Research into critical caving span of gob in stoping the hanging wall ore with combined mining

There are many kinds of mining methods of hanging wall ore during the transition period of open-pit to underground,in which combined mining is the effective method of solving the output balance during the transition period.Employing the combined mining method can form the discontinuous gob which will influence the safety production of mine,so it is necessary to study the safe and rationale gob processing.The induced caving is a new rising type of gob processing method in recent years.When adopting this way,there is necessity for ensuring critical caving span of the gob and safe thickness of the bulk solid cushion layer in advance.This paper combines the actual situation of hanging wall ore bodies of iron mine,firstly making use of analytical method to calculate the critical caving span of gob and the safe thickness of bulk solid cushion layer,and then analyzes the displacement and stress of gob roof surrounding rock by means of numerical simulation in the process of jamb recovery.This not only ensures the validity of the critical caving span of gob further,but also testifies the feasibility of employing this program in processing the gob.This paper has a certain guiding significance for the production and construction of mine.