A Heuristic Approach to Predict the Tensile Strength of a Non-Persistent Jointed Brazilian Disc under Diametral Loading

The mechanical response of rock bridges plays a key role in the stability of concrete and rock structures. In particular, the tensile failure of non-persistent discontinuities can result in their coalescence and the failure of rock or concrete engineering structures. The effect of non-persistent joint parameters on rock structures\u27 failure under tensile mode has not been investigated by many researchers yet. Many non-persistent jointed Brazilian concrete discs are tested under diametral loading in this work, to study the influence of joint spacing, joint continuity factor, loading direction with regard to joint angle, and bridge angle on their tensile behavior. Heuristic methods like artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS) and a combination of ANFIS with particle swarm optimization (ANN-PSO) and genetic algorithm (ANFIS-GA) were adopted to explore the relationship between tensile strength and stiffness as the response and non-persistent joint parameters as input parameters. The results revealed that all the applied intelligent methods have the ability to predict tensile strength of non-persistent jointed discs, and their outputs are consistent with laboratory results; however, the ANN approach had the best performance with R2 = 0.966, RMSE = 0.176. In addition, parametric analysis of the proposed model showed that the model is highly sensitive to joint continuity factor and loading direction, while it is sensitive to joint spacing and bridge angle

Tensile Behavior of Layered Rock Disks under Diametral Loading: Experimental and Numerical Investigations

The Tensile Strength and Cracking Behavior of Layered Rocks in a Tensile Stress Field Are One of the Most Significant Characteristics of Rock Masses, Which May Strongly Affect the Stability of Rock Structures. the Study Presented Here Investigated the Effect of Layer Spacing and Inclination Angle on the Indirect Tensile Strength, Crack Development, Failure Pattern, and Contact Force Chain of Layered Disks under Diametral Loading using Experimental and Numerical Investigations. Numerous Experimental Models Made from Plaster Were Examined under Diametral Loading, and a Two-Dimensional Particle Flow Code (PFC2D) Was Adopted for in Depth Simulation of the Failure Process. Both Numerical and Experimental Results Were Found to Be in Great Agreement and Showed that the Increase in the Layer Orientation Up to 15° Results in the Peak in the Tensile Strength Followed by a Decrease. Specimens with the Spacing Ratio (SR) of 0.5 and 0.1 Showed the Highest and Lowest Tensile and Compressive Stresses at the Disk Center, respectively. Moreover, the Numerical Analysis Indicated the Formation of Three Failure Pattern Types: TL, PB, and TL-PB. Tensile Cracks Mainly Formed in the Direction of Diametral Loading, and their Maximum Number Formed at 15° and SR = 0.5. Additionally, the Shear Ones Formed in a Conjugate System and Had Negligible Numbers. the Analysis of the Contact Force Chain Showed that the Layers Do Not Affect the Compressive Force Chain at Α \u3c 45° But at Higher Angles, the Stronger Layers Transfer Compressive Force. However, when Α Ranges from 0° to 30°, Tensile Forces Are Distributed in Stronger Layers, and with an Increase in Α, the Concentration of These Forces in These Layers Diminishes and the Forces Are Reoriented in the Direction of Diametral Loading

Three-Dimensional Geostatistical Analysis of Rock Fracture Roughness and Its Degradation with Shearing

Three-dimensional surface geometry of rock discontinuities and its evolution with shearing are of great importance in understanding the deformability and hydro-mechanical behavior of rock masses. In the present research, surfaces of three natural rock fractures were digitized and studied before and after the direct shear test. The variography analysis of the surfaces indicated a strong non-linear trend in the data. Therefore, the spatial variability of rock fracture surfaces was decomposed to one deterministic component characterized by a base polynomial function, and one stochastic component described by the variogram of residuals. By using an image-processing technique, 343 damaged zones with different sizes, shapes, initial roughness characteristics, local stress fields, and asperity strength values were spatially located and clustered. In order to characterize the overall spatial structure of the degraded zones, the concept of ‘pseudo-zonal variogram’ was introduced. The results showed that the spatial continuity at the damage locations increased due to asperity degradation. The increase in the variogram range was anisotropic and tended to be higher in the shear direction; thus, the direction of maximum continuity rotated towards the shear direction. Finally, the regression-kriging method was used to reconstruct the morphology of the intact surfaces and degraded areas. The cross-validation error of interpolation for the damaged zones was found smaller than that obtained for the intact surface

Correction To: A Heuristic Approach to Predict the Tensile Strength of a Non-Persistent Jointed Brazilian Disc under Diametral Loading (Bulletin of Engineering Geology and the Environment, (2022), 81, 9, (364), 10.1007/s10064-022-02869-8)

Originally, there is a mistake in the affiliation of the third author. Taghi sherizadeh has just one affiliation as follows: Department of Mining and Nuclear Engineering, Missouri, University of Science and Technology, Rolla, MO 65409, USA The original article has been corrected

Study on failure mechanism of room and pillar with different shapes and configurations under uniaxial compression using experimental test and numerical simulation

Experimental and discrete element methods were used to investigate the failure behavior of room and pillar with different configurations under uniaxial loading. Concrete samples with dimension of 15 cm × 15 cm × 5 cm were prepared. Within the specimens, rooms and pillars with different configurations were provided. The room dimension was 1 cm × 1 cm, and the pillar dimension was according to the room configuration. Twelve different configurations were chosen for rooms and pillars. The axial load was applied to the model by rate of 0.05 mm/min. The results show that the failure process was mostly governed by both the non-persistent joint angle and joint number. The compressive strength of the specimens was related to the fracture pattern and failure mechanism of the pillars. It was shown that the shear behaviour of pillars was related to the number of the induced tensile cracks, which increased by increasing the room angle. The compressive strength of samples increased with the increase of the room angle. The failure pattern and failure strength are similar in both methods, i.e., the experimental testing and the numerical simulation

The Evolution of Dynamic Energy during Drop Hammer Testing of Brazilian Disk with Non-Persistent Joints: An Extensive Experimental Investigation

Rock mass is well known as a discontinuous, heterogeneous, and anisotropic material. The behavior and strength of rock mass is heavily controlled by the condition and orientation of discontinuities (faults, joints, bedding planes) and discontinuity sets. Under dynamic loading conditions, rock bridges along non-persistent discontinuity planes may crack, and a fully persistent discontinuity may form, potentially affecting the stability of a rock structure. The study of the dynamic behavior of rock discontinuities has critical implications for civil engineering, the mining industry, and any other areas where rock mass is utilized as a structural foundation in areas prone to dynamic loading conditions, such as those formed during earthquake events. In this paper, cement-mortar-based Brazilian disks containing open, non-persistent joints were constructed and subjected to impact loading to investigate their impact energy behavior. The effect of some parameters, such as joint continuity factor (the relationship between joint length and rock bridge length), bridge angle, joint spacing, joint orientation, and impact angle were investigated to estimate the required Dynamic Energy for Crack Initiation (DECI), Dynamic Energy for Crack Coalescence (DECC) and failure pattern of specimens. The results of the experiments revealed an increasingly continuous joint reduces the DECI and DECC, while larger joint spacings past the middle value of those experimented increase the DECI and DECC. The bridge angle and loading direction do not affect DECI, but by increasing bridge angle DECC decreases, and it increases by increasing loading direction angle. Finally, an optimization analysis was conducted which showed that joint spacing and joint continuity factors significantly affects DECI, and joint continuity factor and loading direction have significant effect on DECC