Strength Criterion Research Articles

Investigation of anisotropic strength criteria for layered rock mass

Layered rock mass is a type of engineering rock mass with sound mechanical anisotropy, which is generally unfavorable to the stability of underground works. To investigate the strength anisotropy of layered rock, the Mohr-Coulomb and Hoek-Brown criteria are introduced to establish the two transverse isotropic strength criteria based on Jaeger's single weak plane theory and maximum axial strain theory, and parameter determination methods. Furthermore, the sensitivity of strength parameters (K1, K2, and K3) that are used to characterize the anisotropy strength of non-sliding failure involved in the strength criteria and confining pressure are investigated. The results demonstrate that strength parameters K1 and K2 affect the strength of layered rock samples at all bedding angles except for the bedding angle of 90° and the angle range that can cause the shear sliding failure along the bedding plane. The strength of samples at any bedding angle decreases with increasing K1, whereas the opposite is for K2. Except for bedding angles of 0° and 90° and the bedding angle range that can cause the shear sliding along the bedding plane, K3 has an impact on the strength of rock samples with other bedding angles that the specimens' strength increases with increase of K3. In addition, the strength of the rock sample increases as confining pressure rises. Furthermore, the uniaxial and triaxial tests of chlorite schist samples were carried out to verify and evaluate the strength criteria proposed in the paper. It shows that the predicted strength is in good agreement with the experimental results. To test the applicability of the strength criterion, the strength data of several types of rock in the literature are compared. Finally, a comparison is made between the fitting effects of the two strength criteria and other available criteria for layered rocks.

Hand Grip Strength Assessment Based on Sarcopenia Diagnostic Criteria Predicts Swallowing Function.

The purpose of this study is to clarify whether swallowing function can be inferred from grip strength. Based on the diagnostic criteria of sarcopenia, patients were divided into two groups according to grip strength, and it was analyzed whether there was a difference in the evaluation index for swallowing function between the two groups. Among the cases requesting evaluation of swallowing function from June 10, 2020 to October 28, 2020, 83 cases (mean age: 71.7years, 59 males and 24 females) who received assessment tests and swallowing endoscopy were included. According to the diagnostic criteria for grip strength in the Asian working group in Sarcopenia, less than 28 kgf and 18 kgf were defined as the weak group for men and women, respectively. Hyodo scores, repeated salivary swallowing tests (RSST), maximum vocalization time (MPT), and dysphagia severity classification (DSS) were compared between the two groups. Of the 83 patients, 29 and 54 were in the normal group and weak group, respectively. In all indicators, the normal group showed significantly better results than the weak group: Hyodo score (2.4 vs. 4.0, p < 0.01), RSST (4.1 times vs. 2.4 times, p < 0.01), MPT (12.1s vs. 5.9s, p < 0.001), DSS (4.5 vs. 5.9, p < 0.001), respectively. In multiple regression analysis with DSS as the dependent variable, grip strength was a significant independent variable of DSS even after adjusting for age, gender, and body mass index. Grip strength assessment based on sarcopenia criteria can be a useful tool for estimating swallowing function.

Технологические режимы раздачи и обжима при локальном нагреве

The processes of spread and reduction of a heated rough piece under visco-plasticity conditions are viewed. The ratio for force stress calculating in operations, damage to the material of the rough pieces is obtained. In the branches of special en-gineering, high-strength alloys based on titanium and aluminum are used. In the branches of special engineering, high-strength alloys based on titanium and aluminum are used. These alloys have mechanical properties anisotropy. Processing of these alloys is difficult. For this reason, the pressure treatment operation is performed with heating of the deformation zone. The material in the deformation zone exhibits viscous properties. Deformation hardening and softening (stress relaxa-tion) of the material take place simultaneously. Besides, the lower the deformation rate, the greater the softening. In this regard, a constitutive equation representing these processes is found. The factor of hardening and softening creates condi-tions for reducing the power mode of pressure treatment operations and increasing the degree of primary part forming. Stress relaxation calculation with the help of analytical dependencies is necessary at the stage of expansion and pressing development. The calculated ratios are recorded as a function of the speed of these operations. In this case, the specified deformation (the change in the degree of forming) is taken into account, adjusted depending on the speed and mechanical characteristics of the bearing alloy anisotropy. The calculated ratios are obtained under conditions of a flat voltage scheme, which corresponds to expansion and pressing. Stress equilibrium equation and yield condition of anisotropic material are used. The joint solutions of this equation and yield conditions determine values of the meridional and circumferential stress-es arising in the piece part material. The values of the stresses allow calculating the forces of operations. It is shown that the speed of expansion and pressing and mechanical properties anisotropy affect the damage to the material of the «green body». Dependences for the calculation of damage are obtained on the basis of energy and deformation strength criteria. These dependencies allow predicting the quality of products. It is also shown that anisotropy affects the technological modes of expansion and pressing. As the anisotropy coefficient increases, the stresses and forces of operations decrease. Calculations of stresses, forces and material damage in the process of expansion of anisotropic titanium alloy VT14 at 875 ℃ are made.

Progress in Lightweight Design Methods for Large-Size Panel Structures in Manned Pressurized Capsules

The pressurized capsule structure provides the pressure environment for astronauts or payloads in space, which is thus considered as the most crucial structural component for manned spacecraft. The manned deep space exploration mission (MDSEM) brings new challenges to the pressurized capsule structure: extremely low structural weight, long service life, reusability and adaptability to the harsh deep space environment. The conventional welded panel pressurized capsule structure (WPPCS) is not able to meet these new requirements. To address the above challenges, this paper comprehensively expounds why the current WPPCS cannot meet the requirements of MDSEMs based on the analysis of the vibration environment and structural characteristics of the pressurized capsule structure. Furthermore, a new type of integrated panel pressurized capsule structure (IPPCS) is proposed, showing the lightweight advantage compared with WPPCS. Finally, the technical details and research results of the strength criterion, design method, material upgrading and structural integrity manufacturing process of the IPPCS are fully introduced. The conclusions drawn in this paper will provide useful and meaningful references for the future development of large-size, lightweight pressurized capsule structures.

Strength properties of unidirectional laminated engineered bamboo boards under off-axis tension and compression tests

The strength properties of 30-mm unidirectional laminated engineered bamboo boards under off-axis tension and compression tests at seven different loading directions were studied in this research. The different failure modes, stress-displacement curves, and the corresponding full-field surface strain field measured through the digital image correlation (DIC) method were reported. The probability plots of off-axis strength values and the estimated characteristic strength values were given. Based on the original test data, the strength criteria based on Tsai and Wu theory was developed for the engineered bamboo panels studied herein. The values of strength tensors Fi and Fij were estimated based on the test results, which can be used to accurately model engineered bamboo products under complex stress conditions such as joint or notch regions. The characteristic off-axis strength values based on the Hankinson's formula given by the current standards are suggested to be further calibrated for design applications.

Substitution of self-reported measures for objectively assessed grip strength and slow walk in the Physical Frailty Phenotype: ramifications for validity

BackgroundFrailty assessment promises to identify older adults at risk for adverse consequences following stressors and target interventions to improve health outcomes. The Physical Frailty Phenotype (PFP) is a widely-studied, well validated assessment but incorporates performance-based slow walk and grip strength criteria that challenge its use in some clinical settings. Variants replacing performance-based elements with self-reported proxies have been proposed. Our study evaluated whether commonly available disability self-reports could be substituted for the performance-based criteria in the PFP while still identifying as “frail” the same subpopulations of individuals.MethodsParallel analyses were conducted in 3393 female and 2495 male Cardiovascular Health Study, Round 2 participants assessed in 1989–90. Candidate self-reported proxies for the phenotype’s “slowness” and “weakness” criteria were evaluated for comparable prevalence and agreement by mode of measurement. For best-performing candidates: Frailty status (3 + positive criteria out of 5) was compared for prevalence and agreement between the PFP and mostly self-reported versions. Personal characteristics were compared between those adjudicated as frail by (a) only a self-reported version; (b) only the PFP; (c) both, using bivariable analyses and multinomial logistic regression.ResultsSelf-reported difficulty walking ½ mile was selected as a proxy for the phenotype’s slowness criterion. Two self-reported weakness proxies were examined: difficulty transferring from a bed or chair or gripping with hands, and difficulty as just defined or in lifting a 10-pound bag. Prevalences matched to within 4% between self-reported and performance-based criteria in the whole sample, but in all cases the self-reported prevalence for women exceeded that for men by 11% or more. Cross-modal agreement was moderate, with by-criterion and frailty-wide Kappa statistics of 0.55–0.60 in all cases. Frail subgroups (a), (b), (c) were independently discriminated (p < 0.05) by race, BMI, and depression in women; by age in men; and by self-reported health for both.ConclusionsCommonly used self-reported disability items cannot be assumed to stand in for performance-based criteria in the PFP. We found subpopulations identified as frail by resultant phenotypes versus the original phenotype to systematically differ. Work to develop self-reported proxies that more closely replicate their objective phenotypic counterparts than standard disability self-reports is needed.

Numerical analysis, experimental tests and non-linear analytical models in the study of bent timber beams reinforced with FRP strips

The paper presents selected methods for modelling bent timber beams strengthened with fibre-reinforced polymers (FRP). The assumptions are described, and the main analytical models representing the non-linear bending behaviour of wood are shown. Based on the models presented, analytical approaches considering reinforcement in the tension zone are proposed. The problem of determining the appropriate material parameters of the wood used in analytical calculations and numerical models is discussed. The main numerical methods used in timber analyses are presented. The Hill yield criterion and the generalised Hill yield criterion are discussed in more detail. A method for retrospective estimation of material properties of wood taking into account non-linear material models and fitting the generalised Hill yield criterion is described. Experimental bending tests of technical-scale beams reinforced with composites are presented. The numerical analysis was carried out and discussed. The generalised Hill yield criterion was applied to represent the behaviour of the wood, distinguishing the different yield stresses in compression and tension. The suitability of using non-linear models and advanced strength criteria in the numerical analysis of timber elements is discussed.

Two-dimensional face stability analysis in rock masses governed by the Hoek-Brown strength criterion with a new multi-horn mechanism

The face stability problem is a major concern for tunnels excavated in rock masses governed by the Hoek-Brown strength criterion. To provide an accurate prediction for the theoretical solution of the critical face pressure, this study adopts the piecewise linear method (PLM) to account for the nonlinearity of the strength envelope and proposes a new multi-horn rotational mechanism based on the Hoek-Brown strength criterion and the associative flow rule. The analytical solution of critical support pressure is derived from the energy-work balance equation in the framework of the plastic limit theorem; it is formulated as a multivariable nonlinear optimization problem relying on 2m dependent variables (m is the number of segments). Meanwhile, two classic linearized measures, the generalized tangential technique (GTT) and equivalent Mohr-Coulomb parameters method (EMM), are incorporated into the analysis for comparison. Surprisingly, the parametric study indicates a significant improvement in support pressure by up to 13% compared with the GTT, and as expected, the stability of the tunnel face is greatly influenced by the rock strength parameters. The stress distribution on the rupture surface is calculated to gain an intuitive understanding of the failure at the limit state. Although the limit analysis is incapable of calculating the true stress distribution in rock masses, a rough approximation of the stress vector on the rupture surface is permitted. In the end, sets of normalized face pressure are provided in the form of charts for a quick assessment of face stability in rock masses.

Estimating shear strength of high-level pillars supported with cemented backfilling using the Hoek–Brown strength criterion

Deep metal mines are often mined using the high-level pillars with subsequent cementation backfilling (HLSCB) mining method. At the design stage, it is therefore important to have a reasonable method for determining the shear strength of the high-level pillars (i.e. cohesion and internal friction angle) when they are supported by cemented backfilling. In this study, a formula was derived for the upper limit of the confining pressure σ3max on a high-level pillar supported by cemented backfilling in a deep metal mine. A new method of estimating the shear strength of such pillars was then proposed based on the Hoek–Brown failure criterion. Our analysis indicates that the horizontal stress σhh acting on the cemented backfill pillar can be simplified by expressing it as a constant value. A reasonable and effective value for σ3max can then be determined. The value of σ3max predicted using the proposed method is generally less than 3 MPa. Within this range, the shear strength of the high-level pillar is accurately calculated using the equivalent Mohr–Coulomb theory. The proposed method can effectively avoid the calculation of inaccurate shear strength values for the high-level pillars when the original Hoek–Brown criterion is used in the presence of large confining pressures, i.e. the situation in which the cohesion value is too large and the friction angle is too small can effectively be avoided. The proposed method is applied to a deep metal mine in China that is being excavated using the HLSCB method. The shear strength parameters of the high-level pillars obtained using the proposed method were input in the numerical simulations. The numerical results show that the recommended level heights and sizes of the high-level pillars and rooms in the mine are rational.

Constitutive strength model for spot joints of thin-walled energy-absorbing elements

The goal of this paper was to determine the strength criterion that causes the failure of point-to-point joints of thin-walled profiles under impact load, as well as to determine the strength parameters that guarantee joint continuity during dynamic folding of crash boxes. For this purpose, extensive quasi-static and dynamic materials tests were conducted for the five most popular steel grades used in the automotive industry: DP600, DP800, DP1000, HSLA and DC01. The strength of the spot joints was investigated in acomplex load state using the original instrumentation. This allowed authors to build and validate mathematical models of the load-bearing capacity of point-to-point joints and to conduct simple and efficient numerical simulations of these elements without the need to account for their geometry. Following the validation of mathematical models and load-bearing models of the joints, extensive experiments of quasi-static and dynamic crushing of thin-walled energy-absorbing top-hat (TH) structures were conducted. The data collected made it possible to calibrate the FEM model correctly and conduct numerical simulations of the dynamic crushing of energy-absorbing structures. As a result, the minimum shear strength (Fs) and cross-tension strength (Fn) of the joints were determined as a function of the sheet thickness and the parameters of Re and Rm. The creation of any spot joint enabling the simultaneous carrying of forces Fs and Fn ensures the preservation of joint continuity throughout the entire crushing process and makes it possible for manufacturers to select the type of spot joint based only on its strength.

Theoretical and experimental study on multiscale coupled Mohr–Coulomb shear strength criterion of fibre-reinforced sand

Fibre-reinforced sand (FRS) is a multiphase and multiscale geo-material, which is widely used in geotechnical engineering as supporting structure of excavation of underground space and reinforcement of foundation of underground structures, and its strength is determined by the properties of the heterogeneous substances of the FRS and their coupling mechanical responses. In order to investigate the influence of fibre characteristics and mechanical properties on the shear strength of the FRS, according to the microscopic interface slip effect generated by the interaction between sand particles and the interaction between these particles and fibre, the material phase of the FRS is divided to conceptualize a micro cell element of the FRS that is capable of reflecting the internal material characteristic information of the FRS. Moreover, based on the coordinated deformation condition between fibres and sand particles at the microscale and the couple stress theory that is capable of effectively describing the discontinuous mechanical responses at the sand-fibre interface, a mesomechanism-based multiscale Mohr–Coulomb shear strength criterion of the FRS is derived, and the yield locus of the FRS is also drawn on the π plane. Furthermore, a series of FRS samples with different fibre content and fibre length were prepared by adopting the freezing method, and consolidated and drained triaxial compression tests were conducted on these samples to validate the proposed multiscale coupled Mohr–Coulomb shear strength criterion. Results show that the multiscale coupled Mohr–Coulomb shear strength criterion is capable of effectively reproducing and predicting the yield strength of the FRS. The yield locus of the FRS extends outwards as fibre content and fibre length increase. The yield stress of the FRS predicted by the proposed multiscale coupled Mohr–Coulomb shear strength criterion is in good agreement with that of the test result.

Impact of conventional and advanced cleaning techniques on the durability of firefighter turnout ensembles

The concern for firefighters’ occupational exposure to harmful contaminants is growing due to the increase in health issues in the firefighting community. At such times, effective decontamination of personnel and equipment is an essential component of a hazard mitigation strategy. The current decontamination practices used for firefighter protective clothing have been shown to not be very effective. Hence, the scientific community is looking for several alternatives to conventional washing procedures. Liquid carbon dioxide (CO2) has been used in laundering and has distinct advantages over conventional dry-cleaning solvents such as perchloroethylene. The following study is aimed to assess how different washing procedures affect the durability of the turnout material. The study includes using three washing procedures on different samples: 1) conventional washing procedure, 2) liquid CO2 washing procedure, and 3) a high-temperature washing procedure. Samples for durability testing were constructed from a common aramid fabric used in firefighter turnout ensembles. These swatches were subjected to different washing techniques. The durability assessment was performed for physical testing of the samples, visual inspection, water repellency, and quantifying color changes using spectrophotometric analysis. The conventional wash and high-temperature washing affected the durability of the outer shell material in a significant manner. The liquid CO2 process did not affect the samples’ water repellency or physical strength. In contrast, conventional and high-temperature washing significantly affected the durability of the outer shell material. However, all samples met the criteria for tearing strength outlined in the NFPA 1971 standard subsection 7.1.11.

Shear strength and failure criterion of geopolymer coral aggregate concrete under compression-shear loading

The utilization of geopolymer and coral aggregate in concrete preparation offers cost and time savings associated with the transportation of raw materials, as well as contributes to reducing carbon emissions and resisting the sulfate ions erosion in the marine environment. Concrete structures, including deep beams, corbels, and column joints, are typically subjected to compression-shear loading. For this purpose, a total of 54 cubic specimens are cast to test the compression-shear behavior of geopolymer coral aggregate concrete (GCAC) with different normal stress ratios (k=0,0.1,0.2,0.4,0.6,and0.8) and concrete strength grades (C20, C30, and C40). Subsequently, the failure patterns, load-shear displacement curves, and normal displacement-shear displacement curves of GCAC are obtained. The shear displacement, the shear strength, and its components are also analyzed. The results reveal that coral aggregate with high brittleness and low strength leads to more spalling powder and debris to occur as k increases, and is cut off on the shear surface. With an increase in k (k≥0.6), the descending phase of the load-shear displacement curve becomes steeper due to the higher severity of failure patterns. The shear dilation angle increases with the increase of the concrete strength grade, and first raises and then falls with the increase of k, reaching a maximum value at k=0.4, the same as the percentage of shear dilation strength. Furthermore, the increase in k has a significant negative impact on the percentage of cohesive strength, but not on that contact friction strength. Finally, based on the test results, the J2−I1fc model is determined to be the most suitable for GCAC among the three failure criterion models in this study.

Experimental and constitutive modeling of the anisotropic mechanical properties of shale subjected to thermal treatment

The physical and mechanical properties of shale exhibit significant anisotropy, impacting the design and construction of high geothermal tunnels and deep resource mining. Laboratory studies on the physical and anisotropic mechanical properties of shale after various thermal treatments showed that rising temperatures caused an exponential decline in shale’s bulk and density, and the uneven expansion of the mineral particles within the rock caused a decrease in its uniaxial compression strength (UCS) and elastic modulus while increasing their anisotropy. The UCS is U-shaped with a change in bedding dip angle, whereas the elastic modulus is U-shaped or shoulder-shaped. Under the assumption that the rock microelement obeyed the Weibull distribution, the microstructure tensor improved Hoek–Brown strength criterion was introduced as the damage basis. Then a thermal–mechanical coupling damage constitutive model considering bedding dip angle and temperature was established. The model was found to be valid via the test results, especially in capturing the compaction and yield softening stages of shale. These findings have reference value for both underground structural engineering and deep resource mining.

Utilizing of 500 MHz Ground Penetrating Radar Antenna Coupling at Different Interval Heights Clearance

Understanding the characteristics of the GPR antenna for underground utility detection purposes is critical to ensuring that buried pipes and cables can be accurately located. Considering the ground coupling antenna is the most effective way to carry out the GPR scan, most of the operators applied this setup to ensure the maximum amount of the electromagnetic wave could be penetrated into the ground. However, the contact between the GPR and the ground surface causes the bottom of the antenna enclosure to become scratched and worn out. Due to the cost and time involved in transportation to replace the antenna protector, a few GPR operators changed the protector to the cheapest one, which affects the characteristics of the antenna and could alter the depth of the underground utilities. A 500 MHz GPR antenna are tested to identify the optimum antenna coupling based on the accuracy assessment at various interval clearance heights in order to reduce damage and preserve the antenna. An experiment was carried out at Department of Survey and Mapping Malaysia (JUPEM) Kuala Lumpur’s Underground Utility Test Base. Based on the result of the signal strength, the higher the antenna is lifted, the higher the rate of the signal becomes weak or lost. For the depth accuracy test, the high differences in depth when the antenna is lifted up at 4cm to 6cm based on the result of comparison with the standard values provided by the JUPEM. On the other hand, the accuracy of each antenna height is compared and validated based on the Residual Mean Square Error (RMSE). Overall, this study could lead to the conclusion that the result of the assessment is within the acceptable RMSE tolerance, which is below 0.1m. The objective of the research is successfully achieved when the antenna at a 3cm to 6cm interval height setup provides the best clearance based on the criteria of signal strength, depth comparison, and accuracy assessment. Finally, the issue of contact between the antenna and the ground surface, which causes the antenna to become scratched and worn out, could be reduced and preserved as a result of the findings.

Use of rice husk ash as a supplementary cementitious material in concrete mix for road pavements

The present research analyzes the feasibility of using Rice Husk Ash (RHA) obtained as a residue from an industrial process as Supplementary Cementitious Materials (SCM) in a concrete pavement mix that meets the minimum requirements for a medium traffic level (NT2) road with reference to the General Road Construction Specifications of INVIAS (Colombia). For this purpose, statistical methodologies such as Composite Central Design (CCD), Response Surface Methodology (RSM), and a Multi-Objective Optimization were used to find an efficient mix design that meets the strength and workability criteria using the highest RHA content in partial replacement of cement. The design optimization results show that replacing 24.9% by weight of cement with RHA in a hydraulic concrete mix produces the highest flexural strength (4.2 MPa) of the combinations proposed in the composite central design. This strength could even be applicable for high traffic level (NT3) road, demonstrates that the use of RHA as SCM in concrete mixes for pavements may be feasible.

Appendicular Skeletal Muscle Mass Associated with Sarcopenia as a Predictor of Poor Functional Outcomes in Ischemic Stroke.

Several studies have examined the clinical impact of poststroke and stroke-related sarcopenia on stroke recovery. However, few studies have investigated the effect of sarcopenia detected shortly after stroke on functional prognosis. We predicted functional outcomes using early screening for sarcopenia in patients with acute ischemic stroke. We also examined the effect of sarcopenia detected shortly after stroke on functional prognosis. Patients diagnosed with acute ischemic stroke within 2 days of symptom onset were consecutively enrolled at a tertiary university hospital. Appendicular skeletal muscle mass (ASM) was measured using dual-energy X-ray absorptiometry during early hospitalization. Sarcopenia was diagnosed based on low ASM and strength criteria of the Asian Working Group for Sarcopenia (AWGS) and European Working Group on Sarcopenia in Older People (EWGSOP2). The primary outcome was poor functional outcome, defined as a modified Rankin score of 4-6 and all-cause mortality at 3 months. Of the 653 patients, 214 (32.8%) and 174 (26.6%) had sarcopenia according to the AWGS and EWGSOP2 criteria, respectively. Irrespective of the definition, the sarcopenia group had a significantly higher proportion of patients with poor functional outcomes and all-cause mortality. Multivariate logistic regression analysis revealed that height-adjusted ASM was independently associated with poor functional outcomes (odds ratio: 0.61; 95% confidence interval: 0.40-0.91; P <0.005), and they were negatively correlated. However, the association between 3-month mortality, skeletal muscle mass, and sarcopenia was not sustained in multivariate analyses. Height-adjusted ASM associated with sarcopenia is a potential predictor of poor functional outcomes at 3 months in patients with acute stroke. However, owing to the limitations of this study, further research is required to confirm these findings.

СТРІЧКОВИЙ ФУНДАМЕНТ З ПОВЗДОВЖНІМ ВИРІЗОМ ПО ПІДОШВІ МАСИВНОЇ ПІДПІРНОЇ СТІНИ

The paper analyzes the designs of traditional strip foundations with a flat bottom, the load from which causes the plane strain stress state of the soil base, and other variations of conventionally strip (continuous) foundations, which due to their shape (configuration) of the contact area with the base change its stress state, which enables designing more sustainable foundations for continuous buildings and structures. Proceeding from the solutions to the mixed problem of the theory of elasticity and plasticity using the Mohr-Coulomb criterion strength criterion, analytical studies of the development of plastic zones in the base of a strip foundation with a longitudinal cut-out have been conducted, which show that the limit state always occurs first in the foundation’s edge zones, that is, underneath the outer edges of the foundation. It is also noted, however, that the design resistance of soil decreases when there is no additional load in the area of the cut-out; therefore, a patented design has been proposed of a strip foundation with a longitudinal cut-out in the bottom, where the cut-out with the height is filled with low-modulus material to improve the design resistance of soil. Based on experimental and theoretical studies, methods have been proposed for calculating the soil base (design resistance , settlement and inclination ) for a strip foundation of a massive retaining wall with a longitudinal cut-out in the bottom. A real example shows that the total width of the strip foundation with a cut-out is shorter by 1.5 m in comparison with the continuous shape of the bottom of the foundation, which has a significant economic effect on every linear meter of the wall foundation. Overall, the proposed methods make it possible to reasonably design effective eccentrically loaded foundations with cut-outs in the bottom and to improve the permissible vertical pressure on the base in comparison with a continuous bottom, all other things being equal. Keywords: strip foundation, massive retaining wall, eccentricity, bottom, cut-out, soil base, calculation procedure.

Ballistic performance of optimised light weight composite armour

This research paper presents a comprehensive investigation into the response of a 3D finite element model when subjected to 7.62 AP projectiles. The study utilises Hetherington's armour composite equation and incorporates the Johnson-Holmquist material model to analyse the strength and failure criteria of the ceramic and Kevlar/epoxy components, respectively. The results highlight the remarkable resilience of the composite armour, demonstrating its ability to withstand projectile velocities up to 1500 m/s. However, as the ballistic velocity limit increases, the armour experiences significant damage, including projectile erosion and panel delamination. Through numerical simulations and advanced modelling techniques, the paper thoroughly explores the failure modes and energy absorption characteristics of composite armour systems under projectile impact. It investigates key parameters such as velocity, acceleration, kinetic energy, internal energy, pressure distribution, displacement, and damage progression. The analysis reveals a progressive decrease in kinetic energy as the projectile interacts with the armour, underscoring the crucial role of energy absorption in preventing projectile penetration. Moreover, the impact velocity influences the distribution of internal energy within the composite armour, with higher velocities leading to greater energy absorption up to a threshold limit. The study also determines the ballistic limit velocity (V50) using the velocity history approach and validates the findings with existing literature. Overall, the research provides valuable insights into the limitations of composite armour and offers important recommendations for designing and improving materials to achieve superior ballistic protection. It emphasises the significance of reaching the maximum ballistic limit while maintaining a lightweight armour structure by optimising the total armour thickness. This study contributes to the advancement of armour technology and enhances our understanding of the behaviour of composite materials under high-velocity impacts. It offers valuable guidance for the development of more robust armour systems suitable for various defence and protection applications.

Measures of slope stability in bonded soils governed by linear failure criterion with tensile strength cut-off

The linear failure criterion with a tensile strength cut-off is increasingly applied to geotechnical stability problems in response to the uncertainty originating from the predicted tensile strength in soil. However, several attempts at slope stability analysis have employed classical failure mechanisms with geometrical and computational constraints. In the context of limit analysis, an advanced failure mechanism was utilized in this study for more accurate and comprehensive solutions of practical stability measures, including stability factors and factors of safety. This mechanism delivers lower stability factors and enables the estimation of the traditionally defined factor of safety, particularly in the tensile regime associated with the nonlinear part of the envelope. A technique that transforms the Hoek–Brown rock strength criterion into the equivalent linear failure criterion with a tensile strength cut-off is presented. The factors of safety based on the equivalent Mohr–Coulomb envelope subjected to the tension cut-off showed exceptional agreement with those based on the original Hoek–Brown equation, owing to the truncation of the overestimated strength in the low-stress regime.