Results Of Compression Tests Research Articles

A new state-dependent constitutive model for cyclic thermo-mechanical behaviour of unsaturated vegetated soil

Climate change has resulted in increasing attention being paid to the effects of temperature and humidity on vegetated soil. However, existing constitutive models rarely investigate the thermo-mechanical behaviour, such as the accumulation of plastic strain under non-isothermal conditions, of unsaturated vegetated soil. To address this issue, this study developed a comprehensive constitutive model by adopting state-dependent dilatancy in conjugation with loading, memory, and bounding surfaces. Moreover, root-induced hardening due to pore occupancy and internal bonding is modelled with dependence on the root volume ratio. The performance of this newly developed constitutive model is then evaluated using previous laboratory element tests. Comparisons between the computed and measured results reveal that the model is capable of capturing variations in soil state at a range of temperatures, suctions, and root volume ratios. The shearing behaviour of vegetated soil, especially its volumetric response, is well predicted by the model, as confirmed by comparing it with triaxial compression test results. Moreover, the model predicts that the accumulated volumetric strain of unsaturated vegetated soil (0.2%) is significantly less than saturated bare soil (1.1%) after four thermal cycles. These computed results imply that vegetation can mitigate the effects of climate change on soil through both transpiration-induced suction and mechanical reinforcement.

Penerapan Teknologi Kompresi Data untuk Optimalisasi Manajemen Bahan Ajar Digital Pada Aplikasi Respository Menggunakan Personal Extreme Programming (PXP)

This research aims to create an educational environment integrated with technology through the implementation of educational technology, particularly by managing and storing digital learning device documents, known as a repository. The developed Repository System aims to optimize the management of storage for learning device documents within an educational institution. A case study was conducted at a Vocational High School (SMK). The management and storage system for learning device documents was developed using the Personal Extreme Programming (PXP) method, adopting an adaptive and flexible Agile approach. The repository system also applies data compression technology to optimize the storage capacity of learning device documents. Based on the results of data compression testing, the developed system proves to be suitable, achieving an average storage efficiency of 40.04% for each uploaded file. This research contributes to practical insights into the implementation of a repository system in an educational environment, particularly in Vocational High Schools, with a focus on curriculum transitions and the efficiency of managing learning device documents.

Comparison between methods for determining the effective vertical yield stress of intermediate fine-grained soils.

Effective vertical yield stress (σ'xy) is essential in accurately describing fine-grained soils' mechanical properties and their behaviour under load over time. It helps assess settlements and stress history. In most constitutive models, this parameter indicates changes in the soil behaviour due to the development of recoverable and irrecoverable strains resulting from loading. The results of oedometric compression tests for 25 soil samples with a wide range of plasticity parameters were used for the investigation. The intermediate fine-grained soils comprised different proportions of clayey, silty and sandy fractions. An in-depth, two-staged statistical analysis was carried out to compare twelve methods of determining effective vertical yield stress, namely: Casagrande (CM), Pacheco Silva (PSM), Butterfield (BTM), Oikawa (OIM), Onitsuka (ONM), Boone (BM), Becker (WM), Morin (WPUVSM) Wang & Frost (DSEM), Tavenas (SEM), Senol (SLSEM), and Janbu (JM). It aimed to check the association of these methods and the consistency of the obtained results. Based on the difference analysis, the methods originated in the work approach (i.e. WM, WPUVSM, DSEM) and CM gave comparable σ'xy values. The methods utilised bi-logarithmic plots (i.e. BTM, OIM, ONM) received slightly greater or lesser σ'xy values than BM and JM. The remaining methods were characterised by medium to the high variability and were sensitive to even the slightest disturbances resulting from the procedure of determining σ'xy.

Enhancing the Compressive Strength of M30 Grade of Concrete Using Pumice With 50% GGBS and Metakaolin Comparing with Conventional Concrete

The aim is to compare the conventional concrete by employing a mix of M30 grade concrete, a novel pumice aggregate is used to partially replace the coarse aggregate to create lightweight concrete. All groups were prepared at the composition of 40% Cement and replacing 50% GGBS, 10% Metakaolin is kept constant in our concrete. Coarse aggregate replaced by novel pumice stone and M-sand as Fine aggregate. The group of 6 cubes was formed according to the curing dates of 28 days. Metakaolin and GGBS are procured from Scientific Company and Novel Pumice Aggregate are arranged from online traders. Cement and M sand were arranged from the local shop. The group of 18 cubes was formed according to the Curing date for 28 days. To determine the compressive strength, two groups and a total of 36 cubes were constructed. The average compressive strength test result for conventional concrete of grade M30 at 28 days is 30.28 N/mm2. The average result for Group I and for 18 cubes for the M30 grade of concrete @ 28 days Compressive Strength test result of Concrete with Novel Pumice Aggregate stone and Partial Replacement of GGBS and Metakaolin by the weight of cement is 35.19 N/mm2. From the independent t-test analysis p=0.000, i.e., smaller than p=0.05(p<0.05) which indicates that there is a noteworthy statistical distinction between the two groups. The compressive strength of concrete of M30 grade at 28 days of compressive strength test results of concrete with new pumice aggregate stone and partial replacement of GGBS and Metakaolin by the weight of cement is increased.

CPT-based design of pile foundations in sand and clay: Perspectives

This paper provides some perspectives and guidance for the design of pile foundations in sand and clay using cone penetration test (CPT) results. A key variable in the estimation of the limit unit shaft resistance qsL of piles in sand is the critical-state interface friction angle δc, which is a function of the critical-state friction angle ϕc of the sand. In the absence of direct shear or triaxial compression test results, which is often the case for routine infrastructure projects, engineers typically assume a conservative value for ϕc in pile design. In addition, effective stress-based methods for estimation of qsL of driven piles in clay rely on the residual interface friction angle δr, among other variables; however, in these methods, δr does not vary with the normal effective stress on the pile operative at the time of shearing. In this paper, we present relationships and approaches to address these issues. Finally, a relationship between the cone resistance qc and the corrected standard penetration test (SPT) blow count N60 was also developed so that engineers may obtain an estimate of qc for use in a CPT-based design method when only SPT blow counts are available for a site.

Experimental Investigation of the Effect of Die Shape on Mechanical Properties of Aluminum Alloy by Hot Direct Extrusion Process

This experimental study examined the impact of die shape on the mechanical characteristics of the AA7075, the aluminum alloy, extruded by hot direct extrusion. These characteristics include the extrusion load, hardness and compression tests, and stress-strain curve. Three alternative widths of the extruded metal exit zone (16, 18, and 20 mm) and three different die angles (15°, 30°, and 45°) were considered in the experiments. According to the findings, the extrusion load for the extruded items was the highest at an angle of 30° and the lowest at an angle of 15°. In terms of the hardness test of extruded materials specimens, the hardest areas were located at the outer circumference for all extrusion diameters and angles. Although the extruded samples’ compression test results showed variations in the samples’ loads before and after extrusion, it was also noticed that some of the other samples’ stress and strain curves converged while others had only slight differences.

Experimental investigation on static and dynamic properties of nanosilica modified cement soil

Experimental investigation on static and dynamic properties of nanosilica modified cement soil

Synergistic effects of supplementary cementitious materials and compressive strength prediction of concrete using machine learning algorithms with SHAP and PDP analyses

Synergistic effects of supplementary cementitious materials and compressive strength prediction of concrete using machine learning algorithms with SHAP and PDP analyses

Compression Strength and Critical Impact Speed of Typical Fertilizer Grains

The application of fertilizer is necessary for the growth and yield of crops, especially for paddy rice. Precision application is important for the fertilizer utilization rate and sustainable development of agriculture. However, the crushing of fertilizer grains will reduce the quality of fertilization, for the decrease in the size and mass of the fertilizer particles and the degree of crushing mainly depend on the physical and mechanical properties of the fertilizer grains. In this study, the compression strength and critical impact speed of four typical commonly used fertilizer grains, a compound fertilizer of nitrogen, phosphorus, and potassium (NPK compound fertilizer), organic fertilizer, large granular urea, and small granular urea, were measured and analyzed. The static compression test was carried out using a TMS-Pro texture analyzer and the results show that the four kinds of fertilizer grains are brittle materials, and their elastic moduli are 208 MPa, 233 MPa, 140 MPa, and 107 MPa, respectively; the theoretical impact model of fertilizer granules is established based on the compression test result and Hertz elastic contact theory, the theoretical formula for the critical impact speed of fertilizer grains is derived, and the theoretical critical impact strength and speed are worked out. An image capture system for the impact process of fertilizer grains was developed, and the impact test was conducted. The results show that the critical impact speed of the four kinds of fertilizer grains decreases with the increase in granule size, while the variance analysis shows that the effect is not significant. The comparison of the experimental results with the theoretical values shows that the theoretical formula could be used to predict the trends of the critical impact speed of fertilizer grains. The model was optimized with the MATLAB 2018 function fitting tool based on the test and analysis. The goodness of fit of the formula is 0.824, which is 13.43% greater than that of the original theoretical formula, indicating that the modified formula based on the compression test data might estimate the critical impact speed of the granular fertilizer with brittle material properties more accurately. The results may provide a reference for the parameter design of a precision fertilization machine.

Investigating the effects of printing temperatures and deposition on the compressive properties and density of 3D printed polyetheretherketone

Polyetheretherketone (PEEK) is a biocompatible high-performance thermoplastic that can be processed through material extrusion (ME) additive manufacturing (AM) for load-bearing implant applications. In this work, density measurements and compression testing were used to investigate the relation between printing temperatures and deposition patterns of PEEK 3D printed samples. Different deposition patterns were tested with different nozzle and zone heater temperatures to observe how the heat input from the printing process influenced the deposition stability with different nozzle paths. Compression test results showed that samples with concentric-based deposition patterns resulted in higher compressive yield strength and modulus than the rectilinear samples. These results were correlated with the samples’ void contents estimated from density measurements. Both the highest 0.2% offset yield strength of 100.3 MPa and the highest modulus of 3.58 GPa were obtained with an interlayer offset deposition which resulted in reductions in estimated void contents between 48 and 72% in relation to concentric deposition. Different printing temperatures and deposition sequences were tested, where higher printing temperatures resulted in lower yield strength and stiffness. Alternating deposition between the outer and inner lines of the concentric pattern resulted in a reduction of about 43% in void contents and increased elastic modulus and yield strength from 3.12 to 3.40 GPa and 94.4 to 95.2 MPa respectively. The results from this work suggest that the relation between printing temperatures and deposition strategy for different print geometries plays a significant role in the ME-AM of PEEK for high-performance applications.

Characterizing piezoelectric properties of PVDF film under extreme loadings

Polyvinylidene fluoride (PVDF) as a polymer has been proven to be an effective piezoelectric sensor with advantages of good flexibility, high mechanical strength, and high chemical resistance. Numerous studies have focused on the response of PVDF film at high strain rates, but few on low strain rate response, and the response of PVDF film at different strain rates is unknown. To address these limitations, we examine the piezoelectric properties of PVDF film at extreme high and low loading rates. We design quasi-static compression and dynamic split Hopkinson pressure bar (SHPB) test setups to examine the response of PVDF film. Quasi-static compression test results show that PVDF films have good repeatability and linearity. The charge shift phenomenon is observed at quasi-static loading conditions, and the charge shift rate is found to be related to the gain coefficient of charge amplifier. Next, SHPB tests are performed and results show that PVDF film can well capture the propagation of stress wave. Moreover, it is observed that the PVDF film under high loading rate has a higher failure strength in comparison to that of low loading rate. Finally, based on the measured points by quasi-static compression and SHPB tests, the piezoelectric coefficients of PVDF film under extreme low (on the scale of strain rate of 10−2 s−1) and extreme high (on the scale of strain rate 105 s−1) loading rates are found to be 30.79 pC/N and 27.72 pC/N, respectively. Note that, the strain rate difference is seven orders of magnitude, the piezoelectric coefficient difference is only 9.97%. We believe our findings can advance the design and application of PVDF films in practical engineering.

A progressive damage model associated with dynamic fracture toughness and IFF criterion with a fast search algorithm of fracture angle

A progressive damage model associated with dynamic fracture toughness and IFF criterion with a fast search algorithm of fracture angle

Evaluation of ultimate load - bearing capacity of piles based on static compression test and pile dynamic analysis (PDA)

Determining the load bearing capacity of piles from field tests is a reliable method that allows for the verification of load carrying capacity according to theoretical calculations, thereby the ultimate load-bearing capacity of the piles can be evaluated, serving as the basis for selecting the design load-bearing capacity that is suitable for the site conditions. Among the various pile load testing methods, static compression testing is a traditional method known for its high reliability and early adoption. However, when piles are constructed at significant depths or large diameter drilled piles have higher load bearing capacities, static compression testing encounters difficulties due to the large experimental load and extends testing times. In contrast, the pile dynamic analysis method (PDA) introduced by the Case Institute of Technology in the United States in the 1960s determines the load bearing capacity of piles based on stress wave propagation theory in elastic bars. It offers several advantages, including shorter testing times and no need for static loading, making it suitable for challenging terrain conditions. Nowadays, this method is widely used and integrated into the design guidelines and testing standards of many countries. In this article, base on the results of axial static compression tests and PDA method on reinforced concrete piles and drilled piles at several real project to compare and evaluate the load bearing values of the piles and assess the reliability of the testing methods.

Statistical Evaluation and Comparison of Concrete Produced in Eskisehir with Concrete Produced in Different Provinces in Turkey

In the research, statistical analysis of the compressive strength test results of concrete samples from C25/30 and C30/37 class ready-mixed concretes (RMC) produced in various concrete plants in Eskişehir in 2022 and poured in various construction sites and different construction sections (foundation and column, beam, slab) were made. The concrete quality was attempted to be evaluated in accordance with the C25/30 and C30/37 concrete classes created in different construction sites and building sections in Eskişehir using the results of the strength tests performed on a total of 1355 samples. The previous scientific studies were carried out within the framework of the statistical analysis of the compressive strength results of the C25/30 and C30/37 concrete class samples that were brought to the laboratory from various locations of different construction sites in Eskişehir, within the framework of the standards determined by the quality grades determined by ACI and TS EN 206. In the investigations, the information from the same strength classes that were poured in Eskişehir and different provinces in Turkey at various dates was compared and reviewed.

COMPARATIVE ANALYSIS OF PORTLAND AND WHITE CEMENT IMPACT ON UNCONFINED COMPRESSIVE STRENGTH OF SOIL

Soil improvement plays a vital role in any engineering project, as the entire load from the superstructure is transmitted on the underlaying soil. Weaker soil increases foundation dimension, which is costly and soft soil generally causes difficulties on construction sites when it has low strength and low stiffness. Hence, in order to reduce cost and achieving better structural stability, soil must be stabilized with a mixture in order to achieve larger load carrying capacity. When soils fail to meet the geotechnical requirements, stabilizing the soil using cement is an essential process in geotechnical practice. Clay soil was stabilized in this study using white cement and regular Portland cement. White cement and Portland cement were collected and mixed with clay soil in amounts of 2%, 4%, 6%, 8%, and 10%. Soil tests such as grain size distribution, specific gravity test, unconfined compressive test, soil tests were performed on samples. The report includes field sampling, laboratory testing and engineering analysis and evaluation. From the result of unconfined compressive strength test, it is found that the addition of 6%, 8%, 10% of Portland cement and 10% of white cement increases the shear strength of the clay soil.

Effects of metakaolin and sodium silicate treatment on highwater content dredged clay for improved construction fill performance

Effects of metakaolin and sodium silicate treatment on highwater content dredged clay for improved construction fill performance

Study on Mechanical Performance and Reinforcement Mechanisms of Geocell-Reinforced Soil

A concept for a reinforcement mechanism is presented and analyzed combined with test results to explain the reinforcement effect of a geocell. A series of pull-out and unconfined compression tests were carried out to investigate the effect of various parameters, including water content, compactness, and the number of geocell-reinforced layers, on the mechanical performance of geocell-reinforced soil. The results of the pull-out tests were mutually verified by the formulas for the reinforcement mechanism and demonstrate that the compactness and water content significantly affect the friction coefficient of the geocell–soil interface, which increases as compactness rises and water content falls. Compared with lowering the water content, improving compactness was better for enhancing the frictional properties of the geocell–soil interface; this had the highest increase, at 90%, as compactness rises from 92% to 94%. According to the unconfined compression test results, the unconfined compressive strength of geocell-reinforced soil is raised by higher compactness, more geocell-reinforced layers, and lower water content; this had the highest increase, at 93.1%, as the water content dropped to its optimum, from 19% to 15%. The compactness of filled soil dramatically influences the unconfined compressive strength of unreinforced specimens, which had an increase of 59.6% when compactness rose from 92% to 94%. However, this effect was weakened as more geocell was added to filled soil. As the number of geocell-reinforced layers rose from 0 to 1 under the compactness level of 92%, the increase of ultimate unconfined compressive strength reached 82.6%, higher than in other reinforcement layers.

Theoretical and Experimental Investigation of 3D-Printed Polylactide Laminate Composites' Mechanical Properties.

The purpose of this work is to theoretically and experimentally investigate the applicability of the Tsai-Hill failure criterion and classical laminate theory for predicting the strength and stiffness of 3D-printed polylactide laminate composites with various raster angles in mechanical tests for uniaxial tension and compression. According to the results of tensile and compression tests, the stiffness matrix components of the orthotropic individual lamina and strength were determined. The Poisson's ratio was determined using the digital image correlation method. It was found that the Tsai-Hill criterion is applicable for predicting the tensile strength and yield strength of laminate polymer composite materials manufactured via fused deposition modeling 3D printing. The calculated values of the elastic moduli for specimens with various raster angles correlate well with the values obtained experimentally. In tensile tests, the error for the laminate with a constant raster angle was 3.3%, for a composite laminate it was 4.4, in compression tests it was 11.9% and 9%, respectively.

Salicylic acid-loaded gelatin methacryloyl (GELMA) microneedles as a potential drug delivery system in plant diseases

Salicylic acid-loaded gelatin methacryloyl (GELMA) microneedles as a potential drug delivery system in plant diseases

Mechanical behavior and design applicability of ultra-high-performance concrete-filled circular steel tubular short columns under axial compression

Mechanical behavior and design applicability of ultra-high-performance concrete-filled circular steel tubular short columns under axial compression