Study on mechanics and micropore characteristics of chemically grouted sand

Chemical grouting is a common method to prevent and control water and sand inrush disaster in coal mining face caused by overlying thick unconsolidated aquifer connected with water flowing fractured zone. In order to study the variation law of micropore, permeability and mechanical properties of chemical grouting consolidated sand, mercury injection test, 3D-XRM system, SLB-1triaxial shear permeameter and uniaxial compression test are mainly used. The variation law of pore characteristics, permeability coefficient, uniaxial compressive strength and Protodyakonov coefficient of chemical grouting consolidated sand are emphatically analyzed.The chemical slurry used in the experiment is modified urea formaldehyde resin, oxalic acid solution is catalyst which can adjust and control the gelation time of chemical slurry. The main conclusions are as follows: the cumulative mercury curve of the sample is S-shaped, which can be divided four stages, namely slow mercury entry stage, accelerated mercury entry stage, decelerated mercuryentry stage and stagnated mercury entry stage;the mercury removal rate is between 52.62% and 99.46%, most of the pores are semi open with poor connectivity; the pore filling rate is higher and the impermeability is better near the slurry splitting vein; the average permeablity coefficientof the test samples is 7.23×10-6cm/s. According to the grading method of rock's Protodyakonov coefficient, the chemical grouted sand can achieve a solid state, which hardness of loose sand sample has been significantly improvedafter chemical grouting, and a good effect of sand consolidation and seepage reduction can be achieved.