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The recommended bearing capacity of medium weathering mudstone foundation is less than the capacity of the rock structure to withstand loads in Southwest China. A comprehensive failure characterization of medium weathering mudstone in Chengdu has been performed including bearing plate test (BPT), binocular vision measurement (BVM) test, uniaxial compressive strength test, trial trench test of shallow rock surface and 3D imaging in this paper. Failure behavior of rock has been modeled with 3D imaging algorithm that utilizes Zhang's calibration method in BVM system combination with trial trench test of shallow rock surface. The bearing capacity of medium weathering mudstone foundation were extracted from uniaxial experiments and BPT-BVM test by fitting relevant material properties to the data. The results revealed that: Bearing capacity of medium weathering mudstone of layered isotropic in Chengdu is undervalued. Specifically, the characteristic load carrying value is in the range 1500–2500 kP, that is 50% higher than in the local standard system. Failure process is different from Hoek–Brown Failure Criterion, presenting a wave peak transfer phenomenon of the increment displacement into the distance. Thus, it can be reduced to that of punching failures for thin bedded structures of Moudstone foundations. Compressive strength of soft rock proves to be main factor limiting the bearing capacity, a clear correlation between the uniaxial compressive strength reduction coefficient and the bearing capacity has been used to establish, leading to the proposal of a load bearing capacity prediction model. [ABSTRACT FROM AUTHOR]

Sandy Dolomite is a kind of widely distributed rock. The uniaxial compressive strength (UCS) of Sandy Dolomite is an important metric in the application in civil engineering, geotechnical engineering, and underground engineering. Direct measurement of UCS is costly, time-consuming, and even infeasible in some cases. To address this problem, we establish an indirect measuring method based on the convolutional neural network (CNN) and regression analysis (RA). The new method is straightforward and effective for UCS prediction, and has significant practical implications. To evaluate the performance of the new method, 158 dolomite samples of different sandification grades are collected for testing their UCS along and near the Yuxi section of the Central Yunnan Water Diversion (CYWD) Project in Yunnan Province, Southwest of China. Two regression equations with high correlation coefficients are established according to the RA results, to predict the UCS of Sandy Dolomites. Moreover, the minimum thickness of Sandy Dolomite was determined by the Schmidt hammer rebound test. Results show that CNN outperforms RA in terms of prediction the precision of Sandy Dolomite UCS. In addition, CNN can effectively deal with uncertainty in test results, making it one of the most effective tools for predicting the UCS of Sandy Dolomite. [ABSTRACT FROM AUTHOR]

In the Chengdu-Chongqing economic circle in China, the recommended bearing capacity of a medium-weathering mudstone foundation is less than the capacity of the rock structure to withstand loads. The aim of this paper was to perform plate loading tests (PLTs) with binocular vision measurement (BVM) to obtain the accurate deformation of the foundation under vertical loading. The results revealed that vertical load–bearing foundations have a failure mode that can be reduced to that of thrust failures for thin bedded structures of mudstone foundations. By analyzing the differences in results between the PLTs and the uniaxial compressive strength tests under the same conditions, a new formalism for calculating foundation-bearing capacity was proposed; there is only a 5% difference compared to in situ tests. The results of this research provide theoretical support and a practical benchmark for the full development of the load-bearing capability of soft red rocks. As the Chengdu-Chongqing economic circle progresses toward the international urban cluster, inevitably, soft rock is used as a foundation retaining layer in the construction of superhigh and super-rise buildings in the region. However, owing to antiquated testing methods and poor intelligibility of the testing equipment, the bearing capacity of such a mass of rock has yet to be fully developed and cannot meet the dual-carbon economic goals and sustainable development of architectural design. Based on this, the study introduces a noncontact method to measure the bearing capacity of soft rock within the traditional method of in situ testing and combines the concept of big data analysis to advance an empirical method for calculating the bearing capacity accurately. Based on the results of this study, the concept of natural foundations can be adopted and the engineering dilemma that the treatment of building foundations cannot be economical and practical can be solved. [ABSTRACT FROM AUTHOR]

This paper presents the details of experimental testing of masonry prisms, which were tested in compression. The experimental program consisted of prisms made with hollow and solid blocks of thickness 100 and 150 mm. Five different proportions of mortars were employed in the casting of these prisms, which included 1:2, 1:3, 1:4, 1:5, and 1:6 by weight. Three prisms were cast and tested using each of these mortar types for each block type. It was found that the failure modes and compressive behaviors of the prisms were not significantly influenced by the mortar types, although these were different for the prisms made of solid and hollow blocks. The deformation behaviors of the prisms in the postpeak region were also different for these block types. The compressive strength of the prisms (fp) varied with the block strength and was not dependent on the block type. All the prisms exhibited typical behaviors of uniaxially compressed prismatic members. An average elastic modulus of 1,720 fp was found for the tested prisms, while Poisson's ratio varied from 0.10 to 0.15. Analytical models for estimating fp and strain corresponding to fp have been proposed for design practice. A new constitutive equation for capturing the falling branch of the stress–strain curve of block masonry prisms has also been proposed. [ABSTRACT FROM AUTHOR]

This study explored the influence mechanism on the water resistance of magnesium phosphate repair mortars. The fluidity, setting time, mechanical properties, water resistance, and interfacial bonding strength of red mud–modified magnesium phosphate repair mortars (RMPMs) were systematically investigated. Through capillary absorption tests, the effect of the water-binder ratio (W/B) on the water transfer characteristics was explored, and then the actuating mechanism of capillary porosity and capillary absorption coefficients on water resistance was clarified. The results show that the fluidity and setting time of RMPM increase with the increase of W/B. When W/B increased from 0.18 to 0.20, the compressive strength, flexural strength, strength retention, and interfacial bonding strength of RMPM changed little and decreased linearly. And the interfacial bonding strength of RMPM was significantly reduced after 7 days of water curing. The capillary water absorption of RMPM was linear with the square root of time. The capillary absorption coefficient and capillary porosity of the RMPM increased greatly with increasing W/B when the W/B is between 0.20 and 0.28, while the water resistance, mechanical properties, and interfacial bonding property decreased linearly. Variations in W/B changed the capillary pore characteristics of the RMPM, which in turn affected the mechanical properties, capillary water absorption characteristics, and water resistance. [ABSTRACT FROM AUTHOR]

The strength of rock under uniaxial compression, commonly known as Uniaxial Compressive Strength (UCS), plays a crucial role in various geomechanical applications such as designing foundations, mining projects, slopes in rocks, tunnel construction, and rock characterization. However, sampling and preparation can become challenging in some rocks, making it difficult to determine the UCS of the rocks directly. Therefore, indirect approaches are widely used for estimating UCS. This study presents two Machine Learning Models, Simple Linear Regression and Step-wise Regression, implemented in Python to calculate the UCS of Charnockite rocks. The models consider Ultrasonic Pulse Velocity (UPV), Schmidt Hammer Rebound Number (N), Brazilian Tensile Strength (BTS), and Point Load Index (PLI) as factors for forecasting the UCS of Charnockite samples. Three regression metrics, including Coefficient of Regression (R2), Root Mean Square Error (RMSE), and Mean Absolute Error (MAE), were used to evaluate and compare the performance of the models. The results indicate a high predictive capability of both models. Notably, the Step-wise model achieved a testing R2 of 0.99 and a training R2 of 0.988 for predicting Charnockite strength, making it the most accurate model. The analysis of the influential factors indicates that UPV plays a significant role in predicting the UCS of Charnockite. [ABSTRACT FROM AUTHOR]

Herein, we conducted a comprehensive statistical assessment of the ultrasonic pulse velocity (UPV) method's effectiveness in predicting concrete strength under diverse conditions, specifically early age, middle age, and high-temperature exposure. The concrete mixtures, with water-to-cement (W/C) ratios of 0.33 and 0.28, were classified as granite aggregate or coal-ash aggregate mixes. Compressive strength and UPV measurements were performed under these conditions, and subsequent statistical analyses treated the identified factors as distinct groups. The results revealed a substantial difference in compressive strength between specimens at early age (average of 13.01) and those at middle age (average of 41.96) and after high-temperature exposure (average of 48.08). Conversely, UPV analysis showed an insignificant difference between the early-age specimens and those after high-temperature exposure. The analysis of the W/C ratio and coarse aggregate demonstrated significant differences (p-value < 0.05) in compressive strength between specimens in middle age and those exposed to high temperatures, excluding the early-age specimens. However, UPV analysis revealed insignificant differences, with p-values of 0.67 and 0.38 between specimens at an early age and post-high-temperature exposure, respectively. Regression analysis identified suitable functions for each scenario, emphasizing the importance of a strength prediction model for concrete after high-temperature exposure, particularly considering the W/C ratio. Since concrete showed statistically different compressive strength, UPV, and strength prediction models in three conditions (early age, middle age, and high temperature), different strength prediction models must be used for the purpose of accurately predicting the strength of concrete. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the interlayer bonding characteristics between double-layered asphalt systems. Three typical asphalt structures were chosen for evaluation. In each case, the bottom layer comprised of a dense graded asphalt concrete (AC-20) while three different asphalt mixtures were applied in surface layer: a dense graded mixture (AC-13), stone mastic asphalt (SMA-13), and open-graded friction course (OGFC-13). The effects of interface morphology, loading, and temperature conditions on interlayer bonding properties were considered. The interlayer shear and tensile strengths of the asphalt systems were tested using 'shear-compression' and 'shear-tensile' loading mode set ups, and the relationship between interface morphology and interlayer bond strength was quantitatively analyzed using 3D laser scanning. In addition, statistical analysis was performed to determine the significance level of each factor, followed by developing and validating prediction models for interlayer bond strength using multivariate nonlinear regression. The results showed that all factors had a significant effect on interlayer bonding performance, with temperature being the most prominent contributing factor. Increasing normal pressure had a positive effect on preventing the attenuation of interlayer shear strength, while an increase in shear stress was found to intensify the degradation of interlayer tensile strength. Moreover, interlocking and ensuring sufficient contact at the layer interface were demonstrated to enhance the interlayer friction effect positively. However, high normal stress could potentially lead to damage at the interface. Finally, the developed prediction models exhibited a high level of accuracy in estimating interlayer bond strengths and were able to explain over 97% and 98% of measured interlayer shear and tensile strengths, respectively. Employing a properly graded surface layer can improve the frictional and contact effects at the layer interface, thereby enhancing the overall interlayer bonding performance. [ABSTRACT FROM AUTHOR]

Compressive strength (CS) is concrete's most important mechanical property, as it plays an important role in setting design criteria. Thus, an accurate and early assessment of the CS of concrete can minimize time, labor, and cost. This paper investigated the ability of the Radial Basis Function (RBF) to handle the prediction of CS. The nonlinearities raised from the novel utilized admixtures between the input variables and output CS is tried to be conducted with the RBF model. In order to make a flexible framework combination of the RBF model with the African Vulture Optimization (AVOA) and Salp Swarm Algorithm (SSA) techniques are considered. The results achieved from the RBF-AVOA model indicated good agreement between the actual and predicted values. The proposed model provides a very accurate HPC compressive strength prediction. In addition, the correlation coefficient R2 is equal to (0.997), and the values of mean absolute error (MAE) (0.1917 MPa), root mean square error (RMSE) (0.937 MPa), and variance account coefficient (VAF) (99.73%) are low. The performance of the RBF-AVOA model, compared to other models, provided the desired advantage and more stable predictions. AVOA plays a key role in modeling results, improving generalization capabilities, avoiding redundant data, and decreasing uncertainty. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) are new alloy systems that leverage solid solution strengthening to develop high-strength structural materials. However, HEAs are typically cast alloys, which may suffer from large as-cast grains and entrapped porosity, allowing for opportunities to further refine the microstructure in a non-melting near-net shape solid-state additive manufacturing process, additive friction stir deposition (AFSD). The present research compares the microstructure and mechanical behavior of the as-deposited AFSD Al0.35CoCrFeNi to the cast heat-treated properties to assess its viability for structural applications for the first time. Scanning electron microscopy (SEM) revealed the development of fine particles along the layer interfaces of the deposit. Quasi-static and intermediate-rate compression testing of the deposited material revealed a significant strain-rate sensitivity with a difference in yield strength of ~400 MPa. Overall, the AFSD process greatly reduced the grain size for the Al0.35CoCrFeNi alloy and approximately doubled the strength at both quasi-static and intermediate strain rates. [ABSTRACT FROM AUTHOR]

The stability of cemented backfill Is compromised via Hasting disturbances in the two-step stopping method. To obtain the dynamic compressive strength of the backfill quickly and accurately, 40 sets of uniaxial impact experiments with different strain rates were conducted using the separated Hopkinson pressure bar(SHPB). Input parameters included the times and ratio, backfill density, curing age, and average strain rate, while the dynamic compressive strength of the backfill served as the output parameter. A prediction model, optimized using the back propagation neural network (BPNN) based on the logistic chaotic sparrow search algorithm (CSSA), was established and compared with the BPNN optimized by the traditional BPNN and sparrow search algorithm. The results demonstrate that the average relative error of the CSSA-BPNN model Is 4.11%, with fitting correlation coefficients among the predicted and measured values exceeding 0.96, indicating high prediction accuracy. The root- mean-square error of the CSSA-BPNN model is 0.395 0 MPa, the average absolute error is 0.359 2 MPa, and the coefficient of determination Is 0.995 2, all of which outperform the other two prediction models. This enables accurate prediction of the dynamic compressive strength of the backfill, greatly reducing the need for physical experiments and providing a novel approach to the strength design of mine cemented backfill. [ABSTRACT FROM AUTHOR]

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 p 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. [ABSTRACT FROM AUTHOR]

Cement-based composite is a kind of heterogeneous and discontinuous material. It is not appropriate to conduct stress analysis on a model constructed by continuous mean theory when subjected to external loads. A granular flow model based on discrete element theory is constructed to simulate the dynamic process of cementstabilized macadam during uniaxial compression test in this article. The appropriate contact bonding model is selected, and the contact parameters are calibrated. After the uniaxial compression test in the laboratory, the relative displacement, stress transfer process and crack propagation between aggregate particles in the structure are verified by the results calculated by the model. It can be seen from the research results that the parallel bond model can well reflect the mechanical characteristics of cementstabilized macadam. In the process of the specimen being loaded, the vertical displacement between particles leads to the specimen being compacted, and the horizontal displacement between particles leads to the crack. The displacement angle of cementitious particles in the upper model is larger than that of coarse aggregate. The displacement angle of cementitious particles in the lower model is less than that of coarse aggregate. The particle displacement angle generally shows a decreasing trend. [ABSTRACT FROM AUTHOR]

Rock bursts pose a significant risk to coal mine operation safety. Thus, accurately discriminating coal bursting liabilities is crucial for predicting and preventing rock burst events. To better understand the effects of a varying bedding angle on the crack propagation rule, failure mode and bursting liability level of coal and coal-rock combinations, we propose an optimized machine learning-based model. Additionally, uniaxial compressive tests are conducted using PFC3D software on samples with different bedding angles. The results indicate that, among the nine light gradient boosting machine discriminant models constructed using three data preprocessing methods and three parameter optimization algorithms, the optimal model is identified as the particle swarm optimization-light gradient boosting machine discriminant model based on Z-score standardization method, which exhibits the best stability and has a F1-score of 93.6%. Bedding has a significant impact on the failure modes of two kinds of samples, resulting in an evident bedding effect on their bursting liability. The uniaxial compression strength and bursting energy index of both samples show a reduction-rising trend with an increasing bedding dip angle. However, the bursting liability level of these samples is not affected by 0°C or 90°C bedding dip angle. Therefore, when assessing the bursting liability of samples, the influence of coal seam bedding and its dip angles should be thoroughly considered. [ABSTRACT FROM AUTHOR]

This paper presents the mechanical behavior of thermally sprayed coatings produced using an arc wire coating material. The produced coatings were cut and subjected to strength resistance tests in static and in dynamic loading. The compressive behavior for the strain rates between 0.001 1/s and 2612 1/s was examined. The strain rate sensitivity of the material was recognized in the material during dynamic loading using the SHPB technique. Microstructural observations were made, and properties such as changes in porosity and the microhardness of the coatings tested were examined. A significant reduction in coating porosity was demonstrated after static loading (90%) and dynamic loading (86%). The result of porosity reduction is the strengthening of the coatings through an increase in the microhardness of these coatings after loading in the static test (160 HV 0.3/8) and the dynamic test (278 HV 0.3/8). As a result of the tests, the coatings retain their cohesion and remain consistent. At the same time, they can absorb a significant amount of mechanical energy due to plastic deformation and porosity reduction. The presented results concern a completely new coating material created from a core wire. [ABSTRACT FROM AUTHOR]

A variety of 3D printing parameters have been investigated including reinforcement material and print orientation, as well as reinforcement pattern, distribution and volume. From these evaluated parameters, the optimal values are taken into account to select the highest compressive properties. By using Scanning Electron Microscopy (SEM) imaging, reinforcement and thermoplastic layers have been clearly identified alongside sample flaws. Horizontally printed samples exhibited higher mean values with less standard deviation than vertically printed ones for compressive modulus and compression strength. For the sample set with the Nylon and carbon fibre; concentric and isometric fill patterns were compared in three different fibre distributions. Concentric fill pattern with equidistantly fibre distribution exhibited the highest compressive modulus as 1.8 GPa. It also exhibited a higher proportional limit of 12.80% and compressive modulus of 11.64% than its counterpart with the isometric fill pattern. For the set with 12.5% fibre volume, Onyx + CF (matrix + reinforcement) exhibited higher compressive modulus and compressive strength than Nylon + CF by 18.5%, and 28.1%, respectively. Within the experimental set of different reinforcements (carbon fibre, Kevlar, fibreglass), and different fibre volumes (6.25%, 12.5%, 25%) with Onyx matrix; Onyx thermoplastic with fibreglass reinforcements and a fibre volume of 25% exhibited the highest compressive properties. [ABSTRACT FROM AUTHOR]

The establishment of deformation mechanisms of Mg-metal matrix composite (Mg-MMC) is important to improve the high-temperature challenging applications. In this present work, an AZ91/TiC + TiB2 hybrid in-situ Mg-MMC was synthesized, and its deformation mechanisms were studied through a uniaxial hot compressive test at different temperatures and strain rates. The Johnson-Cook (JC) model and constitutive equation were established using experimental stress-strain data. Through the development of JC model, it was revealed that the TiC--TiB2 particles enhanced the yield strength parameter and increased the activation energy of the in-situ composite compared to the parent alloy. The load- shifting capability and grain refinement were found to be the dominating mechanisms, which effectively restricted dislocation movement during deformation, resulting in improved deformation resilience of the composite. A detailed study of JC model and constitutive equation parameters was analyzed with a focus on their microstructures. [ABSTRACT FROM AUTHOR]

Approximately 82% of amputees prefer microprocessor knees (MPKs) to the passive alternatives. However, the cost of these devices makes them inaccessible for many patients. The aim of this research is to develop an affordable MPK that allows for stumble reduction and flexion dampening at a fraction of the cost of similar devices. The GKnee was developed by a sophisticated mathematical model that can effectively calculate geometric configuration and simulate forces transferred through a prosthetic knee at any given point through the gait cycle. With a median error of 6%, the mathematical model was developed to the point of reasonable accuracy for determining component placement and force interactions. The model served as a valuable tool to assist in the iterative design process of the GKnee, influencing component selection for the hydraulic system and frame design. This model was then validated using a compression rig and a mock GKnee prototype. The GKnee was then evaluated for its ability to perform under expected loading conditions, using compression testing and dynamic flexion testing. This research led to the development of a sub USD 500 microprocessor prosthetic, while remaining under 2.27 kg. [ABSTRACT FROM AUTHOR]

This research investigates the quantitative impact of incorporating epoxy resin and crumb rubber powder (CRP) into cement asphalt mortar (CAM) for railway track stabilization. The study reveals significant improvements in various key parameters compared to conventional CAM. The modified CAM exhibits a 12.7% reduction in flow time, indicative of enhanced flowability, and a substantial 62.4% decrease in the mixing stability gap, demonstrating superior mixing stability. Additionally, the modified CAM displays remarkable early-age compressive strength, with increases of up to 15.3% compared to traditional CAM formulations. Importantly, the modified CAM showcases robust resistance to challenging environmental conditions, with only a 6.7% strength reduction after exposure to sulfuric acid, highlighting its acid resistance, and exceptional freeze–thaw resistance, with a mere 1.5% strength reduction after undergoing six cycles. In a mock-up test simulating real-world conditions, the modified CAM effectively prevents ballast layer settlement, underscoring its potential to enhance the durability of railway track infrastructure. These quantitative findings not only endorse the practical feasibility of epoxy resin and CRP-enhanced CAM but also suggest its potential to contribute significantly to railway track longevity, reduce maintenance expenditures, and ensure operational reliability. [ABSTRACT FROM AUTHOR]

Fuel cladding is a first protective barrier against the loss of fission products that must withstand extreme conditions, from normal operation to final and interim dry storage. This hostile environment results in mechanical and microstructural damage of cladding caused by different stress levels, temperature, corrosion, hydrogen pick up and other degradation processes further enhanced by radiation. For this reason, the integrity of the cladding is a critical issue. The aim of this work is to simulate a ring compression test to evaluate the stress-strain behavior and hoop fracture properties of a zirconium-based alloy with niobium, which was chosen because it is widely used as fuel cladding in light water nuclear reactors. [ABSTRACT FROM AUTHOR]

High-performance concrete performs better than normal concrete because of using additional components than usual concrete components. Several artificially based analytics were used to evaluate the compressive strength (CS) of high-performance concrete (HPC) made with fly ash and blast furnace slag. In the present research, the Aquila optimizer (AO) was used to find the best values for the determinants of the adaptive neuro-fuzzy inference system (ANFIS), and radial basis function neural network (RBFNN) that may be changed to enhance performance. The suggested approaches were established using 1030 tests, eight inputs (a primary component of mix designs, admixtures, aggregates, and curing age), and the CS as the forecasting objective. The results of the outperformed model were then contrasted with those found in the existing scientific literature. Calculation results point to the potential benefit of combining AO-RBFNN and AO-ANFIS study. The AO-ANFIS demonstrated significantly higher R2 (Train: 0.9862, Test: 0.9922) and lower error metrics (such as: RMSE at 2.1434 (train) and 1.2763 (Test)) when compared to the AO-RBFNN and previously published articles. In summation, the proposed method for determining the CS of HPC supplemented with blast furnace slag and fly ash may be established using the suggested AO-ANFIS analysis. [ABSTRACT FROM AUTHOR]

The ultrasonic pulse velocity (UPV) technique, which is an efficient technique for concrete quality evaluation, can be affected by several factors. Many studies have proposed compressive-strength prediction models based on UPV in concrete; however, few studies have investigated the factors resulting in statistically different UPV results for different models. This study examined the difference between compressive strengths of various concrete specimens calculated by age-dependent and temperature-dependent UPV-based prediction models. Furthermore, a statistical analysis was conducted to evaluate the influence of aggregates and water/cement ratio (design compressive strength), which are said to affect UPV, on the compressive-strength prediction models. The experimental results revealed that the residual compressive strength of concrete after high-temperature exposure was about 9.5 to 24.8% higher than the age-dependent compressive strength. By contrast, after high-temperature exposure, UPV tended to be about 34.5% lower. The compressive strengths and UPVs were significantly different with respect to high temperature, aggregate density, and design compressive strength. The compressive-strength prediction model derived from the regression analysis showed a high R2 (average 0.91) and mean error converged to zero compared to the compressive-strength prediction model without considering these factors. Finally, the differences between the age- and temperature-based compressive-strength prediction models were analyzed according to the corresponding microstructures. [ABSTRACT FROM AUTHOR]

In this research, a series of compression tests were carried out, under oedometric conditions, on sand samples prepared with different moisture contents. In these tests, in addition to the usual measurements of the stress and deformation of the sample, a series of acoustic emission sensors were used to monitor the parameters of the acoustic signals coming from inside the sample. This is a rather novel technique with great potential, but sometimes difficult to approach due to the large amount of acoustic emission data generated. In this paper, a correlation and regression analysis has been performed to quantify the correlations between the geotechnical variables and the parameters characterizing the acoustic emissions. The results presented open an interesting horizon of possibilities since, as it has been shown, it is possible to determine the values of the geotechnical properties from the acoustic variables, by means of the regression functions obtained for each type of soil or for each practical case. At the very least, this is a complementary tool in the determination of the mechanical properties of soils subjected to compression, although it could also be useful in those situations in which the monitoring of geotechnical variables describing the tenso-deformational behavior of the soil may be difficult or impossible. [ABSTRACT FROM AUTHOR]

Stability of twin and single elliptical tunnels in Hoek–Brown rock masses subjected to surcharge pressure is estimated by lower bound finite element limit analysis with power cone programming. The tunnels are considered to be unlined. The maximum normalized surcharge pressure (qs/σci) is evaluated and its positive value implies that the tunnel is stable, where qs is the intensity of the surcharge pressure and σci is the uniaxial compressive strength of the intact rock. The effect of different Hoek–Brown parameters, uniaxial compressive strength of rock mass, cover depth ratio, the aspect ratio of the tunnel profile, and clear spacing between twin tunnels on the magnitude of qs/σci of elliptical tunnels have been studied. For a few cases, the stress state proximity to failure has also been presented to study the failure patterns of twin elliptical tunnels. Following regression analysis design equations are provided to estimate the magnitude of qs/σci for dual as well as single elliptical tunnels. [ABSTRACT FROM AUTHOR]

This study aims to determine the physical properties and mechanical properties at axial (base, middle, and top) and radial (near the pith, middle, and near the bark) positions, as well as the relationship between the specific gravity and mechanical properties of Acacia aulacocarpa wood. Three 27-year-old trees planted at KHDTK Wanagama were used. Wood physical and mechanical properties were tested per British Standard 373:1957. The statistical analysis used was a two-way ANOVA and a follow-up test of Tukey HSD. The results showed that the average moisture content was 98.95%; the green and air-dry sepesific gravity were 0.58 and 0.61. Radial, tangential, and longitudinal shrinkage from green to oven-dry conditions (total shrinkage) were 2.02%, 5.09%, and 0.33%. The tangential/radial (T/R) ratio was 2.80%. The static bending strength of stress at proportion limit, MoE, and MoR were 498.13 kg/cm², 116.16x1000 kg/cm², and 1043.68 kg/cm², respectively. The compressive strength parallel to the grain and perpendicular to the grain were 596.05 kg/cm² and 227.25 kg/cm², respectively. The results of the variance analysis showed that the radial position factor has a significant effect on green moisture content, green and air-dry specific gravity, total radial shrinkage, T/R ratio, static bending strength at stress of proportion limit, MoE, MoR, compressive strength parallel to the grain, and compressive strength perpendicular to the grain. However, the axial position factor did not show any significant differences in the physical and mechanical properties of the wood. Furthermore, air-dry specific gravity has a significant moderate to high positive correlation with all mechanical properties. [ABSTRACT FROM AUTHOR]

During the thermal simulation compression test, the formation of an obvious bulge in the specimen leads to a certain deviation between the calculated and actual values of the true stress. The finite element method was used to simulate the single-pass compression of specimens of 34CrNi3MoV steel and obtain the actual nonuniform deformation of the bulging belly during the compression process, and the results were applied to correct experimental flow curves. The results showed that the deformation conditions had a significant influence on the nonuniformity of the specimen deformation during the compression process, and all the modified flow curves were lower than the original ones. The size of the bulge and the metal flow line in the finite element simulation were consistent with the test results. The load value obtained by using the modified flow curve was similar to the load value measured in the test, which indicated that the modified flow curve was very close to the real flow force curve of the material. The method used to modify the flow force curve is simple and practical. [ABSTRACT FROM AUTHOR]

This work proposes the comparison of two models of 3D printed hip prostheses, using microscopic and chemical analysis, but also compression and bending testing. The comparison was made using a hip prosthesis designed in the Autodesk Inventor 2020 program and a model freely available on the Internet. The work includes some details about the virtual prototyping of prostheses and results from the chemical analysis of the components of the hip prostheses, carried out using an X-ray spectrometer to identify the elements contained in the PETG (polyethylene terephthalate glycol) material that was used to obtain the samples. The second method of analysis was the microscopic one and finally the samples were subjected to external forces, through bending and compression testing. This comparison aimed to demonstrate the dependence between the shape of the prosthesis and the mechanical properties of the analysed samples. [ABSTRACT FROM AUTHOR]

In this study, tests were carried out on repaired 300 × 250 mm composite stiffened panels. The initial damage was assumed to be extended in a depth of the first six plies and a repair with scarf ratio of 1:50 was employed. A circular repair took place, utilizing laser-assisted ablation and the wet patches approach. The panels were tested in compression and Digital Image Correlation (DIC) and Acoustic Emission (AE) were used in order to monitor the damage initiation and propagation of the panels. In addition, Phased Array (PA) was used in order to monitor the patch failure. Detailed Finite Elements (FE) models were validated against the test findings and their performance as a prediction tool for the performance of repairs on composite aeronautical structures was assessed. [ABSTRACT FROM AUTHOR]

A rockburst is a geological disaster that occurs in resource development or engineering construction. In order to reduce the harm caused by rockburst, this paper proposes a prediction study of rockburst propensity based on the intuitionistic fuzzy set-multisource combined weights-improved attribute measurement model. From the perspective of rock mechanics, the uniaxial compressive strength σ c , tensile stress σ t , shear stress σ θ , compression/tension ratio σ c / σ t , shear/compression ratio σ θ / σ c , and elastic deformation coefficient W e t were selected as the indicators for predicting the propensity of rockburst, and the corresponding attribute classification set was established. Constructing a model framework based on an intuitionistic fuzzy set–improved attribute measurement includes transforming the vagueness of rockburst indicators with an intuitionistic fuzzy set and controlling the uncertainty in the results of the attribute measurements, as well as improving the accuracy of the model using the Euclidean distance method to improve the attribute identification method. To further transform the vagueness of rockburst indicators, the multisource system for combined weights of rockburst propensity indicators was constructed using the minimum entropy combined weighting method, the game theory combined weighting method, and the multiplicative synthetic normalization combined weighting method integrated with intuitionistic fuzzy sets, and the single-valued data of the indicators were changed into intervalized data on the basis of subjective weights based on the analytic hierarchy process and objective weights, further based on the coefficient of variation method. Choosing 30 groups of typical rockburst cases, the indicator weights and propensity prediction results were calculated and analyzed through this paper's model. Firstly, comparing the prediction results of this paper's model with the results of the other three single-combination weighting models for attribute measurement, the accuracy of the prediction results of this paper's model is 86.7%, which is higher than that of the other model results that were the least in addition to the number of uncertain cases, indicating that the uncertainty of attribute measurement has been effectively dealt with; secondly, the rationality of the multiple sources system for combined weights is verified, and the vagueness of the indicators is controlled. [ABSTRACT FROM AUTHOR]

The present analysis was developed by creating a detailed analysis of each article selected for the corroboration of the information and the subsequent comparison between them in order to encourage research of alternative methods of concrete production that will allow the reduction of pollution and will improve the quality and efficiency of concrete. The materials used were nanosilica, pozzolana, and recycled crushed brick that were subjected to laboratory studies with the goal of knowing their properties and of developing mix designs with different content percentages to have a broad study population and achieve representative results. These mix designs were used to create specimens that were tested in different periods to analyze their behavior in various situations. After testing, it was possible to determined that the addition of these materials are effective, in creating concrete of greater strength in the case with the addition of nanosilica, in the case of pozzolana, greater strength can be obtained at a reduced cost due to it being a natural material with various deposits where the material can be obtained in this country and throughout the world, and in the case of the addition of crushed brick, concrete with a similar strength to a conventional type can be obtained at a reduced cost of fabrication due to being a recycled material. [ABSTRACT FROM AUTHOR]

In this study, the application of characteristic impedance in estimating specific energy and average fragment size of rocks was investigated during rock breakage at high strain rates. To achieve this, rock specimen was prepared in accordance with recommendations of the International Society for Rock Mechanics and broken at high strain rates using the split Hopkinson's pressure bar system. Results reveal that although strain rate is well related to specific energy and average fragment size of broken rocks, the product of characteristic impedance and strain rate is more reliable for estimating the forementioned parameters. In addition, strain rate and dissipated energy generally increase at higher incident energies while the average fragment size of broken rocks reduces at higher strain rates. Based on these findings, more studies on indirect estimation of energy requirement for rock breakage to desired average fragment sizes is recommended from the product of characteristic impedance and strain rate. Highlights: Rock classification and rate parameters are crucial for estimating breakage characteristics of rocks at high strain rates. Novel application of the product of characteristic impedance and strain rate is proposed for estimating breakage characteristics of rocks at high strain rates. The product of characteristic impedance and strain rate is more reliable for estimating specific energy and average fragment size from impulse rock breakage. [ABSTRACT FROM AUTHOR]

In this study, the mechanical characteristics of Norway spruce wood (Picea abies) from Bosnia and Herzegovina were investigated by thermal treatment at three different temperatures (specifically, 180, 190, and 210°C) and treatment durations (namely, 2, 3, and 4 hours). For this purpose, the maximum 4-point bending force, the modulus of elasticity in bending, the compression strength parallel to the grain, and the compression strength perpendicular to the grain in treated and untreated specimens were evaluated. Results indicated that the relationship between temperature and duration modification affects the mechanical properties of wood specimens. The results revealed that the relationship between temperature and duration modification influenced the mechanical properties of the wood samples. Specifically, in terms of compression strength, it was observed that the heattreated specimens exhibited improved mechanical properties compared to the unmodified specimens. However, for the maximum 4-point bending force and modulus of elasticity, the results indicated a decrease in mechanical properties. [ABSTRACT FROM AUTHOR]

Lightweight alumina-silica castables were prepared using closed-cell perlite (2-4 mm), open-cell perlite (4-6 mm) and coal gangue ceramsites (2-5 mm) as aggregates, floating beads (0.3-0.5 mm), sinking beads (0.6-0.8 mm), silica micropowder, α-Al2O3 micropowder, zirconia and zircon micropowder as fines, and Secar 71 cement (calcium aluminate cement) as the binder. The effects of the coal gangue ceramsites addition (0, 6%, 12%, 18% and 24%, by mass) on the properties of the as-prepared lightweight alumina-silica castables were investigated. The results show that: (1) the addition of coal gangue ceramsites can reduce the sintering shrinkage of the specimens and help to improve the strength and thermal shock resistance; (2) the samples with the addition of coal gangue ceramsites can produce pores in the matrix of the sintered samples, which provides enough space for the growth of CA6 complex solid solution and expands the irregular lamellar structure; (3) with the addition of coal gangue ceramsites increasing, the linear shrinkage of the samples heat treated at 1 000 or 1 200 ℃ firstly reduces and then increases, the bulk density increases and the apparent porosity decreases; the cold compression strength and the thermal shock resistance of the specimens heat treated at 1 200 ℃ firstly increase and then decrease. Thus, the optimal addition of coal gangue ceramsites is 18%. [ABSTRACT FROM AUTHOR]

This study proposes a novel hierarchical tetrachiral structure inspired by the shell structure of nautilus animals. The parameters of unit cells were designed in compliance with the dimensions of the universal testing machine and the 3D printer. A model made up of 5×5 unit cells of the novel structure was designed and simulated in SolidWorks and ABAQUS software, respectively. To verify the accuracy of the simulated result, the fused deposition modeling 3D-printing technique was adopted to fabricate both traditional and novel structures with acrylonitrile butadiene styrene material and then the quasi-static compression test was conducted. Additionally, the influence of relative density and strain rate on the performance of the structures also was investigated in this study. The findings showed that the novel structure possesses higher energy absorption than the traditional structure. Furthermore, strain rate and relative density have a significant effect on the performance of the structure. Finally, the proposed novel structure can be used in energy-absorbing, impact-resistant devices. [ABSTRACT FROM AUTHOR]

Urbanized areas are known to have significantly higher temperatures than rural areas. The Urban Heat Island (UHI) effect is caused by surfaces such as asphalt, buildings, and other heat-absorbing surfaces that store more heat than natural vegetation. Sunlight reflecting properties of building materials are improved with different applications. The present study investigates the mechanical, durability and solar reflectance properties of the colored self-compacting concrete. SCCs containing yellow, green, and black pigments were produced and evaluated. The fresh properties were determined with the slump, L-Box and V-funnel tests. Furthermore, compressive strength, solar reflectance and magnesium sulfate resistance tests were conducted. Yellow pigment added SCC showed a great potential (with the albedo of 0.42) in terms of solar reflectance and decreasing the contribution to the urban heat island effect. [ABSTRACT FROM AUTHOR]

The employment of breast silicone implants, both in aesthetic and reconstructive medicine, is widespread thanks to their recognized biocompatibility and durability. Some critical situations, for example, in the case of accidental impacts, may induce concerns by potential patients about their use. Dynamic tests reproducing frontal impacts at speeds up to 90 km/h, with anthropomorphic dummies carrying 330 cc prostheses and wearing safety belts, were conducted. Tests showed a significant probability of internal gel loss following implant damage at the highest speed. Moreover, considering that prostheses may remain implanted for many years, the effects of accelerated aging at 37 °C, 60 °C, 75 °C and 90 °C in physiological solution were also investigated. Tensile tests of the shell material and compressive tests of the full prosthesis showed evidence of variation in the prostheses' mechanical characteristics after aging, which affects their stiffness, deformability and strength. These results stress the importance of medical investigations for possible damages of the implanted prostheses in the case of an accident. [ABSTRACT FROM AUTHOR]

The aim was to create magnesium calcium phosphate bone cements (MCPCs) based on struvite and newberyite phases and having antibacterial properties due to the presence of Ag+ ions. An increase of Ag+ concentration from 0.5% to 1.0% substantially enhanced mechanical properties of the cements [compressive strength reached 41 ± 2 MPa (mean ± SD)] and increased the inhibition zone up to 8 mm in a disk diffusion test against Escherichia coli and Staphylococcus aureus without toxicity to MG-63 cells in vitro. Analyses of the MCPC samples soaked in Kokubo's simulated body fluid showed the formation of coatings on the cements' surface, corresponding to a merrillite phase and, after 28 days of the soaking, to a bobierrite phase. Histological examination and micro-CT analysis revealed that the newly developed MCPCs are osteoconductive and biodegradable and may be used as a bone substitute. [Display omitted] [ABSTRACT FROM AUTHOR]

Pectus carinatum (PC) is a chest deformity caused by disproportionate growth of the costal cartilages compared with the bony thoracic skeleton, pulling the sternum forwards and leading to its protrusion. Currently, the most common non-invasive treatment is external compressive bracing, by means of an orthosis. While this treatment is widely adopted, the correct magnitude of applied compressive forces remains unknown, leading to suboptimal results. Moreover, the current orthoses are not suitable to monitor the treatment. The purpose of this study is to design a force measuring system that could be directly embedded into an existing PC orthosis without relevant modifications in its construction. For that, inspired by the currently commercially available products where a solid silicone pad is used, three concepts for silicone-based sensors, two capacitive and one magnetic type, are presented and compared. Additionally, a concept of a full pipeline to capture and store the sensor data was researched. Compression tests were conducted on a calibration machine, with forces ranging from 0 N to 300 N. Local evaluation of sensors' response in different regions was also performed. The three sensors were tested and then compared with the results of a solid silicon pad. One of the capacitive sensors presented an identical response to the solid silicon while the other two either presented poor repeatability or were too stiff, raising concerns for patient comfort. Overall, the proposed system demonstrated its potential to measure and monitor orthosis's applied forces, corroborating its potential for clinical practice. [ABSTRACT FROM AUTHOR]

A rockburst is a dynamic disaster that may result in considerable damage to mines and pose a threat to personnel safety. Accurately predicting rockburst intensity is critical for ensuring mine safety and reducing economic losses. First, based on the primary parameters that impact rockburst occurrence, the uniaxial compressive strength ( σ c ), shear–compression ratio ( σ θ / σ c ), compression–tension ratio ( σ c / σ t ), elastic deformation coefficient ( W et ), and integrity coefficient of the rock ( K V ) were selected as the evaluation indicators. Second, an improved game theory weighting method was introduced to address the problem that the combination coefficients calculated using the traditional game theory weighting method may result in negative values. The combination of indicator weights obtained using the analytic hierarchy process, the entropy method, and the coefficient of variation method were also optimized using improved game theory. Third, to address the problem of subjectivity in the traditional unascertained measurement using the confidence identification criterion, the distance discrimination idea of the Minkowski distance was used to optimize the identification criteria of the attributes in an unascertained measurement and was applied to rockburst prediction, and the obtained results were compared with the original confidence identification criterion and the original distance discrimination. The results show that the improved game theory weighting method used in this model makes the weight distribution more reasonable and reliable, which can provide a feasible reference for the weight determination method of rockburst prediction. When the Minkowski distance formula was introduced into the unascertained measurement for distance discrimination, the same rockburst predictions were obtained when the distance parameter (p) was equal to 1, 2, 3, and 4. The improved model was used to predict and analyze 40 groups of rockburst data with an accuracy of 92.5% and could determine the rockburst intensity class intuitively, providing a new way to analyze the rockburst intensity class rationally and quickly. [ABSTRACT FROM AUTHOR]

Recently, researchers are conducting studies to improve the mechanical and chemical properties of cementitious composites mixed with nanomaterials. Defects may occur inside nano-cementitious composites due to nanomaterial agglomeration in the manufacturing process. These defects can degrade the mechanical performance of the nano-cementitious composite. This study performs ultrasonic non-destructive and compressive strength tests according to the size of defects in nano-cementitious composites. Multi-walled carbon nanotubes (MWCNTs) were used for the nanomaterial, and internal defects of various sizes were considered in the center of the specimens. Ultrasonic pulse velocity was measured according to the defect size until 30 curing days, after which the compressive strength was measured. The ultrasonic pulse velocity of the nano-cementitious composites decreased by up to 9.6% in relation to that of the specimens without defects as the defect size increased, and the compressive strength decreased by up to 35.7%. This study's findings revealed a correlation between ultrasonic pulse velocity and compressive strength according to defect size. Future ultrasonic non-destructive tests will allow for the prediction of mechanical performance and the detection of defects within nano-cementitious composites. [ABSTRACT FROM AUTHOR]

Objectives: The study was done to assess the implant--abutment interface static compressive. strength of three design types and implant--abutment connection failure style. Materials and Methods: The implants at 306 with respect to the y-axis were aligned using a stainless steel holding device. Twenty specimens from each system totaled 60 total. A unidirectional vertical piston in a computer-controlled universal testing machine (MTS 810) generated static compression loading until failure. Specimens were macroscopically examined for fracture of the screw and implant, abutment looseness, and longitudinal displacement. Analysis of variance was used to analyze the data (ANOVA). Result: The screw-vent system had a mean compressive strength of 335.6 22.7 psi for the Unipost system, 384.3 37.1 psi for the screw-vent system, and 245.3 25.4 psi for the ITI-1 piece abutment connection. Conclusion: The connection between the Unipost implant and abutment showed a statistically significant variation. [ABSTRACT FROM AUTHOR]

(1) Background: In recent years, 3D printing has become a highly popular tool for manufacturing in various fields such as aviation, automobiles, plastics, and even medicine, including dentistry. Three-dimensional printing allows dentists to create high-precision models of teeth and jaw structure, and enables them to develop customized tools for patients' treatment. The range of resins used in dentistry is quite large, and this branch is developing rapidly; hence, studies comparing different resins are required. The present study aimed to compare the mechanical properties of two chosen resins used in dentistry. (2) Materials and methods: Ten specimens each of two types of 3D-printable resins (BioMed Amber and IBT, developed by Formlabs) were prepared. The samples were printed on a Formlabs Form 2 3D printer according to ISO standards. Samples for the compression test were rectangular in shape (10 ± 0.2 mm × 10 ± 0.2 mm × 4 ± 0.2 mm), while the samples used for the tensile test were dumbbell shaped (75 mm long, with 10 mm end width and 2 mm thickness). Tensile and compression tests of both materials were performed in accordance with the appropriate ISO standards. (3) Results: The BioMed Amber resin was more resistant to compression and tensile forces, thus implying that the resin could withstand higher stress during stretching, pulling, or pushing. The IBT resin was less resistant to such loads, and failure of this material occurred at lower forces than those for Biomed Amber. An ANOVA test confirmed that the observed differences were statistically significant (p < 0.001). (4) Conclusions: Based on the properties of both materials, the IBT resin could be better used as a tray for placing orthodontic brackets through an indirect bonding technique, while the BioMed Amber resin would be more useful as a surgical guide for placing dental implants and mini-implants. Further potential fields of application of the resins should be investigated. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations on circular concrete‐filled double steel tubular (CFDST) members under flexural load. Seven specimens including five CFDST specimens were tested and the test parameters included the effects of concrete compressive strength, the thickness of the steel tubes, and the diameter ratio on their flexural performance. The final failure modes, moment (M)‐curvature (ϕ) curves, deflection curves of specimens, and distributions of section longitudinal strains were analyzed and reported in this study. A nonlinear finite element model (FEM) was then developed for the CFDST members. After successful validation in ultimate strengths and failure modes, parametric studies were performed by using the verified FEM. A simple formula for calculating the flexural capacity of CFDST members was proposed and compared against several design codes to investigate the design accuracy. Based on this study, it was found that the CFDST members exhibit ductile behavior under flexural load. Increasing the steel area, particularly for the outer tube improved the flexural capacities of the members. Furthermore, the existing design codes were found to be remarkably underestimating the moment capacities of CFDST members whereas the design formula proposed can predict the ultimate flexural capacity with reasonable accuracy. [ABSTRACT FROM AUTHOR]

The strength of the backfill body is an important aspect of safe production in backfill mining technology. In order to quickly and accurately obtain the strength of coal gasification slag -based cemented backfill materials with different ratios, the orthogonal design of 4 factors and 5 levels and variance analysis method were used to study the mass concentration (A), coal gasification slag (CGS)/cement (B), bone glue ratio (C), activator content (D) on the compressive strength of backfill body and a genetic algorithm with 28-day compressive strength of CGS-based backfill material as the response value was constructed, and verify the applicability of the model. The results show that: the primary and secondary factors affecting the 28-day compressive strength are C > A > B > D, the optimal ratio is 80% mass concentration, CGS/cement ratio 4:1, bone glue ratio 3:7, and activator 3%, according to orthogonal variance analysis; the activity of CGS is gradually stimulated as the curing age grows, the hydration products Ettringite and C-S-H are continually generated, and the compressive strength of the backfill material increases in tandem; In the GA-ELM model test set, the intensity correlation coefficient between the prediction and the measured value reached an average of 0.99, and the prediction accuracy was 71.8% and 43.5% higher than that of ELM and PSO-ELM respectively; Laboratory studies have shown that the GA-ELM prediction model has a prediction accuracy of 98.2% and that it can accurately estimate the strength of CGS cemented backfill. [ABSTRACT FROM AUTHOR]

Calcium phosphate cement (CPC) has been widely studied, but its lack of osteoinductivity and inadequate mechanical properties limit its application, while strontium is able to promote bone formation and inhibit bone resorption. In this study, different proportions of tristrontium silicate were introduced to create a novel strontium-modified calcium phosphate cement (SMPC). The physicochemical properties of SMPC and CPC were compared, and the microstructures of the bone cements were characterized with scanning electron microscopy assays. Then, the effect of SMPC on cell proliferation and differentiation was examined. Furthermore, local inflammatory response and osteogenesis after SMPC implantation were also confirmed in the study. Finally, a rat model of isolated vertebral defects was used to test the biomechanical properties of the cements. The results showed that SMPC has better injectability and a shorter setting time than CPC. Meanwhile, the addition of tristrontium silicate promoted the mechanical strength of calcium phosphate cement, and the compressive strength of 5% SMPC increased to 6.00 ± 0.74 MPa. However, this promotion effect gradually diminished with an increase in tristrontium silicate, which was also found in the rat model of isolated vertebral defects. Furthermore, SMPC showed a more preferential role in promoting cell proliferation and differentiation compared to CPC. Neither SMPC nor CPC showed significant inflammatory responses in vivo. Histological staining suggested that SMPCs were significantly better than CPC in promoting new bone regeneration. Importantly, this osteogenesis effect of SMPC was positively correlated with the ratio of tristrontium silicate. In conclusion, 5% SMPC is a promising substitute material for bone repair with excellent physicochemical properties and biological activity. [ABSTRACT FROM AUTHOR]

This study was carried out to evaluate the effect of steel slag (SS) as a by-product as an additive on the geotechnical properties of expansive soil. A series of laboratory tests were conducted on natural and stabilized soils. Steel slag (SS) was added at a rate of 0, 5, 10, 15, 20, and 25% to the soil. The conducted tests are consistency limits, specific gravity, grain size analysis, modified Proctor compaction, free swell, unconfined compression strength, and California Bearing Ratio. The Atterberg limit test result shows that the liquid limit decreases from 90.8 to 65.2%, the plastic limit decreases from 60.3 to 42.5%, and the plasticity index decreases from 30.5 to 22.7% as the steel slag of 25% was added to expansive soil. With 25% steel slag content, specific gravity increases from 2.67 to 3.05. The free swell value decreased from 104.6 to 58.2%. From the Standard Proctor compaction test, maximum dry density increases from 1.504 to 1.69 g/cm3 and optimum moisture content decreases from 19.77 to 12.01 %. Unconfined compressive strength tests reveal that the addition of steel slag of 25% to expansive soil increases the unconfined compressive strength of the soil from 94.3 to 260.6 kPa. The California Bearing Ratio test also shows that the addition of steel slag by 25% increases the California Bearing ratio value from 3.64 to 6.82%. Hence, steel slag was found to be successfully improving the geotechnical properties of expansive soil. [ABSTRACT FROM AUTHOR]

The complexity of fracture geometries impedes reliable prediction of the mechanical properties of frozen fractured rocks. Here, we combine the experimental, numerical, and machine learning methods to predict the uniaxial compressive strength and the Young's modulus of frozen fractured rocks with five fracture geometries, including persistence factor of ice-filled fractures, spacing between the fractures, as well as inclination angle, thickness, and number of the fractures. We use the results of laboratory uniaxial compression tests to validate the numerical model and the results of two-dimensional particle flow code simulations to train the random forest (RF) models. Our study demonstrates reliable prediction of the uniaxial compressive strength and the Young's modulus of frozen fractured rocks and compares the prediction performance with the Ramamurthy criterion. We also conduct a sensitivity analysis to reveal dominant geometries and obtain the simplified RF models with three fracture geometries (i.e., persistence factor, inclination angle, and fracture number) for similar prediction accuracy. We finally use additional experimental results to further test the reliability of the simplified RF models. The combined method can be further applied to study other mechanical properties of complex fractured rocks and is particularly suitable for the cases with limited and scattered data from the fractured rocks in experimental and field investigations. Highlights: The experimental and numerical studies show how the complexity of fracture geometries influences the mechanical properties of frozen fractured rocks. The combined experimental, numerical, and machine learning method is developed to predict the mechanical properties of frozen rocks with complex fracture geometries. The sensitivity analysis is used to determine the dominant geometries to simplify the machine learning models for similar prediction accuracy. [ABSTRACT FROM AUTHOR]

The diagenesis of welded tuffs is a process in which volcanic debris undergoes degassing, compaction, and quenching, and vitreous rheologic, which indicates that the welding occurred in a high-temperature, high-pressure diagenetic environment and that different temperatures and pressures result in different degrees of welding in the welded tuffs, which can also result in differences in the mechanical properties of the rock. In this study, based on petrographic identification, mineral composition analysis, and pore structure characterization, uniaxial compression combined with linear accelerator CT and Brazilian splitting tests was carried out to investigate the influence of the welding degree on the strength and failure modes. The test results showed that although they had almost similar mineral composition and porosity, the uniaxial compression strength and tensile strength of the strongly welded tuffs were greater than that of the weakly welded tuffs. Their failure modes were also different. Fractures in the weakly welded tuffs developed gradually, while the strongly welded tuffs showed a higher brittleness with sudden failure. The results of this study shed light on the influence of the diagenetic environment on the mechanical properties of rock from a geological perspective and can provide a mechanical basis for rockfall risk evaluation in scenic areas of welded tuff. [ABSTRACT FROM AUTHOR]

In engineering practices, it is critical and necessary to either measure or estimate the uniaxial compressive strength (UCS) of the rock. Measuring the UCS of rocks requires comprehensive studies in the field and in the laboratory for the rock block sampling, coring, and testing. These studies are time-consuming, expensive and go through difficult processes. Alternatively, the UCS can either be estimated by empirical relationships or predictive models with various measured mechanical and physical parameters of the rocks. Previous studies used different methods to predict UCS, including least squares regression techniques (MLR), adaptive neuro-fuzzy inference system (ANFIS), Sequential artificial neuron networks (SANN), etc. This study is intended to estimate the UCS of the carbonate rock by using a simple, measured Schmidt Hammer (SHVC) test on core sample and a unit weight (γn) of carbonate rock. Principal components regression (PCR), MLR, SANN, and ANFIS are employed to predict the UCS. We are not aware of any study compared the performances of these methods for the prediction of the UCS values. Based on the root mean square error, mean absolute error and R2, the Sequential artificial neural network has a slight advantage against the other three models. [ABSTRACT FROM AUTHOR]