CMC改性海水泥浆性质变化及砂地层成膜试验研究

Experimental Study on the Property Change of CMC-Modified Seawater Slurry and Filter Cake Formation in Sand Strata

为探究泥水盾构穿越海底砂地层时羧甲基纤维素钠(CMC)对海水泥浆性质及成膜效果的影响,配制不同CMC掺量的海水泥浆,分析泥浆泌水率、黏度、Zeta电位等性质的变化情况,并开展了泥浆渗透成膜试验。研究结果表明:相对于海水泥浆,加入CMC后的泥浆黏度逐渐增大,2h泌水率显著减小,形成的泥膜中结合水含量逐渐变大,泥膜渗透系数减小至4.03×10^(-8)cm/s;改性海水泥浆中粒径小于75μm的细颗粒含量显著增加,静置24h后,泥浆上部呈现浑浊,下部依然存在较严重的沉淀;当CMC掺量达到0.16%时,改性海水泥浆2h泌水率小于10%,成膜渗透流量小于0.01m^(3)/m^(2),可以保证泥浆短期稳定性并形成致密泥膜。

In order to investigate the impact of sodium carboxymethyl cellulose(CMC) on the properties of seawater slurry and filter cake forming effect when a slurry shield drives through sand strata in the seabed, this paper prepares seawater slurry with different CMC dosages to analyze variation of properties of the slurry, such as water bleeding rate, viscosity and Zeta potential etc., and conducts tests on the slurry infiltration and filter cake formation. The results show that the viscosity of the slurry after the addition of CMC gradually increases compared with that of the seawater slurry, the 2 h water bleeding rate decreases significantly, the bound water content in the formed filter cake gradually increases, and the permeability coefficient of the filter cake decreases to 4.03×10^(-8) cm/s. The content of fine particles less than 75 μm in the modified seawater slurry increases significantly, and after resting for 24 hours the upper part of the slurry shows turbidity while the lower part still has serious precipitation. When the CMC dosing reaches 0.16%, the 2 h bleeding rate of the modified seawater slurry is less than 10%, and the permeation flow rate of the formed filter cake is less than 0.01 m^(3)/m^(2), which can ensure the short-term stability of the slurry and form a dense filter cake.