絮凝剂对过江盾构隧道同步注浆浆液性能的影响研究

Study on Influence of Flocculant on Performance of Synchronous Grouting in Cross-river Shield Tunnel

在过江盾构隧道修建过程中,当丰富的地下水充填盾尾间隙时,易稀释同步注浆浆液,从而造成浆液胶凝时间延长、胶凝材料流失、后期强度不足等问题,工程中常通过改善同步注浆浆液稳定性予以解决。因此,依托常德沅江过江盾构隧道工程,研究常用絮凝剂聚丙烯酰胺、羟乙基纤维素、羟乙基甲基纤维素对水泥基浆液性能的影响。净浆抗水分散性试验结果表明,不同絮凝剂净浆表现出相似规律,即随着絮凝剂掺量的增加,试验水样均表现出由浑浊逐渐变为清亮透明的状态,继续增加絮凝剂掺量,水样仍处于清亮透明状态。净浆塑性黏度、剪切应力及扩展度试验结果表明,随着絮凝剂掺量的增加,净浆塑性黏度和剪切应力呈增大趋势,扩展度呈递减趋势;净浆塑性黏度和剪切应力的增加,使净浆颗粒间的黏结能力增强,导致净浆在重力作用下自由流动的能力减弱,削弱浆体流变性。相比其他絮凝剂,黏度100000mPa·s羟乙基甲基纤维素临界掺量最小,完全溶于水后不会出现块状物,且相同掺量下其塑性黏度和剪切应力适中,符合实际应用需求。

During the construction of the cross-river shield tunnel,the abundant groundwater fills the gap between the shield machine and the surrounding rock,it is easy to cause the dilution of the synchronous grouting.Moreover,it may even cause problems such as prolonged gelation time of the grouting,loss of gelled material,and severely insufficient strength in the later period.This kind of problem needs to be solved in the project by improving the stability of synchronous grouting slurry.Based on the Changde Yuanjiang Cross-river Shield Tunnel project,this paper selected four commonly used flocculants to study the effect on the properties of cement-based grouting.Flocculants include polyacrylamide,hydroxyethyl cellulose,hydroxyethyl methyl cellulose.The results of the water-dispersion resistance test of the pulps showed that the pulps with different flocculants showed similar laws.With the increase of the amount of flocculant,the test water samples showed a state gradually changed from turbid to clear and transparent.Continue to increase the amount of flocculant,and the water sample is still in a clear and transparent state.The test results of pure pulp plastic viscosity,shear stress and expansion degree showed that with the increase of flocculant content,the pure pulp plastic viscosity and shear stress showed an increasing trend,and the expansion degree showed a decreasing trend.The increase of the plastic viscosity and shear stress of the slurry increases the bonding ability between the particles of the slurry,which leads to the weakening of the ability of the slurry to flow freely under the action of gravity,and the rheology of the slurry is weakened.Compared with other flocculants,the critical dosage of hydroxyethyl methyl cellulose with a viscosity of 100,000mPa·s is the smallest,and no lumps will appear after being completely dissolved in water.Under the same dosage,its plastic viscosity and shear stress are moderate,which is in line with practical application requirements.