基于宾汉体浆液的黄土可控劈裂注浆研究

Study on Controllable Splitting Grouting of Loess Based on Bingham Fluid

浆脉在土体的分布在很大程度上影响注浆效果,为了在黄土中实现浆脉可控劈裂注浆,采用平板窄缝模型推导了宾汉体浆液在黄土中的扩散理论,得出扩散半径与注浆压力差、裂缝参数、浆液性质等参数有关。以此为出发点,设计现场注浆试验,结果表明:通过控制注浆参数和施工过程可基本实现浆脉尺寸、间距等与设计值偏差在±40%以内;浆液压力较低时在黄土中主要以挤压作用为主,挤压扩散半径约为注浆管直径的1.2~2倍,压力较高时以劈裂为主;试验最终形成的复合地基桩芯结实体在深度越浅处强度越低,实际注浆中应考虑提高地表处结实体强度,为实际注浆工程中注浆参数的设计提供一定参考。

At present,most grouting designs are blind,some grouting parameters rely on experience,and the control of grouting process is not suitable enough,which cannot ensure the grouting quality,but also hinder the further promotion of splitting grouting.The slurry is mainly in the form of softening of the loess.Most of the cracks formed in the grouting hole surface are vertical cracks and horizontal cracks which appear at the shallow depth.The slurry diffuses in the cracks and eventually condenses and hardens to form slurry veins.The distribution of the slurry veins in the soil greatly affects the grouting effect.In order to realize controllable splitting grouting in the loess,The diffusion theory of Bingham slurry in loess is extrapolate by using the flat narrow seam model.It is concluded that the diffusion radius is related to the parameters such as grouting pressure difference,crack parameters and slurry properties.Taking this as the starting point,the field grouting test is designed.The results show that by controlling the grouting parameters and construction process,the deviation of slurry vein size and spacing of the design value can be realized within±40%;when the grout pressure is low,the loess is mainly extrusion is the main effect,and the extruding diffusion radius is about 1.2~2 times the diameter of the grouting pipe.Splitting is dominant when the pressure is higher;the core structure of the composite foundation pile formed in the test has a lower strength at a shallower depth.Therefore,the actual grouting should consider increasing the strength of the surface structure,which provides a certain reference for the design of grouting parameters in the actual grouting project.