Compressive Strength Of Rock Research Articles

STUDY OF THE EFFECT OF WATER CONTENT AND POROSITY ON THE UNIAXIAL COMPRESSIVE STRENGTH OF ANDESITE ROCK IN SAOKA SORONG WEST PAPUA PROVINCE

Rock physical properties such as water content and porosity affect mechanical properties such as the compressive strength value or rock strength value. This parameter is an input parameter for geotechnical or structural design purposes. To understand the effect of water content and porosity on the rock's compressive strength a laboratory test is needed. Rock samples are taken in the form of lumps and then prepared and tested according to predetermined standards. The result is a decrease in water content and a porosity results in an increase in the compressive strength. Based on the correlation value of the original water content = 0.061, saturated water content = 0.001, and porosity = 0.408, it shows a weak influence or relationship. This is due to the water content and porosity having a coefficient of determination or R2 value of less than 0.6.

Geomechanical rock properties of the Officer Basin

The Officer Basin spanning South Australia and Western Australia is the focus of a regional stratigraphic study being undertaken as part of the Exploring for the Future (EFTF) program, an Australian Government initiative dedicated to increasing investment in resource exploration in Australia. Despite numerous demonstrated oil and gas shows, the Officer Basin remains a frontier basin for energy exploration with significant uncertainties due to data availability. Under the EFTF Officer–Musgrave Project, Geoscience Australia acquired new geomechanical rock property data from forty core samples in five legacy stratigraphic and petroleum exploration wells that intersected Paleozoic and Neoproterozoic aged intervals. These samples were subjected to unconfined compressive rock strength tests, Brazilian tensile strength tests and laboratory ultrasonic measurements. Petrophysical properties were also characterised via X-ray computerised tomography scanning, grain density and porosity-permeability analysis. Accurate characterisation of static geomechanical rock properties through laboratory testing is essential. In the modern exploration environment, these datasets are a precompetitive resource that can simplify investment decisions in prospective frontier regions such as the Officer Basin.

Experimental investigation on concrete rock breaking performance of self-excited oscillation pulsed waterjet

To obtain the influence of structural parameters, system pressure, standoff distance, rock characteristics on rock breaking volume and specific energy consumption, the rock breaking experiment using self-excited oscillation pulsed waterjet (SOPW) was carried out. The relationship among rock initial crushing pressure, fracturing pressure with rock compressive strength was investigated, and the change trend between rock breaking morphology and standoff distance was also observed. In addition, the order and optimal parameter combination of influential factors on rock breaking performance using SOPW was obtained through an orthogonal test. The research results show that the rock breaking performance under the impact of SOPW is better than that of continuous water jet in the initial stage, and the difference of rock breaking volume under the action of two-type jet is getting larger as the time going on. Moreover, the initial crushing pressure and fracturing pressure increases with the increase of the compressive strength, and the initial crushing pressure and the fracturing pressure is predicted as 54.4 MPa and 125.8 MPa, respectively, when the rock compressive strength is 80 MPa. Furthermore, the primary and secondary order of various factors on rock breaking performance is system pressure, standoff distance, oscillation cavity length, section cone angle, and the optimal combination is 40 MPa, 10 mm, 70 mm, and 140° for the system pressure, standoff distance, oscillation cavity length and section cone angle, respectively.

Research on the Conversion Relationship between Dynamic Point Load Strength and Dynamic Compressive Strength Based on Energy System

Point load test is a simple and fast method to obtain the compressive strength of rock. According to the maximum load at failure and the distance between two cone ends, the compressive strength of specimens can be calculated by the empirical formula. Because the test process does not need to process the sample into laboratory size type, so it is widely used. At the same time, with the rapid development of rock dynamics, the dynamic strength index of rock becomes more and more important under dynamic load. But dynamic point load is seldom mentioned by scholars. In order to explore the correlation between dynamic point load test and dynamic compressive strength, a large number of dynamic point load and uniaxial dynamic compressive strength tests were carried out using a split Hopkinson pressure bar for granite. Based on the energy theory, the crushing energy consumption during dynamic point load and uniaxial dynamic compressive strength tests were statistically analyzed, and the transformational relation between uniaxial dynamic compressive strength and crushing energy consumption during the dynamic point load test was determined. At the same time, the influence of the cone angle on crushing energy consumption during the dynamic point load test was investigated by changing the conical angle. The results show that with the increase in conical angle, the energy consumption of rock crushing decreases gradually during the dynamic point load test. And the decreasing trend tends to be gentle. The conclusion can provide a reference for obtaining the numerical value of the dynamic compressive strength of the rock in the future.

A novel model for prediction of uniaxial compressive strength of rocks

This paper presents an empirical model for predicting the uniaxial compressive strength (UCS) of rocks using gene expression programming (GEP). A total of 44 datasets collected from the literature was used to construct the GEP model. The GEP model developed is evaluated using four conventional regression models and an artificial neural network (ANN) model in terms of three statistical indices. The comparison results confirmed that the proposed GEP model has the lowest root mean square error (RMSE) and the highest coefficient of determination (R 2 ) and correlation coefficient (R) values compared to the four conventional regression models and the ANN model in the literature. It is concluded that the proposed GEP model can be applied to predict the UCS of rocks.

Study of the Characteristics Mechanical Damage and Constitutive Model of Crushed-Rocks from High-Grade Highway in Permafrost Region

Three types of rocks are selected to conduct uniaxial compression and microscope experimental to study the influences of freeze-thaw cycles on crushed-rocks from Gonghe-Yushu high-graded highway, which is the first high-grade highway built in permafrost regions in China. Using the hypothesis of Lemaitre’s strain equivalence principle and a theoretical model of crushed-rock deterioration after freeze-thaw cycles was established and verified by the experimental data. The experimental results showed that with an increase of the number of freeze-thaw cycles, the microcracks of saturated red sandstone increased, and this phenomenon is not obvious on other rocks. Moreover, different degrees of spalling and cracks appeared, with common physical parameters gradually decreasing. The uniaxial compressive strength of rock decreases exponentially with the increase of the number of freeze-thaw cycles. The mechanism of the influence of freeze-thaw cycles on the fine structure of the three different crushed-rocks were then analyzed using SEM scanning. Freeze-thaw cycles weaken the connection between rock mineral particles and increase the surface micropores. The damage model of freeze-thaw and load can well describe the damage law of crushed-rocks.

A Combined Non-Destructive Prediction Method for Evaluating the Uniaxial Compressive Strength of Rocks Under Freeze–Thaw Cycles

A Combined Non-Destructive Prediction Method for Evaluating the Uniaxial Compressive Strength of Rocks Under Freeze–Thaw Cycles

Relationships between the Petrographic and Abrasive Properties of Sandstones in the Aspect of Their Cutting

The research described in this article was carried out on samples of sandstone obtained from the underground excavations of four hard coal mines that operate in the region of Poland with the highest energy resources, i.e., Upper Silesia. The majority of underground tunnel excavations are mainly drilled using roadheaders, the organs of which are equipped with conical picks. The selection of pick type is usually based on rock compressive strength. However, sandstones often cause more problems during cutting compared to other waste rocks because of their variety. This article’s primary purpose is to emphasize the importance of researching various properties of waste rock in addition to uniaxial compression strength, which is crucial in the selection of both the appropriate cutting method and appropriate cutting tools. Accordingly, relations between mineralogical, petrographic, physical and mechanical properties were examined in this study, with special attention paid to the abrasive properties that comprise rock abrasivity. Sandstones from the regions of Upper Silesia are characterized by a heterogeneity of mineralogical and petrographic features that strongly affect the physical and mechanical properties of these rocks, especially their abrasive properties. The determined correlations can aid understanding of the behavior of rocks during their mechanical cutting and facilitate the selection of appropriate cutting tools.

IDENTIFICATION OF ROCK COMPRESSION STRENGTH IN RABAK VILLAGE AND SURROUNDINGS, RUMPIN DISTRICT, BOGOR REGENCY, WEST JAVA.

. To determine the compressive strength of rocks, a Point Load test is needed where this method is commonly used in the world of rock mechanics in order to determine the point of rock damage to the maximum load that can be accepted by the rock. To find out how strong the rock can accept the load it receives, the rock's breaking point is the benchmark. The purpose of this study was to identify the compressive strength of Andesite, Tufa sandstone, Sandstone, and Claystone when under pressure. This research was conducted at the Geological Engineering Laboratory, Trisakti University, Jakarta. Rock sampling was carried out in the village of Rabak and its surroundings, Rumpin District, Bogor Regency, West Java. After carrying out the Point Load test, the results of the compressive strength of Andesite are 16 Kn / cm2, Sandstone 12.5 Kn / cm2 (in the direction of layer) & 11.11 Kn / cm2 (opposite layer), tuffaceous sandstone 8 Kn / cm2 (in the direction of layer) & 6.25 Kn/cm2 (opposite layer) , and Claystone 3.33 Kn/cm2. Based on the measurement results, a rock strength map in the study area can be made.

Stability Risk Assessment of Underground Rock Pillars Using Logistic Model Trees.

Pillars are important structural elements that provide temporary or permanent support in underground spaces. Unstable pillars can result in rock sloughing leading to roof collapse, and they can also cause rock burst. Hence, the prediction of underground pillar stability is important. This paper presents a novel application of Logistic Model Trees (LMT) to predict underground pillar stability. Seven parameters—pillar width, pillar height, ratio of pillar width to height, uniaxial compressive strength of rock, average pillar stress, underground depth, and Bord width—are employed to construct LMTs for rock and coal pillars. The LogitBoost algorithm is applied to train on two data sets of rock and coal pillar case histories. The two models are validated with (i) 10-fold cross-validation and with (ii) another set of new case histories. Results suggest that the accuracy of the proposed LMT is the highest among other common machine learning methods previously employed in the literature. Moreover, a sensitivity analysis indicates that the average stress, p, and the ratio of pillar width to height, r, are the most influential parameters for the proposed models.

A cutting mechanics model of constant cross-section type disc cutter and its application based on dense core theory

The rock-cutting mechanism and force prediction model of disc cutter considering the effect of dense core are proposed in this study. According to the working characteristics of disc cutter and rock breakage theory, the contribution of dense core in the complex process of rock-cutting by disc cutter is investigated in detail. Based on the Mohr-Coulomb failure criterion of the rock, a theoretical analytical expression of dense core length is derived, and a cutting mechanics model of constant cross-section (CCS) type disc cutter is established; thus, the quantitative relationship between normal force and rolling force of a disc cutter and rock mechanical characteristics, cutter geometric parameters and cutting parameters is obtained. This model incorporates the size of a dense core. A rich full-scale linear cutting machine (LCM) database is developed from the literature and the theoretical force is compared with the experimental force. The results show that the proposed theoretical model can accurately predict 93% of the average disc cutter force acting on the rock uniaxial compressive strength (UCS) ranging from 8.4 to 355.6 MPa. As the rock UCS increases, the model prediction ability is significantly improved. In addition, the results comparison and performance evaluation between the proposed model and existing classical models prove that the proposed model is reasonable and reliable. Finally, the effects of model parameters (penetration, rock compressive strength, cohesion, internal friction angle and blade angle) on forces and efficiency of rock-cutting by disc cutter are also discussed. The results illustrate that the rock breakage regularity of disc cutter obtained based on theoretical model is consistent with that of actual engineering. The developed force prediction model for CCS-type disc cutter is a very practical tool for engineers in TBM excavation project.

THE INFLUENCE OF PHYSICAL PROPERTIES ON THE COMPRESSIVE STRENGTH OF THE ROCK IN THE SAMIGALUH AREA, KULON PROGO, INDONESIA

The Samigaluh area, Kulon Progo, Indonesia, is composed of rocks from the Old Andesite and Jonggrangan Formations, with very different physical properties. The difference in physical properties indeed results in the engineering properties of rocks, for example, in terms of compressive strength. Studying the relationship between physical properties and rock compressive strength in these two different formations is exciting to find out the extent of the relationship between physical properties and rock engineering. A geological engineering survey was carried out simultaneously with the collection of six rock samples representing intrusive andesite, andesite (breccia and lava fragments), and tuff of the Old Andesite Formation (OAF), limestone (reef/calcarenite) Jonggrangan Formation. Furthermore, rock samples were analyzed physically (petrographically) and mechanically (compressive strength) in the laboratory. The results of field surveys and analysis of laboratory data yield knowledge about the relationship between the physical properties of rocks and their compressive strength. The intrusion andesites and OAF andesites generally have a porphyroaphanitic texture, anhedral - subhedral, hypocrystalline, inequigranular crystal form, with a massive structure, and the composition of plagioclase, quartz, and accessory minerals (hornblende). Fine-textured tuff, hypocrystalline, in the form of glass and crystal tuffs. The Jonggrangan limestones are fine to medium textured, well-sorted, grain supported, with variations of wackestone – packstone. The compressive strength of andesite is 39.98 – 49.36 MPa, calcarenite is 43.32 MPa, reef limestone is 20.44 MPa, and tuff is 11.15 MPa. The compressive strength of rock is influenced by texture (grain size/crystal) with a correlation coefficient of 68% (strong correlation). In comparison, rock composition (percentage of quartz) has a very weak correlation (correlation coefficient of 18%).

Micro-Fracture Simulation of Rock Under Unloading Condition by Grain-Based Discretized Virtual Internal Bond Method

Rock burst is a multiscale dynamic fracturing process induced by unloading. To further investigate the dynamic fracturing mechanism of rock burst, a grain-based discretized virtual internal bond (GB-DVIB) method is developed. The Voronoi diagram is used to discretize the background discretized virtual internal bond (DVIB) mesh to generate the micro-structure of rock. The bond cell within a Voronoi diagram is termed as the grain cell, characterized by the linear Stillinger–Weber potential. While the bond cell cut by the Voronoi polygon edge is termed as the interface cell, in which both the tension and the shear failure are considered. The simulation results suggest that this method can reflect the contact and friction between grains and reproduce the confining pressure-dependency of compressive strength of rock. With this method, the unloading effects of the in situ stress, the grain size and the heterogeneity on rock failure are studied. The simulated results show that more tensile cracks and less shear cracks are generated when unloading a higher confining stress. When the axial stress is fixed, the total created crack area is almost a constant. The tensile crack area is basically a constant while the shear crack area increases under the condition of a higher axial stress. With decreasing the grain size, more cracks are generated, but the area ratio of the shear to the tensile cracks is almost a constant. It is suggested that GB-DVIB is an effective method for the rock burst simulation. The findings provide deep insight into the rock burst from the standpoint of dynamic fracture.

Prediction of Rockburst Intensity Grade in Deep Underground Excavation Using Adaptive Boosting Classifier

Rockburst phenomenon is the primary cause of many fatalities and accidents during deep underground projects constructions. As a result, its prediction at the early design stages plays a significant role in improving safety. The article describes a newly developed model to predict rockburst intensity grade using Adaptive Boosting (AdaBoost) classifier. A database including 165 rockburst case histories was collected from across the world to achieve a comprehensive representation, in which four key influencing factors such as maximum tangential stress of the excavation boundary, uniaxial compressive strength of rock, tensile rock strength, and elastic energy index were selected as the input variables, and the rockburst intensity grade was selected as the output. The output of the AdaBoost model is evaluated using statistical parameters including accuracy and Cohen's kappa index. The applications for the aforementioned approach for predicting the rockburst intensity grade are compared and discussed. Finally, two real‐world applications are used to verify the proposed AdaBoost model. It is found that the prediction results are consistent with the actual conditions of the subsequent construction.

Sulfonated lignin modified with silane coupling agent as biodegradable shale inhibitor in water-based drilling fluid

A series of sulfonated lignin (SL) samples modified with a silane coupling agent (Si–SL) was investigated as a biodegradable shale inhibitor for water-based drilling fluid (WBDF). Cutting dispersion, linear swelling, bentonite inhibition, and mud ball tests were used to evaluate the inhibition performance of the Si–SL series of and compared with conventional shale inhibitors including potassium formate (HCOOK), polyethylene alycol (PEA), Ultrahib polymer, and polyacrylamide potassium salt (K-PAM). The results showed that the inhibition performance of a series of Si–SL was similar to that of Ultrahib and was significantly better than that of HCOOK, PEA and K-PAM at normal temperature. In addition, compared with other inhibitors, Si–SL showed optimal temperature resistance. The inhibition mechanism of Si–SL was studied by particle distribution, rock compressive strength measurement, shale micro-fracture propagation synthesis, X-ray diffraction (XRD) measurement, adsorption measurement, contact angle measurement, scanning electron microscopy (SEM) observation and atomic force microscopy observation. At high temperature, Si–SL can be strongly adsorbed on the surface of clay particles, while phenyl in molecular chain of Si–SL is conducive to improving the temperature resistance and reducing the hydrophilicity of the surface of clay particles, thus effectively preventing the migration of water molecules to the clay layer. More importantly, through biotoxicity and biodegradability test, the results showed that Si–SL had no toxicity and was easy to be biodegraded. In field application of Bei 213-21HF well, the Si–SL effectively inhibits the hydration of water-sensitive cuttings and maintains the wellbore stability of the shale formation, providing a guarantee for safe and fast drilling. • The new shale inhibitor was tested in water-based drilling fluids. • It shows a better inhibition performance than the most of available inhibitors. • It shows excellent temperature resistance and environmental friendliness. • The mechanism of the inhibitor was investigated. • The product was successfully applied on Bei 213-21HF well (Jilin, China).

A numerical integrated approach for the estimation of the uniaxial compression strength of rock from point load tests

The point load test (PLT) has been considered a flexible approach to estimate the uniaxial compressive strength (UCS) of rocks. Previously, empirical equations were obtained by mathematical fitting or machine learning to predict the UCS of rocks. The acquisition of these equations usually required a large amount of experimental data, while the corresponding parameters often lacked clear physical meanings, and the applicability of these empirical equations was limited. In this work, we attempted to develop a new method to predict the UCS of rocks by using the concept of a digital twin (numerical modelling). First, an automatic calibration procedure was used to obtain the numerical parameters of a digital twin for the PLT. Next, the UCS was predicted numerically by using a digital twin of the UCS test with the calibrated parameters. We performed a comprehensive comparison of our proposed method with previously obtained empirical equations and showed the superiority of our approach in better predicting the UCS of rocks. In this paper, we also discuss the influence of particle size and heterogeneity of rock material to illustrate the possible merits of the proposed method. Our work also shows the possible benefits of integrating numerical modelling into physical experimental tests of rocks.

Prediction and Evaluation of Coal Mine Coal Bump Based on Improved Deep Neural Network

Coal bump prediction is one of the key problems in deep coal mining engineering. To predict coal bump disaster accurately and reliably, we propose a depth neural network (DNN) prediction model based on the dropout method and improved Adam algorithm. The coal bump accident examples were counted in order to analyze the influencing factors, characteristics, and causes of this type of accidents. Finally, four indexes of maximum tangential stress of surrounding rock, uniaxial compressive strength of rock, uniaxial tensile strength of rock, and elastic energy of rock are selected to form the prediction index system of coal bump. Based on the research results of rock burst, 305 groups of rock burst engineering case data are collected as the sample data of coal bump prediction, and then, the prediction model based on a dropout and improved Adam-based deep neural network (DA-DNN) is established by using deep learning technology. The DA-DNN model avoids the problem of determining the index weight, is completely data-driven, reduces the influence of human factors, and can realize the learning of complex and subtle deep relationships in incomplete, imprecise, and noisy limited data sets. A coal mine in Shanxi Province is used to predict coal bump with the improved depth learning method. The prediction results verify the effectiveness and correctness of the DA-DNN coal bump prediction model. Finally, it is proved that the model can effectively provide a scientific basis for coal bump prediction of similar projects.

Numerical study on the attenuation of high-amplitude stress wave in rock bar along with rock damage evolution

The attenuation of high-amplitude stress waves in the rock and the rock failure caused by the stress waves have significance for vibration source analysis and rock engineering support design, where the interactions between the two deserve further study. In this paper, a FEM based numerical investigation on high-amplitude stress wave attenuation and rock damage evolution in one-dimensional rock bar is performed, aiming to understand the interaction between the variation of rock damage and wave attenuation. The numerical model is calibrated by experimental results. The spatial distribution of damage in rock bar is quantified by statistical windows. The effects of wave amplitude and heterogeneity index of rock on wave attenuation as well as the distribution of damage are analysed in details. The results indicate that the high-amplitude stress wave decays exponentially in the rock bar, and the attenuation of wave becomes significant as the incident wave amplitude increases. The incident wave amplitude corresponding to the lower limit of the amplitude effect is approximately 30% of the static compressive strength of rock, while that corresponding to the upper limit is the dynamic compressive strength of rock. Under the same incident wave amplitude, the attenuation of stress wave is more obvious in the rock with higher heterogeneity. The rock damage is quantified in a specific window, and its spatial distribution is described along with the movement of the window. The rock damage is concentrated in a region near the incident end. The damage development in space is consistent with that of high-amplitude stress waves and is more obvious in the models with higher heterogeneity. Findings in this work is helpful for the understanding of interaction between high-amplitude stress wave attenuation and rock damage and facilitate design and protection of rock engineering.

Influence of Joint Dip Angle on Dynamic Mechanical Properties and Crack Propagation Law of Rock-like Materials

The main objective of this study is to investigate the dynamic mechanical properties and crack propagation law of rock-like materials with different joint dip angles. The precast cement mortar specimens are impacted by split Hopkinson pressure bar (SHPB). The meso damage of the specimens before and after impact is detected by nuclear magnetic resonance system (NMR), and the crack propagation path is extracted. The influence of joint dip angles on dynamic response characteristics of rock-like materials is analyzed from the aspects of dynamic compressive strength, meso damage and crack propagation path. The analysis indicates that joints make the internal stress distribution of rock-like materials uneven, resulting in the weakening of the dynamic compressive strength of rock-like materials. At the same time, joint characteristics affect the weakening degree of the dynamic compressive strength of rock-like materials. With the increase of joint dip angle, the weakening degree of dynamic compressive strength of rock like materials first increases and then decreases. The relationship between the damage degree and the dynamic compressive strength of rock-like materials is approximately negative linear. With the increase of joint dip angle, the damage degree changes in an inverted “U” shape. Tensile stress or the combination of tensile stress and shear stress leads to the initiation and propagation of cracks. The intact specimens, the specimens with joint dip angle of 0°, and the specimens with joint dip angle of 90° develop axial tensile cracks. The specimens with joint dip angles of 15°-75° develop tensile cracks and shear cracks at the joint tips.

Dynamic properties and fracture damage characteristics of granite under impact load

The goal of this research is to study the dynamic properties and fracture damage laws of granite at the meso-scale under impact load. The quasi-static and dynamic mechanical properties of granite were studied through laboratory tests (Uniaxial compression, split Hopkinson pressure bar). The establishment of three-dimensional coupled numerical model of rock specimen and split Hopkinson pressure bar was realized by new coupling technology of PFC-FLAC. Three wave superposition and end stress distribution were discussed to determine the stress balance of the specimen during the loading process. The dynamic compression mechanics response characteristics and crack growth laws of granite under different strain rates were studied. The results indicated that PFC-FLAC coupling technology can solve the problems of tedious modeling process and long calculation time in the past three-dimensional discrete element model, and can better describe the dynamic mechanical behaviour of rock. There is obvious rate dependency in the dynamic strength of rock material, and the dynamic compressive strength of rock increases with the increase of strain rate. The macro fracture of rock mass is the result of the continuous development, expansion, aggregation and connection of the internal microcracks. With the increase of strain rate, the increase and cross propagation of cracks lead transformation of rock from intact to crushing destruction. Under dynamic loading, the failure process of rock is crack initiation, propagation, crossing, transfixion and rupture.