# Design Parameters Affecting Rill Swell Events for Block Caving Applications  
[PERSON]  
1 Advanced Mining Technology Center, Universidad de Chile, Santiago 8331051, Chile;  
1 [EMAIL_ADDRESS] (C.V.)1  
[PERSON]  
1 Advanced Mining Technology Center, Universidad de Chile, Santiago 8331051, Chile;  
1 [EMAIL_ADDRESS] (C.V.)1  
[PERSON]  
2 Faculty of Engineering, Universidad de Concepcion, Concepcion 4070386, Chile  
23 Faculty of Civil Engineering and Resource Management, AGH University of Krakow, Mickiewcza 30 Av.,  
30-059 Krakow, Poland  
34 Faculty of Mechanical Engineering and Robotics, AGH University of Krakow, Mickiewcza 30 Av.,  
30-059 Krakow, Poland  
3 [EMAIL_ADDRESS] (K.S. )4  
[PERSON]  
4 Faculty of Mechanical Engineering and Robotics, AGH University of Krakow, Mickiewcza 30 Av.,  
30-059 Krakow, Poland  
3 zagkrzys@agb. haul dump (LHD) loading, when fine material located over the drawpoint is destabilized and flows out. This kind of event has been observed at Mt. Wright and Cadia East PC1, and recently, minor runoff of fines has also been observed in the Chuquicamata underground mine. Both mechanisms require a previous accumulation of fine material in the drawbell, while the presence of coarse fragments can also contribute to the occurrence of RS in either mechanism. The presence of fine material is critical in caving mines with inrush risk potential. Fine materials can appear due to the mining process, or they can originate from previous adjacent mine sectors [7]. Four sources of fine material have been identified in RS events: secondary fragmentation, fine material migration, fine material from open pits, and fine material from previous mine sectors. These sources can be independent or occur in combination to influence the quantity of fine material found in underground mines. Secondary fragmentation is the last fragmentation stage that ore undergoes in the broken column before being extracted from the drawpoints. Here, the rock is mainly fragmented by compression and abrasion [8; 9; 10]. Additionally, some authors [10; 11; 12] include fragmentation by impact, when a rock block falls from the cave-back. Several models have been used to estimate these fragmentations in block caving mines [9; 12; 13; 14; 15]; however, none has been specifically calibrated to estimate fine fragments. The main mechanism of fine material generation during secondary fragmentation is by abrasion generated by shear strain during gravity flow [13; 16; 17]. The problem is that shear strain and overload are difficult to estimate. Moreover, both variables are influenced by ore extraction. The shear strain can be determined based on the shear band during ore flow [12; 13]. This approach has been used in a secondary fragmentation model [18] based on fragmentation studies involving shear [19; 20]. This approach has improved the accuracy of fine material fragmentation models. However, fine material can also be observed under uniform draw due to large travel distances [21; 22], which the previous models have failed to consider. Fines migration occurs when fine materials flow more rapidly than coarse materials inside the broken column and eventually arrive at the drawpoint [7; 23]. In block caving, this process has been studied mainly through physical modeling [1; 24; 25] and also through numerical modeling [26; 27; 28]. In cave mining, fine migration is mainly governed by the ratio between coarse and fine fragment size, the particle size distribution of ore, rock density, and draw strategies. Authors [12; 13] suggest that fine migration also occurs around the ellipsoid of movement induced by shearing. Fine material migration can accumulate fine material in drawbells, increasing the risk of RS events. Additionally, cave mining methods are sometimes developed after open-pit mining has ceased [29; 30]. Due to the caving process, material from the pit slope can fail and become part of the caving-induced subsidence. Material incorporated from the pit is softer and more fractured than the in situ mineralized rock.