantar pressure distribution, metatarsal stress patterns, navicular subsidence, and plantar fascial strain. Increasing the stiffness of the DTML has significant effects on foot biomechanics. Specifically, higher DTML stiffness leads to elevate von Mises stress in the 1st, 2nd, and 3rd metatarsals, while concurrently reducing plantar pressure by 14.2% when the Young's modulus is doubled. This stiffening also impedes navicular bone subsidence and foot lengthening. Notably, a 100% increase in the Young's modulus of DTML results in a 54.1% decrease in scaphoid subsidence and a 2.5% decrease in foot lengthening, which collectively contribute to a 33.1% enhancement in foot longitudinal stiffness. Additionally, doubling the Young's modulus of DTML can reduce the strain stretch of the plantar fascia by 38.5%. Preserving DTML integrity sustains the transverse arch, enhancing foot longitudinal stiffness and elastic responsiveness. These findings have implications for treating arch dysfunction and provide insights for shoe developers seeking to enhance propulsion.

Analysis and Experimental Study on the Stability of Large-Span Caverns’ Surrounding Rock Based on the Progressive Collapse Mechanism

The collapse failure of rock surrounding caverns involves a progressive collapse process. Based on the nonlinear Hoek–Brown failure criterion and the upper limit theorem, the whole process curve of the progressive collapse of the surrounding rock of a large-span cavern is outlined in this paper. The progressive collapse process of the surrounding rock of the large-span cavern is experimentally studied using an independently developed visualized large-span-cavern geomechanical model test device with variable angles. The results show that, through theoretical calculation and model tests, the surrounding rock at the top of the large-span cavern undergoes three collapses. Under the condition of rock mass and the shape of the cavern, the larger the span of the cavern, the more times the surrounding rock collapses; with the increase in surrounding rock pressure, the first collapse occurs in the middle part of the arch roof. When the overlying load reaches a certain level, the arch foot becomes the weakest part, and the rock undergoes shear failure along the arch foot, gradually extending upwards, accompanied by multiple collapses, forming a progressive collapse process. The theoretical calculation results of this paper are basically consistent with the scope of the model test, and the research results can provide a basis for the construction and support design of the large-span cavern.

Experimental research on the mechanical properties of alkali-resistant glass fiber concrete acting as tunnel seismic isolation layer under periodic cyclic dynamic loading

The installation of seismic isolation layer is an effective measure to ensure the safe operation of underground projects such as tunnels during extreme seismic activities. Material parameters, mechanical properties, and design patterns of the seismic isolation layer are key research topics in exploring effective reduction of seismic response. This study mainly focused on the dynamic performance of the seismic isolation layer in tunnels. A series of drop hammer impact tests and laboratory shaking table tests were performed to reveal the seismic features of the seismic isolation layer under periodic external loading. The test results indicated that all cracks in the specimen initiated from the center and dispersed outwards under the cycle impact of the drop hammer. The incorporation of alkali-resistant glass fibers in concrete (AR-GFRC) effectively provided "reinforcement " and "crack resistance" under cyclic loading of the drop hammer, and the minimum number and width of cracks were observed at a 0.75 % HD fiber content and a 0.5 % HP fiber content. In the x- and y-axis directions, the seismic isolation layer effectively mitigated peak acceleration, strain response, and displacement at the tunnel vault and invert, but significant nonlinearity was identified. When the thickness of seismic isolation layer was 10 mm, the peak seismic response of the lining were minimum at a 0.75 % HD fiber content and a 0.5 % HP fiber content. However, the thickness of the lining was not directly related to the destruction of the lining. The tunnel mainly experienced shear deformation in the x-axis direction, with significant deformations from the left arch waist to the right arch foot (45°-225°), resulting in transverse cracking. The tunnel primarily underwent tensile and compressive deformation in the y-axis direction, with significant deformations occurring in the inverted vault (0°-180°), resulting in tension and circumferential cracks. This research can provide valuable data support and reference for the design and construction of underground projects such as tunnels.

Distribution of Foot Arch Type and Associated Symptoms in Medical Students at Faculty of Medicine, Thammasat University

Objective: To determine the distribution of foot arch type, associated symptoms, and factors associated with moderate to severe pain Materials and Methods: The cross-sectional study was collected data from 5th year medical students, Faculty of Medicine, Thammasat University in academic year 2020. The distribution of foot arch type used the footprint and classified by Harris imprint index (HII), Chippaux-Smirak index (CSI), Staheli index (SI). The associated symptoms were collected into pain and tightness. Pain score was rated by the volunteer using numeric rating scale (NRS) at each foot/leg separately. Results: A total of ninety-eight medical students (196 feet) were recruited and analyzed. The distribution of foot arch type by HII, CSI and SI were 1) bilateral normal arched feet: 42.9%, 67.3%, 54.1% 2) bilateral pes planus: 8.2%, 12.2%, 21.4% 3) bilateral pes cavus: 25.5%, 6.1%, 5.1% 4) unilateral pes planus: 2%, 9.2%,15.3% 5) unilateral pes cavus: 21.4%, 5.1%, 4.1%, respectively. The most commonly associated symptom of pes planus was midfoot pain (17%) while pes cavus and normal arched foot were hindfoot pain (22.4% and 17.3%). The factor associated with moderate to severe pain was BMI ≥ 23 kg/m2 (OR = 3.23, 95%CI 1.63 - 6.41, p-value = 0.001). Conclusion: Bilateral normal arched feet were mostly found. Midfoot pain in pes planus and hindfoot pain in pes cavus and normal arched foot were the greatest symptoms. BMI was a risk factor.

Planovalgus Foot Deformity in Patients Undergoing Total Hip Arthroplasty Is Associated With Increased Risk of Falls, Implant-Related Complications, and Revisions: A Case-Control Analysis

BackgroundPes planus occurs due to the loss of the longitudinal arch of the foot, resulting in altered gait mechanics. This may lead to increased complications following total hip arthroplasty (THA). Thus, the aim of this study was to assess the effects that pes planus has on rates of falls, implant complications, fall-related injuries, and times to revision among THA patients. MethodsA retrospective review of a private insurance claims database was conducted from 2010 to 2021. Patients who had a diagnosis of congenital or acquired pes planus and cases of THA were identified. Patients undergoing THA with a diagnosis of pes planus were matched to control patients 1:5 based on age, sex, and comorbidity profiles. Logistic regression was utilized to assess for differences in complication rates. ResultsA total of 3,622 pes planus patients were matched to 18,094 control patients. The pes planus group had significantly higher rates of falls than the control group (6.93 versus 2.97%, OR [odds ratio]: 2.43; CI [confidence interval]: 2.09 to 2.84; P < .001). Pes planus patients also had significantly greater odds of dislocation (OR: 1.89; CI: 1.58 to 2.27; P < .001), mechanical loosening (OR: 2.43; CI: 2.09 to 2.84; P = .019), and periprosthetic fracture (OR: 2.43; CI: 2.09 to 2.84; P < .001). The pes planus group had significantly greater rates of proximal humerus fractures (P = .008), but no difference was seen in distal radius fractures (P = .102). The time to revision was significantly shorter in the pes planus group (190 versus 554 days, P < .001). ConclusionsPes planus in patients undergoing THA is associated with increased risk of complications and faster time to revision. These findings may allow orthopaedic surgeons to identify those patients at risk and allow for more educated patient counseling and operative planning.

Internal Brace Fixation Technique for Lisfranc Injury: A Retrospective Study.

BACKGROUND The Lisfranc ligament is crucial for maintaining the transverse and longitudinal arch of the foot. Owing to the disruption between the medial cuneiform bone and the base of the second metatarsal bone, the currently preferred fixation method remains controversial. Our fixation technique involves screwing one anchor to the medial and intermediate cuneiform bones and using the anchor to carry the ligament to bind the Lisfranc joint and first and second metatarsal joints altogether for elastic fixation. This study evaluated the clinical and functional outcomes of InternalBrace fixation for Lisfranc injury. MATERIAL AND METHODS This retrospective study included 58 patients who underwent InternalBrace fixation for Lisfranc injury between January 2019 and September 2022 by an experienced surgeon. One-way analysis of variance or t test was used. Preoperative classification was performed according to the Myerson classification with imaging data. Postoperative follow-up was performed based on intraoperative blood loss, fracture healing time, visual analog scale (VAS) score, the American Orthopedic Foot and Ankle Society (AOFAS) score, Tegner score, and complications. RESULTS Surgery was completed in all patients, and follow-up was performed. The patients' ages ranged from 19 to 62 years (average: 34.6±9.4 years). The postoperative follow-up time was 12-24 months (average: 16.9±3.0 months). The average time for fracture healing was 12.8±3.0 (10-24) weeks. The VAS, AOFAS, and Tegner scores significantly improved postoperatively (from 5.33±1.0 (3-7) to 1.24±0.57 (0-2); 28.02±6.70 (18-51) to 91.59±4.76 (82-96); and 2.40±0.67 (1-4) to 6.53±0.54 (6-7), respectively), which was statistically significant (P<0.01), and the good rate of AOFAS was 91.4%. The postoperative complications were traumatic arthritis, incision infection, and temporary dorsal foot numbness, which gradually recovered. No other rejection reactions or Lisfranc fracture/dislocations recurrence occurred during the follow-up period. CONCLUSIONS InternalBrace fixation for Lisfranc injury is beneficial for restoring Lisfranc joint stability and function and allows for early and more aggressive rehabilitation for patients, with fewer surgical complications.

Time-frequency analysis of nonlinear structures under nonstationary excitation by directly solving structural dynamic equation through absolute displacement

The time-frequency evolution of seismic ground motion energy under strong earthquakes, which can be described by the evolutionary power spectral density (EPSD) matrix, will amplify the most unfavorable responses of members in nonlinear structural systems. However, the existing general finite element software fails to reduce the dimension of the EPSD matrix and then decouple time from frequency in frequency domain analysis. This failure greatly limits the simulation and calculation of multi-dimensional nonlinear structures with multiple degrees of freedom by the stochastic vibration theory. In this study, the pseudo excitation method (PEM), which can direct solve structural dynamic equations using absolute displacement, is used to derive the self-spectral and cross-spectral densities of seismic ground motions in one-dimensional and multi-dimensional cases. In MATLAB, the EPSD matrix is transformed into a four-dimensional uniform modulation excitation matrix independent of the time variable. Nonlinear iteration is conducted and the precise integration method (PIM) is employed through a transient analysis module. Furthermore, a simple one-dimensional example is presented to verify the correctness of the proposed algorithm herein. Finally, as an example, we select important parameters of the coherence model at different supports of a half-through three-span concrete-filled steel tubular (CFST) tied-arch bridge in view of real engineering conditions, and calculate the time-varying power spectrum and variance of the responses of arch ribs, arch feet and the bridge deck system. The results show that the theoretical derivation and the algorithm constructed in this paper can simulate the time-delay effect of the nonlinear structural system. This proves the feasibility of general finite element software in solving and analyzing random responses to multi-dimensional and multi-support non-stationary excitation of nonlinear structures.

Effect of 8 Weeks Foot Reflexology Massage on Balance, Foot Arc, and Pain in Girls Aged 14 to 18 Years With Flat Foot

Background and Aims A flat foot is associated with complications, such as pain, fatigue, and balance decline. The present study investigated the effect of 8 weeks of foot reflexology massage on balance, foot arch, and pain in girls aged 14 to 18 years with flat feet. Methods In this quasi-experimental research, 30 girls with flat feet (mean age: 15.1±1.1 years, mean height: 156.1±2.2, and mean weight: 47.3±2.2 kg) voluntarily and conveniently were selected and randomly divided into two equal experimental and control groups. The massage program consisted of eight weeks (three sessions per week) of foot reflexology massage on the entire sole of both feet, in which two to three relaxation techniques were used in each session, according to the subject’s condition, for six minutes. Twenty-four hours before and 24 hours after the end of the massage therapy protocol, foot arch, dynamic balance, static balance, and pain intensity were assessed using the index of navicular drop test, star excursion balance test, balance error scoring system, and visual analog scale, respectively. Data analysis was done with an analysis of covariance at a significance level of 0.05. Results The results showed that reflexology massage significantly affects static balance (P=0.0001) and pain intensity (P=0.0001) of young girls with flat feet. However, no significant effect was observed on the arch of the foot (P=0.38) and the dynamic balance (P=0.36). Conclusion Reflexology massage improves the proprioceptive information of the skin. Accordingly, it has improved static balance and reduced the pain intensity of girls with flat feet.

Model test on the collapse mechanism of subway tunnels in the soil-sand-rock composite strata

Collapse is a typical type of accident during subway tunnel construction. Complex geological conditions, particularly soil-sand-rock composite strata, significantly contribute to strata instability, posing a serious threat to tunnel safety. Indeed, the progressive failure leading to the collapse of subway tunnels in these composite strata exhibits distinct characteristics from that of single strata and warrants further research. In this paper, model tests were conducted to investigate the collapse process of the soil-sand-rock composite strata under different overlayer rock thicknesses. Soil pressure sensors monitored the mechanical response of the strata, while a two-dimensional full-field deformation measurement and analysis system (XTDIC-2D) provided displacement and strain fields. Additionally, an industrial camera captured video footage of the failure process. The results demonstrated that the collapse characteristics of the soil-sand-rock composite strata were significantly impacted by overlayer rock layer thickness. As the thickness of the rock layer decreased, the collapse easily expanded to the sand layer under a slight loading. The sand layer exhibited distinct behaviors with high compressibility, thixotropy, and flowability during the collapse process. The high compressibility of the sand layer before collapse resulted in strain concentration within it, thereby resisting the deformation of the rock strata. After the collapse of the rock strata, the thixotropic and flowability properties caused the collapse surface to expand in a funnel shape towards both sides. A stabilized stratigraphic arch could not be formed due to the arch foot being located above the sand layer, which cannot provide stable support. Overall, the results of this research offer valuable guidance for the prevention and control of tunnel collapse in soil-sand-rock composite strata.

Critical Failure Characteristics of a Straight-Walled Arched Tunnel Constructed in Sandstone under Biaxial Loading

To characterize the failure of rock mass surrounding underground tunnels, biaxial compression tests were conducted on a real sandstone model with a straight-walled arched hole. The acoustic emission (AE) system and digital image correlation (DIC) optical inspection equipment were used to investigate the crack evolution process and failure precursors of the tunnel. A two-dimensional particle flow code (PFC2D) was used to conduct numerical simulations on the sample, so as to investigate the mesoscopic failure mechanism of rock mass. The results show that the failure of the single tunnel constructed in sandstone occurs mainly in the walls on both sides (between the spandrels and arch feet), showing slabbing failure characteristics and a certain abruptness. The crack initiation in sandstone in early stage is not obvious, and the crack propagation in rock mass is rapid when acoustic emissions are enhanced. The small increments in the AE count and amplitude and the continuous reduction in the b-value can be used as precursors for the failure of rock mass. When the height–span ratio is 0.8 and 1.0, the stress distribution around the chamber is more uniform, and when the height–span ratio is greater than 1.0, the stress is mainly concentrated in the vault and arch bottom. In the PFC simulations, tensile fractures firstly initiate in the middle of walls and at the arch feet, arcuate fracture concentration zones are then formed, in which shear fractures appear and a few particles spall from the surfaces. When approaching the ultimate bearing capacity, rock masses on both sides of the tunnel are fractured over large areas, and the slender coalesced fractured zone develops to the deep part of rock mass, causing failure of the sample.

Revisiting the inferior supports of Chopart joint complex.

The Chopart joint complex is a joint between the midfoot and hindfoot. The static and dynamic support system of the joint is critical for maintaining the medial longitudinal arch of the foot. Any dysfunction leads to progressive collapsing flatfoot deformity (PCFD). Often, the tibialis posterior is the primary cause; however, contrary views have also been expressed. The present investigation intends to explore the comprehensive anatomy of the support system of the Chopart joint complex to gain insight into the cause of PCFD. The study was conducted on 40 adult embalmed cadaveric lower limbs. Chopart joint complexes were dissected, and the structures supporting the joint inferiorly were observed and noted. The articulating bones exhibit features like a cuboid shelf and navicular beak, which appear to offer inferior support to the joint. The expanse of the spring ligament complex is more medial than inferior, while the superomedial part is more extensive than the intermediate and inferoplantar parts. The spring ligament is reinforced by the tendons in the superomedial part (the main tendon of tibialis posterior), the inferomedial part (the plantar slip of tibialis posterior), and the master knot of Henry positioned just inferior to the gap between the inferomedial and inferoplantar bundles. This study highlights that the medial aspect of the talonavicular articulation has more extensive reinforcement in the form of superomedial part of spring ligament and tibialis posterior tendon. The findings are expected to prompt further research in weightbearing settings on the pathogenesis of flatfoot.

Pressure-relief joints of initial support structural system used in tunnels with high-stress surrounding rock.

To address the problem of large deformations in weak surrounding rock tunnels under high ground stress, which cause damage to initial support structures, this study proposes a novel type of circumferential pressure-relief joint based on the concept of relieving deformation pressure of the surrounding rock. Key parameters of the pressure-relief joint, such as initial bearing capacity peak, constant bearing capacity, and allowable pressure-relief displacement, were obtained through numerical simulations and laboratory experiments. A comparison was made between the mechanical characteristics of rigid joints and the new type of pressure-relief joint. The applicability of the pressure-relief joint was verified through field tests, monitoring the surrounding rock pressure, internal forces in the steel frames, and the convergence displacement of the support structure. The results show that: (1) In the elastic stage, the stiffness of the new pressure-relief joint is similar to that of rigid joints. In the plastic stage, rigid joints fail directly, whereas the pressure-relief joint can control deformation and effectively release the deformation pressure of the surrounding rock while providing a constant bearing capacity. (2) The right arch foot in the experiment had poor rock quality, leading to high stress in the steel frame and significant horizontal displacement. After the deformation of the pressure-relief joint, the stress in the surrounding rock and steel frame significantly reduced, and the rate of horizontal deformation of the support structure slowed down. (3) The vertical and horizontal final displacements of the pressure-relief joint in the experiment were 61mm and 15mm, respectively, which did not exceed the allowable deformation values. The components of the support structure remained intact, ensuring safety. However, this study has limitations: the design of the new pressure-relief joint only allows for a vertical deformation of 150mm and a horizontal deformation of 50mm, limiting the range of pressure-relief deformation.