Permeation And Diffusion Mechanism Of Chemical Grout In Porous Sandstone

Construction quality, coal production and coal mine workers’ safety have been deeply threatened by coal mine well construction water damages which always exist in the sandstone of Luohe Formation, the lower of Zhiluo Formation and Xiashihezi Formation in the Western and South margin of Ordos Basin nowadays. The aquifers, as typical poor seepage aquifers, often come from micro-cracks and pores dual media water that shows porous seepage and high flow rates.The water damages always be governed by cement grouting that has been proved to be non-suitable in this area due to some problems, i.e., the low groutability and unsatisfactory reduced permeability. Likewise, chemical slurry grouting also has lots of defects that low filled rate and reduced permeability rate are outstanding.Through comprehensive study of model experiments and theoretical analysis, the seepage channel of porous sandstone, slurries’ groutability and filled effect, as well as their main factors are analyzed, on the basis of rock sampled from several coal mines and structural characteristics of sandstone analysis by SEM and physical index test. Through the study, conclusions can be drawn as follows:(1) Rock were sampled from Luohe Formation, Zhiluo Formation and Xiashihezi Formation that have similar micro and meso structural characteristics, physical and mechanical properties, which show bad grain composition, strong water yield property, low strength, Good pore connectivity and high permeability.(2) From the micro-seepage characteristic analysis of porous sandstone, the result shows that the seepage channels of sandstone are extending in all directions, while still be influenced by seepage channels’characteristic, and only parts of them are active. Converge and by pass happen in turn, and the fluid direction and channel are being changing all the time.(3) The different groutabilty and internal mechanism of slurries are studied using macro and meso model experiments and theoretical analysis. The study shows that the groutabilty of solution chemical slurry is mainly affected by its properties and morphology of seepage channel. The groutabilty of chemical slurry is low due to its high viscosity and tiny seepage channel. Also, particles suspended grouting materials whose disruption mechanism shows “decelerate and gather” is lower due to the resistance of seepage is high in the diameter and direction changing positions.(4) Dimensional seepage unit of porous sandstone was built on the base of water seepage behavior of sandstone. The slurry diffusion and reduced permeability mechanism of miscible and immiscible were studied by the synthesized analysis of uniform laminar flow theory and chemical slurry grouting experimental result. The results show that immiscible slurry flows as piston driven flow in the porous channel. But the flow essence of miscible slurry may be considered as the water flow along with grains. The low reduced permeability after chemical slurry grouting may mainly caused by the changed position of slurry that has been grouted and the systole of slurry.(5) Slurry cylindrical diffusion theoretical model was deduced from the slurry diffusion mechanism. The grouting diffusion radius, grouting pressure, grouting flow rate and grouting lasting can be calculated by this model. The conclusions have been tested and verified effectively, during the chemical slurry grouting of lower sandstone aquifer of Zhiluo formation in the vice shaft of Meihua Coal Mine.