The techniques of reclaiming subsidence areas by use of a hydraulic dredge pump in Chinese coal mines

The technique of reclaiming disturbed lands by use of a hydraulic dredge pump (HDP) has been used in the reclamation of subsidence areas in Chinese coal mines. This paper discusses the operation principle of the technique and its available conditions and summarizes its reclamation procedures, which are being used in current reclamation practice. The characteristics of the soil reclaimed by HDP were studied. The results showed that the reclaimed soil by use of HDP resulted in a massive structure soil, which was the mixture of original topsoil and subsoil, and had high clay content and no district horizontal layers. The moisture characteristics of the reclaimed soil was the most severe influence factor to plant growth because of the high moisture content and slow infiltration. The soil fertility assessments indicated that the reclaimed soil was very poor. Therefore, the improvements of the reclaimed soils and the HDP technique are needed. Based on the analysis of the previous technical processes, a new technical process for the HDP reclamation method was presented in this paper. The author thought that the two processes such as excavation of soil and backfill and sedimentation needed to be improved, and the other important processes such as removal and backfill of topsoil, establishment of drainage system, etc., should be added