Abstract: Solid backfilling mining can reduce the buildings’ damage caused by mining greatly。 The reduction of subsidence value, the slow advancing speed and the subsidence caused by backfilling body compaction are the main reasons that solid backfilling mining velocity decreases significantly。 Based on the research of mechanism, some principles on subsidence control of solid backfilling mining under buildings were proposed。 The equivalent mining height was designed according to the fortification criteria of buildings and their attachment structures, which enables the ground movement and deformation caused by mining to be less than the corresponding fortification criteria。73857

Key words: solid backfilling mining; subsidence control; mining under buildings

1 Introduction

Coal resources exploitation leads to a series of environmental problems, such as solid waste pollution, farmland reduction, and buildings damage。 Meanwhile, plenty of coals under buildings, water and railways are not exploited in China。 According to the data from China Coal Ministry, coal under buildings accounts for  63。5% of the total buried 13。79 billion tons coal [1]。 Conventional mining technologies (caving method, strip mining, etc) usually cause contradiction between coal mine and local residents in addition to loss of resources。

Solid backfilling mining is the technology which uses equipment to fill gangue, coal ashes and other solid waste into goaf to occupy the space caused by coal exploitation。 Therefore, the roof and floor movement space decrease, and the surface subsidence decreases。 Meanwhile, during the process of filling, large numbers of gangue, coal ashes and other solid wastes are consumed。 So, we can call the solid backfilling mining a green  technology  which  integrates  subsidence  control

with environment protection。

Now, environment pollution and mining under buildings, water and railways are big problem in China。 More coal mines pay attentions to solid backfilling method due to its successful industry experiments。 Recently, several coal mines, such as Xingtai [2], Jining No。3 [3], Zhaizhen [4] have successfully applied this new method。

Based on the analysis on subsidence control mechanism of solid backfilling mining, principles of solid backfilling mining design are given in this work。 Moreover, for the aim of subsidence control, design methods of solid backfilling mining are also proposed。

2 Subsidence control mechanism

2。1 Solid backfilling mining technology

Solid backfilling mining technology contains three classes: fully mechanized solid backfilling mining technology, conventional mechanized solid backfilling mining technology and roadway excavation solid backfilling mining technology。 Among  them,  fully

Foundation item: Project (50834004) supported by the National Natural Science Foundation of China; Project (LEDM2009B01) supported by Key Laboratory for Land Environment and Disaster Monitoring of SBSM; Project (SKLGP2010K002) supported by Opening Fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, China

Corresponding author: ZHA Jian-feng; Tel: +86-516-83591307; E-mail: zha_jf@163。com

mechanized solid backfilling mining, whose working face layout mode is similar to fully mechanized mining, is the most widely used one。 In the case of solid backfilling technology, the filling working face is deployed on one side of the goaf (i。e。, at the back of mining working face), and a transportation belt, which shifts the solid material to scraper chain conveyor, is set in the headentry of working face。 Two scraper chain conveyors with the same direction are set at the front and rear of hydraulic support。 The rear of hydraulic one is called solid backfilling conveyor, which hangs under the horizontal rear canopy and several dropping holes are made on it。 Solid backfilling conveyor is connected with the transportation belt, then solid materials can be transported to solid backfilling conveyor and fall from dropping holes, until the goaf is full of solid filling material。 All the backfilling tasks can be done at the shield of horizontal tail beam (Fig。 1)。