Construction and validation of a mathematical model for the pressure subsidence of mixed crop straw in Shajiang black soil

The soil properties of mixed crop straw do not enable conventional pressure subsidence models to characterize the relationship between straw amount and pressure-bearing properties accurately. Based on the distribution of straw in the field, this study explored the effect of the amount of surface straw cover on the pressure subsidence relationship in Shajiang black soil. The quadratic rotated orthogonal combination test was used to quantify the mathematical relationships of Shajiang black soil pressure subsidence modeling with the amount of surface straw cover (SSC) and mass mixing ratio of soil to straw (MSS). Then, using the weighted least squares method, the pressure subsidence parameters (cohesive deformation modulus, friction deformation modulus, and subsidence index) were obtained, and the Bekker model was modified to construct a pressure subsidence model for the straw-containing soil. Finally, the modified model was verified under conditions of a water content of 18 %, the SSC of 2.5 t·ha⁻¹, and the MSS of 2.5 %. Results showed that the proposed pressure subsidence model predicted the value with a relative error of 2.21 % compared with the experimental measurements. The model’s predicted value accuracy improved by 10.65 % compared to the conventional model. From these results, this study proposes that a mixed crop straw Shajiang black soil pressure subsidence model can predict the soil’s internal stress transfer and stress–strain conditions.