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One of the necessities in drilling operations is the ability to predict the performance of rock drills. To explain the effects of various parameters on the drilling rate (drilling velocity) and the drilling tool wear, the term drillability is being used. In this research, drillability is defined as a penetration rate. The correlation between drilling rate index (DRI) and some rock properties is inspected in this survey in order to examine the influences of properties of strength indexes and brittleness of rocks on drillability. To achieve this, uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) values of different rock samples were used as geomechanical properties data. Then, the brittleness of rocks which use the uniaxial compressive strength and tensile strength of rocks were determined from calculations. Afterwards, artificial neural networks (ANN) as an artificial intelligence technique was employed in order to relate datasets of UCS, BTS and brittleness as input data to the DRI as the target. The suggested correlation between DRI and both mechanical rock properties and brittleness concepts were analyzed, and acceptable correlations between drillability of rocks and the input parameters was achieved. It is concluded that by the use of data of uniaxial compressive strength, Brazilian tensile strength and rock brittleness, ANNs can evaluate drilling rate index accurately.
Nowadays, Tunnel excavation utilizing mechanical excavation techniques such as tunnel boring machines (TBM’s) and roadheaders is growingly becoming common. Choosing the machinery and hardware must be under consideration of physical, mechanical and petrographic properties of rock, otherwise it can result in considerable detriments. Hence, earlier than tunnelling operations, it is vital to investigate rock properties (Yarali and Soyer, 2011).
Macias, Francisco Javier (SINTEF Building and Infrastructure - Rock and Soil Mechanics Group) | Dahl, Filip (SINTEF Building and Infrastructure - Rock and Soil Mechanics Group) | Bruland, Amund (NTNU Department of Civil and Transport Engineering) | Käsling, Heiko (TUM Chair of Engineering Geology) | Thuro, Kurosch (TUM Chair of Engineering Geology)
Drillability is an important parameter in order to assess the influence that intact rock properties have on performance prediction and cost evaluations in connection with drill-and-blast tunnelling, TBM tunnelling, excavations by roadheaders and hydraulic impact hammers and also rock quarrying. Especially in hard rock conditions, drillability will be of great importance for selection of excavation method and a successful project execution. Unanticipated situations and/or inappropriate assessments can result in considerable delays and great risk of cost overruns. Reliable predictions are therefore required; prediction of net penetration rate and tool wear, time consumption and excavation costs, including risk and assessing risk linked to variation in rock mass boreability, establishing and managing contract price regulation. Several methodologies are available to assess drillability (i.e. rock strength, rock surface hardness, rock brittleness, rock abrasivity or rock petrography). This paper includes a review of the state-of-the-art and discussion of relevant parameters that involves drillability assessments in hard rock conditions.
Rock properties have a large impact in connection with excavation and tunnelling by use of drill-and-blast, TBMs, roadheaders, hydraulic impact hammers and also for rock quarrying, especially in hard rock conditions. The term drillability is commonly used to describe the ability of the rock to be drilled or bored and it will be of great importance on performance predictions, cost evaluations and selection of excavation method. Unanticipated situations and/or inappropriate assessments can result in considerable delays and great risk of cost overruns. Reliable predictions are therefore required for; prediction of net penetration rate and tool wear, time consumption and excavation costs, including risk and assessing risk linked to variation in rock mass boreability, establishing and managing contract price regulation. Several methodologies are available to assess drillability (i.e. rock strength, rock surface hardness, rock brittleness, rock abrasivity or rock petrography). This paper includes a brief review of the state-of-the-art and discussion of relevant parameters that involves drillability assessments in hard rock conditions.
ABSTRACT: Rock cuttability is defined with specific energy, specific cutting force, specific normal force and tool wear for given conditions by various researchers. Specific energy and forces are determined with different methods. Most reliable method for determining rock cuttability is laboratory rock cutting tests. For half a century, numerous researchers studied on various aspects of rock cuttability. Some of them tried to correlate different rock properties with outcomes of rock cutting tests to determine rock cuttability empirically. Some other studied on effects of different parameters on rock cuttability. Drilling strength is definition of rock’s overall resistance to external interferences. However, any study was seen examining the effects of drilling strength on rock cuttability. In this study, six rock and two ore samples were subjected to small scale rock cutting test, laboratory drilling test and CERCHAR abrasivity test. Calculated drilling strength values were correlated with specific energy, specific cutting force, specific normal force, and CERCHAR abrasivity index. Tool forces, abrasivity and specific energy increased with drilling strength for a given condition. Results were compared with previous works.
There is no acceptable statistical review about the ratio of mechanical excavation over the conventional drill & blast method usage in both tunneling and mining applications (Kolymbas 2005). However, due to some explicit advantages of mechanical excavation over the conventional methods, such as higher production rate, flexibility, reliability, safety and lesser support requirement, this method is becoming more and more widespread all around the world.
Selection of the tunneling/mining method depends on geotechnical factors, tunnel shape and dimensions, schedule, availability of equipment and cost (Hemphill 2013). After method selection and machine selection (partial-face or full-face), cuttability or performance prediction phenomena arises for the given formation. Factors affecting the performance of the machine subdivided into two main categories such as geological and machine parameters (Fowell et al. 1984).
As a rule of a thumb, machine or method selection is mainly controlled by discontinuities and intact rock strength (Tamrock 1999). Such that, roadheaders can excavate the massive formations having maximum 120 MPa uniaxial compressive strength (UCS). Also tunnel boring machines (TBM) can cut the massive formations having UCS up to 400 MPa (Copur et al. 2012). This situation may be explained by the strength of the cutting tool and installed power of the excavation machine. High pick forces arise during rock cutting can damage cutting tools and result ineffective operation and stability problems.