The mechanical characteristics of asphalt mixture are closely related with its stress state, temperature, and loading rate, therefore, the loading condition of the asphalt mixture's dynamic modulus test should be consistent with the actual temperature, loading frequency, and stress state that are applied to the mixture in actual pavement, thus can the test produce an objective result that can accurately reflect the actual stress-strain relationship for the asphalt mixture. However, due to limitations in the loading capacity of current dynamic modulus test equipment, the present modulus tester cannot yet set such a loading condition whose stress state is consistent with that of asphalt mixture in actual pavement. As a result, the modulus testing results of the current test may not accurately reflect the actual stress-strain characteristics of an asphalt mixture under real traffic loads. Therefore, this paper aims to figure out the impact of stress state on asphalt mixture's dynamic modulus, and firstly conducts a numerical analysis to ascertain asphalt pavement's triaxial stress state at different depth, then, utilizing the nonlinear elasticity theory of Soil Plasticity, proposes a theoretical model that can reflect triaxial stress state's effect on asphalt mixture's dynamic modulus, and then, arranges a series of triaxial dynamic modulus tests for asphalt mixture in different stress state to verify the model's effectiveness, and meantime analyzes stress state's influencing rule to asphalt mixture's dynamic modulus. Their results indicate, the asphalt mixture of the actual pavement is in an obvious triaxial stress state, and that the higher the triaxial stress state, the larger the dynamic modulus, particularly for the mixture near the surface, whose high stress state will lead to their dynamic modulus to be significantly larger than that of the underlying course, while the model proposed in this paper can to a large extent reflect this impact.

To investigate the effects of cyclic loading frequency (f) and loading patterns (90 degrees jump of principal stress, JPS, and continuous rotation of principal stress, CRPS) on the stiffness characteristics of saturated marine coral sands, a series of undrained cyclic shear tests were conducted. pi-plane is introduced as the analytical plane. We propose generalized deviator strain evolution (zeta q) to quantify the evolution of global strain, and introduce generalized dynamic modulus (K) to evaluate the soil's global stiffness. K and maximum generalized dynamic modulus (K0) exhibited a strong correlation with loading direction angle (alpha sigma), maximum loading direction angle (alpha sigma max), and f. Both patterns showed an increase in K0 with increasing f. Under JPS, the K0 initially decreased and then increased as alpha sigma increased, reaching its minimum value at alpha sigma = 45 degrees. Normalizing the effect of f and alpha sigma, we establish a unified empirical formula for K0. Under CRPS, K0 continuously decreased with increasing alpha sigma max. The global level of K0 is higher under CRPS compared to JPS. Additionally, the K/K0 curve was significantly influenced by alpha sigma but remained insensitive to f. A modified generalized Davidenkov model was developed to describe the recession properties of marine coral sands over a wide strain range.

In order to investigate the dynamic characteristics of frozen saline silty clay (studied saline soil) under reciprocating loading, a series of cyclic tri -axial experiments have been conducted for studied saline soil with 0.0, 0.5, 1.5, and 2.5 % of Na 2 SO 4 contents under confining pressures 0 MPa -18 MPa at -6 degrees C, respectively. The test results show that as the increase of number of cycle N , the accumulated axial strain e aN continuously increases, and the relationship between e aN and N can be described by an exponential function: e aN = aN b ; As the number of cycle N increasing, dynamic shear modulus G dN and dynamic bulk modulus K dN increase firstly and then decrease slightly; Salt content and confining pressure have great influences on the e aN , G dN and K dN . Within the same loading cycle, G dN and K dN decrease until reaching their minimums when the salt content is 0.5 %, and then G dN and K dN increase as the increase of salt content. With the change of salt content, e aN presents an opposite change law to G dN and K dN . For the studied saline soil with same salt content, during the same loading cycle, e aN and G dN increase until reaching their minimums, and then decrease as the increase of confining pressure, K dN increases with the increase of confining pressure. This study can be applied to evaluate the elasto-plastic properties of frozen soils and saline soils subjected to cyclic dynamic loading.