Accelerated Experimental Study On Permeability For Broken Mudstone With Mass Loss

When coal seams with collapse columns are mined, because of corrosion,washout and abrasive effect, porosity and permeability parameters of collapsecolumns will change with time, and water flow type always changes, which will resultin water inrush. It is now a foundation issue to study seepage of broken rock withmass loss for preventing and curing the disaster of water inrush in collapse columns.Water inrush in collapse columns will happen after a long time process of mass loss,so that the acceleration test is an effective measure to simulate the mass migration andmass loss in collapse columns. Permeability of broken mudstone with mass loss wasstudied by acceleration tests, and the main results are listed as follows.(1) A penetration testing system for broken rock with mass loss was developed,which could embody corrosion, washout and abrasive effect. The penetration testingsystem is constituted by the subsystem of axial loading and displacement controlling,the subsystem of penetration, the subsystem of data collection and analysis and thesubsystem of fine particles recovery, which could satisfied the requirements of bothpump station type and injection syringe type penetration tests, and these twopenetration types could be switched freely.(2) The process of mass changing for broken rock were analyzed under corrosion,washout and abrasive effect, the expressions of the rate of mass loss and rate ofchange of the apparent density were established, and the mechanism of massmigration and mass loss of broken rock was explained.(3) Based on penetration acceleration test for broken mudstone with mass loss,the function relationship among the rate of mass loss, porosity and time wasestablished, and the genetic algorithm was constructed for the shape parameters of thefunction relationship above. The rules of influence on the rate of mass loss fromTalbol power exponents and initial porosities were obtained.(4) Based on penetration acceleration test for broken mudstone with mass loss,the genetic algorithm was constructed for permeability parameters for brokenmudstone with mass loss, and changing rules of influence on permeability parameters(including permeability, non-Darcy flow β factor and acceleration coefficient) fromTalbol power exponents and initial porosities were obtained.(5) Based on the test of water flow type changing for broken rock with mass loss,relationships between duration of mass loss and Talbol power exponents, initial porosities, pressure gradients were obtained, as well as relationships between lostmass and Talbol power exponents, initial porosities, pressure gradients. Theconditions of water flow type changing were established, and the mechanism ofseepage instability of broken mudstone was explained from the viewpoint of massloss.(6) Considering the influence on the rate of mass loss from acceleration factor,the dynamic model of seepage system for broken rock with mass loss was constructed,and computing method of the response of the dynamic system was designed, the timechanging process of the rate of mass loss, porosity, permeability, non-Darcy flow βfactor, acceleration coefficient, pressure and seepage velocity for broken rock underkinds of Talbol power exponents, initial porosities, pressure gradients were simulated.