Abstract
To achieve the purposes of disposing industry solid wastes and enhancing the sustainability of subgrade life-cycle service performance in seasonally frozen regions compared to previous research of modified silty clay (MSC) composed of oil shale ash (OSA), fly ash (FA), and silty clay (SC), we identified for the first time the axial deformation characteristics of MSC with different levels of cycle load number, dynamic stress ratio, confining pressure, loading frequency, and F-T cycles; and corresponding to the above conditions, the normalized and logarithmic models on the plastic cumulative strain prediction of MSC are established. For the effect of cycle load number, results show that the cumulative plastic strain of MSC after 1, 10, and 100 cycle loads occupies for 28.72%~35.31%, 49.86%~55.59%, and 70.87%~78.39% of those after 8000 cycle loads, indicating that MSC possesses remarkable plastic stability after 100 cycles of cycle loads. For the effect of dynamic stress ratio, confining pressure, loading frequency, and F-T cycles, results show that dynamic stress ratio and F-T cycles are important factors affecting the axial deformation of MSC after repeated cycle loads; and under the low dynamic stress ratio, increasing confining pressure and loading frequency have insignificant effect on the axial strain of MSC after 8000 loads. In term of the normalized and logarithmic models on the plastic cumulative strain prediction of MSC, they have a high correlation coefficient with testing data, and according to the above models, the predicted result shows that the cumulative plastic strain of MSC ranges from 0.38 cm to 2.71 cm, and these predicted values are within the requirements in the related standards of highway subgrades and railway, indicating that the cumulative plastic strain of MSC is small and MSC is suitable to be used as the subgrade materials.
Highlights
Oil Shale is an important energy resource
For better understanding the deformation characteristics of using silty clay modified by oil shale ash (OSA) and fly ash (FA) as the subgrade material in seasonally frozen regions and provide valuable guidance for its practical application, this paper aims to: (1) Present the change characteristics on the total axial strain and cumulative plastic strain of modified silty clay (MSC); (2) discuss the effects of dynamic stress ratio, confining pressure, loading frequency, and F-T cycles on the cumulative plastic strain of MSC, present the cumulative plastic strain equation corresponding to the above conditions; (3) obtain the predicted values on the cumulative plastic strain of MSC, and compare with national standards to confirm the excellent performance of MSC used as the subgrade materials
Research results lead to the following conclusions: (1) As the number of cycle loads increases, the axial strain of MSC begins to increase rapidly, slowly, and tends to be stable
Summary
Oil Shale is an important energy resource. Even with lower oil rates, there are hundreds of billion tons of converted shale oil. Many countries have included oil shales in their national energy reserve systems. The utilization of oil shales has a history of 200 years. The utilization of oil shale is still trapped by high costs and large quantities of byproduct wastes. Estonia has the most advanced oil shale utilization technology [3]. Its oil shale solid wastes exceed 8 × 109 tons, which seriously pollute the forests, lakes, and land environment in the northeastern regions [4,5]. There are 214 × 108 tons of oil shale solid wastes in Maoming oil shale mining area of Guangdong, China during the 70 years of production [6]
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