In order to explore the horizontal diffusion characteristics of different soil types of in the grassland open-pit mining area

three different soil types including undisturbed soil

mine accumulation soil and ecological transformation soil in Wujiata mining area of Yiqi

Ordos City and Inner Mongolia were taken as the objects.The soil texture

diffusion rate and water content were measured

and the infiltration characteristics of undisturbed soil

mine accumulation soil and ecological transformation soil were numerically simulated by HYDRUS-1D software

so as to analyze the influence of various factors on the soil infiltration law in mining area

and to explore the influence and variation law of horizontal diffusion process of different types of soil in grassland open-pit mine area.The results show that under the condition of one-dimensional horizontal infiltration movement

the wetting front migration distance and time curve of three different particle sizes of undisturbed soil

accumulated soil and ecologically modified soil show similar changes as a whole:with the increase of infiltration time

the wetting front migration distance increases rapidly at first and then slowly advances.Under the same soil type

the time required for the wetting front to reach the end of the soil column is inversely proportional to the soil depth:with the increase of soil depth

the time required decreases gradually

and the average diffusion rate is faster;under the same infiltration time

the wetting front migration distance is proportional to the soil depth:with the increase of soil depth

the wetting front migration distance also increases accordingly.The Boltzmann parameter λ decreased with the increase of soil moisture content

and the λ~θ relationship curve of each soil showed a decreasing trend with the increase of soil moisture content.When θ reaches a certain critical value

λ decreases sharply

and the critical values of θ in each soil layer of undisturbed soil

accumulation soil and modified soil are slightly different.The critical values of θ in each soil layer of undisturbed soil are 0.29

and those in each soil layer of accumulation soil are 0.24

0.28

0.30

respectively.However

the θ critical value in the ecological transformation soil except 60—90 cm is 0.31.The soil hydraulic parameters were inverted by HYDRUS-1D model combined with the change of water content in horizontal soil column profile.The changes of water content in three kinds of soil surface were simulated.The R2 was greater than 0.91

The NSE was greater than 0.95

and the RMSE was less than 0.20.Using HYDRUS-1D model to invert soil hydraulic parameters to simulate the horizontal infiltration process of poor quality soil in mining area can better simulate the infiltration process

describe the dynamic changes of soil moisture in different land types in mining area

and provide reference for dynamic supervision and ecological management of soil moisture in mining area.