Abstract：With a specially designed experimental instrument，the mechanism of load transfer within an unconsolidated confined aquifer and its effect on compound breakage of key strata have been studied. The results show that (1) the unconsolidated confined aquifer plays a crucial role in load transfer because of its fluidity and replenishment in time，making the loads of overburden soil evenly transfer into the bedrock through the unconsolidated confined aquifer and the load keep constant during the excavation process； (2) under the condition without unconsolidated confined aquifer，the load on the bedrock will be reduced sharply during the excavation. Therefore，in the process of load transfer within the unconsolidated confined aquifer，the key strata of overburden rock are prone to have a compound breakage when the load on the upper interface of bedrock is great and the bedrock is very thin. Based on the mechanism of the effect of unconsolidated confined aquifer on the compound breakage of key strata，the fully mechanized support crushing accidents taking place during coal mining under the unconsolidated confined aquifer and thin bedrock in some collieries of East China have been well explained.
