scholarly journals Experimental and FEM Investigation of Cob Walls under Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Enrico Quagliarini ◽  
Gianluca Maracchini
Keyword(s):  
Compressive Strength ◽  
Mechanical Behaviour ◽  
Poisson’S Ratio ◽  
Construction Material ◽  
Strong Dependence ◽  
Environmental Benefits ◽  
Poisson's Ratio ◽  
Experimental Program ◽  
Rammed Earth ◽  
Crack Model

Earth has been used as construction material since prehistoric times, and it is still utilized nowadays in both developed and developing countries. Heritage conservation purposes and its intrinsic environmental benefits have led researchers to investigate the mechanical behaviour of this material. However, while a lot of works concern with rammed earth, CEB, and adobe techniques, very few studies are directed towards cob, which is an alternative to the more diffused rammed earth and adobe in specific geographic conditions. Due to this lack, this paper presents an experimental program aimed at assessing the failure mode and the main mechanical properties of cob earth walls (compressive strength, Young’s modulus, and Poisson’s ratio) through monotonic axial compression tests. Results show that, if compared with CEB, adobe, and rammed earth, cob has the lowest compressive strength, the lowest modulus of elasticity, and Poisson’s ratio. Differences are also found by comparing results with those obtained for other cob techniques, underlining both the high regional variability of cob and the need of performing more research on this topic. A strong dependence of material properties on loading rate and water content seems to exist too. Finally, the ability of a common analytical method used for masonry structures (an FEM macromodelling with a total strain rotating crack model) to represent the mechanical behaviour of cob walls is showed.

scholarly journals Experimental Research on the Mechanical Characteristics and the Failure Mechanism of Coal-Rock Composite under Uniaxial Load

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Ke Yang ◽  
Zhen Wei ◽  
Xiaolou Chi ◽  
Yonggang Zhang ◽  
Litong Dou ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Failure Mechanism ◽  
Poisson’S Ratio ◽  
Mechanical Characteristics ◽  
Poisson's Ratio ◽  
Energy Value ◽  
Coal Rock

Due to the influence of the component structure and combination modes, the mechanical characteristics and failure modes of the coal-rock composite show different characteristics from the monomer. In order to explore the effect of different coal-rock ratios on the deformation and the failure law of the combined sample, the RMT rock mechanics test system and acoustic emission real-time monitoring system are adopted to carry out uniaxial compression tests on coal, sandstone, and three kinds of combined samples. The evolution rules of the mechanical parameters of the combined samples, such as the uniaxial compressive strength, elastic modulus, and Poisson’s ratio, are obtained. The expansion and failure deformation characteristics of the combined sample are analyzed. Furthermore, the evolution laws of the fractal and acoustic emission signals are combined to reveal the crack propagation and failure mechanism of the combined samples. The results show that the compressive strength and elastic modulus of the combined sample increase with the decrease of the coal-rock ratios, and Poisson’s ratio decreases with the decrease of the coal-rock ratios. The strain softening weakens at the postpeak stage, which shows an apparent brittle failure. The combined sample of coal and sandstone has different degrees of damages under load. The coal is first damaged with a high degree of breakage, with obvious tensile failure. The acoustic emission energy value presents different stage characteristics with increasing load. Crackling sound occurs in the destroy section before the sample reaches the peak, along with small coal block ejection and the partial destruction. The energy value fluctuates violently, with the appearance of several peaks. At the postpeak stage, the coal samples expand rapidly with a loud crackling sound in the destroy section, and the energy value increases dramatically. The crack propagation induces the damage in the sandstone; when the energy reaches the limit value, the instantaneous release of elastic energy leads to the overall structural instability.

scholarly journals Models for evaluating craters morphology, relation of indentation hardness and uniaxial compressive strength via a flat-end indenter

2018 ◽  
Vol 10 (1) ◽  
pp. 289-296 ◽  
Author(s):  
Ligang Zhang ◽  
Xiao Fei Fu ◽  
G. R. Liu ◽  
Shi Bin Li ◽  
Wei Li ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Internal Friction ◽  
Uniaxial Compressive Strength ◽  
Poisson’S Ratio ◽  
Failure Process ◽  
Apex Angle ◽  
Poisson's Ratio ◽  
Percentage Error ◽  
Indentation Hardness ◽  
Angle Of Internal Friction

AbstractIn this work, the intensive theoretical study and laboratory tests are conducted to evaluate the craters morphology via the flat-ended indenter test, relationship of indentation hardness (HRI) and uniaxial compressive strength (UCS). Based on the stress distribution, failure process and Mohr–Coulomb failure criterion, the mathematical mechanical models are presented to express the formation conditions of “pulverized zone” and “volume break”. Moreover, a set of equations relating the depth and apex angle of craters, the ratio of indentation hardness and uniaxial compressive strength, the angle of internal friction and Poisson’s ratio are obtained. The depth, apex angle of craters and ratio of indentation hardness and uniaxial compressive strength are all affected by the angle of internal friction and Poisson’s ratio. The proposed models are also verified by experiments of rock samples which are cored from Da Qing oilfield, the percentage error between the test and calculated results for depth, apex angle of craters and the ratio of HRI and UCS are mainly in the range of –1.41%–8.92%, –5.91%–3.94% and –8.22%–13.22% respectively for siltstone, volcanic tuff, volcanic breccia, shale, sand stone and glutenite except mudstone, which demonstrates that our proposed models are robust and effective for brittle rock.

In-Plane Compressive Strength Analysis of Novel Folded Honeycomb Material

2019 ◽  
Author(s):  
Ruijun Ma ◽  
Jianguo Cai ◽  
Yutao Wang ◽  
Jian Feng
Keyword(s):  
Compressive Strength ◽  
Poisson’S Ratio ◽  
Local Buckling ◽  
Poisson's Ratio ◽  
Strength Analysis ◽  
Negative Poisson’S Ratio ◽  
Plateau Stress ◽  
Element Simulation ◽  
Negative Poisson's Ratio ◽  
Plateau State

Abstract Two novel folded honeycombs with miura pattern are proposed in this paper. Geometry parameters for design process are given and explained. The in-plane compressive strength of the two proposed novel folded honeycombs has been studied by means of finite element simulation using ABAQUS. Quasi-static loading in two in-plane direction is selected to obtain the deformation and plateau stress. The unique collapse modes and plateau state are obtained and discussed. Compared with the conventional honeycombs, the in-plane strength of the two folded honeycombs is improved significantly. The negative Poisson’s ratio effect and buckling-restrained mechanism are introduced to illustrate the improvement. It is summarized that plateau stress under in-plane loading is improved with the included angle of miura pattern decrease for the local buckling is restrained. The folded auxetic honeycomb has the best in-plane strength for its presented negative Poisson’s ratio in two loading cases.

Analytical Study and Laboratory Tests for Investigating the Application of Polymer for Achieving High Strength Concrete

2019 ◽  
Vol 27 ◽  
pp. 39-51
Author(s):  
Kamrun N. Keya ◽  
Alamgir Habib ◽  
Sampa Akhter ◽  
Hasan M. Tamim ◽  
Maksuda Akhter
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Epoxy Resin ◽  
Construction Material ◽  
High Strength ◽  
Experimental Program ◽  
Polymer Concrete ◽  
Conventional Concrete ◽  
Polymer Resin ◽  
Adequate Quality

Polymer concrete is one kind of which is used as an additive of the binding material. Due to their high thermal stability, tensile and flexural strengths, high compressive strength and resistance to chemical, its popularity increasing rapidly and which is now widely used as a construction material. This paper explores a research study that has been establishing a standard correlation between concrete compressive strength with the amount of polymers and other ingredients. Hence a comparison was made between the conventional concrete and polymer concrete. As per ASTM C31, the mix design of polymer concrete is calculated and estimated the material quantity. In this research, a total of twenty-two trail mixes of polymer concrete were prepared with different amount of epoxy resin and hardener. In implementation of experimental program compressive strength test was performed for conventional concrete, polymer resin (epoxy resin) concrete with resin percentage 10%, 12%, 15%, 17% and 20% was performed and compared the results with polymer concrete (no-fly ash) with polymer concrete (fly ash) percentage 15%. It was found that the compressive strength of the polymer concrete was increased with increasing the percentage of a polymer. Compressive strength of the 17% and 20% polymer resin-based polymer concrete was 46.75 MPa and 48.32 MPa and cost was around 1,17,110.00 TK and 1,37,152.00 TK; respectively and also it was observed that by using fly ash the strength of the concrete could be increased significantly. It can be said that higher strength can be achieved with a comparatively high cost. However, the cost can be reduced by proper materials selection, mix ratio, curing and adequate quality control of the material.

scholarly journals Vertical Rods as a Seismic Reinforcement Technique for Rammed Earth Walls: An Assessment

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Q.-B. Bui ◽  
T.-T. Bui ◽  
R. El-Nabouch ◽  
D.-K. Thai
Keyword(s):  
Compressive Strength ◽  
Numerical Study ◽  
Construction Material ◽  
Thermal Inertia ◽  
Embodied Energy ◽  
Rammed Earth ◽  
Seismic Action ◽  
Horizontal Force ◽  
The Subject ◽  
Earth Walls

Rammed earth (RE) is a construction material which is manufactured by compacting soil by layers within a formwork to build a monolithic wall. RE material is the subject of numerous scientific researches during the last decade because of the significant heritage of RE buildings and the sustainable properties of this material: low embodied energy, substantial thermal inertia, and natural regulator of moisture. The seismic performance of RE buildings is an interesting topic which needs to be thoroughly investigated. This paper presents a numerical study which assesses the relevancy of a seismic reinforcement technique for RE walls by using two vertical steel rods installed at two extremities of the walls. The discrete element method (DEM) was used to model unreinforced and reinforced RE walls. These walls were first loaded with a vertical stress on the top to simulate the vertical loads and then submitted to a horizontal loading on the top to simulate the seismic action. Two current cases of RE buildings were investigated: one-storey and two-storey buildings. The results showed that the reinforcement technique enhanced the maximum horizontal force about 25% and 10%, respectively, for the cases of one- and two-storey buildings. Higher effectiveness of this reinforcement technique is expected for RE materials having higher compressive strength, for example, stabilized RE.

scholarly journals Elastic Mechanical Properties of 45S5-Based Bioactive Glass–Ceramic Scaffolds

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3244 ◽  
Author(s):  
Francesco Baino ◽  
Elisa Fiume
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Shear Modulus ◽  
Glass Ceramic ◽  
Poisson’S Ratio ◽  
Mechanical Performance ◽  
Poisson's Ratio ◽  
Shear Moduli ◽  
Bioactive Scaffolds

Porosity is recognized to play a key role in dictating the functional properties of bioactive scaffolds, especially the mechanical performance of the material. The mechanical suitability of brittle ceramic and glass scaffolds for bone tissue engineering applications is usually evaluated on the basis of the compressive strength alone, which is relatively easy to assess. This work aims to investigate the porosity dependence of the elastic properties of silicate scaffolds based on the 45S5 composition. Highly porous glass–ceramic foams were fabricated by the sponge replica method and their elastic modulus, shear modulus, and Poisson’s ratio were experimentally determined by the impulse excitation technique; furthermore, the failure strength was quantified by compressive tests. As the total fractional porosity increased from 0.52 to 0.86, the elastic and shear moduli decreased from 16.5 to 1.2 GPa and from 6.5 to 0.43 GPa, respectively; the compressive strength was also found to decrease from 3.4 to 0.58 MPa, whereas the Poisson’s ratio increased from 0.2692 to 0.3953. The porosity dependences of elastic modulus, shear modulus and compressive strength obeys power-law models, whereas the relationship between Poisson’s ratio and porosity can be described by a linear approximation. These relations can be useful to optimize the design and fabrication of porous biomaterials as well as to predict the mechanical properties of the scaffolds.

scholarly journals Experimental Study on the Influence of Moisture Content on the Mechanical Properties of Coal

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Mingxing Gao ◽  
Yongli Liu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Moisture Content ◽  
Uniaxial Compressive Strength ◽  
Poisson’S Ratio ◽  
Triaxial Compression ◽  
Test System ◽  
Poisson's Ratio ◽  
Compression Tests

Water injection in coal seams will lead to the increase of moisture content in coal, which plays an essential role in the physical and mechanical properties of coal. In order to study the influence of moisture content on the mechanical properties of soft media, the forming pressure (20 MPa) and particle size ratio (0-1 mm (50%), 1-2 mm (25%), and 2-3 mm (25%)) during briquette preparation were firstly determined in this paper. Briquettes with different moisture contents (3%, 6%, 9%, 12%, and 15%) were prepared by using self-developed briquettes. Uniaxial and triaxial compression tests were carried out using the RMT-150C rock mechanics test system. The results show that the uniaxial compressive strength and elastic modulus of briquette samples increase first and then decrease with the increase of briquette water, while Poisson’s ratio decreases first and then increases with the increase of briquette water. When the moisture content is around 9%, the maximum uniaxial compressive strength is 0.866 MPa, the maximum elastic modulus is 1.385 GPa, and Poisson’s ratio is at the minimum of 0.259. The compressive strength of briquettes increases with the increase of confining pressure. With the increase of moisture content, the cohesion and internal friction angle of briquettes first increased and then decreased.

Application of Tire Waste Material to Enhance the Properties of Saudi Class G Oil Well Cement

2021 ◽  
Author(s):  
Abdulmalek Ahmed ◽  
Ahmed Abdulhamid Mahmoud ◽  
Salaheldin Elkatatny ◽  
Rahul Gajbhiye ◽  
Abdulaziz Al Majed
Keyword(s):  
Compressive Strength ◽  
Poisson’S Ratio ◽  
Density Variation ◽  
Waste Material ◽  
Plastic Viscosity ◽  
Poisson's Ratio ◽  
Oil Well ◽  
Cement Sample ◽  
Oil Well Cement ◽  
Well Cement

Abstract Cementing is an important operation for the integrity of the wellbore due to its role in providing several functions. To perform these functions, a high performance cement is required. Different types of additives and materials have been added to the cement slurry to improve its performance. Tire waste material is considered one of the greatest wastes globally. It is a dangerous material to the environment and human. Subsequently, it has been included in many industrial processes to reduce its hazards. This work evaluated the application of tire waste material in oil and gas industry to improve the properties of Saudi class G oil well cement. Two cement slurries were formulated under high pressure and high temperature of 3000 psi and 292 °F, respectively. The first slurry was the base cement without tire waste and the second slurry contained the tire waste. The effect of using the two slurries on the cement properties such as density variation, compressive strength plastic viscosity, Poisson's ratio and porosity was evaluated. The results showed that, when tire waste material was used, lower density variation was accomplished. Using tire waste was efficient to decrease the density variation to an extremely low proportion of 0.5%. Adding tire waste to the cement composition decreased its plastic viscosity by 53.1%. The tire waste cement sample had a higher Poisson's ratio than the base cement sample by 14.3%. Utilizing the tire waste improved the cement's compressive strength by 48.3%. The cement porosity was declined by 23.1% after adding the tire waste. Beside the property's enhancement in the cement, the application of tire waste has also an economical advantage, since it is inexpensive material which is influential in our daily life.

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