Development TBM performance prediction model by using portable linear rock cutting machine

Many factors such as environmental and market conditions are forcing civil or mining companies to be more profitable and competitive. These companies aim to complete more projects in a short time or they want to increase productivity. One way of to do this is to use mechanized excavators. For these reasons the application of mechanical excavators for rock excavation in both civil construction and mining engineering fields has increased significantly in recent years. Proper machine and cutter selection, cutter head design and performance prediction for mechanized excavators such as tunnel boring machines (TBM) or roadheaders are the most important parameters for a mechanized tunneling or mining project. The most used machine design parameters are cutter layouts, cutting power of the machine, torque and thrust. Besides, the performance prediction of machines can be done by predicting cutting parameters from physical and mechanical properties of rocks. Full and small scale linear cutting tests are widely used for the prediction of excavation performance. In addition of these University of Trondheim model is widely used for the performance prediction of tunnel boring machines. The small scale cutting test for rock was developed to cut core samples by a standard chisel tool for predicting performance of roadheaders. Small scale rock cutting machine (SLCM) tests have some advantages such that it doesn't require large block samples however this test method have lots of disadvantages. The basic disadvantage of this test method is using an index cutter instead of a real life cutter and disc cutters cannot be used in this method. In addition, the database is based only on the field performance of light and medium weight Dosco roadheaders used in coal mines in England. The full-scale linear cutting machine (LCM) tests are widely used on large rock samples having size of (1 x 0.8 x 0.6 m) is cut in the laboratory with a real-life cutter. Orthogonal forces (rolling force, normal force, sideways force) acting on the cutter are measured with a data logger with different cutter spacing and depth of cut. Specific energy values are determined using rolling force values. The production rate of a mechanical miner is calculated based on the optimum specific energy or using a computer model/simulation requiring forces acting on the cutters. The basic disadvantage of the full-scale rock-cutting test is that it requires large blocks of rock samples, which are usually difficult, too expensive, or sometimes impossible to obtain. However LCM and SLCM test methods have some disadvantages and for this reason a new portable linear cutting machine (PLCM) (prototype) was developed in Mining Engineering Department of Istanbul Technical University after evaluating disadvantages of LCM and SLCM test methods. After carrying out some researches by using PLCM, it was shown that PLCM could be used for the performance prediction of mechanical excavators. However, prototype portable linear cutting machine had some disadvantages such as the cutter spacing could not to be changed, mini CCS type disc cutters could not be used in this machine and it was not suitable for cutting tests on hard rock due to low power of the machine. For these reasons in this study a new portable linear rock cutting (PLCM©) machine was developed in the Mining Engineering Department of Istanbul Technical University and financially supported by The Scientific and Technological Research Council of Turkey (TUBITAK-112M859). This machine minimized disadvantages of other linear cutting tests and it was designed such as a mini full scale linear cutting machines. This new machine does not requires too much manpower or large blocks of rock samples and it can also be used for cutting small core samples or small block samples by a real-life mini scaled conical and disc cutters. In addition, PLCM tests are cheaper than LCM tests and the rock cutting tests results can be obtained in a short period of time. The newly developed portable linear cutting machine has many advantages but the accuracy of PLCM test results should be checked. The PLCM test results can be checked by comparing to LCM test results and mechanical excavators' field data. In this study, these comparisons were performed and investigated to understand the usage of the new portable linear rock cutting machine for the performance prediction of mechanical excavators. In the first part of this study relieved and unrelieved linear rock cutting tests are performed with the newly developed portable and the full scale linear cutting machines. For PLCM tests two mini disc cutters (one CCS and one V type disc) are used. Mini CCS and V type disc cutters have 144 mm (5.7 inch) disc diameters and they have 5 and 0.7 mm tip width respectively. For LCM tests one CCS type disc cutter having 432 mm çaplı (17 inch) disc diameter and 18 mm tip width is used. Five different rock samples (beige marble, sandstone, limestone, kufeki limestone and travertine) are selected for rock cutting tests (PLCM, LCM) and the cutting tests are performed on different cutting depths and cutter spacing values. Orthogonal forces (normal, rolling and side) acting on a disc cutter are measured and specific energy values were determined for PLCM and LCM tests and the relationships between cutting depth and cutter forces for unrelieved and relieved PLCM and LCM rock cutting tests and relationships between s/d ratio and cutter forces for relieved PLCM and LCM rock cutting tests were evaluated and then PLCM and LCM test results compared for each rock sample and a good relationship was obtained between LCM and PLCM test results. In order to develop a better model by using PLCM, the comparison of experimental and theoretical results should be extended with more rock samples. In the second part of this study, theoretical cutting forces in cutting five different rock samples (beige marble, sandstone, limestone, kufeki limestone and travertine) with mini CCS and V-type disc cutters were calculated by using the theories defined by Rostami and Ozdemir (1993) and Roxborough (1975), respectively. Then experimental PLCM tests results were compared with the theoretical models and these comparisons showed that the relationships between experimental and theoretical results were strong for normal and rolling forces. Then TBM performance parameters were estimated for a selected tunnel boring machine using the LCM and PLCM test results respectively. The estimated performance parameters were compared for the LCM and PLCM test results and these comparisons showed that the relationships between the LCM and PLCM are strong for TBM trust force, torque, power and instantaneous cutting rate (ICR). In the next part of this study, five different rock samples were obtained from Uskudar – Umraniye – Cekmekoy subway tunnel project in Istanbul. First, physical and mechanical property tests performed on these rock samples. All experiments (uniaxial compressive and Brazilian tensile strength, P and S velocity test, Young modulus, Schmidt hammer, Shore scleroscope tests) done according to ISRM and ASTM methods. Then, relieved and unrelieved linear rock cutting tests are performed with PLCM. For PLCM tests, two mini disc cutters (one CCS and one V type disc) have 144 disc diameter are used. TBM performance parameters were estimated by using PLCM test results and estimated performance parameters compared to the TBM field data but the relationship between PLCM laboratory results and field data was not strong. In conclusion, the results of the study indicate that PLCM test method can be used for the selection of proper mechanical excavator and prediction of its performance parameters. However PLCM test results should be used with a correction factor that can be determined based on rock physical and mechanical properties. In addition, in order to develop a better model for PLCM, the comparison of laboratory results and field data should be extended with more rock samples.