Rock Strength Research Articles

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.

Impacts of frost heave susceptibility and temperature-changing conditions on freeze-thaw deterioration of welded tuffs

Damage development in rocks by freeze-thaw cycles, a phenomenon that is typical to cold regions, is known to reduce the strength and durability of structures. In this study, a series of freeze-thaw tests were performed on frost and non-frost heave rocks to examine the impact of frost heave susceptibility and temperature-changing conditions on rock behaviors. The freeze-thaw life and uniaxial compressive strength (UCS) of rocks subjected to freeze-thaw cycles were estimated using a model that was based on fatigue damage mechanisms. Furthermore, we proposed a method for estimating the freeze-thaw life of rocks, using expansive strain as an important factor. The results indicated that the Shikotsu welded tuff (a non-frost heave rock) exhibited higher durability than the Noboribetsu welded tuff (a frost heave rock); this may be because the Shikotsu welded tuff had a larger pore radius and more unsaturated pores. The one-dimensional (1D) cooling-heating conditions induced significantly less damage than the three-dimensional (3D) conditions, owing to the continuous migration of free water into the unfrozen zone. The damage model estimated that for the Noboribetsu welded tuff, the freeze-thaw life in the 1D conditions was approximately eight times longer than that in the 3D conditions. Notably, with respect to the Shikotsu welded tuff, a critical freeze-thaw period induced significant expansion, resulting in damage development in the tuff. The freeze-thaw life of each rock sample was estimated based on the magnitude of the volumetric expansive strain. This study contributes to the rational assessment of the stability and durability of rock structures in cold regions.

Simulation method of asphalt mixture based on fracturable digital aggregate model

This study proposed an approach to construct a fracturable aggregate model to make the fracture patterns consistent with the real situation. Firstly, this study utilized three-dimensional structured light technology to obtain the geometric shell of aggregate and divide them into four categories of spherical, angular, elongated and flaky aggregates according to the minimum bounding box algorithm. Secondly, this study proposed a discrete-spheres filling algorithm based on the Bubble Pack Filling algorithm to fill the shell accurately. Thirdly, this study established the conversion equations between the macro and micro parameters of aggregate by using the linear parallel bonding model, and used it to establish the fracturable aggregate model. Through the indoor and virtual static fracture tests, this study found that the fracture patterns of the fracturable aggregate models are similar to the real situation and characterized the fracture patterns of four types of aggregates. Further analyzing the virtual static fracture tests, this study found that the bearing capacity of aggregates is determined by the compressive strength of host rocks and the shape of aggregate. Through the indoor and virtual uniaxial compression creep tests, this study investigated the behavior of the mixture specimens consisted by the fracturable aggregate model. The stress-strain curves of the fracturable and unfracturable aggregate model in this test were plotted in this study, and the results showed that the relative error between the results obtained by the fracturable model and those of the indoor test is much smaller than that of the unfracturable model. Considering that existing simulation tests on asphalt mixture often ignore aggregate deformation and fracture, so this study used the method mentioned above to obtain the fracturable aggregate model, which can improve the confidence of asphalt mixture simulation results.

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.

Assessment of Uniaxial Strength of Rocks: A Critical Comparison Between Evolutionary and Swarm Optimized Relevance Vector Machine Models

Assessment of Uniaxial Strength of Rocks: A Critical Comparison Between Evolutionary and Swarm Optimized Relevance Vector Machine Models

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.

Complex function method considering rock strength for determining critical warning deformation of deep-buried complex cavern

Most existing deformation warning methods for the safety of surrounding rock rely on empirical index or complicated numerical simulation and are unable to accurately and quickly determine the critical warning deformation, so an accurate determination method of critical warning deformation based on rock strength was investigated by the complex function theory in this study. The complex function theory was used to demonstrate that the elastic deformation of surrounding rock at a point is linearly related to its circumferential stress. Based on this demonstration, the critical warning deformations for blue warning, yellow warning, and red alert can be theoretically determined according to the crack initiation stress, dilatancy stress, and uniaxial compressive strength of surrounding rock, respectively. In addition to these critical stresses, the cavern’s shape, the in-situ stress, the deformation properties, and the position of the surrounding rock were also considered in the determination. The accuracy of the proposed theoretical method was verified by a finite element simulation of an example tunnel. Subsequently, the method was applied to the underground powerhouse on the left bank of the Baihetan hydropower station. Compared with the on-site monitoring displacements of the surrounding rock, the resulting warning displacements could accurately indicate the safety status of all monitoring areas around the cavern after each layer of excavation. In addition, the resulting warning positions, warning times, and warning grades matched the on-site failures of the surrounding rock very well. Thus, the proposed method is highly reliable and can be used for real-time warning of underground engineering.

Numerical simulation analysis of the influence of karst cave orientation and surrounding rock properties on tunnel excavation

Abstract The underground distribution of complex karst geology in the Zhangjiajie region of China poses a significant threat to the construction safety of tunnels, not only increasing project investments but also severely impacting the stable operation of engineering construction. This paper, based on ABAQUS numerical simulation, explores the influence of karst caves around tunnels in different orientations of surrounding rock environments through the rock strength, stress field, and dimension of surrounding rock mass. The results are as follows: (1) With the decrease in cohesive strength of the cave surrounding rock, the stability of the tunnel is enhanced. (2) The maximum displacement of the lower cave is 0.02011 m, greater than that of the side cave, which is 0.01965 m; the maximum principal stress of the lower cave is 7.457 MPa, greater than that of the side cave, which is 7.423 MPa. The lower cave has a greater impact on tunnel construction and can further reduce the stability of the karst tunnel surrounding rock. This paper has researched the influence of caves on tunneling through surrounding rock and investigated the effects of cave orientation, cohesive strength, and other parameters on tunnel construction. It provides theoretical guidance for tunnel alignment and pre-processing of concealed caves.

Drilling Process Monitoring for Predicting Mechanical Properties of Jointed Rock Mass: A Review

Reliably assessing the quality and mechanical properties of rock masses is crucial in underground engineering. However, existing methods have significant limitations in terms of applicability and accuracy. Therefore, a field measurement method that meets the real-time monitoring and safety requirements for the quality of engineering rock masses is needed. Firstly, the research findings of domestic and international scholars on the application of drilling process monitoring technology are comprehensively analyzed. Rotary cutting penetration tests are conducted on tuff rock masses containing fractures and joints. Various rock mass classification and evaluation standards are integrated with rotary penetration tests. Rotary cutting penetration tests are used to determine the residual strength of rock, based on this review. The rationality of the calculated mi parameter values is validated. The peak strength, residual strength, and errors of the rock are obtained based on the penetration method. The rock quality index rock quality designation from drilling (RQDd) is redefined, based on the drilling process monitoring apparatus (DPMA). Rock mass classification is conducted, based on the correlation between the standard deviation of rotary drilling energy and the rock quality designation (RQD). Additionally, a new relational formula is introduced to determine the RQD from variations in drilling energy, based on discontinuity frequency. This field measurement method undoubtedly provides a crucial scientific basis for rock design and construction, ensuring long-term safety in engineering applications.

The Potential for Fracture Growth in Stepped Subglacial Topography as a Quarrying Mechanism

AbstractUnderstanding the rates and mechanisms of erosion by subglacial quarrying is a major unsolved problem in geomorphology. Stress enhancement due to load concentration on bedrock ledges between cavities is hypothesized to drive the growth of fractures. Prior work assumed the formation of vertically oriented tensile fractures at the downstream margins of cavities as the controlling process, but did not account for the evolution of the stress field as fractures lengthen, and in particular the dominance of the shearing mode at fracture tips. We used 2D finite element analysis and J‐integral methods to analyze stress intensity factors and fracture growth potentials at the tips of preexisting fractures in loaded bedrock steps, taking into account normal and shear components and measured rock strengths. By examining different step heights, step riser angles, rock types, prior fracture locations and orientations, and extents of ice‐rock contact zones, we identified some situations favorable for fracture growth, especially in brittle rock types. Typically, however, the growth direction will not be vertically downward but angled up‐glacier away from the step riser, a situation unfavorable for quarrying. Moreover, in many situations, the normal stress across fracture planes will be compressive. Non‐vertical step risers buttress the bedrock and also suppress fracture growth. In contrast, reducing the sizes of ice‐rock contact zones not only increases the loading magnitude, as previously recognized, but also increases intensification of tensile stress at the tips of fractures located just up‐glacier. Thus, larger cavities, and hence, fast sliding and low effective pressures, favor quarrying more strongly than previously recognized.

Research into mechanical properties of ore and rocks in the ore deposits with assessment of the mass stress state natural field

Purpose. The research aims to conduct a comprehensive study of the mechanical properties of ores and rocks within the Zhilandy Group field, as well as to assess the natural field of mass stress state to solve geomechanical problems in optimizing mining operations. Methods. To determine the boundary conditions when measuring the stress-strain state of the mass, a complex methodology is proposed, including stress measurements using hydraulic fracturing methods of the wells and determining the physical-mechanical properties of rocks. Five rock probes have been tested. Twelve tests (six tests in natural and six in water-saturated states) have been conducted for each probe. Findings. Hydraulic fracturing tests at the metering stations show significant tectonic stress due to the shape of structural folds and the mass fracturing. It has been revealed that the hard rock mass is characterized by non-uniform fracturing. It is of tectonic origin and averages between 10-15 and 15-25 fractures per meter for different lithological varieties. The maximum horizontal stress at the stations is oriented along an azimuth of 70° ± 10. Originality. The influence of water saturation on the reduction of strength and deformation characteristics of rocks has been determined for the conditions of the Zhilandy Group field, which shows significant variations depending on the rock type. Especially important is the revealed fact of a significant decrease in uniaxial compression and uniaxial tensile strength, as well as a decrease in Young’s modulus and cohesion factor. Linear dependences of stresses occurring with depth have been obtained from the measurement results. Practical implications. The results obtained are of significant importance for the mining industry. Understanding the extent of reduction in strength characteristics during water saturation and assessing the natural field of the stress mass state allows more accurate prediction of rock behavior.

Study of the relationship between uniaxial compressive strength vs non-destructive testing and specific weight in bank rocks from the Seybaplaya Campeche Mexico

This research study focuses on analyzing the uniaxial compressive strength of rocks and its correlation with non-destructive testing (Schmidt hammer) and specific gravity. It is important to note that Seybaplaya, located in Campeche, Mexico, is known for its fishing, industrial, and commercial activities. Samples from one of the main active quarries in the state of Campeche were used for the investigation. As a result, equations were developed to predict the simple uniaxial compressive strength based on values obtained from the Schmidt hammer and specific gravity. It is relevant to highlight that these relationships are only valid for rocks with lithological characteristics similar to those used in this study. The results of the analysis and the conclusions demonstrate the non-linearity of the relationships between simple uniaxial compressive strength, non-destructive testing, and specific gravity.

Investigation of Wellbore Instability in Southern Rumaila Oil Field

This study aims to address the issue by providing valuable insights into the factors contributing to the wellbore instability and proposing effective measures to mitigate the problem in the southern part of the Rumaila oil field. A comprehensive one-dimensional mechanical earth model (1D MEM) was developed by utilizing various logs data from 4 wells across the south part of this field, including gamma ray, bit size, caliper, bulk density, and sonic compression and shear logs. The model was validated with laboratory tests, including Brazilin and Triaxial tests, as well as repeated formation tests. To analyze the wellbore stability, three different failure criteria, namely Mohr-Coulomb, Mogi-Coulomb, and Modified lade, were employed. The results indicated that the Mogi-Coulomb criterion was the most accurate failure criterion in predicting rock failure. Wellbore instability problems had been observed across the shale sections throughout the Rumaila oil field, particularly through Tanuma, Khasib, top and bottom of Ahmadi, Nahr Umr, and Upper Shale members and Middle Shale members of Zubair formations. The 1D MEM results indicated that Shaly formations exhibited low stiffness rocks (low Young's Modulus (YME)), low rock strength, and high Poisson's ratio (PR), suggesting potential challenges related to wellbore instability in the Tanuma, top and bottom of Ahmadi, Nahr-Umr, and Zubair formations. A sensitivity analysis was performed to determine the safest mud weight and the optimum well trajectory for future drilling operations. According to the updated mud window of this field in 2023, the pressure in the Mishrif and Zubair formations was reinforced by injection wells, as it was noted that the pressure behavior shifted from depletion (2000 Psi). Based on the findings of this study, the good inclination of (0-25°) can be drilled with the mud weight of 1.24-1.26 sg, while the good inclination of (25-40°) can be drilled with the mud weight of 1.28-1.30 sg in all directions (i.e., all azimuths). The stress regime in most of the formations was found to be a strike-slip to a normal fault regime. The findings of this study can significantly benefit the oil industry and enhance overall productivity.

Experimental investigation on the anisotropy of friction property for dry and water-saturated rock

Friction properties of rock are closely connected with the anisotropy. The anisotropy of rock friction can provide a valuable assessment for geotechnical and geological engineering. In this study, the rotary friction tests were conducted to analyze the water effect on the friction property and the friction anisotropy of the four types of rock. The drilling response model (DD-model) was employed to characterize the rotary friction behavior of the rocks. The parameters of this model include the three types of friction parameters: 1/ς, μ, and f, where 1/ς and μ are constant, and f is a variable. A quantitative method is proposed for assessing the anisotropy of rock friction. The results of the rotary friction tests indicate that the relation between torque force and thrust force conforms to the DD-model. The changes of two friction constants 1/ς and μ from dry state to water-saturated state suggest that the water effect on the friction strength of the rocks exhibits significant anisotropy. The friction strength determined by the friction variable f increases first, then decreases, and finally stabilizes with the increasing of depth. AIf is an anisotropy index calculated by the proposed method. The percentage difference of the average value of AIf between water-saturated and dry states shows the degree of the water effect on the friction anisotropy of the rocks, mudstone (MU) > granite (GR) > fine sandstone (FS) > argillaceous siltstone (AS). The quantitative model is hopefully constructed for characterizing the relation between the anisotropic friction strength of rock and the moisture state in future.

Safety evaluation method of bottom coal thickness in thick coal seam roadway

In recent years, the number of roadway floor rock burst accidents is increasing, which seriously restricts the safe production of the mine. Therefore, safety evaluation method of bottom coal thickness in thick coal seam roadway was studied. The research results shown that the stress concentration area of composite floor is distributed in coal seam or rock stratum with large elastic modulus. With the increase of floor rock strength, the stress of coal-rock composite floor increased gradually, but the displacement and energy decreased gradually. When floor rock strength was equal to bottom coal strength, the increase of floor stress and displacement with the change of bottom coal thickness was the smallest, which was 34.29% and 33.61% respectively. The elastic strain energy decreased from 14.58 to 9.85%. With the increase of bottom coal thickness, the stress and displacement of coal-rock composite floor increased first and then decreased, and the elastic strain energy decreased gradually. It puts forward the safety evaluation method of bottom coal thickness: floor failure depth → reasonable thickness of bottom coal → safety thickness of bottom coal. It can provide reference for design of roadway bottom coal retention and surrounding rock control in thick coal seam face.

Pengaruh Sifat Fisik Terhadap Nilai Uniaxial Compressive Strength Batuan Dengan Kondisi Natural, Jenuh dan Kering Pada Formasi Balikpapan dan Pulaubalang Provinsi Kalimantan Timur

The uniaxial compressive strength value is one of the important parameters that is widely used in rock engineering projects in determining rock mass. The strength of rocks is greatly influenced by the water content and degree of saturation in the rock. Reduction of strength in rock is associated with an increase in water content, a slight increase in water content will cause a significant deviation in the compressive strength test value.This research is quantitative research, so to obtain accurate calculation data, testing methods are used in the form of compressive strength tests on rocks and physical properties tests in the treatment of samples of original rock, saturated rock and dry rock before testing. In this research, 2 types of rock were used, including limestone and sandstone in 2 rock formations, namely the Balikpapan formation and the Pulaubalang formation, so that the accuracy of the test result values ​​could be obtained well. Based on the results of observations and calculations that have been carried out, the water content values ​​of limestone in natural, saturated and dry conditions in the Balikpapan formation are obtained with average values ​​of 1.709%, 2.262% and 0.961% respectively. The water content of sandstone in natural, saturated and dry conditions is the Pulaubalang formation with average values ​​of 2.491%, 9.425% and 0.463% respectively. The UCS value of limestone in natural, saturated and dry conditions in the Balikpapan formation has an average value of 25.29 Mpa, 37.57 Mpa and 40.70 Mpa respectively. The UCS value of sandstone in natural, saturated and dry conditions in the Pulaubalang formation has an average value of 9,565 Mpa, 6,537 Mpa and 12,730 Mpa. It can be concluded that the correlation between uniaxial compressive strength values ​​and water content values ​​in limestone and sandstone shows a positive linear correlation, which means they have a strong relationship. The higher the compressive strength value of limestone and sandstone, the lower the water content value.

Porosity and bedding controls on bio-induced carbonate precipitation and mechanical properties of shale and dolomitic rocks: EICP vs MICP

Biocementation is an emerging field within geotechnical engineering that focuses on harnessing microbiological activity to enhance the mechanical properties and behavior of rocks. It often relies on microbial-induced carbonate precipitation (MICP) or enzyme-induced carbonate precipitation (EICP) which utilizes biomineralization by promoting the generation of calcium carbonate (CaCO3) within the pores of geomaterials (rock and soil). However, there is still a lack of knowledge about the effect of porosity and bedding on biocementation in rocks from a mechanistic view. This experimental study investigated the impact of porosity and bedding orientations on the mechanical response of rocks due to biocementations, using two distinct biocementation strategies (MICP and EICP) and characteristically low porosity but interbedded rocks (shale) and more porous but non-bedded (dolostone) rocks. We first conducted biocementation treatments (MICP and EICP) of rock samples over a distinct period and temperature. Subsequently, the rock strength (uniaxial compressive strength, UCS) was measured. Finally, we analyzed the pre- and post-treatment changes in the rock samples to better understand the effect of MICP and EICP biocementations on the mechanical response of the rock samples. The results indicate that biocementations in dolostones can improve the rock mechanical integrity (EICP: +58% UCS; MICP: +25% UCS). In shales, biocementations can either slightly improve (EICP: +1% UCS) or weaken the rock mechanical integrity (MICP: −39% UCS). Further, results suggest that the major controlling mechanisms of biogeomechanical alterations due to MICP and EICP in rocks can be attributed to the inherent porosity, biocementation type, and bedding orientations, and in few cases the mechanisms can be swelling, osmotic suction, or pore pressurization. The findings in this study provide novel insights into the mechanical responses of rocks due to MICP and EICP biocementations.

Studi Kuat Tekan Batulanau Berdasarkan Uji Lapangan dan Uji Laboratorium Pada Formasi Kampungbaru dan Pulaubalang Daerah Kutai Kartanegara Kalimantan Timur

Rock strength is the ability of a rock to maintain its strength until it breaks when a force is applied. Rock compressive strength is a very important parameter in the world of mining. The compressive strength of the rock determines the mining method that will be used. Several things that influence the compressive strength of rock include porosity, true specific gravity, and water content. With the same volume, if the porosity value is high, the true specific gravity value will be low because of the large number of pores in the rock. This allows the compressive strength value to be low because the rock will crumble more easily when pressure is applied. After testing, the highest compressive strength value was in the Pulaubalang Formation, location 2, with a value of 2.19 MPa. Meanwhile, the lowest compressive strength value was in the Kampungbaru Formation, location 1, with a value of 1.49 MPa. In accordance with the stratigraphic layers in the Kutai Basin, the Pulaubalang Formation is older than the Kampungbaru Formation.

Unconfined compressive strength prediction of rock materials based on machine learning

It is costly, time-consuming, and difficult to measure unconfined compressive strength (UCS) using typical laboratory procedures, particularly when dealing with weak, extremely porous, and fractured rock. By efficiently choosing the variables from a subset of the dataset that includes the Schmidt hammer rebound number (SRn), bulk density (BD), bulk tensile strength (BTS), dry density (DD) test, p-wave velocity test (Vp), and point load index test (Is(50)), this study seeks to establish predictive models for the UCS of rocks. A prediction model for UCS was prepared using K-nearest neighbor (KNN). KNN was preferred over machine learning algorithms because it is simple, versatile, and interpretable. It is particularly useful when it has limited training time, faces non-parametric data with changing distributions, or requires straightforward explanations for predictions. In order to improve KNN’s prediction performance in this research, two optimization procedures (namely, Alibaba and the Forty Thieves (AFT) and Improved Manta-Ray Foraging Optimizer (IMRFO)) were used. Through comparison of KNN single modal performance with that of optimized versions, it is concluded that the KNIM (KNN model optimized with IMRFO) is an excellent possible applicant for the forecast of the UCS of rocks. This study’s results showed that the KNIM model is more suitable than the KNN single model and its counterpart KNAF in terms of accuracy as its correlation of determination (R2) values were 1.1% and 2% higher than KNN and KNAF and its root mean squared error (RMSE) values were 37.9% and 43.7% lower than KNN and KNAF. The improvement in R2 and RMSE values for the KNIM model compared to KNN and KNAF is highly significant for the reliability and accuracy of the predictive model. R2, measuring the proportion of variance predictable in the dependent variable (UCS of rocks) from the independent variables (model predictions), signifies a better fit to observed data. The elevated R2 values for KNIM indicate a stronger correlation with actual UCS values, enhancing the model’s accuracy in representing underlying patterns. Additionally, the reduction in RMSE values for KNIM implies that its predictions are, on average, closer to actual UCS values, contributing to a more accurate and reliable estimation of rock strength.

Exploring the Influence of Sample Geometry on the Tensile Strength of Rock and Concrete: An Integrated Experimental and Numerical Analysis

Exploring the Influence of Sample Geometry on the Tensile Strength of Rock and Concrete: An Integrated Experimental and Numerical Analysis