Grouting Diffusion Mechanism In Mud Filled Fault Fracture Zoneof Tunnel And It’s Engineering Application

With the development of tunnel construction in our country, faults and karsts and other bad geological conditions are often encountered during construction process. Especially weak water fault fracture zone are easily caused by tunnel construction geological hazards, such as sudden water inrush of mud, is an important factor affecting the safety of tunnel construction. At present, grouting method has been widely used for geological disaster governace, with a series of success. However, rock mass media interact with slurry and its mechanism is very complex, the development of study of grouting theory is far left behind engineering practice. Especially weak watery stratum of grouting diffusion theory research is still in the initial stage of exploration and reinforcement mechanism and not formed the system theory, leading to result in grouting project design and construction of blindness and empirical. So it urgent need for a system scientific theory guidance. The article is based on tunnel of sudden water inrush disasters mud grouting governance theory and technology as the research target, research is mainly focused on the slurry in the fault argillaceous filling medium splitting diffusion theory, and studies the fault structure of grout in the fault section and surface diffusion mechanism. Finally considering the comprehensive condition and medium conditions, studied mechanism of reinforcement surrounding rock in splitting, penetration and comprehensive, and put forward the preferred method of grouting reinforcement ring thickness is proposed.(1) Study the slurry splitting diffusion theory in fault argillaceous filling medium. The process of split grouting is suggested as horizontal radiation circle, centered on grouting hole, and the equation of slurry motion in splitting channel is derived. The fracture mechanics theory is introduced; the theoretical model of a circle crack in axle symmetrical space, under nonlinear distribution loading on crack surface, is established; and finally, width of splitting channel and spatial regression equation of grouting pressure is obtained. The influences of width of splitting channel, spatial attenuation law of grouting pressure, slurry parameters and soil mechanic parameters on the process of slurry diffusion are analyzed.(2) A set of variable angle in 2-D single structural plane for grouting diffusion model test system is designed to research the diffusion law of grout in fault zone structure. Simplified the fault zone structure to a single flat surface structural plane, designed a variety of structural angle to simulate its anisotropy. Based on this system,45 groups of tests are carried out. Tests showed the grout in flat surface formed a U-shape, which changed into comet-like when oblique.(3) A large proportion of the 3-D fault grouting model test device is designed, which consisted of the main medium filling section, grouting section, grouting information acquisition section, real time image information acquisition section and high pressure sealing section. The device has the function of filling in-situ fault medium, high pressure grouting and restoring the fault real grouting environment. Data showed that grouting pressure and velocity take on a feature of oscillating change, when grout reinforce fault medium with a joint action, which splitting plays a major role and compaction and filling play a minor role. Seepage and soil pressure responded apparently in the grouting process, with the increase of grouting times, pressure presented a certain wave pattern, but the overall increased gradually.(4) Based on the Fluid-solid Coupling Theory, considering the interaction of seepage field and stress field during the tunneling process, a finite element model is established. The coupling system which is consisted of faults, surrounding rocks, grouting reinforced ring and tunnels is simulated and the influence of grouting reinforced ring on the stress field, displacement field and seepage filed is also analyzed. In addition, the thickness of grouting reinforcement ring is optimistically selected by using the variation law of outflow and deformation in tunnel with the thickness of the ring. Finally, the optimum thickness of grouting reinforced ring in Yong Lian tunnel curtain grouting engineering is determined to be 8 meters.(5) For the big flow and high pressure confined water-bearing body, the design methods of grouting and stepped control is presented. This method reliefs the pressure of right tunnel dynamically by drill holes, combined with the water inflow and water pressure of the exposing aquifer, using a stepwise approach to control grouting rate. The Research has achieved a good control effect in the field test of Jiangxi Yong Lin tunnel Treatment Project. And it has broad prospects for engineering applications.