Effects of root systems on crack formation: experiments, modeling, and analyses

Abstract

Plant roots can increase soil shearing resistance directly by mechanical reinforcing. The 2D crack pattern of the surface soil near the plant were observed experimentally, and it was found that the soil cracking near the plant roots was inhibited, which may be due to the influence of the plant roots. This paper focuses on the mechanical reinforcement of soil by plant roots and investigates the development rule and formation mechanism of desiccation cracking under the influence of plant roots. A numerical model describing the process of desiccation cracking of soils in the presence of root systems, which is based on a lattice of Hooke springs model, was combined with a non-stationary random field characterized by a trend term and a random fluctuation term. The root density distribution function was introduced to describe the root distribution, and an exponential function of critical strain and root density was constructed to obtain the trend of critical strain distribution of the root systems (the root systems of a single plant). The random fluctuation term was generated by the conditional simulation technique. Minkowski densities (i.e., area density, length density and Euler number density) were adopted to quantify the crack patterns. Parameters of the model were calibrated and verified by the field experimental results, and its precision was evaluated. The effect of most input parameters (include the new parameters maximum critical strain value hc and the lateral distribution radius of RDDF rm) on the model output was analyzed. The results show that in the validation process the coefficients of determination R2 for the Minkowski densities is between 0.749 and 0.948. Root mean square error is between 0.000 2–0.120 9. BIAS is between 0.049 5–0.139 0, and the consistency index is between 0.908 and 0.987. The model is effective in predicting the formation and development of cracks in farmland soils under the influence of the root systems. The model produces the dynamic development of the desiccation cracking network of farmland soils under the influence of the root systems. The simulation results provide ample indication of the reinforcing effect of the root systems on the soil and the limiting effect of the root systems on desiccation cracking.