Cognition, Application and Discussion on Shaped Charge Hydraulic Smooth Blasting Technology

In the past, the main method of tunnel excavation in China was drilling and blasting, but the biggest shortcoming of the traditional drilling and blasting method is that it is easy to cause serious overexcavation and underexcavation. At the same time, the operation cycle time of this method is long, which leads to a serious waste of resources. Not only that, a large number of toxic gases and dust produced after blasting also do harm to the health of construction workers. So this is an urgent need for a new construction technology to solve this worldwide problem. In this situation, the leading experts in the field of tunnel, "The survey and design master of China" Shi Yuxin, Liu Pei, and well known expert in explosion field, yan-sheng ding, professor Chen Chengguang and Gu Yicheng, the experts group, cooperate with The Fifth Branch of China Railway 18th Bureau in northwest project management department, developed a new technology. This technology has passed the appraisal of scientific and technological achievements organized by Tianjin Science and Technology Commission, which is shaped hydraulic smooth blasting technology. The comprehensive evaluation of the technology is "international leading" level.This paper is mainly aimed at the drawbacks of drilling and blasting construction,combined with the author's cognition and discussion on the introduction of the new technology of cumulative hydraulic blasting and the practical application effect in the tunnel excavation process of the fourth company of China Railway 14th Bureau Group in the second division of the 9th bid section of Zhangjihuai Railway in Huainan Province

Near-field blast vibration monitoring and analysis for prediction of blast damage in sublevel open stoping

The work presented in this thesis investigates near-field blast vibration monitoring, analysis, interpretation and blast damage prediction in sublevel open stoping geometries. As part of the investigation, seven stopes at two Australian sublevel open stoping mines were used as case studies. The seven stopes represented significant ranges in stope shapes, sizes, geotechnical concerns, extraction sequences, stress conditions, blasting geometries and rock mass properties.The blast damage investigations at the two mine sites had three main components. The first component was rock mass characterisation, which was performed using static intact rock testing results, discontinuity mapping, mining-induced static stress modelling and geophysical wave propagation approaches. The rock mass characterisation techniques identified localised and large-scale variations in rock mass properties and wave propagation behaviours in relation to specified monitoring orientations and mining areas. The other components of the blast damage investigations were blast vibration monitoring and analysis of production blasting in the seven stopes and stope performance assessments.The mine-based data collection period for the case studies lasted from January, 2006 to February, 2008. A key element of the data collection program was near-field blast vibration monitoring of production blasts within the seven study stopes. The instrumentation program consisted of 41 tri-axial accelerometers and geophone sondes, installed at distances from 4m to 16m from the stope perimeters. A total of 59 production firings were monitored over the course of the blast vibration monitoring program. The monitoring program resulted in a data set of over 5000 single-hole blast vibration waveforms, representing two different blasthole diameters (89mm and 102mm), six different explosive formulations and a wide range in charge weights, source to sensor distances, blasthole orientations and blasting geometries.The data collected in the blast vibration monitoring program were used to compare various near-field charge weight scaling relationships such as Scaled Distance and Holmberg-Persson prediction models. The results of these analyses identified that no single charge weight scaling model could dependably predict the measured near-field peak amplitudes for complex blasting geometries. Therefore, the general form of the charge weight scaling relationship was adopted in conjunction with nonlinear multivariable estimation techniques to analyse the data collected in the study stopes and to perform forward vibration predictions for the case studies.Observed variations in the recorded near-field waveforms identified that instantaneous peak amplitude such as peak particle velocity (PPV) did not accurately describe the characteristics of a large portion of the data. This was due to significant variations in frequency spectra, variable distributions of energy throughout the wave durations and coupling of wave types (e.g. P- and S-wave coupling). The wave properties that have been proposed to more accurately characterise complex nearfield vibrations are the total wave energy density (ED[subscript]W-tot), stored strain energy density (ED[subscript]W-SS) and the wave-induced mean normal dynamic strain (ε[subscript]W-MN). These wave properties consider the activity of the blast-induce wave at a point in the rock mass over the entire duration instead of the instantaneous amplitude.A new analytical approach has been proposed to predict blast-induced rock mass damage using rock mass characterisation data, blast vibration monitoring results and rock fracture criteria. The two-component approach separately predicts the extent of blast-induced damage through fresh fracturing of intact rock and the extent from discontinuity extension. Two separate damage criteria are proposed for the intact rock portion of the rock mass based on tensile and compressive fracture strain energy densities and compressive and tensile fracture strains. The single criterion for extension of existing discontinuities is based on the required fracture energy density to activate all macro-fractures in a unit volume of the rock mass.The proposed energy-based criteria for intact rock fracture and extension of discontinuities integrate strain rate effects in relation to material strength. The strainbased criterion for intact rock fracture integrates the existing mining-induced static strain magnitudes. These factors have not been explicitly considered in existing empirical or analytical blast damage prediction models. The proposed blast damage prediction approach has been applied to two stopes during the two mine site case studies

The development of a directional primer charge for blasting in mines

Student Number : 0210528 - PhD thesis - School of Mining Engineering - Faculty of Engineering and the Built EnvironmnetThis thesis describes the development of a directional primer charge for use in blasting in mining operations. The directional primer charge is an explosive gun which takes the place of a standard primer charge in a blasthole. It is a shaped charge which directs the explosive energy forwards into the blasthole. Its effectiveness is enhanced by a metal liner which is located at a specified stand-off distance from the toe of the hole. The explosive energy of the column charge is converted into the kinetic energy of the metal liner which transforms into an ultrasonic slug. This in turn converts into the impact energy of the slug impacting on the rock. This rock is axially compressed to such a degree that a radial fracture is developed. This radial fracture is termed an umbrella crack. Prior to the development of the directional primer charge, the phenomenon of the umbrella crack had only been observed in experimental Perspex blasting models and its formation mechanism had never been satisfactorily explained. If the directional primer charge could cause an umbrella crack in hard rock mining at the end of blastholes, then more rock would be broken out per blast than is currently achieved in practice. This thesis records the historical development of the explosive shaped charge with particular reference to the development of the explosively-forged projectile. It describes the classical theories and models which apply in determining the theoretical prediction of the physical properties of the designed directional primer charge. It describes the experimental procedures and measurements using flash X-ray radiography and electronic shorting screens to freeze the flight of a metal slug traveling at speeds of over 2000 metres per second. Underground tests were undertaken under full mining production conditions to compare the rock breaking effects of various designs. The theoretical calculation of the extent of the movement of the rock at the toe of the blasthole indicates that umbrella cracks should be formed. The underground tests confirm their formation. It is concluded that the use of the directional primer charge in stoping operations can improve the blasting efficiency in South African hard rock mines by up to 15 %

Proceedings of the 8th International Conference on Civil Engineering

This open access book is a collection of accepted papers from the 8th International Conference on Civil Engineering (ICCE2021). Researchers and engineers have discussed and presented around three major topics, i.e., construction and structural mechanics, building materials, and transportation and traffic. The content provide new ideas and practical experiences for both scientists and professionals

The use of cellular materials to alleviate the damage from blast-induced fragments

Includes bibliographical references.This study aims to understand how different cellular materials mitigate the damage that is caused by a blast‐induced fragment. In the experimental arrangement, a front plate is subjected to localised blast load to release a “controlled” fragment (cap) to impact a similar plate positioned 190mm apart. A cylindrical charge of Plastic Explosive 4 (PE4) of different diameters (27mm, 36mm and 43mm) and masses ranging from 7g to 11g are used to create fragments of different sizes and masses propelled at different velocities to impact the rear plate. Both front and rear plates are made from 1.6mm thick mild steel sheet with an exposed circular area of 106mm diameter. Tests are carried out with and without energy absorbing materials to investigate the protective performance of the different materials investigated by means of the mode of failure and maximum deflection of the rear plate. The different energy absorbing cellular materials investigated in this study include aluminium foam, aluminium honeycomb, balsa wood, Corecell M‐80 foam, Divinycell H200 PVC foam and rigid polyurethane 200 foam. The 40mm thick energy absorbing materials are 106mm in diameter (same size as the exposed plate area) are placed in front of the rear plate

Proceedings of the 8th International Conference on Civil Engineering

This open access book is a collection of accepted papers from the 8th International Conference on Civil Engineering (ICCE2021). Researchers and engineers have discussed and presented around three major topics, i.e., construction and structural mechanics, building materials, and transportation and traffic. The content provide new ideas and practical experiences for both scientists and professionals

Dust control handbook for industrial minerals mining and processing

"This handbook was written by a task force of safety and health specialists, industrial hygienists, and engineers to provide information on proven and effective control technologies that lower workers' dust exposures during all stages of mineral processing. The handbook describes both dust-generating processes and the control strategies necessary to enable mine operators to reduce worker dust exposure. Implementation of the engineering controls discussed can assist operators, health specialists, and workers in reaching the ultimate goal of eliminating pneumoconiosis and other occupational diseases caused by dust exposure in the mining industry. Designed primarily for use by industrial minerals producers, this handbook contains detailed information on control technologies to address all stages of the minerals handling process, including drilling, crushing, screening, conveyance, bagging, loadout, and transport. The handbook's aim is to empower minerals industry personnel to apply state-of-the-art dust control technology to help reduce or eliminate mine and mill worker exposure to hazardous dust concentrations - a critical component in ensuring the health of our nation's mine workers." - NIOSHTIC-2NIOSHTIC no. 20055113Suggested citation: NIOSH [2019]. Dust control handbook for industrial minerals mining and processing. Second edition. By Cecala AB, O\u2019Brien AD, Schall J, Colinet JF, Franta RJ, Schultz MJ, Haas EJ, Robinson J, Patts J, Holen BM, Stein R, Weber J, Strebel M, Wilson L, and Ellis M. Pittsburgh PA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2019\u2013124, RI 9701. https://doi.org/10.26616/NIOSHPUB2019124201910.26616/NIOSHPUB2019124606

Progress of Fiber-Reinforced Composites

Fiber-reinforced composite (FRC) materials are widely used in advanced structures and are often applied in order to replace traditional materials such as metal components, especially those used in corrosive environments. They have become essential materials for maintaining and strengthening existing infrastructure due to the fact that they combine low weight and density with high strength, corrosion resistance, and high durability, providing many benefits in performance and durability. Modified fiber-based composites exhibit better mechanical properties, impact resistance, wear resistance, and fire resistance. Therefore, the FRC materials have reached a significant level of applications ranging from aerospace, aviation, and automotive systems to industrial, civil engineering, military, biomedical, marine facilities, and renewable energy. In order to update the field of design and development of composites with the use of organic or inorganic fibers, a Special Issue entitled “Progress of Fiber-Reinforced Composites: Design and Applications” has been introduced. This reprint gathers and reviews the collection of twelve article contributions, with authors from Europe, Asia and America accepted for publication in the aforementioned Special Issue of Applied Sciences

NASA Tech Briefs, December 1988

This month's technical section includes forecasts for 1989 and beyond by NASA experts in the following fields: Integrated Circuits; Communications; Computational Fluid Dynamics; Ceramics; Image Processing; Sensors; Dynamic Power; Superconductivity; Artificial Intelligence; and Flow Cytometry. The quotes provide a brief overview of emerging trends, and describe inventions and innovations being developed by NASA, other government agencies, and private industry that could make a significant impact in coming years. A second bonus feature in this month's issue is the expanded subject index that begins on page 98. The index contains cross-referenced listings for all technical briefs appearing in NASA Tech Briefs during 1988

STRUCTURAL BEHAVIOUR OF VARIOUS CORRUGATED SANDWICH STRUCTURES SUBJECTED TO QUASI-STATIC AND DYNAMIC LOADING

New designs of sandwich structures for modern high performance shipcraft have been proposed to be used in the Royal Thai Navy ships. Here, novel hybrid sandwich structures based on corrugated reinforced foam cores have been developed by combining various corrugated cores and Fibre Metal Laminates (FMLs) based on aluminium alloy and fibre reinforced composites, to maximise the functionality of the structures. New manufacturing and fabrication techniques have been introduced to improve the integrity of the corrugated core and the skins by achieving a strong bond across the skin-core interface, as well as the fabrication efficiency. The aim of this research work is to investigate the mechanical properties and structural response of the various novel hybrid corrugated sandwich structures under three-point bending, quasi-static and dynamic compression, impact and blast loading. Firstly, tests are conducted to obtain mechanical properties of constituent materials. Then extensive experimental work is undertaken to determine the load-displacement relationships, the failure mechanisms and energy-absorbing characteristics of a large number of corrugated-cores with different cell wall thickness, core configurations and reinforcement, types of foam cores, foam core densities, unit cell sizes, core-layers, core materials and cores with vertical reinforcements. The results reveal relationships of the structural response and types of the failure mode occurred during the tests. The finite element models have then be developed to simulate the response of the corrugated structures tested, which are validated against the corresponding experimental results in terms of deformation and failure modes. The agreement between the numerical predictions and the experimental results is very good across the range of the structures and configurations investigated. Here, the fibre reinforced composites before the onset of damage is modelled as an orthotropic linear elastic material and the damage is modelled using Hashin’s criteria. The aluminium alloys are simulated as an isotropic elastic material before the yield point, followed by strain hardening. The ultimate failure is modelled using the shear failure and ductile failure available in the commercial code Abaqus. Parametric studies are also carried out using the validated numerical models to investigate the structural responses of the corrugated curvilinear aluminium structures subjected to various loading and geometric and material conditions. The dynamic characteristics of the composite sandwich structures through series of experimental tests and numerical predictions investigated in this project can be used in the design of lightweight composite structures for energy-absorbing applications in aerospace, marine and vehicle transportation industries