膨润土泥浆改良土压盾构粉细砂渣土流动性机制分析

为了揭示膨润土泥浆改良土压盾构粉细砂地层渣土流动性机制，采用跳桌和十字板剪切仪分别测试改良后渣土的流动度和剪切参数变化规律，分析改良粉细砂渣土剪切应力-应变关系和流变模型。结果表明： 1）采用膨水比为1KG-*4]∶KG-*4]4的泥浆掺入质量比7%~13%、膨水比为1KG-*4]∶KG-*4]6的泥浆掺入质量比7%以及两者之间的配比和掺量，改良粉细砂渣土可以满足其流动性的要求； 2）仅添加对应量的自由水来改良粉细砂渣土的流动性，无法达到良好的效果； 3）随着泥浆掺入质量比的提高和膨水比的降低，改良渣土的流动度显著增大，且其流动度与剪切应力大小存在负相关关系； 4）采用膨润土泥浆改良后的粉细砂渣土符合Bingham模型，塑性黏度和屈服应力的降低是其流动性增大的根本原因。

Fluidity Mechanism Analysis of Bentonite Slurry ImprovedSoil for Earth Pressure Shield in Silty Fine Sand Layer

To investigate the soil fluidity mechanism of a silty fine sand stratum that is improved by bentonite slurry for earth pressure balance shield, a jumping table and cross plate shear tester are used to test the fluidity and shear parameters of the improved soil. Furthermore, the shear stress strain relationship and rheological model are analyzed. The results are as follows: first, in slurry with bentonite to water ratio of 1∶4 is mixed by a mass ratio of 7% ~ 13%; similarly, that with bentonite to water ratio of 1∶6 is mixed by a mass ratio of 7% to improve the fluidity of the silty fine sand. Second, adding an equal amount of free water does not improve the fluidity of silty fine sand. Third, as the amount of the slurry increases, the ratio of bentonite to water decreases; thereby, leading to an increase in the fluidity of the improved soil. Thus, fluidity is negatively related to shear stress. Fourth, the improved silty fine sand follows the Bingham model, and the decrease in plastic viscosity and yield stress is the primary cause of its increased fluidity.