Study On The Numerical Simulation Of The Goaf Grouting Of The South-to-north Water Transfer Project

Multiple coal mine goafs under the South-to-North Water Transfer Project havebrought serious threat to the safety of its construction and operation. It becomes anurgent engineering problem to reinforce the coal mine goaf by grouting reinforcementprocess. Grouting is widely used in foundation engineering, pile foundationengineering, tunnel engineering and coal mining fields. Considering the masking ofgrouting and the complexity of lithostratigraphy, numerical simulation has proved tobe a useful tool in grouting projects, which is more flexible and economic thantraditional test methods.Current numerical grouting simulations use single fracture or single grouting holeconditions, which is different from actual grouting situations with complex fracturesor dense grouting holes that interact with each other. Furthermore, in most of thesestudies, the grout flow was assumed to be approximately laminar and described by theseepage control model, which does not correspond to the actual turbulent fluid flow.Therefore, the study of the3D simulation of turbulent fluid for sub-sequence groutingprovided important theoretical significance and practical value for the safe and stablelong-term operation of the South-to-North Water Transfer Project in China.Firstly, based on the3-D geometry model coupled with various geologicalinformation models, a three-dimensional non-steady k turbulence mathematicalmodel considering Bingham liquid character was built on the basis of the research athome and abroad. Body-fitted grid technology was applied for the mesh generation ofthe grouting physical model. Different geological parameters, porosity, resistancecoefficient are adopted for the different geological layers, and then turbulent diffusionlaw of Bingham fluid in goaf was simulated. According to the grouting hole sequence,sub-sequence grouting was achieved. Then, Using the a certain coal mine goaf in themiddle route of the South-to-North Water Transfer Project in China as an example, theturbulent diffusion of a Bingham fluid in a goaf was simulated. The diffusion andpermeation law of grout was analyzed. The numerical simulation results werecompared with the theoretical analysis results and the actual engineering date,showing good agreement and reasonably verifying the model. What’s more, thegrouting effects under grouting pressure standards of0.5,1.0and1.5MPa were compared. The simulation results are as follows:1.Because of the doubled effects of gravity and grouting pressure, the distributionof the Bingham fluid was approximately an inverted funnel shape.2.The diffusion radius of the grout increased as the change rate decreasedgradually with time when the I、II sequence were grouting grouting.3.The filling rate increased as the change rate decreased gradually with time whenthe I、II sequence were grouting grouting.