A significant volume of waste slurry with high water
content and ultrahigh clay particle content is
produced during slurry shield tunneling in the second Jiangyin crossriver tunnel project. The water and slurry are hard to separate,
resulting in low separation efficiency. Hence, various flocculants are used for
slurry flocculation experiments to investigate the effect on flocculation and
dehydration. The equivalent water content of sediment as well as interface
sedimentation rate, supernatant turbidity, slurry dehydration rate, and Zeta
potential are selected as evaluation indices to study the influence of
flocculant type, dosage, and composite form on its flocculation effect.
Finally, the flocculation mechanism of different substances is preliminarily
discussed. The results reveal the following: (1) The slurry dehydration effect
of different flocculants is in the following order: APAM＞PAFC+APAM≥PAC+APAM＞PAFC≥PAC, whereas the order of turbidity removal effect is as follows:
PAFC＞PAC＞PAFC+APAM＞PAC+APAM＞APAM. (2) The optimal dosage of
organic flocculant APAM is closely related to its molecular weight, and the
maximum rate of dehydration varies for APAMs with different molecular weights.
The best dehydration effect is achieved when the molecular weight of the agent
is maintained at 12-14 million. (3) The PAFC+APAM composite flocculant exhibits
the best conditioning effect on the waste slurry with high water content and
ultrahigh clay particle content. In this research, the
optimal dosages for PAFC and APAM solutions are 33 and 233 g·L-1,
respectively, and the corresponding dosages of dry matter for PAFC and APAM are
1.6 and 0.466 g·L-1, respectively. Under this condition, the dehydration rate of the
slurry is 29.6% after 90 min, and the turbidity of the supernatant can be
reduced to 62.0 NTU. (4)The primary mechanism responsible for the dehydration effect
of composite flocculants is the adsorption bridging effect of the long chain of
the organic flocculant APAM. Meanwhile, turbidity removal is mostly associated
with the electrical neutralization of the inorganic flocculants PAC and PAFC.
DOU Liupan
,
WANG Jun
,
LI Haitao
,
WU Dongyang
,
ZHANG Xinyuan
,
WEI Lifeng
. Flocculation and Dehydration Experiment on Waste
Slurry Produced by Slurry Shield Tunneling With High Water and
UltraHigh Clay Particle Contents[J]. Tunnel Construction, 2024
, 44(4)
: 771
-782
.
DOI: 10.3973/j.issn.2096-4498.2024.04.015
