Experimental Study on Dynamic Resilient Modulus of Circulating Fluidized Bed Combustion Ash Subgrade

Abstract

Purposes To explore the dynamic performance of circulating fluidized bed(CFB) combustion ash subgrade under the driving load, the dynamic resilient modulus characteristics of GF and DTH combustion ashes under different curing ages, compaction degrees, water contents, and stress levels were investigated on the basis of laboratory dynamic triaxial tests. Methods With the aid of mercury intrusion porosimetry(MIP), the pore distribution characteristics of CFB combustion ash were analyzed. Findings The measured results reveal that within a certain range, the dynamic resilient modulus of CFB combustion ash increases with the increase of f-CaO and SO3 content and curing age, and increases significantly in 0~7 d, and slowly in 7~28 d; the increase of compaction degree, water content, confining pressures, and deviator stress increase the dynamic resilient modulus of CFB combustion ash. With the increase of compaction degree and water content, the improvement of dynamic resilient modulus gradually decreases. Both deviator stress and confining pressure affect the dynamic resilient modulus of CFB combustion ash, and the effect of confining pressure is relatively more significant. The results of MIP show that the total porosity and large pore diameter (>2 000 nm) density of GF combustion ash sample are lower than those of DTH combustion ash sample under the same conditions. With the decrease of water content, the total porosity and the large pore size density become higher, the dynamic resilient modulus becomes lower. Fitting the results of dynamic resilient modulus of two kinds of CFB combustion ash with different water contents and compaction degrees after curing for 28 days shows that the prediction results of the three-parameter theoretical model with bulk stress and octahedral shear stress as variables have a high correlation with the test results (R2>0.96), suggesting that the model can effectively predict the dynamic resilient modulus of CFB combustion ash.

Keywords

• subgrade engineering
• circulating fluidized bed combustion ash
• dynamic resilient modulus
• mercury intrusion porosimetry