微裂隙中水泥浆液渗滤效应的可视化试验研究

在微裂隙岩体注浆过程中,水泥浆液的渗滤效应对注浆效果的影响显著。自主研制了一套微裂隙注浆可视化试验系统,该系统由注浆系统、微裂隙模型以及监测系统3个部分组成,监测系统又分为显微监测系统和压力流量监测系统。当水泥浆液进入微裂隙模型后,利用显微监测系统对裂隙入口处的渗滤效应进行实时观测。利用压力流量监测系统对注浆试验过程中的注浆压力以及累计流量进行自动记录。运用自主设计的微裂隙注浆可视化试验系统,对微裂隙中的水泥浆液渗滤过程进行试验研究。采用3种水泥浆材(超细水泥Ⅰ、超细水泥Ⅱ和普通水泥),研究在注浆压力2.0 MPa、水灰比1.0的条件下,不同水泥颗粒粒径大小在不同裂隙开度下的浆液渗滤效应。通过试验发现,当裂隙开度较小时,在裂隙入口处形成了完整的半圆拱形滤饼;随着裂隙开度的增加,在裂隙入口处形成断续分布状滤饼;当裂隙开度增加到无渗滤发生时,裂隙入口处仅残留少量水泥颗粒附着物。通过试验获得了3种水泥的最小可注入裂隙开度大小b min和最小无渗滤裂隙开度大小b crit:超细水泥Ⅰ的b min和b crit分别为80和280μm;超细水泥Ⅱ的b min和b crit分别为100和300μm;普通水泥的b min和b crit分别为140和310μm。研究结果发现水泥粒径的减小对最小可注入裂隙开度大小的影响较大,但对最小无渗滤裂隙开度大小的影响较小。结合渗滤趋势k值,发现随着水泥粒径的减小,相应的k min和k crit值会随之增加,水泥浆液更容易在裂隙入口处发生渗滤,这是因为超细水泥比表面积更大,水泥颗粒间易发生团聚。

Visual experimental study on the infiltration effect of cement slurry in micro-fractures

During the grouting process of micro-fractured rock mass,the infiltration effect of cement slurry has a significant influence on the grouting effect.The self-designed micro-fracture grouting visualization test system was developed,which consists of grouting system,micro-fracture model and monitoring system.Monitoring system are further divided into the microscopic monitoring system and the pressure and flow monitoring system.After the cement slurry enters the micro-fracture model,the microscopic monitoring system is used to observe the infiltration effect at the entrance of the fracture in real time.The pressure and flow monitoring system is used to automatically record the grouting pressure and cumulative flow during the grouting test.The self-designed micro-fracture grouting visualization test system is used to conduct experimental research on the cement slurry infiltration process in micro-fissure.Using three types of cement slurry materials(ultrafine cement I,ultrafine cement II,and ordinary cement),under the conditions of grouting pressure of 2.0 MPa and water-cement ratio of 1.0,the slurry infiltration effect of different cement particle sizes under different fracture openings was studied.The results show that when the fracture opening is small,a complete semi-circular arch filter cake is formed at the entrance of the fracture.With the increase of the fracture opening,intermittent filter cakes are formed at the entrance of the fracture.When the fracture opening is increased to the extent that no infiltration occurs,only a small amount of cement particle attachment remains at the fracture entrance.The minimum injectable fracture opening size b min and the minimum non-infiltration fracture opening size b crit of the three cements were obtained.The b min and b crit of the ultrafine cement I were 80μm and 280μm,respectively.The b min and b crit of ultrafine cement II were 100μm and 300μm,respectively.The b min and b crit of ordinary cement were 140μm and 310μm,respectively.The reduction of cement particle size has a greater impact on the minimum injectable fracture opening,but has a smaller effect on the minimum non-infiltration fracture opening.Combined with the percolation trend k value,as the particle size of the cement decreases,the corresponding kmin and kcrit values increase accordingly,and the cement slurry is more susceptible to percolation at the fracture entrance.This is because the ultrafine cement has a larger specific surface area and is prone to agglomeration between cement particles.