适于富水岩溶大孔隙地层防渗加固的水泥砂膏浆

富水岩溶大孔隙地层灌浆是基础处理的一个难题,地层的充填、防渗以及加固要求高,以往常采用砂浆或水泥膏浆进行处理,存在砂浆抗水冲释性能差及水泥膏浆可控性弱、浆液浪费严重等不足。基于膏浆良好的可控性、抗冲释性及砂浆的骨架和填充加固作用等优势,通过大样本长周期室内试验,研制了一种可用于富水岩溶大孔隙地层灌浆充填的新型可控水泥砂膏浆材料。研究表明:水泥砂膏浆与水泥膏浆及砂浆相比,浆液析水率降低至0%~3%;流动度最低可达到10~20 cm,凝结时间在2~30 min内可控可调,浆材具有较高的黏度和初始屈服应力;在流速为0.4~0.6 m/s时,浆材抗水流冲释后的留存率达到85%;浆材的结石率近100%,28 d的抗压强度达到10 MPa左右;浆材成本与普通水泥膏浆相当,且具有环保等方面的社会效益。通过实际工程应用,水泥砂膏浆是富水岩溶大孔隙地层防渗加固的优选材料,但在应用时注意可泵性。

Cement-Sand Paste-slurry for the Seepage-proofing and Reinforcement of Water-rich Karst Macrovoid Formation

The grouting of water-rich karst macrovoid formation is a difficult problem in foundation treatment as the filling, seepage-proofing and reinforcement requirements are high. Commonly used mortar is of poor water-dilution resistance, while cement paste-slurry is of weak controllability and serious waste. In view of the respective advantages of paste-slurry and sand, a novel controllable cement-sand paste-slurry which is suitable for water-rich Karst macrovoid formation is proposed in this paper via long-term indoor test with large sample. Results demonstrate that the cement sand paste-slurry is of large viscosity and initial yield stress with the bleeding rate declining to 0%-3%, the minimum fluidity reaching 10-20 cm, and the setting time adjustable in 2-30 min. In the flow rate of 0.4-0.6 m/s, the slurry retention rate reaches 85% after water scouring and dilution, stone rate is nearly 100%, and the 28 d compressive strength reaches about 10 MPa. Moreover, the cost of the cement-sand paste-slurry slurry is equivalent to ordinary cement paste-slurry; the slurry also has social benefits such as environmental protection. Although cement-sand paste-slurry is the preferred material for the seepage-proofing and reinforcement of water-rich karst macrovoid formation, the pumpability should receive enough attention in practical engineering application.