Uniaxial Compression Tests Research Articles

Experimental Study on the Effect of Polycarboxylate Superplasticizer on the Performance of Cement-Based Grouting Materials.

Polycarboxylate superplasticizers BMC-L and BMC-S were utilized as modifiers in the formulation of novel cement-based grouting materials. Indoor tests were conducted on 32 groups of cement slurries, varying by water-cement ratio (0.5:1 and 0.6:1) and modifier content (0, 2‱, 4‱, 6‱, 8‱, 10‱, 12‱, and 14‱), to test their density, funnel viscosity, water separation rate, and stone rate. Four groups of slurry modified with BMC-L were selected as the preferred slurry, and the apparent viscosity test, uniaxial, and triaxial compression test of the slurry stone body were conducted. The study investigated the influence of BMC-L on various properties of the slurry, including its apparent viscosity, uniaxial compressive strength, stress-strain relationships, shear strength parameters, and elastic modulus. Ultimately, the pore structure and phase composition of the slurry stone body were detected by Nuclear Magnetic Resonance (NMR) and X-ray Diffraction (XRD), and the impact of BMC-L on slurry performance was examined from a microstructural perspective. Results indicate that the two polycarboxylate superplasticizers exert minimal influence on the density and water separation rate of the slurry. Within the effective incorporation range of the polycarboxylate superplasticizer, increasing the dosage correlates with a decrease in both the stone rate and viscosity of the slurry. BMC-L significantly enhances the mechanical properties of the slurry stone body by promoting more complete cement hydration and reducing porosity. The uniaxial compressive strength of slurry stone body with a 6 ‱ BMC-L dosage reached 29.7 MPa after 7 days and 38.5 MPa after 28 days of curing, representing increases of 118.4% and 64%, respectively, compared to masonry with 0 BMC-L dosage. The shear strength parameters and elastic modulus of the slurry stone body also showed corresponding increases.

A periodic micromechanical model for the rate- and temperature-dependent behavior of unidirectional carbon fiber-reinforced PVDF

The rate- and temperature-dependent mechanical behavior of unidirectional carbon fiber-reinforced polyvinylidene fluoride (PVDF) is investigated through uniaxial tension and compression experiments under various off-axis loading conditions. To improve the understanding of the behavior of the composite, a 3D micromechanical model is developed. Microscopic analyses are used to characterize the geometrical properties of the UD composite at the fiber length-scale. These properties are used to construct a periodic 3D representative volume element (RVE). In combination with periodic boundary conditions, uniaxial macroscopic deformation (in any possible direction) is applied to the RVE to accurately and efficiently model off-axis loading. The rate- and temperature-dependent behavior of the PVDF matrix is accurately described using an elasto-viscoplastic constitutive model. The finite element simulations of uniaxial tension and compression tests are compared to the experimental data and the micromechanical response is analyzed. The micromechanical model accurately describes the rate-dependent macroscopic behavior of unidirectional carbon fiber-reinforced PVDF for various off-axis loading directions at different temperatures. Analysis of the local matrix response in the RVE reveals the influence of the matrix on the macroscopic behavior of the composite.

Effect of Grain Size on the Uniaxial Compressive Strength of Ice Forming with Different Wind Speeds in a Cold Laboratory

This study investigated the uniaxial compressive strength of distilled water ice prepared in a low-temperature laboratory at −30 °C at varying wind speeds of 0 m/s, 1 m/s, 2 m/s, 4 m/s, 6 m/s, and 8 m/s. The crystal structure and grain size of the ice were measured. The results indicated that, during the ice forming period, the higher the wind speed, the lower the grain size. Uniaxial compression tests were conducted parallel to the ice crystal long axis direction within a strain rate range of 10−6 s−1 to 10−2 s−1. The experimental temperature was controlled at −10 °C. Stress–strain curves were generated, elucidating the mechanical properties and failure modes of the ice. The results suggest that the uniaxial compressive strength of ice is related to the strain rate by a power–law function and shows a linear correlation with −1/2 power of grain size. The results explain the physical fact that the strength of ice is higher when the ice is formed in low-temperature and high-wind-speed environments. Additionally, this highlights how wind speed influences ice strength by controlling grain size during ice forming.

Mechanical Properties of Rock Salt from the Kłodawa Salt Dome-A Statistical Analysis of Geomechanical Data.

Rock salt is a potential medium for underground storage of energy resources and radioactive substances due to its physical and mechanical properties, distinguishing it from other rock media. Designing storage facilities that ensure stability, tightness, and safety requires understanding the geomechanical properties of rock salt. Despite numerous research efforts on the behaviour of rock salt mass, many cases still show unfavourable phenomena occurring within it. Therefore, the formulation of strength criteria in a three-dimensional stress state and the prediction of deformation processes significantly impact the functionality of storage in salt caverns. This article presents rock salt's mechanical properties from the Kłodawa salt dome and a statistical analysis of the determined geomechanical data. The analysis is divided into individual mining fields (Fields 1-6). The analysis of numerical parameter values obtained in uniaxial compression tests for rock salt from mining Fields 1-6 indicates an average variation in their strength and deformation properties. Upon comparing the results of Young's modulus (E) with uniaxial compressive strength (UCS), its value was observed with a decrease in uniaxial compressive strength (E = 4.19968·UCS2, R-square = -0.61). The tensile strength of rock salt from mining Fields 1-6 also exhibits moderate variability. An increasing trend in tensile strength was observed with increased bulk density (σt = 0.0027697·ρ - 4.5892, r = 0.60). However, the results of triaxial tests indicated that within the entire range of normal stresses, the process of increasing maximum shear stresses occurs linearly ((σ1 - σ3)/2 = ((σ1 + σ3)/2)·0.610676 + 2.28335, r = 0.92). A linear relationship was also obtained for failure stresses as a function of radial stresses (σ1 = σ3·2.51861 + 32.9488, r = 0.73). Based on the results, the most homogeneous rock salt was from Field 2 and Field 6, while the most variable rock salt was from Field 3.

Development of an enhanced damage law for typical steel fiber reinforced concrete based on uniaxial compression and tension tests

Understanding the stiffness of a concrete structure is crucial to analyze it, particularly for statically indeterminate structures. Stiffness degradation – commonly referred to as damage – occurs with the onset of cracking or large compressive strains. For most conventional and specialized types of concrete, damage studies and models for predicting damage development are available. However, more information is needed about the damage behavior for the most common steel fiber reinforced concrete in Europe with strength class C30/37 and modern end-anchored high-strength fibers in dosages of 20–40 kg/m3. Therefore, in this study, these common steel fiber concretes were subjected to multiple load cycles in (1) uniaxial compression tests on cylinders and (2) direct tensile tests on bone specimens to investigate their damage behavior. The resulting damage was then compared to known damage laws, but none of the models predicted accurate damage results. Finally, an existing damage law for plain concrete was modified as a function of the residual flexural tensile strength—the relevant parameter for describing the performance of the steel fiber reinforced concrete. Hereby, we were able to decisively improve the agreement between experimental results and the theoretical prognosis by utilizing our modified damage law.

Experimental investigations and material modeling of an elastomer jaw coupling

Abstract This work investigates the hyper-viscoelastic behavior of a thermoplastic polyurethane IROGRAN A 92 E 5670 FCM used in the gear rim of a jaw coupling. The aim is to provide the material parameters for the modeling of jaw couplings in engineering tasks. Uniaxial compression tests were conducted at various temperatures and loading speeds to fit a hyper-viscoelastic material model. The material model uses the Yeoh free energy and the power law model with one Maxwell element. The parametrized material model showed very good results in comparison to experimental data. In addition, the influence of friction on the experiments was modeled, investigated, and discussed. Further component tests for a jaw coupling of size 28 were conducted with two different specimen types. The original gear rim and a modified gear rim with central boreholes for integrated sensors were used in the test. The influence of such a modification was investigated with four different loading cases, focusing on the torsion-torque characteristic and the relative damping. These component tests enable the validation of numerical models of jaw couplings.

Study on mechanical properties and meso-damage mechanism of carbon-polyvinyl alcohol hybrid fiber reinforced recycled coarse aggregate concrete under the coupling action of sodium sulfate and dry-wet cycles

In order to investigate the influence of the coupling effect of sodium sulfate dry-wet (DW) cycles on the mechanical properties of carbon-polyvinyl alcohol hybrid fiber reinforced recycled coarse aggregate concrete (HFRAC), HFRAC specimens were subjected to uniaxial compression tests. The total volume fraction of fibers was kept constant at 0.4%, and various volume fractions of carbon fibers (CF) were added to the recycled coarse aggregate concrete (RAC), namely 0%, 0.1%, 0.2%, 0.3%, and 0.4%, with polyvinyl alcohol (PVA) fibers replacing a portion of CF in equivalent volume. Uniaxial compressive stress–strain curves were obtained for HFRAC specimens subjected to different numbers of DW cycles (0, 30, 60, and 120 cycles). Microscopic testing methods including acoustic emission (AE), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) were employed to analyze the microstructure, erosion product composition, and pore structure changes of the specimens. The results revealed that, for RAC specimens, the peak stress (σp) and elastic modulus (E) initially increased and then decreased, whereas the peak strain (εp) initially decreased and then increased with an increase in the number of DW cycles. After adding hybrid fibers, the σp values of CF, Hybrid 3:1, Hybrid 1:1, Hybrid 1:3, and PVA specimens increased (or decreased) by 12.0%, 11.43%, 0.9%, −9.5%, and −8.5%, respectively, compared to RAC. The Hybrid 1:3 specimen exhibited a negative hybrid effect. With an increase in the erosion age, the Hybrid 3:1 specimen demonstrated enhanced resistance to sulfate attack and achieved the highest σp value after 120 cycles. The influence of sulfate DW cycles coupling on the microscopic damage mechanism of HFRAC was analyzed using a statistical damage constitutive model. The microscopic damage evolution process was characterized by five characteristic parameters: E0, εa, εh, εb, and H. The analysis results indicated a clear correlation between the variation of these characteristic parameters and the number of DW cycles. An effective connection was established between the microscopic damage mechanism and the macroscopic nonlinear constitutive behavior. The phenomenon of relative lagging of acoustic emission signals during the uniaxial compression process was explained from the perspective of effective stress. This study provides a theoretical basis for the promotion and application of RAC under sulfate DW cycle environments.

Coupled Effects of High Temperature and Steel Fiber Content on Energy Absorption Properties of Concrete.

The associated effects of temperature and steel fiber content on the energy absorption properties of concrete were examined using quasi-static uniaxial compression tests of concrete materials with varied steel fiber contents (0%, 0.5%, 1%, and 1.5%) at various temperatures (20 °C, 200 °C, 400 °C, and 520 °C). The experimental findings demonstrate that steel fibers can greatly boost concrete's ability to absorb energy and that the toughness index rises with steel fiber concentration. The energy absorption capacity of concrete under high-temperature conditions also significantly decreases as temperature rises, and the energy absorption ability of steel fiber concrete under the same temperature is superior to that of plain concrete. The coupled influence factor K of temperature-steel fiber percentage characterizing the energy-absorbing ability of concrete was determined, and the coupled influence law of temperature and steel fiber content on the energy-absorbing capacity of concrete materials was summarized and analyzed on the basis of the experimental data of high-temperature compression. Equivalent equations for steel fiber reinforcing and temperature weakening effects when they are comparable (K = 1) are developed and equivalent parameters for concrete materials are given.

Study on mechanical behavior of inclined cemented tailings composite backfill (CTCB) under uniaxial compression

The goaf volume in the vacancy method of hard rock mines is significantly larger than the filling capacity, forming layered and inclined planes during the large-scale filling process. This results in unclear mechanical impact mechanisms on the backfill. To investigate the effect of interface inclination angle on the mechanical behavior of backfill, a set of cemented tailings composite backfill (CTCB) samples with interface inclination angles of 15°, 30°, and 45° are prepared. Uniaxial compression tests and digital image correlation techniques are used to investigate the influence of various interface inclination angles on the strength, deformation behavior, and failure mode of the CTCB. The results show that: (1) The uniaxial compressive strength (UCS) of the CTCB weakens with increasing interface inclination angle but consistently shows exponential growth with curing age (CA) regardless of the interface inclination angle. (2) The interface inclination angle controls the behavior and classification characteristics of the stress-strain curve of CTCB samples, and the increase of interface inclination angle weakens the elastic modulus. (3) The interface inclination angle significantly influences the failure mode and classification characteristics of the samples compared to CA and tailing-to-cement ratio (TCR), with shear slip failure induced by the former and axial splitting failure induced by the latter. The research provides a theoretical basis for understanding the mechanical behavior and stability control of inclined CTCB in underground mining.

The Effect of Mineral Composition on the Correlation between Point Load Index with the Uniaxial Compressive Strength of Sulfate Rocks and their Point Loading Deformation

Point load test is a common, inexpensive and fast test for the indirect achievement of compressive or tensile strength of the rocks in the laboratory and the field. In this research, by conducting uniaxial compression test (UCT), axial (APLT), and diametral (DPLT) point load tests on gathered sulfate rock blocks from the Gachsaran Formation outcrops at the four under-construction reservoir dam sites in Iran, investigate the effect of mineral composition on the relationships between point load index, the uniaxial compressive strength (UCS) and their point load deformation. Regarding that, firstly by creating a correlation between axial (APLI) and diametral (DPLI) point load index and UCS, relationships for each specific mineral composition were provided. Secondly, by comparing the reliability of the APLT and DPLT results in predicting UCS, the conversion factors of the APLI and DPLI to the UCS were calculated. Thirdly, the effect of unique or multiple sampling locations in the analysis results was compared, and finally, for the first time, the deformation of loading points in point load tests was investigated. The results of this study confirmed that by variation of mineral composition of sulfate rocks, the relationships between APLI and DPLI, and UCS, conversion factors as well as loading points deformation patterns during point load tests are changed significantly, and the results of APLT and DPLT can be used to predict UCS with the same reliability in dry and saturated conditions.

Mechanical property and frost resistance of phase–change/NanoSiO2 concrete in a low–temperature environment

To study the effect of phase–change materials and nanomaterials as new composite materials on the mechanical properties and frost resistance of concrete, it is beneficial for low–carbon and environmentally friendly buildings to be achieved. The effects of freeze–thaw cycles and different preloading strains were considered. ICT scanning was performed, and the compression performance of composite–modified concrete (CMC) were tested. The internal pore structure and strength indicators of the CMC were analyzed during uniaxial compression. Meanwhile, by conducting uniaxial compression tests on CMC at different temperatures, changes in the mechanical properties during real–time freezing and thawing processes were obtained. The results demonstrated that the fractal dimension grows and the compressive performance of the CMC declines as the number of freeze–thaw cycles and preloading strain increases. The proportion of spheroids in the internal pore shape gradually decreases, whereas the proportions of rods, discs, and blades increases. CMC effectively delays the rise or fall of internal temperature during the freeze–thaw process and reduces its internal structural deterioration. Compared with the freeze–thaw effect, an increase in the preloading strain has a more notable impact on the compressive performance of CMC. A stress–strain constitutive model is proposed for a 10 % microencapsulated phase–change materials and a 1.5 % nanoSiO2 composite–modified concrete (10 mPCMs/1.5 NS CMC), influenced by temperature, through regression analysis. Meanwhile, under low temperatures, the degradation of mechanical properties of 10 mPCMs/1.5 NS CMC and the influence of different preloading strains are considered, leading to the development of stress–strain constitutive models for freeze–thaw cycles and different preloading conditions.

Analysis of size effect and its influencing factors of brittle red sandstone with different heights

We carried out uniaxial compression tests on brittle red sandstone with different heights. The test results show that the uniaxial compressive strength of rock sample increases first and then tends to be stable with the increase of the size, which is approximately stable between 75 and 81 MPa. Both elastic energy and dissipated energy increase with the increase of rock sample size. In order to further analyze the mechanism behind these phenomena, we combined advanced numerical simulation and theoretical analysis to explain these phenomena, and systematically analyzed the end face effect as one of the key factors affecting the uniaxial compression characteristics of brittle red sandstone for the first time. Small sized rock samples are very sensitive to end effect. The middle of the large sized rock samples is in a uniform compression state, and the effect of end effect is weakend. When there are rigid pads at both ends of the rock sample, there is an obvious elastic vertebral body during the loading process of the rock sample. The bearing capacity of rock samples with rigid pads is greater than that of rock samples without rigid pads, and the energy released during instantaneous failure of rock samples without rigid pads is greater than that of rock samples with rigid pads. The findings of this paper make a valuable contribution to establishing optimal study sample sizes and advancing the utilization of laboratory test mechanics parameters in engineering applications.

Analytical Study on the Load-Bearing Performance of RC Beams Subjected to ASR Expansion

The alkali–silica reaction (ASR), a major cause of cracks in concrete, is a critical issue in the maintenance of social infrastructure. In this study, a concrete mesoscale model was meticulously developed, and a coupled stress–moisture model was also developed to reproduce ASR degradation. The aim was to investigate the effect of ASR degradation on the bending load-carrying capacity of RC beams. The concrete mesoscale model, specifically designed to reproduce ASR degradation, was modeled from three phases: coarse aggregate, mortar, and ITZ (interfacial transition zone). ASR was considered as the expansion of the coarse aggregate, and the objective was to reproduce expansion cracks with numerical analysis using the mesoscale model. Uniaxial compression tests were carried out on cylindrical specimens with ASR-accelerated deterioration to clarify the relationship between ASR deterioration and compressive properties, and the experimental results were used to identify material parameters in the mesoscale analysis model. The results showed that the model proposed in this study can reproduce the change in compressive properties due to expansion cracking. Finally, RC beams were constructed using the mesoscale model, and the effect of ASR degradation on the bending load-carrying capacity of the RC beams was investigated. The results showed that the presence of expansion cracks caused the initial stiffness of the load-displacement curves to decrease, but the bearing capacity tended to increase. This suggests that factors other than cracks, such as chemical prestress and boundary conditions in this model, have a strong influence on the load-bearing capacity of deteriorated RC beams.

Study on the Influence of Temperature and Water Content on the Static Mechanical Properties of Sandstone.

The area of permafrost worldwide accounts for approximately 20% to 25% of land area. In cold-climate regions of China, which are garnering international attention, the study of low-temperature and moisture effects on rock mass mechanical properties is of significant importance. China has a wide area of cold regions. This research can provide a foundation for China's exploration activities in such extreme environments. This paper examines the mechanical behavior of rock specimens subjected to various low temperatures and water contents through uniaxial compression tests. The analysis encompasses failure modes, stress-strain relationships, uniaxial compressive strength (UCS), and elastic modulus (EM) of these specimens. Findings reveal that at lower temperatures, the rock specimens' fracture patterns transition from compressive shear failure to cleavage failure, reflecting a shift from a plastic-elastic-plastic to a plastic-elastic response. Specifically, saturated rocks exhibit a 40.8% decrease in UCS and an 11.4% reduction in EM compared to their dry counterparts. Additionally, in cold conditions, an increased water content in rocks primarily leads to vertical cracking. Under such conditions, saturated rocks show a 52.3% decline in UCS and a 15.2% reduction in EM, relative to their dry state.

An Optimized Strain-Compensated Arrhenius Constitutive Model of GH4169 Superalloy Based on Hot Compression.

A precise constitutive model is essential for capturing the deformation characteristics of the GH4169 superalloy in numerical simulations of thermal plastic forming processes. Hence, the aim of this study was to develop a precise modified constitutive model to describe the hot deformation behavior exhibited by the GH4169 superalloy. The isothermal cylindrical uniaxial compression tests of the GH4169 superalloy were carried out at temperatures of 950~1100 °C and strain rates of 0.01~10 s-1 using a Thermecmastor-200KN thermal-mechanical simulator. The original strain-stress curves were corrected by minimizing the effects of plastic heat and interfacial friction. Based on the true stress-strain curves, the original strain-compensated Arrhenius constitutive model was constructed using polynomial orders of 3, 5, and 10, respectively. The results showed that once the polynomial order exceeds the 5th, further increasing the order has little contribution to the accuracy of the model. To improve prediction ability, a higher precision Arrhenius constitutive model was established by extending a series of material parameters as functions that depend on temperature, strain, and strain rate, in which the error can be reduced from 4.767% to 0.901% compared with the classic strain-compensated Arrhenius constitutive model.

Study on the failure mechanism of high-temperature granite under two cooling modes

In the geothermal development of hot dry rock (HDR), both the drilling of the wellbore and the heat exchange of the heat reservoir involve the effects of different cold and hot conditions on the high-temperature rock mass. The testing machine for rock mechanics was used to conduct a uniaxial compression test and carry out micro testing on the treated samples; furthermore, with the help of scanning electron microscopy the fracture mechanism of granite subjected to different temperatures and cooling methods was studied. The results show: (1) With the gradual increase in temperature, the compressive strength of granite under the two cooling methods gradually decreases. (2) The failure modes of the samples under the two cooling methods are mainly shear failure of the "Y" type. The degree of damage of the sample under water cooling is significantly greater than that under natural cooling. Electron micrographs could confirm these results. (3) It can be obtained by testing the mineral composition and element changes of granite at different temperatures. When the temperature reaches 600℃, its change is more pronounced. The results of this study can provide a theoretical reference for the failure of the wellbore and the degree of fracture of the thermal reservoir rock mass during geothermal development.

A micro-meso coupled model for coral reef rocks based on CT Scanning

The coral reef rock has a rich porous structure, and establishing an entity model with a realistic porous structure will do great good to study the mechanical behavior and its mechanisms. However, the pore's characterized size of coral rocks spans four orders of magnitude from micro to meso scales (1 μm to 10 mm). This requires a large specimen size and a very small element size in the model, which leads to extremely high computational costs. To overcome this fundamental challenge, this paper uses CT to scan a macro coral specimen to obtain an entity model and establishes a micro-meso scale coupled model: (1) retaining pore’s equivalent diameter larger than 1mm in the overall CT entity, and regarding the rest part as a uniformly dense matrix material with unknown material’s properties, which is called the meso model; (2) extracting a small entity containing pore’s equivalent diameter less than 1mm from the CT entity, which is called the micro model also with unknown matrix material properties; (3) the unknown matrix material parameters in meso model are derived from mechanical response of the micro model, and the unknown matrix material parameters in micro model are confined by that meso model's mechanical responses should be coincident with that of a real coral specimen. Comparing with the uniaxial compression test result, this micro-meso coupled model has high precision and retains the influence of pores at various scales. The computational result shows that it can reduce the computational complexity of a single CT entity model by four orders of magnitude. It provides a new approach for studying similar materials' mechanical behavior and mechanisms under complex loading conditions.

Study on fatigue parameters of high modulus asphalt pavement

High Modulus Asphalt Mixtures (HMAM) have gained widespread utilization in asphalt pavement construction. It is great critical to study the fatigue characteristics of HMAM. At present, various fatigue test methods are employed in indoor testing to assess HMAM under different mechanical states. Therefore, there is a critical problem that the value of fatigue parameters is not unique in the structural design of HMAM. In this study, three fatigue testing methods were initially used to address the above issues: direct tensile testing, indirect tensile testing, and uniaxial compression testing. These tests help to determine the strength yield surface states at different loading rates. And to reveal the effect of loading rate on the mechanical behavior of HMAM. The results show a power function fit and a good correlation between strength and loading rate. The relationship models of strength with speed for indirect tensile, direct tensile and uniaxial compression tests are SI=3.22(v)0.14, SD=3.22(v)0.15 and SU=3.22(v)0.12, respectively.The higher the loading rate for the three fatigue test results, the greater the expansion of the strength yield surface.The fatigue life (Nf) of HMAM underwent testing, yielding its fatigue effective stress ratio. The relationship between the two was and then established. It is found that the point (1, 1) appears on the backextension line, thus effectively complementing the conventional S-N equation. In addition, the fatigue equations for various fatigue test methods were unified based on effective stress strength ratio and the fatigue life. This paper introduces a novel method for the antifatigue design of HMAM.

Studi Uji Kuat Tekan Uniaksial dan Uji Kuat Tarik Tidak Langsung Untuk Menentukan Brittleness Index (BI) Pada Batupasir di Formasi Pulau Balang dan Balikpapan

In the process of designing mine slopes, drilling or tunneling, to determine the level of strength and brittleness factors of rock on a slope, it is necessary to carry out a uniaxial compressive strength test or indirect tensile strength test of the rock. Compressive strength testing is carried out to determine how long the rock maintains its strength or elastic properties when pressure is applied. This data can be used as information to understand the analysis of factors that influence the physical properties of rocks on the compressive strength of rocks from physical properties and compressive strength testing activities. and indirect tensile strength testing is carried out to determine the stress value contained in the rock. To determine the level of rock brittleness, it can be done by comparing the uniaxial compressive strength value and the indirect tensile strength value. This data can be used as information and reference for companies that will design a mine slope, drill and tunnel, how strong the strength and level of brittleness of rocks in areas dominated by sandstone. This research uses quantitative methods, so that to obtain accurate calculation data, testing methods are used in the form of uniaxial compressive strength tests and indirect tensile strength tests, in this case tested on sandstone samples obtained from 2 rock formations including the Pulaubalang formation and the Balikpapan formation, so that accuracy The test result values ​​can be obtained well. And after testing, a comparison is made between the uniaxial compressive strength test value and the indirect tensile strength test to obtain the Brittleness Index value.Based on the observation results, it can be concluded that when the brittleness of the rock becomes greater, the performance of the cutting digger increases several times.

Rock crack initiation triggered by energy digestion

The critical value of rock failure is determined by irreversible deformation (inelastic deformation, damage, and other internal dissipation) processes and external conditions before rock failure. Nevertheless, a thorough explanation of the mechanism causing cracks in rock material has not yet been provided. The strain energy theory is applied in this work to assess the initiation of rock cracks and investigate the relationship between energy digestion and rock strength. Firstly, the uniaxial compression test was conducted on sandstone samples under quasi-static loading conditions and the results of energy evolution, non-linear cumulative digestion, and stored ultimate energy were obtained. Then, a novel algorithm for assessing the initiation of rock cracks has been put forth. The concept of energy digestion index (EDI), which is the ratio of digested energy over the external loading energy, has been developed to characterize the energy absorption capacity of rock material. The result shows a relationship between the maximum growth rate of energy digestion and the increasing rate of variable elasticity modulus and crack initiation. The mechanical characteristics and peak strength of the rock material are negatively correlated with the EDI. By monitoring the digested energy status, an evaluation of the residual strength is introduced based on the relationships, which will initiate further research into in-situ monitoring and failure prediction.