Response of soil hydraulic properties to soil macropore characteristics
from an opencast coal mining area using a CT scanning method
Abstract
Soil compaction resulted from heavy machineries in opencast coal mine
areas alters soil macropore characteristics then affects soil hydraulic
properties. Additional information related to hydraulic characteristics
is needed to assess the effects of soil reconstruction to improve the
soil quality. The aim of this study was to determine the hydraulic
properties and macropore characteristics of compacted soil by simulation
tests and CT scanning in laboratory and to explore the response of soil
hydraulic properties to soil macropore characteristics. 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
designed bulk density (BD) from 1.30 g·cm-3 to 1.70 g·cm-3, and the soil
hydraulic properties, including soil-water characteristic curve (SWCC),
saturated hydraulic conductivity ( Ks), soil moisture diffusivity (D(θ)
), field capacity (FC), wilting coefficient (WC) were measured and the
soil macropore characteristics were obtained using CT scanning in
laboratory. The path analysis method was applied to analyze the effect
of macropore characteristics 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. Soil-water
holding capacity, soil saturated hydraulic conductivity, and soil water
diffusivity decreased with increasing BD. The explanatory variables
(average euler number (AEN), macropore throat number (PTN), and
macropore fractal dimension (PFD)) were main determinants of soil-water
holding capacity, and the indirect path coefficient of macroporosity.
The effects of average euler number (AEN) and macropore fractal
dimension (PFD) on soil infiltration properties were relatively high.
The BD 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 BD <1.4
g·cm-3 for compacted soil in opencast coal mining area. This study
provides valuable data for soil restoration of soil hydraulic and
macropore properties in mining areas.