Experiment and simulation of infiltration from layered soils in open pit mine in jin-shaan-meng adjacent region

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    In order to search for an optimal soil layer structure for constructing an earth dumping site for the open-pit mine at the Jin-Shaan-Meng bordering region, an experiment on soil water percolation through 4 soil columns different in soil layer structure, was carried out. The four soil columns were homogeneously packed with Sandy soil, Pi-sha Sandstone, Loessal soil or Red clay, but different in order, that is, Loessal soil-Sandy Soil-Red clay(L-S-R), Loessal soil-Red clay-Sandy Soil(L-R-S), Sandy Soil-Loessal soil-Pi-sha Sandstone(S-L-P), and Loessal soil-Pi-sha Sandstone-Sandy Soil(L-P-S). With the aid of an automatic observation system (AOS) attached to the columns to monitor variation of soil water content with time, and at the same time, change in water level in the markov bottles and wetting front movement was recorded. Based on infiltration rate, cumulative infiltration, wetting front movement and change in profile water content, water percolation through the soil columns different in soil layer structure was characterized. Taking into consideration the natural conditions of the region, evaluation of the columns was done for one that was optimal for construction of the earth dumping site. Results show that after water flowing into the second layer of the columns, percolation rate continuously decreased. After water flowing into the third soil layer in Columns L-S-R and S-L-P, percolation rate further decreased. When the wetting front got to the interface between the second and the third soil layers in Columns L-S-R, L-R-S, S-L-P and L-P-S within 169.0, 461.1, 88.6 and 229.1 min, respectively, accumulated percolation reached 19.3, 21.3, 17.8 and 19.6 cm, respectively, in the four columns. In the soil columns the wetting front moved through the 3rd layer of soil at a rate, being 0.34, 0.78, 0.34 and 1.07% of the rate at which it went down through the 2nd layer in Columns L-S-R, L-R-S, S-L-P and L-P-S, respectively. In Column L-S-R, the water content monitored by the probe at the bottom of the sand soil layer was apparently higher than that measured by the other two probes in the layer, while no such phenomenon was observed in the same soil layer in the other columns. Columns L-S-R and S-L-P could hold a large amount of water for a short period of time, and the third layers of soil tended to prevent water from percolating downwards, especially in Column L-S-R, where the effect of the third layer of red clay was very significant. Obviously, these two types of layered soil structure are the ideal ones for construction of earth dumping sites for open pit mines. In Column L-R-S water infiltrated and percolated down the column very slowly. In case of heavy rain storm, rain water could not infiltrate into the soil readily. In Column L-P-S, after wetting front reached the third layer of soil, it kept moving through the layer rapidly. Obviously the soil column could not hold water and instead let the water go further down into deep soil layers. So, these two types of layered soil structure are not fit for use in construction of earth dumping sites. Changes in water content in soil profiles were monitored continuously with the aid of TDR. Soil hydraulic parameters inversed by combining HYDRUS - 1D with water content in infiltration profile of homogeneous soil, after being collated and optimized, were used to simulate variation of the water content and infiltration rate in infiltration profile of layered soil structure. Statistical analysis shows that R2 of measured and simulated infiltration rate and profile water content varied between 0.86 and 0.97, and MEP and SDP of the infiltration rate did between -0.000 4 and -0.009 7, 0.025 and 0.039, respectively, and MEP and SDP of the profile water content did between -0.022 2 and 0.005 7, 0.034 and 0.092, respectively. Statistics also shows that the inversed parameters can be used to better simulate water infiltration processes through the layer-structured soil. The findings in earth this experiment may have some theoretical and practical significance in guiding construction of earth dumping sites for open pit mines.

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Wu Qifan, Fan Jun, Yang Xiaoli, Pan Yawen, Wang Yafei, Qiao Yanqin, Wang Sheng. Experiment and simulation of infiltration from layered soils in open pit mine in jin-shaan-meng adjacent region[J]. Acta Pedologica Sinica,2015,52(6):1280-1290.

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  • Received:December 01,2014
  • Revised:March 12,2015
  • Adopted:July 10,2015
  • Online: August 31,2015
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