Important parameters that describe successful sublevel stoping operation are optimal fragmentation and low damage of rock mass around stopes. In current state of operation fragmentation of blasted material is not optimal since high percentage of fragments are oversized which requires additional sizing. Also, excessive damage of surrounding rock mass is found. By proposing new blasting pattern with slightly increased amount of drilling, but with decreased hole diameter decrease of explosive usage is obtained for more than 100kg. Along with better charge distribution it is expected that rock mass damage is to be decreased as well.

Ovaj rad sadrži metodologiju preventivnih i periodičnih pregleda i ispitivanja bagera, izvršen je stručni pregled uz detaljno objašnjenje i donošenje konačne ocene o ispravnosti bagera.

Discrete element modelling is common approach for analysis of dynamical processes that include granular materials. Method is commonly applied for the modeling of the gravity flow of the broken rock in caving operations. Herein, comparison of two different approaches in such modelling was presented. Two models, ring wide and symmetrically divided, were used for comparison. Ore dilution and recovery were monitored as main comparison parameters, but also the processing time of such models and spatial shape of extraction zones. Ring wide model show greater ore dilution and lower recovery, while half wide models show the opposite results. Cumulative dilution differs for 10%, while ore recoveries differ in approximately 15% for same extraction levels. Also, dilution entrance points are different, where ring wide model shows earlier dilution entrance at about 15% of extraction, while dilution enters at 25% in half wide models. Processing speed is increased in half wide model due to the reduction in number of elements, but overall processing time is nearly the same due to the frequent hang ups inside the half wide model. Shape and size of the extraction zones are very different. Half wide model shows much higher extraction zone in contrary with ring wide, while depth of extraction zone is greater in ring wide models which corresponds with higher and earlier entry of dilution.

It is suggested that 2D finite element method models are used for square pillar stability analysis. Equivalent width of strip pillar that is represented by FE models is determined from tributary area method by introducing equivalence of square and strip pillar loads in tributary area method analysis. With FE analysis it is shown that pillar loads are close to expected, but tributary area method is limited to pillars of small heights and with horizontal deposits. Proposed methodology provides opportunity to model much complex conditions and sequencing of excavation with respect of sequential stress redistribution.

Capital mine development is often faced with limited geotechnical databases and designers are faced with more or less accurate estimates of missing parameters. GSI classification if often used with numerical modelling and its rounding unit is ±5 as suggested by its creators. In situ stresses are usually estimated in such manner that vertical component is equal to the weight of the rocks above, while horizontal components may vary in wide range, starting with ratio to vertical component of 0.3 and even be several times higher than vertical component. Influence of estimate error of GSI and horizontal stress is analyzed for the Cukaru Peki location near Bor in Serbia. Zone in the rock mass valued with GSI of 40 at depth 160m is analyzed for the change of GSI value of ±5 and horizontal stress ratio between 0.5-1.5. Change of the unsupported length of decline and shotcrete layer thickness is tracked for different values of input parameters. Finally, best case and worst case scenarios are analyzed with results showing that shotcrete layer thickness could vary in range between 4-33cm, and unsupported lengths between 0.6-2m.