Rock abrasivity plays an important role in characterizing a rock material for excavation purposes. Abrasion can be defined as the wearing or tearing away of particles from the surface, i.e. it is a process causing removal or displacement of material at a solid surface, which will lead to wear, especially on tools that are used in mining, drilling, and tunneling applications. The CERCHAR Abrasivity Test is a method to determine an index called CERCHAR Abrasivity Index (CAI) for the rock's abrasivity.The test was originally developed by the Laboratoire du Centre d'E ´ tudes et Recherches des Charbonnages (CER-CHAR) de France for coal mining applications (Cerchar 1986). Two standards exist for this test method: the French standard AFNOR NF P 94-430-1 (2000) and ASTM D7625-10 (2010). The test is widely used in research and practice. There are essentially two designs of testing apparatus: the original design as developed at the CER-CHAR Centre (Valantin 1973) and a modified design as reported by West (1989). While the designs are similar there are some important differences as well as ambiguities in test conditions that include equipment actuation, mate-rial properties of the stylus and sample preparation as summarized by Plinninger et al. (2003). ScopeThe CERCHAR Abrasivity Test is intended as an index test for classifying the abrasivity of a rock material. The test measures the wear on the tip of a steel stylus having a Rockwell Hardness of HRC 55.A rock specimen, disc-shaped or irregular, is firmly held in the test apparatus. The stylus is lowered carefully onto the rock surface. While under a normal force of 70 N, the stylus is moved a total distance of 10.0 mm across the rock.

Rock abrasivity plays an important role in characterizing a rock material for excavation purposes. Abrasion can be defined as the wearing or tearing away of particles from the surface, i.e. it is a process causing removal or displacement of material at a solid surface, which will lead to wear, especially on tools that are used in mining, drilling, and tunneling applications. The CERCHAR Abrasivity Test is a method to determine an index called CERCHAR Abrasivity Index (CAI) for the rock's abrasivity.The test was originally developed by the Laboratoire du Centre d'E ´ tudes et Recherches des Charbonnages (CER-CHAR) de France for coal mining applications (Cerchar 1986). Two standards exist for this test method: the French standard AFNOR NF P 94-430-1 (2000) and ASTM D7625-10 (2010). The test is widely used in research and practice. There are essentially two designs of testing apparatus: the original design as developed at the CER-CHAR Centre (Valantin 1973) and a modified design as reported by West (1989). While the designs are similar there are some important differences as well as ambiguities in test conditions that include equipment actuation, mate-rial properties of the stylus and sample preparation as summarized by Plinninger et al. (2003). ScopeThe CERCHAR Abrasivity Test is intended as an index test for classifying the abrasivity of a rock material. The test measures the wear on the tip of a steel stylus having a Rockwell Hardness of HRC 55.A rock specimen, disc-shaped or irregular, is firmly held in the test apparatus. The stylus is lowered carefully onto the rock surface. While under a normal force of 70 N, the stylus is moved a total distance of 10.0 mm across the rock.

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ResumoA 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. Palavras-chave:Detonador eletrônico, detonador pirotécnico, perfuração e detonação, detonação de precisão, precisão na temporização. Abstract 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

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Problem statement:The high-velocity railway link between Bologna and Firenze (Italy) is today under construction and several tunnels have to be excavated for this purpose, some of these using TBMs. A small diameter tunnel, named Cunicolo ginori, was realized by TBM parallel to a large railway tunnel (Vaglia), at the distance of only 35 m. Approach: The Vaglia tunnel had been excavated by conventional methods and provided, thanks to a detailed survey and a systematic geotechnical monitoring (rock quality evaluation and convergence measurements) the characterization data of the crossed rock mass; moreover the TBM performance data in Cunicolo ginori were continuously monitored. A tunnel stretch, 587 m long, was recorded and the analysis of the data from both surveys allowed to correlate the geomechanical parameters of the rock-mass to the TBM performances (net advancement rate, thrust, specific energy). Results: Based on this large amount of data a new system to predict the net TBM advancement rate for a tunnel in rock masses of known geological and geomechanical characteristics was then developed. Also the Utilization Coefficient (CU) can be correlated to the rock quality Indices: The net advance rate and the utilization coefficient provide a mean to foresee the gross advancement rate and to evaluate the suitability of a machine for the excavation of a tunnel. Conclusion: In this study, an analysis had been carried out on about 587 m of a service tunnel, excavated by a TBM in a flysch formation.