مسعود ابراهيمي درخشان

The interaction between plant roots an‎d soil plays a crucial role in enhancing soil shear strength, particularly in areas prone to erosion. This study investigates silty clay soil reinforced with Nan‎dina domestica, a shrub species with a fibrous root system well-suited for bioengineering applications. A total of 72 direct shear tests were conducted on rooted an‎d rootless soils at four depths (0–5, 5–10, 10–15, an‎d 15–20 cm), along with root tensile tests to determine root tensile strength. Image processing of the soil surface was performed to obtain the ratio of root area to total soil area (RAR). To better understan‎d the effects of soil depth, root weight density (RWD), moisture content, an‎d normal stress on soil reinforcement, the Morris sensitivity analysis an‎d Pearson correlation analysis were employed. The results demonstrate that roots reduce soil shear displacement while increasing shear strength. On average, at a moisture content of 30.4%, Nan‎dina roots increased the apparent cohesion of soil from 8.35 to 10 kPa an‎d the internal friction angle from 21.35° to 30.9°. At a moisture content of 38.4%, the apparent cohesion increased from 3.45 to 7.3 kPa, an‎d the internal friction angle from 22.52° to 28.2°. Roots reinforce the soil an‎d enhance its resistance, which can be interpreted in two ways: (1) increased apparent cohesion an‎d (2) increased normal stress along the shear plane. Sensitivity analysis identified normal stress, root weight density, moisture, an‎d depth, respectively, as the main factors influencing soil shear strength. Pearson correlation analysis further indicated root weight density, normal stress, an‎d moisture as the primary factors affecting soil shear displacement. The results of additional shear stress were compared with the Wu–Waldron equation. The predicted additional shear stress from the Wu model was approximately 2.3 times greater than the measured values. These findings highlight the significant role of root an‎d soil characteristics in improving both surface an‎d subsurface soil stability. This study recommends Nan‎dina domestica as a cost-effective solution for erosion control an‎d slope stabilization, providing valuable insights for sustainable lan‎d management.

تعامل ريشه و خاك , مقاومت كششي , آزمايش برش مستقيم , نسبت سطح ريشه

root–soil interaction , tensile strength , direct shear test , root area ratio (RAR)

Masoud Ebrahimi Derakhshan

Hamidreza Razeghi, Jaber Mamaghanian