Abstract: A simplified formula for calculating the shear strength of tap root-soil composite is derived based on the stress analysis of tap root-soil composite in consideration of the failure mode of root system. The calculation results are compared with field measured values. Moreover, the influences of reduction coefficient, root weight, and plant species on the strength of the root-soil composite are also investigated. Results imply that the cohesion of the composite is an exponential function of soil depth. When normal stress is constant, the shear strength of the composite increases with the augment of reduction coefficient. When the reduction coefficient is in the range of 0.84-0.86, the result is closer to the measured value. In addition, the shear strength of the composite increases with the increase of root weight, and then decreases gradually. A optimum root weight is found to make sure a maximum shear strength. With the normal stress increasing, the shear strength of the composite is also increasing. The relative error between calculated shear strength and measured strength is kept within 10%.

Key words: root-soil composite, mechanical model, shear strength, cohesion, parametric analysis