| The pit formed by open-pit mining was badly damaged and often the most difficult and cost the highest part of land reclamation,which resulted in a low reclamation rate of the pit.The west of Liaoning Province was a semi-arid region with abundant mineral resources,and many mining pits have been left by mining of mineral resources in recent decades.Taking Songxin Iron Mine in Jianping,Chaoyang city,western Liaoning province as an example,this paper analyzed the specific reclamation conditions in the study area,and put forward a suitable technical scheme for reclamation of the pit.Based on this,the key technologies such as the technology on pit mining filling,soil reconstruction of cultivated land reclamation and rainwater collection and conservancy of mining pit were studied intensively,and the engineering design was carried out.The results can provide a reference for mining pit reclamation in similar mining areas.(1)This paper summarized the research scheme of pit reclamation at home and abroad,investigated and analyzed the reclamation conditions of mining pits in the study area,and put forward the appropriate technical scheme for reclamation according to the relevant regulations and technical orders of mining pit reclamation.The excavated and discarded rocks of the Xiaotang first iron ore in the vicinity of Xinkai Iron Mine were filled with pit by stratigraphic order,then the surface layer was covered with crushed stones,and the soil reconstruction and land construction were carried out later.At the same time,no fissure groove shape and rock pores at the bottom of the pit were used for proper seepage prevention treatment,and rain water runoff storage in the upper reaches of the mining pit was introduced into the pit to form the bottom water storage as an irrigation water source for reclaimed cultivated land.While the pit was filled,the multi-section cast iron well pipe was pre-buried to form the extraction well.A temporary sedimentation pits were arranged at the upper and lower ends of the pit,which made the aggregate runoff seep into the water storage area at the bottom of the pit after natural sedimentation and filtration.According to the above scheme,the reclamation of mining pit was divided into mining pit filling,soil reconstruction,rainwater collection and conservancy and so on.(2)The filling scheme was designed to fill the rocks stripped from the Xiaotang first iron ore in the vicinity of Xinkai Iron Mine according to the original stratigraphic sequence.The topsoil of the Xiaotang first iron ore was piled up and stored first,and then the overlying soil was constructed after filling.The total volume of the pit was 7.0637 million m~3.The total volume of the pit was 7.0637 million m~3,in which the filling capacity of the abandoned rock was 6.8514 million m~3.The porosity of the filled rock was estimated to be 17.56%and the upper limit of water storage in mining pit was 562500 m~3.(3)Soil reconstruction scheme was determined according to the needs of filling a pit.This research adopted the methods of"relative optimal selection distance"(YXR)and"comprehensive optimal selection index"(ZYX):0.2 m gravel+0.3 m brick red sand+0.5 m25%tailings modified soil(12.5 cm tailings+37.5 cm loam mixed).And according to the specific conditions of the filling area,the design of the land reclamation project was carried out,and the terrace was constructed from the top to the bottom in the mining pit filling area,and the terrace was constructed at 21.00 hm~2.(4)The design content of rainwater collection and conservancy scheme of mining pit including feasibility analysis of mining pit water,analysis and calculation of mining pit water and the engineering design of mining pit water and saving technology.Identify standard of surrounding rock mining pit.It was confirmed that the surrounding rock mass of the mining pit conforms to the standard of rainwater conservancy,In dry year,100100 m~3water can be collected and the irrigated area was 27.81 hm~2;In normal flow year,122000m~3 water can be collected and the irrigated area was 45.19 hm~2,while in high flow year,170700 m~3 water can be collected and the irrigated area was 63.22 hm~2.Two temporary sedimentation pits with volumes of 990.58 m~3and 1035.43 m~3were set up above and below the pit respectively,with a well spacing of 194.60 m and a diameter of 0.44 m. |
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