Technology and practice of mechanized backfill mining for water protection with aeolian sand paste-like

In order to overcome the serious problem of Salawusu Formation Aquifer damage caused by caving mining in Yuyang Coal Mine,the technique of mechanized backfill mining with aeolian sand paste-like was developed. Aeolian sand was used as aggregate and alkali-activated fly ash was used as cementing agent in the backfill material. Water- sand ratio was 1 ∶ 1. 3 and the mass concentration was 72% ,while slurry initial fluidity could reach 210 mm. The au- thors proposed the local resistance loss calculation method of slurry pipeline transportation,and the field gravity trans- port test results showed that the resistance loss of unit length elbow was 4. 26 times as big as the loss of resistance a- long path,thus the pipeline diameter with 14. 9 lines of self flowing was determined,and the pipeline flow design pre- cision was improved by more than 10% . The backfill capacity could reach 360 m3 / h and the running energy consump- tion was lower because of adopting backfill station model with double pulping system and underground equipment pool. The authors also put forward whole backfill space sealing which cloth consumption was only 40% of bag backfill. Industrial test showed that the backfill mining technique meet the requirements of water resources protection,primarily because the backfill rate was 98. 5% in goaf,strata behavior appeared slightly,roof water leaching was less than 2 m3 /d,and surface subsidence value was only 38 mm. There were great breakthroughs in cost and production efficiency in this technology comparing with similar one.