Dry Cycles Research Articles

Degradation mechanisms of concrete cold joint surfaces under sulfate cycles and varying pouring intervals

In concrete structures, particularly in arid and saline environments, the cold joint surface often serves as a primary entry point for erosion damage, thus dictating the lower limit of structural durability. This study investigates the erosion and damage mechanisms of cold joint concrete under such conditions, focusing on specimens with varying pouring intervals (0.25 d, 0.5 d, 1 d, 7 d, and 28 d). These specimens underwent 0, 30, 90, and 150 sulfate dry‒wet cycles, with their degradation assessed through compression‒shear tests. The findings reveal a logarithmic relationship between the cold joint surface adhesion and the pouring interval, and similarly, there is a logarithmic relationship between the internal friction angle and the pouring interval. Shorter intervals correspond to a higher rate of decrease in both adhesion and internal friction angle, while longer intervals result in lower, eventually stabilizing, values of these properties. Scanning Electron Microscopy analysis indicates that inherent defects in the cold joint surface expedite sulfate penetration into the concrete. As the number of sulfate cycles increases, ettringite formation in the cracks leads to their expansion and interconnection, diminishing the shear resistance of the cold joint surface. The study shows that the pouring interval significantly influences corrosion resistance, with its effects becoming more pronounced after a threshold of sulfate cycles (approximately 90). Shear strength is found to be more susceptible to sulfate erosion compared to compressive strength, with a faster degradation rate. After 80 to 110 erosion cycles, the adhesion corrosion resistance drops to 75%, while the compressive strength remains above this threshold.

Study on deterioration of mechanical properties and voltage-strength theoretical model of CFRP/ conductive ECC composites under coupling effect of anode polarization, load and erosion environment

This study aims to systematically investigate the deterioration of tensile properties, voltage variation, and voltage-strength theoretical model of CFRP/ conductive ECC composites under coupling effect of anode polarization, load and erosion environment. The effects of testing parameters including conductive ECC mixture type, electric current density, polarization time, tensile stress value, sulfate soak time, and sulfate attack-wet and dry cycle time were synthetically investigated. The experimental results indicated that the voltage increases approximately linearly with the increase of degradation time in the voltage-deterioration time curves. The stress-strain curve can be divided into three stages: the stress-strain linear increase stage, the strain hardening characteristic stage, and the decline stage during failure. The conductive ECC mixture type, polarization time, current density, tensile stress value, sulfate soak time, and sulfate attack-wet and dry cycle time all have significant effects the deterioration of tensile strength and the voltage change ratio of CFRP/ conductive ECC composite. More importantly, an innovative voltage-strength theoretical model was proposed, which can predict the relationship between voltage and material deterioration strength. The theoretical model is in good agreement not only with the experimental results of this study, but also with the results of other studies. The model proposed can be used to predict deterioration degree of materials in real time, which has very important guiding significance for impressed current cathodic protection-structural strengthening technology (ICCP-SS) technology. This study is expected to promote a more comprehensive understanding of the deterioration of mechanical properties and voltage-strength theoretical model of CFRP/conductive ECC composites for ICCP-SS technology.

The Influence of Rainfall and Evaporation Wetting–Drying Cycles on the Open-Pit Coal Mine Dumps in Cam Pha, Quang Ninh Region of Vietnam

Among the slope hazards caused by rainfall, not all of them occur directly during storm washout, and the wetting–drying cycles’ effect on the rainfall–evaporation process is an important cause of shallow slope instability. In this study, taking the slope of the open-pit coal mine dumps in Cam Pha, in the Quang Ninh region of Vietnam, as the research object, we carry out experiments on the physical properties of the rock body under different wetting–drying cycles, as well as numerical analyses. The results show that the wetting–drying cycles significantly affect the physical and mechanical parameters and permeability of the rock body. In the process of the wetting–drying cycle, a transient saturated zone occurs on the surface of the slope, and the range of the unsaturated zone inside the slope body decreases with the increase in the number of wetting–drying cycles. Moreover, the infiltration line keeps moving downward, but the rate of downward movement is slowed down by the decrease in the gradient of matrix suction affected by rainfall. Under the influence of the wetting–drying cycles, the slope displacement, plastic zone, and maximum shear strain increment range gradually approach the slope surface with the wetting–drying cycles, and the displacement peak gradually increases. A dump is a site for the centralized discharge of mining waste, formed by the crushing and stockpiling of the original rock formation. Bang Nau is the name of the dump considered in this study. After multiple rainfall events, the slope stability under five wetting–drying cycles decreases from 1.721 to 1.055, and the landslide mode changes from a whole landslide to a single-step shallow landslide, with a certain landslide risk. It is necessary to strengthen the slope stability as the landslide risk is very high, and it is necessary to strengthen the monitoring and inspection of the slope.

Effects of hydrological dynamics in controlling phosphorus bioavailability in intermittent rivers and implications for estuaries

Several studies on intermittent rivers and ephemeral streams (IRES) have focused on the ecology of populations and communities, and very few explored the biogeochemistry and bioavailability of key elements, such as phosphorus (P) and nitrogen (N). In this study, we aimed to explore the role of environmental seasonality on P bioavailability in an intermittent river in Northeastern Brazil and the implications for nutrient dynamics to downstream ecosystems, such as the estuaries. The study was performed at the Cruxati River, located in the Litoral Hydrographic Basin on the coast of Ceará State, Brazil. We sampled riverine sediments during three hydroperiods (i.e., dry, rewetting, and flow) according to the theoretical model for research in intermittent rivers. We performed a geochemical fractionation of different P forms and determined the physicochemical parameters, particle size distribution, mineralogy, and total organic carbon of the sediments. Mean values were compared using the Kruskal–Wallis non-parametric statistical test (p-value < 0.05) and by discriminant function analysis. We observed that the predominant fractions of P were associated with Fe-oxides, silicates, and refractory organic matter, but there were no statistical differences among these fractions for all hydroperiods. The exchangeable-P form was higher in the dry and flow periods than in the rewetting period. On the opposite side, P associated with humic acids and carbonates was lower in the dry and flow periods but higher in the rewetting period. We concluded that seasonality influences the bioavailability of P in intermittent rivers, being strongly influenced by the organic fraction, including the humic acid fraction and the refractory organic matter, which are important sources of P in the aquatic system. Furthermore, the IRES may act as a source or a sink of nutrients throughout the cycles of wetting and drying, which may release P from the sediments to the aquatic environment. Hence, IRES plays an important role in transporting nutrients to estuaries and maintaining their ecosystem services.

Effects of different aging methods on the ability of biochar to adsorb heavy metal cadmium and its physical and chemical properties.

The aging process can affect the physical and chemical properties as well as adsorption capacity of biochar. This study focuses on the heavy metal cadmium (Cd) as the research object, and artificially ages biochar prepared from rice straw and corn straw through accelerated freeze-thaw cycles, alternating dry wet cycles, and ultraviolet light treatment, in order to evaluate the effects of different aging conditions on the physical and chemical properties of the two different types of biochar and on their adsorption capacities for Cd. After aging, the pH of rice and corn biochar decreased to varying degrees, respectively. The surface structure was ruptured, the average pore diameter was decreased, and the specific surface area was increased by 27.3%, 21.9%, and 9.8% (rice) and 95.4%, 27.7%, and 13.4% (corn). Ultraviolet light aging has the most significant impact on the elemental content of biochar, and the C content was decreased by 12.4% (rice) and 9.3% (corn). The O content was increased by 11.2% (rice) and 44.1% (corn), and the numbers of O/C, H/C, (O + N)/C, and oxygen-containing functional groups were increased. These results demonstrate that the aging process reduces the degree of aromatization of biochar, while enhancing its polarity and Cd adsorption capacity. Rice straw biochar (RSB) has a greater ability to adsorb Cd than corn straw biochar (CSB). In addition, ultraviolet light aging is particularly effective in increasing heavy metal adsorption.

Study of the Initial Cycles Number Influence on the Retentivity of a Commercial Friction Modifier Using the Twin-disk Test

The rails and wheels are one of the most critical and expensive components of railway transport, and any problem could generate numerous consequences. The ability to manage friction at the wheel-rail interface currently represents one of the greatest challenges and one of the most powerful tools in railway engineering. The application of friction modifiers, lubricants, and friction enhancers to friction control have been the focus of extensive research of wheel-rail systems. The friction modifier (FM) provides a targeted coefficient of friction (COF) of 0.3–0.4. Currently, the laboratorial retentivity tests conducted by manufacturers do not describe the standards used, neither the surface integrity before the FM application. This work studies the influence in the retentivity of the different surface integrity states before application of FM using a twin-disk test. It will be possible to define the surface condition necessary for the application of FMs in retentivity tests, using a twin-disk tribometer. A commercial friction modifier was applied before the test (zero cycles) and after 500; 1,000; 1,500; 2,000; 3,000; 4,000; and 5,000 dry cycles, ending the tests when the coefficient of traction (COT) reached 0.4. To compare the retentivity of different FMs, a complete standardization of the twin-disk test is essential, applying the FM in a controlled amount, with over 2,000 dry cycles, and using a disk with controlled initial roughness.

Influence of GFRP Confinement of Reinforced Concrete Columns Exposed to Sodium Chloride on Microstructure and Hydration Products

This paper explores the effect of sodium chloride (NaCl) on microstructure and hydration products of cylindrical column concrete and compares the results after covering it with Glass Fiber Reinforced Polymer (GFRP). 20 short RC columns were prepared with a single concrete mixture. The specimens have cured in different concentration of NaCl (0, 5%, 10%, 15%), some specimens cured directly in solution and other specimens exposed to wet and dry cycle. These specimens were tested, a first group after 28 days of curing, second group after 56 days, while the third group was repaired by GFRP after 28 day then returned to the cured environment and tested after56 day. In order to determine the main crystalline phase composition of concrete specimens and for phase identification of a crystalline material, scanning electron microscopy (SEM) morphology of microstructure concrete and X-ray diffraction (XRD) have been used. The results revealed denser microstructure with the concentration of NaCl crystalline, existence of binding chloride as free halite, chemical pound as a Friedel’s salt or Physical binding held to the surface of hydration products. In addition, the corrosive compounds were observed, and the hydration product phase decreased due to concentration of curing environment. Furthermore, the results from the samples that were covered with GFRP showed that the value of the hydration products didn't change when compared with the samples that were tested after 28 days, moreover, the voids were found in them when compared with the samples exposed to the environment damage without covering it with GFRP.

Establishing a Multi-Vial Design Space for the Freeze-Drying Process by Means of Mathematical Modeling of the Primary Drying Stage

Primary drying is the most critical stage of the freeze-drying process. This work aimed to establish a design space for this process by means of mathematical modeling of the primary drying stage, capable of addressing the thermal characteristics of distinct vial suppliers. Modeling of primary drying was implemented on Microsoft Excel using steady-state heat and mass transfer equations at two extreme conditions as assessed by risk analysis, to predict product temperature and primary-drying time. The heat transfer coefficients (Kv) of four different vial suppliers were experimentally determined, both, at the center and edge of the freeze-dryer's shelf. Statistically significant differences (ANOVA p<0.05) were observed between suppliers throughout the assessed pressure range. Overall, the average Kve/Kvc (edge/center) ratio was higher than 1.6 for all suppliers due to the radiation effect. A design space for the drying process was established using mathematical modeling taking into account the Kv of the worst-case supplier, in the shelf edge. A primary drying cycle was carried out at a shelf temperature of -25 °C and a chamber pressure of 45 mTorr for 8 % sucrose and at -10 °C and 75 mTorr for 5 % NaCl. Freeze-dried products with good cosmetic appearance were obtained for the four vial suppliers both, in the shelf center and edge. The results show that it is possible to predict and establish the critical parameters for the primary drying stage, under a design space concept, considering the differences in the Kv of vial suppliers without adverse consequences on the quality of the finished freeze-dried product.

Nonequilibrium Wet-Dry Cycling Acts as a Catalyst for Chemical Reactions.

Recent experimental studies suggest that wet-dry cycles and coexisting phases can each strongly alter chemical processes. The mechanisms of why and to what degree chemical processes are altered when subjected to evaporation and condensation are unclear. To close this gap, we developed a theoretical framework for nondilute chemical reactions subject to nonequilibrium conditions of evaporation and condensation. We find that such conditions can change the half-time of the product's yield by more than an order of magnitude, depending on the substrate-solvent interaction. We show that the cycle frequency strongly affects the chemical turnover when the system is maintained out of equilibrium by wet-dry cycles. There exists a resonance behavior in the cycle frequency where the turnover is maximal. This resonance behavior enables wet-dry cycles to select specific chemical reactions, suggesting a potential mechanism for chemical evolution in prebiotic soups at early Earth.

Degradation mechanism and life prediction of cemented tailings backfill under dry–wet cycles and salt erosion

In this paper, the effects of drywet cycling and salt erosion on the unconfined compressive strength (UCS), relative dynamic elastic modulus and mass of cemented tailings backfill (CTB) were investigated, and the mechanism for CTB deterioration was explored with scanning electron microscopy-energy dispersive spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The reliability lifespan of CTB was predicted with the Wiener stochastic process. The results showed that with the increases in the number of drywet cycles, the damage to the CTB deepened continuously, including skin peeling, corner damage, and aggregate exposure; the UCS, relative dynamic elastic modulus and mass of CTB immersed in a sodium chloride solution, a sodium sulfate solution, and a solution of both first increased and then decreased; and the UCS, relative dynamic elastic modulus and mass of CTB immersed in a magnesium chloride solution, a magnesium sulfate solution, and a solution of both showed a decreasing trend. Cl- inhibited the erosion of CTB by SO42- but did not inhibit erosion by Mg2+. Cl- and SO42- invaded the CTB to produce calcium hydroxide, gypsum, Friedel's salt, ettringite, C-S-H and other products. The reliable lifetime predicted with the relative dynamic elastic modulus used as the degradation index was the longest, followed by the UCS, and the lifetime predicted with the mass was the shortest.

Multiscale study of the strength deterioration and microstructure changes in loess during dry‒wet and freeze‒thaw cycles

ABSTRACT To study the influence of climate and the environment on the stability of loess slopes in Yan’an, China, the macromechanical deterioration and changes in its internal structure were explored by simulating its behavior during drying, wetting, freezing and thawing under natural conditions. A triaxial apparatus was used to conduct multiple shear tests to obtain stress‒strain relationships and shear strength parameters of the soil under different cycle modes, and the results were applied to analyze the macromechanical changes of the loess samples with increasing numbers of cycles. The results of the stress‒strain curves and the trends of the shear strength parameters showed that when a sample experienced coupled dry‒wet and freeze‒thaw cycles, its shear strength was considerably lower than that under a single type of cycle. Additionally, dry‒wet cycles had a stronger negative effect than freeze‒thaw cycles on soil strength. Microscopic tests showed that the contact mode of particles tended to be unstable due to the effects of dry‒wet and freeze‒thaw cycles, resulting in the reduction of soil cementation. The results of this multiscale research provide a reference for future work on geological disaster prevention and engineering control in areas where loess is present.

The Release and Migration of Cr in the Soil under Alternating Wet-Dry Conditions.

In recent decades, chromium contamination in soil has emerged as a serious environmental issue, demanding an exploration of chromium's behavioral patterns in different soil conditions. This study aims to simulate the release, migration, and environmental impact of chromium (Cr) in contaminated soils under natural rainfall conditions (wet-dry cycles). Clean soils sourced from Panzhihua were used to cultivate chromium-containing soils. Simulated rainfall, prepared in the laboratory, was applied to the cultivated chromium-containing soils in indoor simulated leaching experiments. The experiments simulated three years of rainfall in Panzhihua. The results indicate that soils with higher initial Cr contents result in higher Cr concentrations in the leachate, but all soils exhibit a low cumulative Cr release. The leachate shows similar patterns in total organic carbon (TOC), pH, electrical conductivity, and Cr content changes. An analysis of the speciation of Cr in the soil after leaching reveals a significant decrease in the exchangeable fraction for each Cr species, while the residual and oxidizable Cr fractions exhibit notable increases. The wet-dry cycle has the following effects on the soil: it induces internal reduction reactions in the soil, leading to the reduction of Cr(VI) to Cr(III); it alters the binding of Cr ions to the soil, affecting the migration of chromium; and it involves microorganisms in chemical processes that consume organic matter in the soil. After three years of rainwater leaching, chromium-containing soils released a relatively low cumulative amount of total chromium, resulting in a reduced potential risk of groundwater system contamination. Most of the chromium in the chromium-containing soil is fixed within the soil, leading to less biotoxicity.

Influence of Different Powder Conditioning Strategies on Metal Binder Jetting with Ti-6Al-4V.

Metal binder jetting shows great potential for medical technology. This potential can be exploited by integrating binder jetting into existing process routes known from metal injection molding. The biggest challenge here is the flowability and packing behavior of the powders used, due to their low size distributions. This paper investigates different powder-drying strategies to improve flowability using a statistical experimental design. Because of its relevance for medical applications, spherical Ti-6Al-4V powder with a size distribution under 25 µm is dried under various parameters using vacuum and gas purging. The investigated parameters, time and temperature, are selected in a central-composite-circumscribed test plan with eleven tests and three center points. The target parameters-water content, flowability and impurity levels (oxygen, nitrogen)-of the powder are analyzed. For validation, practical test trials are carried out on an industrial binder jetting system with unconditioned powder and conditioning with optimized parameters, comparing the manufactured parts and the powder bed. An optimized drying cycle with a duration of 6 h at 200 °C was determined for the investigated powder. Significant improvements in the dimensional accuracy (from ±1.5 to 0.3%) of the components and the visual impression of the powder bed are demonstrated.

Date-Palm-Based Sustainable Hybrid Composite with Cotton and Kevlar Fibre Participation

This research aims to evaluate the physical and mechanical performance of three types of hybrid composites made of date palm (Phoenix dactylifera L.) (DP), additional layers of cotton (DP/C) and Kevlar fibres (DP/K). The fibres were formed into flat sheets and employed as reinforcement layers embedded in a polyester matrix. Three-layer and five-layer hybrid composites were created using the hand layup method. The layers have alternative longitudinal–transversal orientation. The composites were investigated for density, thickness swelling (TS), water absorption (WA), flexural strength and modulus of elasticity (MOE) properties. Moreover, the composites were subjected to cycles of water immersion, freezing and drying, and the changes in mass and mechanical performance were analysed before and after the cyclic testing. The hybrid composite with Kevlar as the inner layers displayed better physical and mechanical properties when compared to the other two hybrid composites. A stereo-microscopic investigation revealed that poor adhesion between the layers of composites contributed to a reduction in the mechanical properties of DP/C and DP hybrid composites. The DP/C composite had the highest thickness swelling and water absorption, with the water uptake more pronounced than in the cases of the other composites. The hybridisation of date palms with Kevlar fibres improved the properties of the hybrid composites.

Analysis of compressive strength, durability properties, and micromechanisms of solidified loess using industrial solid waste: Slag–white mud–calcium carbide residue

Traditional lime-solidified loess presents the issue of high carbon dioxide emissions. This paper presents the development of a kind of cementitious material using industrial solid waste: slag–white mud–CCR (calcium carbide residue). The slag mainly contains CaO, SiO2, and Al2O3, with a 10.6 pH value. The white mud and CCR mainly contain CaCO3 and Ca(OH)2, respectively. We further assessed the efficacy of slag–white mud–CCR in solidified loess and employed SEM and TG/DTG to explore their micromechanisms. The pH value of the CB4 sample (slag–white mud–CCR with the lowest CCR content) was 42.3 % higher than that of pure loess. Considering the 3-day and 28-day compressive strength and the material costs, the optimal mortar mixture ratio was found to be slag–white mud–CCR = 60:32:8, and this mixture was used to solidify loess. The unconfined compressive strength of 15 % slag–white mud–CCR-solidified loess is almost 5.0 times and 6.0 times higher than that of lime-solidified loess at 7 and 28 days of curing age, respectively. The durability of the solidified loess after freeze–thaw and wet–dry cycles was significantly improved compared with that of lime- or slag-solidified loess. Specifically, 10 % and 15 % slag–white mud–CCR-solidified loess maintained a high compressive strength after eight freeze–thaw and wet–dry cycles. SEM and TG/DTG analyses of the mortar and solidified loess confirmed the formation of hydration products of C–S–H- and C-A-(S)–H-type gels. The compressive strength results were obtained using a dual mechanism: the cementation of loess particles through the formation of hydration products and their subsequent filling action.

Conceptual Modelling of the Dynamics of Soil Macroporosity Based on an in Situ and Direct Observation of Major Soil Structuring Agents During Early Stage of Pedogenesis

Many factors affect soil porosity but major of them are soil fauna, plant roots and the climate. Many studies attempted to investigate the effect of these factors on the evolution of soil porosity separately. The objective of this study is, based on an in situ experiment including three major porosity factors, propose a conceptual model of soil macroporosity evolution. In situ observation and quantification of the evolution of macroporosity under the influence of each agent separately and the three agents combined allow to propose a model for each case. Results show that the evolution of macroporosity due to plant roots is linear and reachs its maximum at the end of the plant cycle. Earthworms create and destruct macroporosity during the up and down movement for food searching. At long term, the consequence of earthworm action results to an increase of macroporosity. Wetting and drying cycle has the same effect as earthworm. At the beginning, when soil shrinks, it leads to a creation of macroporosity that could be disturbed by swelling during soil humectation. Some soil particles migrate in the shrink and reduce the surface of macroporosity. When faced to many wetting drying cycles, the surface of macropores increase during time. Mathematical algorithms and computing are necessary to formalize this model and long-term experiment is needed to validate it.

Cracking Behavior and Hydraulic Conductivity of Amended Soils Used in Landfill Cover Under Wetting–Drying Cycles

Cracking Behavior and Hydraulic Conductivity of Amended Soils Used in Landfill Cover Under Wetting–Drying Cycles

Response of granite residual soil slopes under dry–wet cycles

Granite residual soil is widely distributed in the southern coastal areas of China, and the slopes of granite residual soil are prone to instability and failure under the alternating action of rainfall and drying, which will cause great disasters to human society. In order to study the response mechanism of granite residual soil slopes under the alternating action of rainfall–drying–static–rainfall (RDSR), this study conducted indoor scaling model tests to analyze the response during dry and wet cycles. This study presented the response process of the slope under the influence of dry and wet cycles and discussed the change laws of slope deformation, water content, and matric suction. The results show that, under the alternating action of rainfall–drying–static–rainfall, 1) the network cracks on the slope form a dominant channel for rainwater seepage, which is the main reason for the rapid decline in soil anti-sliding ability within a short time; 2) at a rainfall intensity of 1.7–2.4 mm/min, the erosion effect of rain on the slope is obviously stronger than that of osmotic erosion, and the surface erosion failure of the granite residual soil slope tends to occur without an obvious sliding surface; 3) after the loss of matric suction over a certain period, the phenomenon of channeling and loss failure on the slope serve as a sufficient condition for slope instability failure but is not a necessary condition. The above research results are expected to provide the basis and reference for preventing and controlling landslide hazards in granite residual soil slopes under similar conditions.

Designing Tough Hydrogel Shells for Glucose Sensing.

Conventional hydrogel microcapsules often suffer from inadequate mechanical stability, hindering their use. Here, water-cored double-network (DN) hydrogel shells are designed, formed by polyacrylamide and calcium alginate networks using triple-emulsion templates. These DN hydrogel shells offer robust mechanical stability, optical transparency, and a precisely-defined cut-off threshold. The feasibility of this platform is demonstrated through the development of a fluorometric glucose sensor. Glucose oxidase is enclosed within the water core, while a pH-responsive fluorescent dye is incorporated into the DN shells. Glucose diffuses into the core through the DN shells, where the glucose oxidase converts glucose into gluconic acid, leading to pH reduction and a subsequent decrease in fluorescence intensity of DN shells. Additionally, the pH-sensitive colorant dissolved in the medium enables visual pH assessment. Thus, glucose levels can be determined using both fluorometric and colorimetric methods. Notably, the DN shells exhibit exceptional stability, enduring intense mechanical stress and cycles of drying and rehydration without leakage. Moreover, the DN shells act as effective barriers, safeguarding glucose oxidase against proteolysis by large disruptive proteins, like pancreatin. This versatile DN shell platform extends beyond glucose oxidase encapsulation, serving as a foundation for various capsule sensors utilizing enzymes and heterogeneous catalysts.

Mesoscopic damage study of red sandstone considering initial defects under drying-wetting cycles

Abstract In order to study the mechanical properties and microscopic damage of red sandstone by dry and wet cycling, this paper establishes a 3-dimensional uniaxial compression model of red sandstone by using PFC3D software. On this basis, microscopic cracks were introduced to analyze the influence of different cracks on the mesoscopic cracking of the model. The results show that the error between the simulation results and the test results is less than 10% for the model established by PFC3D software. Based on the discrete element model, displacement and velocity maps were obtained, and the values are larger at the contact with the load and smaller at the distance from the load. With the increase of the initial crack angle, the peak stress gradually increases, and with the decrease of the crack size, the peak stress gradually decreases, and the contact force also decreases.