EXPERIMENTAL RESEARCH ON LOESS GROUTING MATERIAL FOR COAL GOB FILLING

Coal has been widely mined in China to support the rapidly developing economy. A great number of gob zones have appeared in almost all provinces of China, especially some provinces with rich coal resources such as Shanxi province, Shaanxi province and Xinjiang province. Gob is dangerous to construction, especially to highways and high speed railways. At present, grouting filling is the main way to reduce engineering hazards in gob area. Fly ash cement slurry is the most commonly used materials in goaf management. Because of lack of fly ash in some goaf treatment project, it is necessary to look for another low-cost grouting material. Loess cement slurry has the advantages of both simple process and reserves of local material. It is considered to be one of the best alternative grouting materials for grouting filling. The property of loess cement slurry is studied in this paper. Firstly, loess samples are collected in Jingyang city of Shaanxi province, Lanzhou city of Gansu province and Lvliang city of Shanxi province. They are taken as experimental materials. Secondly, a large number of loess cement slurry tests on slurry viscosity, stone rate and consolidation strength are performed. Finally, the factors affecting the characters of loess cement grouting material are discussed. They include cement content, water solid ratio and loess type. Results show that with the increase of loess content, the consolidation strength and the liquidity of slurry are reduced, and the setting time is extended. The early consolidation strength of cement loess slurry is low, and the later strength grows larger. The main reason that leads to the difference of loess cement slurry properties lies in regional distribution of loess. The consolidation strength becomes higher as the average grain size becomes coarser. Compared with the Lishi loess slurry, Malan loess slurry performance is stable and intensity is higher. For this reason, Malan loess is more suitable for grouting filling. With the increase percentage of sodium silicate, the viscosity and concretion rate increased, the setting time shortened, and the strength decreased. This research provides a new material of goaf grouting filling and has important practical values.