Background The black soil area in northeast China is one of the important commercial grain supply areas such as corn and japonica rice. However, studies show that the soil erosion in this area is deteriorating, which seriously affects the fine fertility of black soil, and soil erosion is the main reason for this situation. Therefore, improving the anti-erosion ability of black soil is a necessary means to alleviate the current situation of soil erosion. Physical and mechanical properties and microstructure are the basic properties of black soil, which can indicate its resistance to erosion.

Methods Natural zeolite used in this study was mainly inclined zeolite. XRF, XRD and SEM respectively were used to determine the main chemical composition of natural zeolite, mineral composition and surface morphology and structure. The black soil was taken from Songliao Plain as the research object. Natural zeolite was mixed into the black soil in the proportions of 0, 5%, 10%, 15% and 20%, and after 60 d of pot culture, triaxial compression test method, ring knife method, mercury injection instrument method were adopted to determine and analyze the mechanical properties, physical properties and microstructure change rules of different remolded soil.

Results 1) With the increase of dosage of added natural zeolite, the cohesive force of the black soil increased gradually and was positively related with added natural zeolite dosage. Internal friction angle increased more than that of control group with added natural zeolite dosage, but there was no obvious regular pattern. The density of black soil increased gradually and was positively related with added zeolite dosage. Total porosity decreased and negatively related with added zeolite dosage. 2) As the mixing dosage of natural zeolite gradually increased, the microstructure of black soil changed, and the total pore volume showed a decreasing trend. The changes at both ends of each curve showed a slight upward trend of small pores and a slight downward trend of large pores, indicating that the proportion of smaller diameter pores in the black soil increased slightly. 3) Based on the analysis of relevant literature, it is reasonable and economic to select 10% natural zeolite to improve black soil.

Conclusions Natural zeolite may improve the mechanical properties, physical properties and microstructure of black soil. The changes of microstructure and macroscopic physical properties are consistent with each other, which will lead to the changes of mechanical properties of the black soil and effectively improve the shear strength of the black soil. And this change can be explained to some extent by the internal structure changes of the black soil.