Design Method for Specific Charge in Deep Mining considering Influence of In Situ Stress

In situ stress has a large influence on blasts in deep mines and should be considered in blasting design. In this study, explosion crater tests were conducted to investigate the variation of specific charges under different stress loading conditions. It was revealed that rock blasting under high stress is different from that under low stress. A correction coefficient for specific charge was defined to consider the influence of in situ stress on blasting. A quantitative relation between the correction coefficient, stress-to-strength ratio, and lateral stress coefficient was presented. Based on the explosion-crater test results, a design method for specific charges was proposed with the consideration of in situ stress. Finally, the design method was applied to a field blasting test at Hongtoushan Copper Mine. The test results indicate that the proposed design method can effectively use the high in situ stress at depth for rock fragmentation. Compared with the original blasting design, the specific charge is reduced by 19.8% and the average block rate is reduced from 6.8% to 2.84%. At the same time, the blasting boundary is well controlled and the ore loss and dilution rates are reduced. This research has important guiding significance to deep mine blasting design.

Study of Two-Step Parallel Cutting Technology for Deep-Hole Blasting in Shaft Excavation

In hard rock deep-hole blasting excavation, blastholes are rarely utilized due to the clamping effect of the lower rock, which affects excavation progress and restricts the development and application of deep-hole blasting technology. Cut blasting is a key to improving excavation speed. In this paper, a new cutting method designating the two-step cutting technology was presented. The blasthole was divided into upper and lower sections without changing the blasthole layout. The upper section was detonated first, creating sufficient free surface for the lower section, which was detonated secondly. This created a larger cavity and improved blasthole utilization. Results showed good blasting effects for two-step cutting technology through theoretical analysis and engineering applications. The blasthole utilization rate was 96.1% when the upper and lower specific charge ratio = 0.78. This paper provides a good reference for resolving the low blasthole utilization problem in deep-hole blasting of vertical shafts within a hard rock.

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.

More on complex Sachdev-Ye-Kitaev eternal wormholes

In this work, we study a generalization of the coupled Sachdev-Ye-Kitaev (SYK) model with U(1) charge conservations. The model contains two copies of the complex SYK model at different chemical potentials, coupled by a direct hopping term. In the zero-temperature and small coupling limit with small averaged chemical potential, the ground state is an eternal wormhole connecting two sides, with a specific charge Q = 0, which is equivalent to a thermofield double state. We derive the conformal Green’s functions and determine corresponding IR parameters. At higher chemical potential, the system transit into the black hole phase. We further derive the Schwarzian effective action and study its quench dynamics. Finally, we compare numerical results with the analytical predictions.

Understanding the avidin-biotin binding based on polarized protein-specific charge

In this study, charge updating schemes based on the local polarized protein-specific charge (LPPC) were introduced to vary the atomic charges of the biotin molecule and the residues in close...

High-capacity capacitor tantalum powders from production waste

The possibility of producing high-quality high-capacity tantalum powder from certain types of tantalum wastes by their oxidation and subsequent magnesium thermal reduction is discussed. Capacitor powders with a specific charge of 100000—150000 µC·g–1 and leakage current less than 0.001 μA·μC–1 were obtained.