The Experimental Research Of Dynamic Strength And Pore Water Pressure Of Flyash Under Traffic Load

The road foundation in project is usually in complex initial consolidation condition and cyclic loading condition. The soil unit in different position of road foundation is not only at three-dimensional pressure state, which three principal stresses are variational in magnitude, the slanting angle between the biggest principal stress and vertical axis may vary from 0° to 90°. Therefore, the definition of initial consolidation pressure state should include more parameters rather than just consolidation pressure and consolidation stress ratio. Moreover, it is complex to describe the cyclic shear stress path of road foundation under traffic loading. It is not suitable only using cyclic triaxial tests or cyclic torsion shear tests for 90° change of principal stresses axes.The soil static and dynamic universal triaxial and torsional shear apparatus was facilized by Dalian University of Technology and Seiken Inc. and made by Seiken, Japan. The apparatus was used to perform undrained cyclic triaxial tests and undrained cyclic cycle couple shear tests for three ratio of consolidation pressure K_c =1.0 1.5 2.0. The cyclic cycle couple shear tests were performed for initial slanting angles of principal stress axes a₀ =0°, 30°, 45°, 90°. Behavior of dynamic strength and pore water pressure of saturated loose flysash under multi-directional anisotropic consolidation condition and different cyclic shear stress path was investigated.In this article, the influence of consolidation stress ratio and initial principal stress direction angle to the dynamic strength of the saturated loose flysash was discussed, also the influence of cyclic shear stress path and failure criterion and dynamic strength definition to the results. Results showed that the effect of the consolidation stress ratio and initial principal stress direction angle to the dynamic strength of saturated flysash was distinct. The trend of results was almost same under different failure criterion and dynamic strength definition, while it was different for dynamic strength with different definition under different consolidation stress ratio.Through regression analysis of test data, the relations between the ratio of peak normalized pore water pressure and ratio of number of cyclic loading or generalized shear strain were established, and the parameters were obtained. The results showed that the stress patterns and the strain patterns of pore water pressure were not effected by the consolidation stress ratio except the values of parameter. It was the same for the initial principal stressdirection angle and consolidation stress ratio but 90°. It was a special situation for the initial principal stress angle 90°, and regression stress pattern of pore water pressure was described in another different function rather than the similar hyperbolic function as it was performed under the condition of other angles. This particularity of 90° was confirmed in the dynamic strength results.For the inherent and induced anisotropy of saturation loose flyash, the strain components were different under different consolidation, as well as the changes of generalized shear strain. All of this was also discussed in the paper.