Effect of soil compaction on hydraulic properties and macropore structure: Evidence from opencast mines in the Loess Plateau of China

Abstract

Affected by heavy machinery, the soil compaction in the opencast coal mine area is serious, which will change the characteristics of soil macropores, then affect the soil hydraulic properties and damage the ecological environment in mining area. In this study, the disturbed soil samples from the dumping area of Pingshuo opencast coal mine of China were collected. The soil samples were processed in bulk density from 1.30 g·cm−3 to 1.70 g·cm−3, and the soil hydraulic properties were measured, and the soil macropore characteristics were obtained using computerized tomography scanning in laboratory. The path analysis method was applied to analyze the effect of macropore characteristics caused by compaction on soil hydraulic properties. Soil compaction resulted in severe effects on soil hydraulic characteristics and macropore properties. Under same soil suction, the water contents remained in soil decreased with increasing compaction. The explanatory variables (average Euler number (AEN), macropore throat number (MTN), and macropore fractal dimension (MFD)) were main determinants of soil-water characteristic curve (SWCC), and the indirect path coefficient of macroporosity. The effects of AEN and MFD on soil infiltration properties were relatively high. The bulk density of 1.4 g·cm−3 was a critical point of affecting macropore properties then affecting soil hydraulic properties, and some soil reclamation measures should be conducted to make bulk density < 1.4 g·cm−3 for compacted soil in opencast coal mining area. This study provides a basis for selecting technology of land reclamation and the subsequent monitoring and maintenance of soil quality in mining areas.