循环流化床固硫灰路基动态回弹模量试验研究

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

【目的】探究循环流化床(CFB)固硫灰用作路基填料时在行车荷载下的动态性能。【方法】基于室内动三轴试验,研究了GF固硫灰与DTH固硫灰在不同养护龄期、压实度、含水率及应力水平条件下动态回弹模量特性,并结合压汞测试分析了CFB固硫灰试样孔隙分布特征与动态回弹模量的关系。【结果】结果表明:在一定范围内,CFB固硫灰的动态回弹模量随f-CaO与SO_(3)含量及养护龄期的提升而增加,在0~7 d内提升显著,7~28 d增长缓慢;压实度、含水率、围压及偏应力的提升均会使CFB固硫灰的动态回弹模量增大,其中随着压实度与含水率的上升,动态回弹模量的提升幅度逐渐下降,偏应力和围压对CFB固硫灰动态回弹模量均有较大影响,且围压的影响更显著。压汞试验的结果表明,同等条件下GF固硫灰试样总孔隙率与大孔径(>2 000 nm)密度低于DTH固硫灰,随着含水率的下降,GF固硫灰试样的总孔隙率与大孔密度增加,动态回弹模量变小。对两种CFB固硫灰不同含水率及压实度成型试件养护28 d后的动态回弹模量结果进行拟合,表明以体应力与八面体剪应力为变量的三参数理论模型预估结果与试验结果具有较高的相关性(R^(2)>0.96),可有效预测CFB固硫灰的动态回弹模量。

【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 SO_(3) 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(R~2>0.96),suggesting that the model can effectively predict the dynamic resilient modulus of CFB combustion ash.