荷载和干湿循环耦合作用下固化淤泥的屈服应力变化规律与机理研究

Coupling effects of loading and drying-wetting cycles on the yield stress of solidified sludge and its mechanism

为研究固化淤泥在荷载和干湿循环耦合作用下的屈服应力变化规律,以取自无锡太湖地区的疏浚淤泥为研究对象,通过有荷条件下的干湿循环试验和固结试验,对不同水泥掺量条件下固化淤泥的屈服应力进行了研究。结果表明:对于水泥掺量为100kg/m^(3)的固化淤泥试样,在上覆载荷不大于25kPa的条件下,经过干湿循环后,固化淤泥试样的屈服应力比同掺量基准试样的小,随着上覆荷载的增大,经过干湿循环后试样的屈服应力不降反增;对于水泥掺量为150kg/m^(3)、200kg/m3的固化淤泥试样,经过干湿循环后,固化淤泥试样的屈服应力比同掺量基准试样的大,且这种增长趋势随着上覆荷载的增加更加明显。经过干湿循环后,固化淤泥试样屈服应力的变化受干燥温度引起的水泥水化产物增加和裂缝发展的双重影响,且裂缝的发展与上覆荷载密切相关。与控制试样相比,经过干湿循环后固化淤泥的屈服应力均呈现明显下降趋势,说明仅考虑裂缝发展的影响时,干湿循环对试样屈服应力具有明显劣化作用。微观分析表明:水泥掺量越高,养护温度越高,固化淤泥生成的水化产物越多,内部孔隙被进一步填充,从而屈服应力越大。本文的研究结论可为固化淤泥土工筑物在上覆荷载作用下的干湿稳定性评价提供参考。

To study the yield stress of solidified sludge under coupling effects of loading and drying-wetting cycles, the drying-wetting test and consolidation test were performed on dredged sludge from Taihu Lake in Wuxi area with various cement contents. Test results show that the yield stress of solidified sludge with cement content of 100 kg/m^(3) decreases after the solidified sludge subjected drying-wetting cycles under the condition that the overlying load is not greater than 25 kPa, whereas, with the increase of overlying load, the yield stress increase after drying-wetting. For the solidified sludge with cement contents of 150 kg/m^(3) and 200 kg/m^(3), the yield stress of the solidified sludge sample increases after drying-wetting cycles. The higher the overlying load, the more the increase of yield stress. The change of yield stress of solidified sludge after drying/wetting cycle is attributed to the dying temperature-induced acceleration of cement hydration and the development of crack. The development of crack is closely related to the overlying load. Compared with the controlled specimen, the yield stress of the solidified sludge decreases obviously, indicating that the drying-wetting cycle had a significant deterioration effect on the yield stress of the solidified sludge when only considering the development of crack. The microscopic experiments demonstrated that the higher the cement content and the higher the curing temperature, the more hydration products generated by solidified sludge, the more internal pores are further enriched and the greater the yield stress. The conclusions of this research can provide reference for evaluating the stability of solidified sludge structures under drying-wetting cycle.