Development of a portable rock cutting rig to determine rock cuttability

Kollu galeri açma makineleri ve tam cepheli tünel açma makineleri gibi mekanize kazı makinelerinin günümüzde kullanımları hem maden hem de inşaat sektöründe hızla artmaktadır. Bu tip makineler kullanılmadan önce kayaçların kesilebilirlik özellikleri çok iyi tespit edilmelidir. Makine seçiminde yapılacak hata projenin bitim süresinin uzamasına ve çok büyük maddi kayıplara yol açabilir. Bu yüzden makine seçimi ve performans tahmini proje başlamadan önce yapılmalıdır. Bu çalışmada taşınabilir, kolay kullanılabilir ve pahalı olmayan ve sonuçları güvenilir olan küçük boyutlu bir kazı seti geliştirilmiştir. Geliştirilen taşınabilir test cihazı için 13 cm çapında 70º uç açılı mini diskler imal ettirilmiştir. Numune boyutları 20x20x10 cm olan kayaç numuneleri 5 mm kesme derinliğinde yardımsız kazı modu ile kesilerek, keskiye gelen FN, FR kuvvetleri geliştirilen dinamometre ile kayıt edilmiştir. Kesme sonucu çıkan pasa miktarı kullanılarak spesifik enerji hesaplanmıştır. TÜBİTAK Proje No: MİSAG-274 kapsamında birim deformasyon ölçer’lerle donatılmış bir dinamometre geliştirilmiş ve saniyede 1000 veri alabilecek bir veri iletişim sistemi seçilmiştir. Dinamometrenin güvenirliliğini denemek için 9o’lik açılı ve düşey yüklemelerle kalibrasyon yapılmıştır, sonuçların güvenilir olduğu ve okumaların tekrar edilebilir olduğu kanısına varılmıştır.13 farklı kayaç numunesi üzerinde tam boyutlu doğrusal kazı setinde mini disk ve sabit kesit alanlı disk ile deneyler yapılmış sonuçlar geliştirilen kazı seti sonuçları ile karşılaştırılmış ve daha önceki çalışmalarda konik keskilerle aynı kayaçlar üzerinde yapılan deney sonuçları da veri tabanına eklenince yeni geliştirilen küçük boyutlu ve taşınabilir kazı setinin mekanize kazı makineleri için performans tahmininde belirli bir istatistiksel doğrulukla kullanılabileceği anlaşılmıştır. Anahtar Kelimeler: Kayaç kazılabilirliği, mekanize kazı makinalarının performs tahminleri, Roadheader, TBM.Full face tunnel boring machines and partial face tunnel boring machines utilization for mining and civil project are increasing enormously. Tunnels for civil projects at highly populated cities dictate minimum ground disturbance while tunneling. Full face tunneling machines are able to excavate through hard rock to soft ground with small surface deformation and faster compared to drill and blast. Selection of correct mechanized excavator for a given rock media is very important for the success of the project. A great care must be taken for equipment selection and performance prediction in the project design phase. Researchers worked on a wide range of parameters to predict the performance of mechanical excavators. Besides the theoretical approaches, the ones who correlate the mechanical properties of intact rock to the field performance of the excavators are more reliable in their data range and tunneling conditions. Full scale linear rock cutting, small scale core cutting and University of Trondheim performance prediction model are widely accepted on the international tunneling society. Laboratory cutting tests are expensive, needs specialists, special equipments and may take long time to perform. Therefore, a portable, easy to use, reliable, costs less than 10000 $ small scale rock cutting rig is developed in the scope of this research. The table of the rig is moved by a hydraulic cylinder powered by a hydraulic accumulator. Rock samples in 20x20x10 cm of size attached to the table with a special mechanism to cut the rock with a mini-disc, diameter of 13 cm and tip angle of 70°, and the forces acting on the mini-disc and specific energy to cut a unit volume of rock is measured. A force dynamometer equipped with strain gauges are developed in the scope of Tübitak Project No: MİSAG-274, to measure the forces and a data acquisition system that can collect 1000 data in a second is chosen. Many calibrations are performed to test the reliability of the dynamometer and data acquisition system. Calibrations are done by a hydraulic cylinder whose cross section area is known. Hydraulic cylinder is pressurized to 10, 20, 30, 40, 50 bar with a 9º inclined surface to the mini disc. Output from the dynamometer strain gauges are compared  to the applied force where it is seen that output is linear and has R2 equals to 0.99. It is proved that the results of the developed cutting rig are reliable and repeatable. While making a cutting on the developed cutting rig, there are two ways to fix the rock sample. One can use the manufactured case where rock sample can be cemented inside. The other is to use the screwed clamp on the moving table. It is hard to adjust the cutting depth while pouring the cement into the case. Another disadvantage is you can only use one face of the rock sample. In this study, screwed clamp is used to make the cutting test because it is easy,  faster to fix the  sample and gives the opportunity to make 4 cuttings per sample.. Rock cutting tests are carried out on 14 different rock samples with the full scale linear cutting rig and the developed portable rock cutting rig. A 13” constant cross section (CCS) disc cutter and mini disc is used for the cutting tests with full scale linear cutting rig. Results from the full scale cutting rig 13” CCS with mini disc equipped developed rig are compared for 8 different rock samples for an unrelieved 5 mm depth of cut. Normal and cutting forces are correlated and correlation coeffients are found to be 0.86 and 0.75 respectively. Disc cutting theories of Roxborough (for discs with an tip angle) and Rostami (for CCS discs) are applied for rock samples used in cutting tests. Trendlines of CCS and mini disk forces are identical to theoretical comparison of disc normal and cutting forces for CCS disc and V shaped disc. The conical cutter results from previous studies on the full scale linear cutting rig are compared with the developed rock cutting rig results. Optimum specific energy values from relieved cutting tests with Sandvik S35/80H cutter are plotted with the index specific energy values from developed cutting rig. A good correlation and 0.62 correlation coefficient is found between optimum SE of conical cutter and mini disc index SE values. Keywords: Rock cutting tests, performance prediction of tunneling machines, Roadheader, TBM.&nbsp