Quantitative Evaluation of the Morphological Characteristics of Sand Hysteresis Curve under Cyclic Load

Taking Fujian Standard Sand (particle size 0.5 mm ~ 1.0 mm) as the test object, dynamic triaxial test was carried out to study the influence of confining pressure, relative density and vibration frequency on the hysteresis curve of sand. The long axis slope of hysteretic curve K, the area of the hysteretic curve S, the area difference between the positive and negative partial stresses of the hysteretic curve S′, the degree of non-closure σ_p and the dissipation modulus α of hysteretic curve are used to quantify the morphological characteristics of the hysteresis curve of Fujian standard sand. The results show that the value of K decreases with the increase of cyclic strain and the decrease of the effective confining pressure. When the strain is small (< 0.1%), K gradually increases with the increase of the cycle times whereas an opposite trend is observed for strain greater than 0.1%. Relative density slightly affects the values of K. In the small strain range (< 0.1%), the values of S, S′ and σ_p are not sensitive to the effective confining pressure and the relative density. While with the increase of strain, S and S′ values increase exponentially but decrease as the cycle times increases. The value of α decreases first and then increases exponentially with the increase of strain, and the strain turning point moves backward with the increase of the effective confining pressure. Lower values of α are observed for larger confining pressure and the smaller cycle times. However, the effect of the relative density on α is unclear.