Experimental Study on Morphological Characteristics of Hysteretic Curves of Straw-Reinforced Red Clay

The dynamic triaxial test is conducted on the straw-reinforced red clay under different conditions (straw reinforcement rate, confining pressure, and frequency) using British GDS dynamic triaxial apparatus. Five parameters, which are slope k of the long axis of the hysteretic curve, the ratio α of the long axis to the short axis of the hysteretic curve, the distance d between the two centers of the adjacent hysteretic curve, the area S of hysteretic curve, and the residual strain ε_p, are used to quantitatively study the morphological characteristics of hysteretic curves. The results show that S, d, α, and ε_p of the hysteretic curve of straw-reinforced red clay increase prominently with the increase of dynamic load, and decrease with increasing confining pressure and frequency. k decreases logarithmically with the increase of dynamic load, and increases with rising frequency and confining pressure. Under the same dynamic stress amplitude and five different reinforcement conditions, the specimen is characterized by the highest dynamic strength, optimal deformation resistance, and excellent reinforcement performance when the reinforcement rate is 0.2%. Compared with the red clay unreinforced with straw, the straw-reinforced red clay has an increased stiffness and elastic modulus, and decreased viscosity, energy dissipation capacity, microscopic damage, and residual plastic strain of soil. To sum up, the dynamic properties of straw-reinforced red clay are significantly improved compared with that of red clay unreinforced with straw.