水泥浆液黏度对全风化花岗岩注浆加固效果的影响

Influence of Grout Viscosity on the Grouting Reinforcement Effect of Completely Weathered Granite

水泥浆液是隧道与地下工程水害治理与地层加固的常用注浆材料。针对利用水灰比调节水泥浆液黏度的传统方法在注浆治理工程中存在的局限性,通过掺加2种外加剂实现了水灰比为1∶1的水泥浆液的黏度和流动度在一定范围内动态可调。选取典型工程中遭遇的全风化花岗岩为被注介质,开展了注浆模拟试验,研究了不同黏度浆液在全风化花岗岩中的扩散规律,分析了浆液黏度对注浆加固效果的影响机制。研究结果表明:水泥浆液在被注介质中整体呈现劈裂扩散模式,随着浆液黏度的增大,主劈裂浆脉扩展形态由"三叉形"逐渐向"折线形"转变,主浆脉宽度变厚,被注介质的单轴抗压强度和抗剪强度不断提高;在水泥浆液黏度为24.6 s时,加固土体的单轴抗压强度提高了87%,内聚力和内摩擦角分别提升了220%和46.6%,内摩擦角与抗剪强度随浆液黏度的变化趋势基本一致,可见内摩擦角的提升可作为影响被注介质抗剪性能的关键指标;临近18.8 s的浆液黏度是浆脉扩展形态转变和被注介质强度增长速率变化的敏感黏度。研究成果可为全风化花岗岩及类似地层注浆治理工程中的注浆材料选型、黏度调控及加固效果评价提供技术参考。

Cement grout is a commonly used grouting material for water disaster control and ground reinforcement in various tunnel and underground engineering applications. Due to the limitations of the conventional method in viscosity adjustment of cement grout by changing the water-cement ratio, this study selected the cement grout with a fixed 1∶1 water-cement ratio as the research object, and two types of admixtures were used to adjust the properties of the cement grout, to realize the aim of dynamic regulation of the grout＇s viscosity and fluidity to a certain extent. The typical completely weathered granite was used as a model medium to conduct the grouting experiment, and the diffusion rules of cement grouts with varying viscosities in the completely weathered granite, as well as the influence of grout viscosity on the reinforcement effect, were investigated. The experimental results indicate that the diffusion of cement grout in the completely weathered granite strata presents a fracturing propagation mode; with the increase in the grout viscosity, the pattern of the grout vein transforms gradually from the ＂three-bifurcation＂ type to the ＂polygonal-line＂ type, and the thickness of the primary grout vein gradually increases. Moreover, an increasing grout viscosity results in the improvement of the overall reinforcement effect, mainly in terms of the compressive and shear strengths of the grouted medium. In addition, as the slurry viscosity reaches 24.6 s, the uniaxial compressive strength of the reinforced soil mass increases by 87%, and the shear strength parameters of cohesive force and internal friction angle increase by 220% and 46.6%, respectively. The change trend of the internal friction angle and the shear strength is basically consistent, which indicates that the increase in the internal frictional angle is a key factor to affect the overall shearing properties of the medium. It is also noted that the viscosity corresponding to approximately 18.8 s is a sensitive value for predicting the change in the grout vein pattern and the variation of rate of improvement of the grouted medium strength. This research can provide references for grout material selection, viscosity regulation, and the evaluation of reinforcement effect in the grouting engineering of completely weathered granite and similar strata.