Crack Development Research Articles

Compressive failure and fragmentation of fused silica glass under quasi-static loading

This paper investigates the failure and post-failure fragmentation processes of fused silica glass cylinders under quasi-static compression, addressing the effects of surface finish on apparent strength. The compressive strengths of cylinders with side-polished sides under dry friction conditions (PSG-D) or lubricated conditions (PSG-L) were 2.52 GPa and 2.32 GPa, respectively. In situ observations showed that these specimens fractured from either the top or bottom contact surfaces, and that friction between the specimen and the loading anvil delayed the development of surface cracks. The unpolished rough side specimens (RSG-D) under dry friction conditions failed at a much lower level of 1.54 GPa, initiated by defects in the side surfaces. Specimens "explosively" fragmented upon failure. The propagation speed of the failure front ranged from 1800 to 2800 m/s. The average sizes and distributions of the fragments were determined through statistical analysis, with results showing reasonably close agreement with theoretical estimations.

Bond Behavior and Failure Mechanisms of the Interface between Engineered Cementitious Composites and Shaped Steel

Due to their excellent ductility and crack-control ability, engineered cementitious composites (ECCs) combined with shaped steel can produce steel-reinforced engineering cementitious composite (SRECC) structures which exhibit significant advantages in prefabricated buildings. The interface bond behavior is the base for the cooperative working performance of the shaped steel and ECC. This study included push-out tests of one ordinary concrete control specimen and ten ECC specimens. The various parameters were the ECC compressive strength, fiber volume content, cover thickness, and the embedded length of shaped steel. The bond stress–slip curves at the loading and free end were obtained, and the effects of various parameters on the characteristic points of curves were analyzed. The results indicated that the ordinary concrete specimen failed in brittle splitting, with the cracks completely penetrating the surface of the specimen. Due to the fiber-bridging effect in ECCs effectively preventing the development and extension of cracks, the shaped steel at the free end was obviously pushed out, and the surrounding matrix maintained good integrity after testing finished. For ECC specimens, bond or splitting-bond failure occurred, exhibiting outstanding ductility. Compared with the ordinary concrete specimen, the standard ultimate and residual bond strength of ECC specimens improved by 37.9% and 27.4%, respectively. Besides the increase in ECC compressive strength, the fiber volume content and cover thickness had a significant positive influence on the ultimate and residual bond strength, whereas the effect of the embedded length was the opposite. Finally, the calculation equations of characteristic bond strength were proposed, and the calculated values matched well with the experimental values.

Soil-water characteristic curve of expansive soils considering cumulative damage effects of wetting and drying cycles

A novel experimental program was undertaken to explore crack development inside an expansive soil column under cyclic Wetting and Drying (W-D) and its influences on the Soil-Water Characteristic Curve (SWCC). Experimental investigations revealed that in the first drying cycle, fine and evenly distributed cracks developed from initial defects in the upper surface. In the subsequent drying cycles, the unhealed cracks during the wetting cycle further grow in width, length and depth while the initiation zone of new cracks was limited. The crack development characteristics within the soil column were described using fractal dimensions. The cracking degree of soil cross-sections gradually reduced with increasing depth. Also, each W-D cycle process contributed to a similar increment in the crack fractal dimension of soil at the same depth. In addition, the saturated water content, air-entry value and residual suction of cracked expansive soils gradually reduced with an increase in the number of W-D cycles. An obvious bimodal phenomenon was only observed in the SWCC of soil samples after the third W-D cycle. In order to quantify the damage induced by crack development to the soils, the damage variable was proposed based on the crack fractal dimensions. Furthermore, the Damage Impact Factor (DIF), as a function of the volume damage variable and soil plasticity index, was introduced into the traditional Fredlund and Xing (F-X) model to estimate the SWCC of cracked expansive soil. The form of modified F-X model is relatively simple and can be conveniently extended into geotechnical engineering practice applications.

Morphological development of drying shrinkage cracks at the rock[sbnd]soil interface in a karst rocky desertification area

Study regionkarst rocky desertification area, China Study focusThe rocksoil interface, where exposed bedrock is in abrupt contact with the soil, is prevalent in rocky desertification areas. As a constraining boundary condition of soils, drying shrinkage cracks are easily developed at the rocksoil interface of outcrops with weak or un-weathered bedrock, but the shrinkage crack development under these conditions is still unknown, which seriously restricts a profound understanding of the hydrological processes on karst slopes with exposed bedrocks. This study aims to quantify the geometric morphological characteristics of these shrinkage cracks and the block areas cut by the crack network during the crack development, as well as to explore the development of drying shrinkage cracks at the rocksoil interface of outcrops. New hydrological insightsWhen the soil moisture content was between 24.1 % and 28.6 %, shrinkage cracks at the rocksoil interface (CRSI) first formed along the border between rocks and soils and then at the soil surface perpendicular to the former, most of the cracks intersected vertically in shapes of "T" or "+". The geometric parameters of shrinkage cracks initially increased before stabilizing and reached a stabilization stage as soon as the moisture content decreased. However, all of them finally shrank slightly in the later stages of soil water loss in thicker soils. Soil thickness was not a crucial factor affecting the CRSI formation. The CRSI were 1.2 times wider than all other cracks, while being infrequent and making up just 40 % of the total length and area of all cracks. As a result, the CRSI may grow into a key pathway for the establishment of preferred flow at the rocksoil interface, which should be paid attention in the hydrological processes in the karst rocky desertification region.

Investigating the flexural behavior of ASR‐damaged RC beam through internal stress and cracking development using 3D Rigid Body Spring Model

AbstractThe alkali‐silica reaction (ASR) is one of the durability issues that affect the safety of concrete structures. Numerical simulation is useful for monitoring the internal condition of a reinforced concrete (RC) structure with ASR damage and predicting its long‐term behavior. Since discrete methods of simulation suit situations where concrete undergoes durability issues associated with expansion and cracking, a mesoscale discrete analysis method known as the three‐dimensional Rigid Body Spring Model (3D RBSM), as already used to simulate concrete ASR damage at the material scale, has been further developed to simulate ASR damage at the structural scale. In this development, the aggregate is not separately modeled and expansive elements are included to simulate ASR expansion, allowing a larger element size (1–2 cm). The number of elements and computation time are reduced to less than 1%. This proposed model is used to simulate ASR damage in a RC beam and the beam's residual flexural capacity. The simulation allows the internal stress and cracking condition to be visualized, leading to an explanation as to why the loading capacity of a RC beam is not affected by ASR damage: first, almost no cracks form at the core of the beam section due to the stirrup confinement, so the effective depth of the cross section is maintained after ASR damage; second, the tensile reinforcements have already yielded although ASR damage exists. Besides, the inhibited development of shear cracks may be one of the reasons for the slight improvement of flexural capacity of the damaged‐RC beam in experiment and simulation.

Characteristics of Center-blast Tube with V-grooves During Blasting

The prediction of fracture time and crack development of metal shell under the impact load is a very significant research direction in engineering. In this paper, a coupling method is used to solve the dynamic expansion fracture process of center-blast tube with V-grooves under the pressure. A one-dimensional two-fluid model was utilized to govern the transient combustion. The nonlinear mechanical behaviors were predicted based on the finite element software ABAQUS, and the pressure and the structure were coupled by applying a user subroutine interface VUAMP in ABAQUS. The coupling approach was validated by comparing the predicted results with experimental results. Based on the validated approach, the characteristics of expansion fracture and the process of crack propagation on the center-blast tube with V-grooves were studied, and the effect grooves depth were analyzed. The results show that the crack propagation on tube can be divided into two stages that stable propagation stage and unstable propagation stage. The burst pressure of the center-blast tube with V-grooves decreases with the increase of crack depth, and the burst pressure decreases by about 7MPa with every depth increase of 0.25mm.

Study on the EC prediction of cracked soda saline-alkali soil based on texture analysis of high-resolution images from ground-based observation and machine learning methods

The rapid and accurate measurement of soil salinity is essential for assessing the level of soil salinization. In natural conditions, the surface of cohesive soda saline-alkali soil experiences shrinkage and cracking phenomena during water evaporation. The propagation and development of these desiccation cracks can be effectively described using texture features due to their statistical randomness. This study aims to establish a relationship between electrical conductivity (EC) values and texture features derived from both gray-level co-occurrence matrix (GLCM) and wavelet decomposition, and to develop a prediction model for EC accordingly. To achieve these objectives, crack images on the surface of 200 soil samples with varying levels of salinity were obtained in the Songnen Plain field. GLCM was computed and wavelet decomposition was performed to extract texture features in different directions and scales. The results demonstrate a significant correlation between texture features and soil EC values. Among the various texture features, 12 GLCM texture features with a grayscale level of 2 and a step size of 1 pixel, and wavelet texture features derived from a 4th level orthogonal decomposition based on the coiflet-1 function were selected as the optimal parameters for establishing and comparing the predictive effects of two machine learning models on soil EC values. In comparison to the testing results of the BP neural network model (R2=0.83, RPD=1.64, RMSE=0.32 dS/m, MAE=0.18 dS/m), the random forest model exhibited higher accuracy and stability (R2=0.95, RPD=3.48, RMSE=0.21 dS/m, MAE=0.07 dS/m), indicating that although both machine learning models demonstrated rapid and nondestructive capabilities, the random forest method was better suited for EC prediction in soda saline-alkali soil due to its superior accuracy.

Cracking mechanism of CMAS-corroded thermal barrier coatings based on a coupled thermo-chemo-mechanically phase-field fracture model

A thermo-chemo-mechanically coupled theoretical framework is proposed to describe the calcium-magnesium-alumina-silicate (CMAS) corrosion process during the cooling process. A phase-field fracture model is developed to investigate the effect of cooling temperature and CMAS concentration on the degree of corrosion reaction, the stress evolution and the crack initiation and propagation. σ11 concentrates in the region beneath the overlay of CMAS and σ22 appears at the interface between top ceramic coating (TC) and bond coating (BC). The higher stress concentration of σ11 and σ22 contribute to the formation of both vertical and transverse cracks. Transverse cracks first emerge at the interface between TC and BC in the edge region, followed by the formation of vertical cracks in the CMAS-coated region. Vertical cracks propagate to the interface and deflect into transverse cracks. The transverse cracks at the interface further propagate and merge, ultimately leading to the coating delamination. The higher initial cooling temperature and CMAS concentration contribute to the accelerated development of vertical cracking and the increase of the quantity and length of transverse and vertical cracks. The model provides a significant advantage in predicting the failure of TBCs during the cooling stage of CMAS corrosion.

Evaluating the impervious performance of hydraulic asphalt concrete in embankment dams: A study of crack evolution at different temperatures

Hydraulic asphalt concrete (HAC) is extensively utilized as impervious interior core walls or upstream facings in embankment dams. This study examines the evolution of crack growth in HAC and its impact on its impervious performance under varying external loadings and temperatures. By employing X-ray computed tomography (CT) scanning in-situ triaxial compressive tests, the behavior of HAC specimens at 5 °C and 20 °C was analyzed. Statistical methods enabled the categorization of cracks by their equivalent diameter, revealing their evolution from shrinkage and initiation to expansion, interconnection, and convergence with increasing deformation. The fractal dimensions of these cracks initially decreased gradually, then stabilized, before increasing sharply. Furthermore, a logarithmic relationship between the fractal dimensions of cracks and the crack ratio was established. At equivalent deformation levels, crack development was more pronounced at 5 °C than at 20 °C. Notably, the specimens did not exhibit complete external interconnection of cracks at either temperature near the peak stress, highlighting HAC's robust impervious qualities at the meso scale. Compared to clay and concrete, HAC demonstrated superior deformation resistance and impervious capabilities in the anti-seepage structure of embankment dams. This research provides valuable insights for the application of HAC as a water barrier in complex geological settings.

Characterization of Acoustic Emissions from Concrete Based on Energy Activity Coefficient

Single-stage compression loading experiments were carried out on concrete specimens of various strengths to explore the characteristic parameters of the acoustic emission signal and its damage evolution law in the concrete damage process. These specimens were monitored in real time with acoustic emission and DIC instruments during the loading process, and internal pores and slices were scanned with CT scanning instruments after compression. The acoustic emission phenomenon was expressed using the energy activity coefficient, and the law relating to the phenomenon was summarized. The results show that when the peak and mean values in the first adjacent time domain grow rapidly, the specimen produces a large crack and enters the stage of rapid crack development, which can be taken as an indication of the impending damage to the specimen. The energy activity coefficient reflects the damage development intensity as follows: the smaller the energy activity coefficient, the more the cracks developed; the faster the speed, the larger the deformation. With an increase in the load level, the energy activity coefficient gradually tends to stabilize, and the specimen enters the stage of rapid crack development. However, when the energy activity coefficient suddenly increases again, the specimen is destabilized and destroyed. Therefore, the energy activity coefficient responds to the degree of congenital defects in the specimen. As the load increases, the energy activity coefficient is more stable, and the defects are smaller; in contrast, the energy activity coefficient drastically oscillating indicates that the material is very defective.

Investigation of quantitative precursory indicators for rock failure using spatio-temporal characteristics of velocity

Stress redistribution and crack development are prominent features in rock failure. However, these processes are complex and challenging to analyze, making early warning of instability in rock engineering difficult. To characterize the rock failure process and obtain reliable precursory indicators, the imaging method that combines active and passive sources was employed to construct the velocity field during the rock failure process in this study. The micro-crack propagation law and its potential connection with the stress environment were investigated by mapping the velocity field, the acoustic emission (AE) density field, and the energy field. Moreover, the Mutation Trend Coefficient (MTC) and Deformation Coefficient (DC) were proposed as precursory indicators of instability based on the spatio-temporal correlation and directional differences of velocity evolution. Results show that the nucleation of AE sources and the release of energy accumulation are key to the formation of the velocity gradient, and progressive rock failure is accompanied by the intensification of velocity anisotropy. Additionally, low-velocity regions usually preferentially extend in the direction parallel to the principal stress, while expansion in the direction vertical to the principal stress is dominant in the plastic stage, indicating that the stress environment controls the spatial heterogeneity of the velocity field. The evolution trend of precursor indicators shows that the increase of MTC from a low value and the continuous decrease of DC can be regarded as the initiation of rock secondary cracks. The proposed indicators and method not only provide beneficial complements to the understanding of the evolution mechanism of rock damage but also have potential in the early warning and identification of the early stage of crack propagation, offering references for the safety prevention and control of rock engineering disasters.

Axial compressive performance of RC columns strengthened with prestressed CFRP fabric and UHPC jacket with spiral stirrups

AbstractTo address the issue of easy shearing damage of Carbon Fiber Reinforced Polymer (CFRP) in enhancing the axial compressive performance of CFRP and Ultra‐High‐Performance Concrete (UHPC) strengthened concrete columns, two methods, prestressed CFRP and UHPC with spiral stirrups, were employed for composite strengthening of reinforced concrete (RC) columns. A total of one unstrengthened column and eight strengthened columns were designed and fabricated to validate the effectiveness of the proposed methods. The axial compressive performance and bearing capacity of each specimen were analyzed by considering parameters such as single or composite strengthening method, presence of spiral stirrups in UHPC, and application of pre‐stressed CFRP. The results show that, compared with any single strengthened specimen, the ultimate bearing capacity of the composite strengthened specimen is greater than the sum of the corresponding single strengthened specimens, and the bearing capacity of the prestressed CFRP with spiral stirrup UHPC composite strengthened specimen is the most significant, reaching 235.63%. By incorporating spiral stirrups in the UHPC jacket, the phenomenon of uneven fragmentation during the failure of the strengthened column is improved. This helps prevent premature shearing damage of CFRP and enhances the fracture strain and effective utilization of CFRP. Additionally, prestressed CFRP effectively restrains the lateral deformation and crack development of the core concrete in the UHPC jacket, fully utilizing the high compressive strength of UHPC. This further enhances the ultimate bearing capacity and ductility of the specimens. Based on the experimental phenomena and strain of each material, the failure mechanism of prestressed CFRP‐spiral reinforced UHPC composite‐strengthened columns is proposed. Finally, a unified bearing capacity calculation formula for single and composite strengthened columns is established, based on the theory of confined concrete strength and the assumption of strength increment superposition. The formula is validated with experimental results from relevant literature, showing small errors in the calculated results and indicating good applicability of the formula.

Elucidating the role of recycled concrete aggregate in ductile engineered geopolymer composites: Effects of recycled concrete aggregate content and size

Utilizing recycled fine aggregate (RFA) as silica sand replacement for ductile engineered geopolymer composites (EGC) provides a high value-added approach to recycling concrete waste and reduces the needs for high-cost silica sand. RFA contains abundant active alkaline substances which can promote the secondary geopolymerization of EGC. Substituting RFA for silica sand can improve EGC micro-characteristics, and the micro-structure of RFA-EGC is further refined with the decreased RFA size. The compressive/flexural strength of EGC is elevated as RFA is incorporated, and the decreased RFA size further enhances the compressive/flexural strength of RFA-EGC. Attributed to the micro-pores and micro-cracks in RFA, including RFA benefits the formation and development of crack, leading to an enhancement in the uniaxial tensile behavior of EGC. The tensile strength and tensile strain capacity of 100 % RFA blended EGC are 5.7 % and 8.6 % higher than those of 100 % silica sand blended EGC. The decreased RFA size can enhance the tensile strength, and an appropriate increase in RFA size improves the tensile strain capacity of RFA-EGC. When RFA size is 0.15–0.3 mm and 0.3–0.6 mm, the tensile strain capacity of 100 % RFA blended EGC is 8.6 % and 12.9 % larger than the reference EGC with 100 % silica sand (0.15–0.3 mm). A moderate increase in silicate modulus can further improve the tensile behavior, and the RFA-EGC with 1.5 M shows the best tensile behavior; besides, the longer fiber length results in the higher tensile strength of RFA-EGC. By optimizing the replacement rate and size of RFA, adjusting the silicate modulus and fiber characteristics, one can achieve a sustainable high-ductility RFA-EGC with exceptional mechanical behavior.

Laboratory testing of desiccation crack growth in terrestrial Martian analog environments using digital image correlation

The unique geologic features of raised ridges and polygonal cracks filled with multiple layers of cement observed in Gale and Jezero craters on Mars have origins that remain uncertain due to limited knowledge and measurement techniques. This study hypothesizes that these cracks result from the volumetric shrinkage of clay fabric due to dehydration and salinity fluctuations in ancient Martian lakes. The research aims to quantify the shrinkage of terrestrial simulants with varying mineral compositions analogous to those found at Gale Crater and Jezero Crater under diverse desiccation conditions. By simulating Martian regolith using the Rocknest soil simulant and examining historical aqueous conditions through sedimentary rock analogs, this study provides new insights into Martian geological structures. The extent and rate of shrinkage in simulant samples were quantified using ImageJ, while strain localization and propagation were measured using the Digital Image Correlation (DIC) technique until full desiccation crack patterns developed. Laboratory testing revealed that desiccation cracks tend to form polygonal patterns, which are patently similar to the polygonal patterns observed in some regions of Mars. However, not all simulants produced visible cracks, with some producing linear rather than polygonal patterns. Key findings indicate that higher temperatures result in wider and deeper cracks, while lower temperatures decrease crack density and length. Increased initial water content leads to more extensive cracking, with higher crack density and length per unit area. Sodium chloride and sodium sulfate significantly impact desiccation cracking, with low concentrations stabilizing the soil and high concentrations promoting extensive cracking. Smectite-rich samples exhibit extensive cracking, and tensile strain distribution during evaporation is non-uniform, influencing crack development based on sample properties and drying conditions. These insights enhance our understanding of polygonal crack formation on Mars, improving Mars sample return missions and informing the design of robust exploration equipment.

Investigation of Desiccation Cracking Behavior of Waste Carbon Fiber–Reinforced Clay Material

Carbon fiber is a common waste building material, but its effect on the drying and cracking properties of clay materials is unknown. In this paper, crack rate and fractal dimension are used to characterize the influence of waste carbon fiber materials on the development of soil cracking. With the rise in carbon fiber content to 0.2%, 0.4% and 0.6%, the crack rate of soil cracking decreased by 7.9%, 17.3% and 23.3%, respectively, while the fractal dimension of soil cracking decreased by 2.4%, 8.7% and 21.2%, respectively. Accordingly, the critical moisture content of the soil samples increased by 33.2%, 110% and 151%, and the time of the soil constant evaporation stage decreased by 5.1%, 13.8% and 34.5%, respectively. When carbon fiber is combined with soil, carbon fiber will increase the interface bonding strength, friction and interlocking force, effectively inhibiting the cracking of soil, and it provides a channel for water transport in the soil in the early stage.

Mechanical properties and enhancement mechanism of iron ore tailings as aggregate for manufacturing ultra-high performance geopolymer concrete

Reusing of iron ore tailings (IOT), particularly as recycled aggregate to prepare concrete, plays an important role in reducing dependence on natural resources and solving the problem of waste accumulation. In this paper, the effects of IOT as aggregate on the flowability, compressive strength of ultra-high performance geopolymer concrete (UHPGC) were studied, and the enhancement mechanism of IOT on compressive strength was elucidated through microscopic characterizations. The results show that with the increase of IOT content, the flowability of UHPGC decreases, and the compressive strength increases first and then decreases. 25 % IOT replacement yielded the best compressive strength, and 50 % substitution of IOT was comparable to the without IOT regarding compressive strength. The microstructure analysis shows that the crystalline components in the IOT do not participate in the hydration reaction and have the effect of micro-aggregate filling. The amorphous components on the IOT dissolve rapidly in the early stage, participate in geological polymerization reaction, and produce synergistic effect with slag to promote the formation of hydration products. However, excessive IOT incorporation will inhibit the dissolution of slag active ions and hinder the formation of hydration products. In addition, the enhanced interfacial transition zone (ITZ) and mechanical interlocking effect formed by IOT can effectively inhibit the crack development of UHPGC.

Experimental study on freeze-thaw resistance of mortar: An attempt to modify hydrophobic materials with hydrophobic nano-silica

In this study, a novel superhydrophobic additive (MPSANS) was developed to enhance the freeze-thaw (F-T) resistance of mortar by modifying mica powder with stearic acid and hydrophobic nano-silica. Firstly, the effects of hydrophobic nano-silica content on the hydrophobic properties of MPSANS modified mortar were studied, and MPSA10NS5 exhibited the best hydrophobic property, the water absorption and water desorption of modified mortar decreased by 65.42 % and 35.84 %, respectively. On this basis, abundant tests were conducted to analyze the effects of MPSA10NS5 content on the F-T resistance of mortar. Analytical findings suggested that MPSA10NS5 noticeably reduced the loss of relative dynamic modulus of elasticity and compressive strength of mortar. Furthermore, the microstructure was determined by using the scanning electron microscopy and mercury intrusion porosimetry. According to the test results, MPSA10NS5 refined the pore structure inside mortar and inhibited the crack development. Meanwhile, MPSA10NS5 effectively reduced the most probable aperture of mortar, resulting in an increase of harmless pores and a decrease of harmful pores.

Study of the flexural behavior of UHPC-HPC composite beams strengthened with BFRP sheet after chloride secondary erosion

To solve the issue of insufficient durability of reinforced concrete (RC) structures, a new structure of ultra-high performance concrete (UHPC)-high performance concrete (HPC) composite beam was designed, and the flexural performance of the composite beam strengthened with basalt fiber reinforced polymer (BFRP) after pre-damage was investigated. Results indicate that main cracks are formed and developed after the secondary erosion of chloride salt, leading to three forms of failure modes of the beams: BFRP sheet fracture and concrete crushing, BFRP sheet debonding and concrete crushing and BFRP sheet debonding. The test beam failure process can be classified into three stages: linear elasticity, crack development and yield. The maximum cracking and ultimate loads increased by 27.9 % and 35.8 %, respectively. The crack load growth rate of the beam decreased after 7 days (d) of secondary chloride salt erosion. The formula for calculating the peel strength of the UHPC-HPC composite beam was modified. The calculated bending capacity of the beam agrees well with the measured value. This study provides a reference for enhancing the lifespan and calculating the flexural bearing capacity of structures in corrosive environments.

A hybrid finite-discrete element method for modelling cracking processes in sandy mudstone containing a single edge-flaw under cyclic dynamic loading

Rock mass deformation and failure are macroscopic manifestations of crack initiation, propagation, and coalescence. However, simulating the transition of rocks from continuous to discontinuous media under cyclic dynamic loading remains challenging. This study proposes a hybrid finite-discrete element method (HFDEM) to model crack propagation, incorporating a frequency-dependent cohesive-zone model. The mechanical properties of standard sandy mudstone under quasi-static and cyclic dynamic loading were simulated using HFDEM, and the method's reliability was verified through experimental comparison. The comparative analysis demonstrates that HFDEM successfully captures crack interaction mechanisms and accurately simulates the overall failure behavior of specimens. Additionally, the effects of pre-existing flaw inclination angle and dynamic loading frequency on rock failure mechanisms were investigated. The numerical results reveal that rock samples exhibit significantly higher compressive strength under dynamic loading compared to quasi-static loading, with compressive strength increasing with higher cyclic dynamic load frequencies. Furthermore, by analyzing the strength characteristics, crack propagation, and failure modes of the samples, insights into the failure mechanisms of rocks under different frequency loads were obtained. This study provides valuable insights into crack development and failure of rocks under seismic loads, offering guidance for engineering practices.

Behavior of ultra-high-performance concrete deep beams reinforced by basalt fibers

Abstract Deep beams are crucial for construction projects due to their load-carrying capacity, shear resistance, and architectural adaptability. Ultra-high strength concrete and ultra-high-performance concrete (UHPC) are used in their production. Basalt fiber is used as an alternative due to its corrosion resistance, tensile strength, and thermal stability. This study investigates the behavior of UHPC deep beams reinforced with basalt fibers. Three sets of 11 specimens were constructed without transverse reinforcement and reinforced with either fibers or steel fibers. The study also analyzes the impact of parameters like shear strength capacity, crack development, and load-deflection behavior on UHPC deep beams. The study discovered that the inclusion of basalt fibers in UHPC deep beam can effectively postpone the onset of diagonal cracks. Incorporating basalt fiber at concentrations of 0.5, 0.75, and 1.0% led to respective increases of 48.17, 70.07, and 86.66% in the diagonal fracture force, as compared to the inclusion of steel fibers which resulted in increases of 18.24, 56.93, and 98.54% in diagonal fracture loads. The ideal ratio for enhancing the maximum shear capacity was found to be 0.75% of basalt. This specific percent resulted in the highest measured force out of the three percentages that were examined. The addition of basalt fibers at concentrations of 0.5, 0.75, and 1.0% resulted in respective improvements of 11.62, 30.08, and 28.69% in the ultimate shear capacities. During that period, steel fibers significantly enhanced the ultimate shear capacity, resulting in an increase of 19.83, 34.49, and 55.24% compared to specimens without fiber reinforcement. Regarding the second parameter of this investigation, a drop in the shear span ratio is linked to an augmentation in shear capacity and a reduction in mid-span deflection to varying extents for both the utilization of basalt and steel fibers.