Support Vector Machines for the Estimation of Specific Charge in Tunnel Blasting

Mine tunnels, short transportation tunnels, and hydro-power plan underground spaces excavations are carried out based on Drilling and Blasting (D&B) method. Determination of specific charge in tunnel D&B, according to the involved parameters, is very significant to present an appropriate D&B design. Suitable explosive charge selection and distribution lead to reduced undesirable effects of D&B such as inappropriate pull rate, over-break, under-break, unauthorized ground vibration, air blast, and fly rock. So far, different models are presented to estimate specific charge in tunnel blasting. In this study, 332 data sets, including geomechanical characteristics, D&B, and specific charge are gathered from 33 tunnels. The data are related to three dams and hydropower plans in Iran (Gotvand, Masjed-Solayman, and Siah-Bishe). Specific charge is modeled in inclined hole cut drilling pattern. In this regard, Support Vector Machine (SVM) algorithm based on polynomial Kernel function is used as a tool for modeling. Rock Quality Designation (RQD) index, Uniaxial Compressive Strength (UCS), tunnel cross-section area, maximum depth of blast hole, and blast hole coupling ratio are considered as independent input variables and the specific charge is considered as a dependent output variable. The modeling results confirm the acceptable performance of SVM in specific charge estimation with minimum error

Mechanical Behavior of Single-Flawed Cylindrical Specimens Subjected to Axial Loading: A Numerical Investigation

Discontinuities are inherent components of rock masses and can range from fissures to large faults. Single fissures, the so-called flaws, may affect the mechanical behavior of rock mass, crack initiation, and propagation. In this paper, numerical investigations have been conducted on central-flawed cylindrical specimens subjected to axial loading to investigate the effect of flaw angle (α), length (2a), and aperture (A) on their mechanical behavior and crack development. Particle Flow Code (PFC3D) was adopted to investigate the cracking process of the cylindrical specimens and maximum principal stresses at flaw tips. The numerical models are calibrated and verified using extensive experimental tests. The results show that increasing α, UCS, and E increase while increasing 2a decreases UCS and E, and A does not affect these two parameters. Moreover, numerical simulations reveal that as α rises, the three principal stresses generally fall when 2a = 13 and 26 mm. σ1 and σ3 peak at α = 45°, and σ2 reaches a maximum at α = 30° in models with 2a = 39 mm. The cracking patterns resulting from both methods are highly consistent in that tensile cracks type 1 mainly form at α = 15° to 75°, and tensile cracks type 3 are dominant at other angles. Finally, it is concluded that flaw aperture scarcely affects failure patterns

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

N,N′-Bis(4-bromo­benzyl­idene)biphenyl-2,2′-diamine

The complete molecule of the title Schiff base, C26H18Br2N2, is generated by crystallographic twofold symmetry. The aromatic rings of the biphenyl­ene portion of the mol­ecule are twisted, as shown by the dihedral of 61.8 (1)° formed between them

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

Prediction of representative deformation modulus of longwall panel roof rock strata using Mamdani fuzzy system

Deformation modulus is the important parameter in stability analysis of tunnels, dams and mining structures. In this paper, two predictive models including Mamdani fuzzy system (MFS) and multivariable regression analysis (MVRA) were developed to predict deformation modulus based on data obtained from dilatometer tests carried out in Bakhtiary dam site and additional data collected from longwall coal mines. Models inputs were considered to be rock quality designation, overburden height, weathering, unconfined compressive strength, bedding inclination to core axis, joint roughness coefficient and fill thickness. To control the models performance, calculating indices such as root mean square error (RMSE), variance account for (VAF) and determination coefficient (R2) were used. The MFS results show the significant prediction accuracy along with high performance compared to MVRA results. Finally, the sensitivity analysis of MFS results shows that the most and the least effective parameters on deformation modulus are weathering and overburden height, respectively. Keywords: Deformation modulus, Dilatometer test, Mamdani fuzzy system, Multivariable regression analysi

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