Properties and field application of the grouting material for water blocking during thawing of frozen wall of deep sand layer

The Salawusu aquifer in the Ordos coalfield is characterized by large thickness and water abundance. Most wells built in such water-rich sand layers are constructed by artificial freezing method. After thawing of the frozen wall, the original crack in the shaft wall gradually expands, penetrates, and even cracks because of the high external water pressure, then, resulting in water inrush and sand collapse. In order to solve the above problems, we adopted the method of laboratory tests to conduct the properties tests of cement slurry with various additives in low temperature environment. The setting time, strength, and rheological properties of the cement slurry with addition of NaCl, Ca(HCOO)2, CaCl2, and sodium silicate were studied respectively. The research results showed that NaCl, Ca(HCOO)2, CaCl2, and sodium silicate could effectively shorten the setting time at low temperature. The addition of NaCl, Ca(HCOO)2, and CaCl2 in cement slurry has a critical amount. When NaCl, Ca(HCOO)2, and CaCl2 amounts were lower than the critical amount, the setting time of the cement slurry was negatively correlated with the addition amount; while when they were higher than the critical amount, the setting time was positively correlated with the addition amount. For cement slurry with sodium silicate, the setting time was negatively correlated with the sodium silicate amount and temperature. The viscosity and shear stress of cement slurry without addition were less affected by temperature, and NaCl, Ca(HCOO)2, or CaCl2 could slightly reduce the viscosity and shear stress. With water-cement ratio of 1:1 and 5%NaCl was added, the cement slurry achieved good results for ground grouting in field application. It has obvious effects on flood control and sand fixation of water-rich sand layer, and could exert great influence on water blocking, material source reducing, and dynamic water head decreasing.