Calculation analysis of bulldozer\u27s productivity in gravitational transport on open pits

Abstract

Analiza točnosti i primjenjivosti proračuna učinka dozera, pri gravitacijskom transportu otkrivke na površinskom kopu, provedena je usporedbom računskih vrijednosti dobivenih prema teoretskim obrascima i rezultatima terenskih mjerenja. Mjerene su i uspoređene vrijednosti obujma vučne prizme i brzine kretanja dozera, koji su osnovni faktori za određivanje učinka stroja, u uvjetima iste duljine transporta. Uočena su znatna odstupanja računski određenih učinaka dozera u odnosu na izmjerene u stvarnim uvjetima. Predložena su poboljšanja proračuna u cilju približavanja stvarnim eksploatacijskim učincima uvođenjem novih obrazaca za obujam vučne prizme i brzinu kretanja dozera. Zakrivljenost noža dozera ima znatan utjecaj na obujam vučne prizme i nije zanemariva u proračunu. Usporedbom računskih vrijednosti po različitim autorima dobivena su odstupanja između 3 % i 40 % od mjerenih vrijednosti. Najtočnijom se pokazala novopredložena formula s odstupanjem od 3 %. Teoretski proračunata maksimalna brzina kretanja dozera prema snazi stroja, značajno odstupa od stvarne izmjerene brzine (>49 %). Brzina kretanja dozera prema vučnom dijagramu, te prilagođenoj formuli koja predstavlja univerzalnu vučnu karakteristiku dozera, primjenjiva je u slučaju transporta gdje prevladava utjecaj otpora vučne prizme na brzinu dozera (odstupanje 160 %) uvodi značajnu pogrešku u procjenu učinka.Analysis of accuracy and calculation applicability of bulldozer\u27s productivity in gravitational transport on open pits has been conducted by comparing computational values obtained by theoretical formulas and results of field measuring. The magnitude of the volume of blade load and the speed of bulldozer\u27s motion, which are the main factors for assessment of machine productivity, have been measured and compared at the same length of transport. Significant deviation of computational specified bulldozer\u27s productivity has been noticed with regard to the ones measured in real conditions. Calculation improvements have been suggested in order to better approximate real exploitation effects by introducing new formulas for the volume of blade load and the speed of bulldozer\u27s motion. The curvature of bulldozer\u27s blade has a substantial effect on the volume of pile in front of blade, and it is not negligible in the calculation. By comparing computational values of different authors, deviations between 3 % and 40 % from measured values have been obtained. The new proposed formula with a 3 % deviation has been proved to be the most accurate. Theoretically calculated maximum speed of bulldozer\u27s motion by means of engine power significantly deviates from the actual measured speed (>49 %). The speed of bulldozer\u27s motion according to the rimpull diagram and the adjusted formula that represents a universal rimpull characteristic of the bulldozer, is applicable in transport where the influence of blade load pushing resistance is prevalent to the bulldozer\u27s speed (deviation 160 %) introduces a significant error in the productivity assessment