砂化白云岩变压力注浆扩散规律研究

Study on the diffusion law of variable pressure gradient grouting in sandy dolomite

为研究滇中引水工程玉溪施工段白云岩砂化对隧道注浆加固的影响,进而揭示浆液扩散规律,综合开展扫描电镜(SEM)试验、理论分析以及多物理场流固耦合数值模拟一系列深入研究。结果表明,白云岩在溶蚀作用下砂化且内部构造发育呈多尺度孔隙-裂隙网络体系分布特征,注浆时浆液扩散迁移的过程中存在前锋面并产生明显指进现象,发育构型不同的裂隙会导致水泥浆液扩散形态的不规则性和非稳定性。相比传统的恒压注浆,变压力梯度注浆更利于对砂化后地层复杂构造发育的多尺度裂隙进行均匀填充,浆液凝固后胶结破碎岩体减小围岩应力分布区域同时缓解拱顶、拱底的应力集中现象,对于提高围岩稳定性具有更加显著的效果。以上研究可为砂化白云岩地层隧道的实际注浆工程设计及施工提供理论参考。

In order to study the influence of dolomite sandification on tunnel grouting reinforcement in the construction section of Yuxi construction section of Yunzhong Water Diversion Project,then reveal the law of slurry diffusion,a series of in-depth studies of scanning electron microscopy(SEM)experiments,theoretical analysis and multiphysics fluid-structure interaction numerical analysis were carried out.The results show that,dolomite sanded under dissolution and developed internal structure with multi-scale pore-fracture network distribution characteristics,during grouting injection,the slurry has a front surface during diffusion migration and produces obvious fingering phenomenon,fractures with different developmental configurations can lead to irregularity and instability of the diffusion morphology of cement slurry.Compared to traditional constant pressure grouting,variable pressure gradient grouting is more conducive to uniform filling of multi-scale fractures developed by complex strata after sanding,after the slurry solidifies,the cemented and broken rock mass reduces the stress distribution area of the surrounding rock,and alleviates the stress concentration phenomenon of the vault and arch bottom,it has a more significant effect on improving the stability of surrounding rock.The above studies can provide a theoretical reference for the actual grouting engineering design and construction of sanded dolomite strata tunnels.