Study On The Grouting Performance Of Nanometer Silica Sol-Ultrafine Cement Based Slurry

The condition of coal occurrence in China is complex,more than half of the coal resources buried under kilometer.Engineering practice shows that it is difficult to solve the problem of water seepage deep in the shaft of a coal mine.Conventional cement-based grout is often difficult to measure in the face of micro-cracks in a kilometer deep well,while chemical grout has some fatal defects,such as toxic and harmful,high price and poor durability.Therefore,it is urgent to develop a new type of ultra-fine cement based slurry with low viscosity suitable for micro-fracture environment.In this paper,on the basis of previous studies,nano-silica sol was used to modify ultra-fine cement-based slurry through laboratory tests.The orthogonal experiment of four factors and three levels was designed,and the viscosity,water dissolving rate,setting time,funnel fluidity,bending strength and compressive strength of nine kinds of slurry were tested.Numerical simulation software was used to analyze and discuss the dominant slurry fluidity in different roughness environments.The main contents of the study include:(1)Analysis of the rheological and strength properties of ultra-fine cement slurry with the admixture under the single factorConfirm the materials used for the slurry by consulting the literature.According to the previous research experience,the general scope of use of admixtures was obtained,the dosage of admixtures was adjusted,and the viscosity,stability and stone strength of each slurry were measured.The optimum proportion range of experimental materials was obtained through the above indexes,based on which the orthogonal test was designed.(2)Performance analysis of nano-silica sol-ultrafine cement-based slurry under orthogonal testBased on the above conclusions,four factors and three levels of orthogonal test are designed.The viscosity,funnel fluidity,setting time,bending strength and compressive strength of each set of ultrafine cement-based slurry were measured in detail.The performance of nine groups of grout was compared,and the influence of various factors on the grout performance was judged by comprehensive scoring method and range analysis,and the order of the main and secondary factors was determined to obtain the dominant solution.(3)Numerical simulation of grouting with different roughness using COMSOL MultiphysicsThree micro-fracture models with different roughness were selected and 2d grouting simulation was conducted using COMSOL Multiphysics to study the influence of different roughness environments on the fluidity of dominant solution nano-silica sol-ultrafine cement-based grout.It is found that the indexes of superfine cement grout change to different degrees under the comprehensive action of various additives.After comprehensive scoring method and range analysis,it was found that under the scoring standard with viscosity as the main technical index and stability,setting time and mechanical properties as the secondary index,the conditions were ranked as ultra-fine fly ash,polycarboxylic acid water reducer,water-cement ratio and nano-silica sol in the order of correlation.The results of numerical simulation show that nano-silica sol can effectively improve the grouting state of ultra-fine cement-based grout,improve the stability of grout while maintaining low viscosity,and improve the fluidity of ultra-fine cement-based grout.It has certain guidance and reference significance for the research and development of low-viscosity grouting and plugging grout suitable for micro-fracture environment.