Experimental Investigation On Grout Propagation Of Grouting Treatment By Horizontal Drilling Along The Floor Aquifer In The Taoyuan Coal Mine

Groundwater inrush from coal seam floor is one of the main factors restricting the safety of coal mining.Grouting into floor aquifers can effectively block the pathway of aquifers,thicken the aquifuges and thoroughly mitigate the threat of groundwater inrush from seam floor to the panels.There have been a lot of studies on floor grouting through vertical boreholes.However,there is lack of related theoretical research with horizontal drilling along layers,which is to be studied and discussed in this paper.The karst medium as the water-conducting pathways affects the connectivity of auifers.It is the direct filling object of grouting.Therefore,it is necessary to study the grout propagation in karst water-conducting media for floor grouting.Based on the grouting treatment project of the floor aquifer in the Taoyuan Coal Mine,Anhui province,theoretical analysis,laboratory model test and microanalysis are adopted in this paper to investigate the grout propagation,mode and pressure responses in different types of water-conducting media.This paper analyzed the characteristics of grout propagation and grouting efficiency.The main conclusions are as follows:?1?The hydrogeological and engineering geological model of grouting by horizontal drilling along floor aquifer was established.By analyzing the geological and hydrogeological conditions of the Taoyuan Coal Mine,it was considered that fracture is the main structural factor affecting the mining area,and that groundwater in limestone of the Taiyuan Formation,gob and fissured sandstone of roof and floor are the direct water filling factors of panels,while groundwater in the Ordovician limestone and the Cenozoic loose strata are indirect water filling factors.The water abundance regularity of limestone in the upper Taiyuan Formation of floor and the karst development characteristics were analyzed.The water abundance is medium to strong of L₁^L₄limestone,and the karst morphology is dominated by karst cracks and holes.The grouting control project and its effect of the floor aquifer in the Taoyuan Coal Mine were analyzed.The regional hydrogeological and engineering geological conditions were generalized.And the hydrogeological and engineering geological model of grouting by horizontal drilling along layer was established.It is clear that the water conducting media are karst pores,fissures,and faults.?2?The scale model tests of grouting by horizontal drilling along floor aquifer were designed and carried out.The limestone in the upper Taiyuan Formation was to be as the geological prototype.Based on the similarity theory and using the similar materials composed of sand,cement and gypsum,the grouting model tests by horizontal drilling along floor aquifer under high pressure were designed,which includes the grouting models of the porous medium,the porous-fissure medium,and the porous-fissure-fault medium.The grouting propagation morphology,fissure filling distance and permeation penetration length were observed in layer by slice stripping model stratum following completion of the tests.And the physical properties of stabilized mass were tested,and micro-analysis was carried out to evaluate the grouting efficiency.?3?According to the test results,the pressure changes and grout propagation of three grouting models were analyzed.Influenced by grouting pressure,the permeation grouting was the main factor in the grouting model of porous media.In the grouting model of the pore-fissure medium,the permeation grouting mainly includes fissure filling,infiltration and fracturing.In the grouting model of the pore-fissure-fault medium,fissure filling was the main mechanism.During the grouting,the changes of pressure and grouting pressure showed a synergistic trend in the grouting model tests,and the increment of water pressure caused by grouting in the closed model would change the stress of the model.?4?The grouting efficiency at different locations from grouting holes was evaluated.The relationship between grout content and position was qualitatively evaluated by the tests of dry density,porosity and mercury injection.The content of pulp vein was the highest,followed by fissure and permeability.The pore types of slurry filling were analyzed.Through mercury injection test and SEM observation,it was found that the slurry is mainly filled in the macro pores,followed by the visible pore.?5?Based on the results of model tests,four grout propagation modes were proposed,including fracture filling mode,fracture filling-permeation mode,fracturing mode and filling-permeation-frcature mode.The injectability of fractured media is divided into three types:injectable,partially injectable and non-injectable.The relationship between grouting injectability and grout propagation mode was summarized.?6?The radius and distance of grout penetration through boreholes in single fissure and karst aquifer was analyzed.The increment of water pressure and water head caused by grouting under closed conditions were analyzed.The penetration length of grout along fissures and karst layers in confined aquifers were obtained.This paper includes 62 figures,25 tables,and 130 references.