Abstract This article deals with a study performed at the Experimental Mine of the Research Center of Responsible Mining of the University of São Paulo, to examine the correlations between geological environment, blasting parameters and energy consumption in the primary crushing phase. The research is designed to appreciate the relationships between the energy provided for size reduction and the resistances to size reduction. For this purpose, Key Performance Indicators (KPIs) are used to describe the possible improvements on the energy consumption due to crushing. Four blast tests were performed: for each blast, KPIs were recorded regarding the blast design, the particle size distribution, the real power energy consumption at the primary crushing unit and its rate of utilization. The results show that energy consumption at the primary crusher is a sum of two components: energy directly involved in crushing the rock, and additional energy used for winning the inertial resistances of the moving parts of the crusher. We show how explosive energy and delay times influence the production of coarse fragments that jam the crusher, therefore influencing machinery stops and inertia loads related to putting the jaws back into movement.

Abstract This paper shows the work conducted at the Experimental Mine of the Research Center of Responsible Mining of the University of São Paulo, taking into account the theoretical issues presented in the first part of the article. The research was performed without changing the production cycle and without resorting to investments in new types of equipment: it has attempted to increase the productivity of the quarry, by lowering production costs and improving the quality of the product. Some Key Performance Indicators (KPIs) were established to monitor the results. A new blast design method, a more appropriate initiation sequence and some simple, inexpensive and effective solutions were identified and applied. The results show that the proper selection of delay timing can be of significant benefit to downstream processes as well as enhanced fragmentation itself.

Drilling and blasting are fundamental operations in the mining cycle and consti tute an important component of the mining costs. Rock fragmentation can in principle be managed by means of two options: by increasing or reducing the specific consumption of explosives, or by modifying the drilling pattern. The choice of one or other type of control depends on the relationship between the unit costs of drilling and explosives, and on technical restrictions or regulations imposed by different reasons. It is then necessary to identify the link between the blast design and some factors affecting the downstream processing of the product. This paper analyzes the theoretical basis aimed at evaluating the main parameters involved when organizing a production blast in open pit quarries. In particular, a method developed through the analysis of the results in a large number of limestone open pit quarries in Italy is described and commented. The first experimental results in Brazil have been obtained by applying this method at the Experimental Mine of the Research Center of Responsible Mining of the University of São Paulo. Experimental methods and results will be analyzed and discussed in the second part of this paper.

A perfuração computadorizada e a temporização eletrônica das detonações são dois avanços tecnológicos que têm tido um papel importante na atualização dos métodos de escavação com explosivos. Apesar disso, a temporização eletrônica dos detonadores ainda é uma solução técnica pouco frequente para problemas de detonação de precisão. Com base em uma extensa pesquisa bibliográfica, esse artigo revisa os resultados alcançados e as principais vantagens esperadas dos dispositivos eletrônicos de iniciação. Após descrever as características primárias desses detonadores, alguns elementos são considerados, a fim de que sejam melhor compreendidas as aplicações em diferentes condições, tanto em céu aberto quanto em subterrâneo, a extensão do número de tempos de retardo, a liberdade na escolha dos intervalos de tempo entre as detonações, a precisão da temporização, a redução das vibrações, o controle do overbreak e da fragmentação. Os resultados são comparados com aqueles obtidos por meio de dispositivos pirotécnicos de temporização e discutidos nas considerações finais.

Computerized drilling and the electronic timing of detonations are two technological breakthroughs which have had an important role in updating drilling and blasting excavation methods, although the electronic timing of detonators is still a comparatively infrequent technical solution to precision blasting problems. On the basis of an extensive collection of published cases, this paper reviews the successes achieved and the main expected advantages from the electronic ignition devices. After describing the primary characteristics of these detonators, some elements will be considered, in order to better understand their applications in different conditions, both in open pit and underground sites: extension of the time delay number, freedom in the choice of time intervals between detonations, timing accuracy, reduction of vibrations, control of back-break and fragmentation. The results are compared to those obtained by pyrotechnical timing devices, and summarized in the concluding remarks.

Este artículo se refiere a los métodos utilizados para la construcción de túneles para un sistema de trenes de alta velocidad entre Bolognay Firenze (Italia), elpunto de interés está sobre el nodo de Bologna, como el corazón de sistema, conectando las líneas principales de la red de alta velocidad. El proyecto incluye nueve túneles, con 73 de los 78 km cruzando por debajo de los Apeninos. Este artículo presenta los principales aspectos a tener en consideración para la correcta selección de máquinas tuneladoras (TBM) utilizadas en las áreas urbanas. El fundamento en el análisis de los aspectos técnicos consiste en un balance de presión de tierra (EPB) de la máquina relacionado a los principales parámetros en la excavación; una vez recogido y organizado los datos, se realizaron análisis estadísticos, se estimaron las velocidades empíricamente y evaluaron los tiempos de espera. La evaluación fue realizada para el cálculo de las energías específicas de excavación (en diferentes fases de perforación) para encontrar una correlación satisfactoria con el tipo de terreno atravesado. Los resultados obtenidos son interesantes en comparación con parámetros de otras excavaciones; en particular, una mejor compresión en el balance de la presión de tierra en cada fase de trabajo, ha sido descrita gracias a un estudio experimental realizado durante la construcción de túneles para un sistema de trenes de alta velocidad en Italia. Este artículo contiene información detallada recogida de la operación de dos maquinas EPB diferentes.

The paper refers to the methods adopted for building a high-speed railway tunnel system between Bologna and Firenze (Italy), focusing attention on the Bologna node which represents the heart of the system, connecting the high speed network's main lines. The project includes 9 tunnels, accounting for 73 km of the 78 km route crossing below the Apennines. The paper pays attention to the main aspects to be taken into consideration for correctly choosing the tunnel boring machinery (TBM) to be used in urban areas. The fundamental point in analysing technical aspects regarding an earth pressure balance (EPB) machine concerned storing the main excavation parameter values; having collected and organised such data, statistical methods were used for processing it, the instantaneous velocities attained were empirically estimated and idle times were evaluated. The evaluation was made by calculating excavation specific energies (during different excavation phases) to find a satisfactory correlation with the type of ground crossed. Interesting results have been found by comparison with other excavation parameters; in particular, a better understanding of an earth pressure balance shield's working phases has been reached thanks to an experimental study conducted during the construction of tunnels for a high-speed railway system in Italy. The paper contains details collected regarding the operation of two different EPB machines.