An Experimental Investigation Of Grouting For Controlling Water And Sand Inrush In Rock Fracture

The disasters of water or sand inrush from rock fractures seriously affect the safety of the underground engineering. Grouting is one of the most popular and important methods to control the water burst and sand inrush in underground construction. Based on the past achievements and experiences, further research of grouting effects and theory is necessary for controlling the disasters. The physical modeling and theoretical analysis were used to study the grouting effects under hydrodynamic condition in rock fractures. Various factors were analyzed for water shutoff, grout diffusion, retaining and seepage pressure in fracture. The mechanism of sealing process and criterion for water shutoff were also studied with the time-dependent viscosity grout in fracture. Grouting was used to control the water and sand inrush with a fracture replica. A visualization test platform was established for grouting to control water and sand inrush. The angle and width of the fracture are investigated in controlling effects. The main contents and results are as follows:(1) The performance of time-dependent viscosity grout and mechanics principle interacting with fractures were studied. The action processes of chemical grout and fractures can be divided into three stages: initial stage, curing stage and stable stage.The cohesion on per unit area increased as a logarithmic function.(2) A grouting test system platform was set up in the laboratory. And the L16(45)orthogonal experimental tests were carried. The results show that the factors for controlling grouting efficiency followed by the initial water flow speed, the fracture aperture width, the grout take and gel time. The grouting effects can be divided into six grades by the sealing effect(SE). The variation of water flow during the tests was summarized as the single peak decreasing type and multi-peak fluctuating. The SE of network-like filling fracture is the best, followed by the flat-shaped fissure, and the opening shape as grouting worst. Grouting effects and reasons were analyzed based on the factors.(3) The grout diffusion in hydrodynamic fracture was analyzed in this paper. The processes of diffusion and sealing can be divided into six types: retained complete sealing, retained sealing and the leading edge with shear crack, scour channel along the side boundary, scour channel cut through the grout, cross-channel and scour broken, zoning stratified diffusion and retained in bottoms. The grout diffusion distance and area during the grouting was analyzed. The grout diffusion scour brokendegree was biggest of the fracture with opening shape along the water flow direction.And the network-like filling fracture was coherent, with a good SE.(4) The diffusion model and mechanism of time-dependent viscosity grouting was established in fractures with flowing water. The model of displaced diffusion-retain / scour model was established. The grout diffusion can be divided into three stages; stage of radiation diffusion, stage of diffusion along the lateral boundaries, and stage of stable retained. The grouting pressure was significantly affected by the SE. The pressure was higher with a better SE. And the value of the seepage pressure near the grouting hole was higher than that on other locations of the fracture. The diffusion mechanism of time-dependent viscosity grouting was discussed based on mechanisms of pressure diffusion and transport diffusion. A mathematical model was discussed based on the Bingham fluid with viscosity time-dependent grout spreading in a fracture with flowing water.(5) The sealing mechanism and criterion of time-dependent viscosity grout were analyzed. According to the gel process of UF resin, the sealing processes can be divided into three stages; fluid diffusion motion stage, gelatinized grout blocking water stage, solidified grout sealing stage. Three targeted conditions for sealing were discussed. The critical values of the grouting flow, time of grouting and the volume of grout were deduced. The grouting criterions of time-dependent viscosity grout were presented, which could be classified into intuitive criterion and conditional criterion.Also the mathematical formulas of each criterion were deduced.(6) The preliminary experiments of grouting for controlling sand inrush in fractures were carried. The grouting experimental platform for simulating sand inrush in tilting fracture was assembled, and the sealing effects and influence factors were analyzed. In the designed condition, the width of fracture had no effect on the critical angle of sand inrush, and there was an upper limit angle of grouting and sealing the sand inrush in fracture. After sand inrush plugged, continuous grouting translated into the osmotic grouting in sand layer, and the seepage pressure had a trend of increasing near the grouting hole. The smaller the fracture width, the lager the seepage pressure.