Study On The Stability Of Slope Influenced By The Underground Vacant Area

Stability analysis of slope is an important research field of disasterprevention and reduction. There are many factors to effect the slopestability, of which underground vacant area is the exterior factor. The slipof slope and the subsidence of the surface of slope are the destructiveforms that underground vacant area acts to slope. According to theexistent relation of underground vacant area and slope, two cases shouldbe considered: the first one, underground vacant area had existed beforeslope was excavated, such as the underground mined-out area under theslope of strip mine; The second one, slope had existed beforeunderground vacant area was excavated, such as the tunnel excavation inmountainous areas. On the basis of the foregone researches, geneticalgorithm,strength reduction theory and FLAC^3D software are adopted inthe analysis of engineering examples, then the slope stability influencedby underground vacant area is researched. The main research contents areas follows:An improved genetic algorithm is present first, and then, on thebasis of simplied Bishop Method and Janbu Method, CMIGA andRMIGA programs are compiled in Matlab to search for the mostdangerous circle slip surface or the random slip surface shaperespectively, with which the safty factors are calculated. The resultsobtained from three numerical examples indicate that genetic algorithmhaven't obvious advantage compared with other methods in simple slope,but it has obvious advantages in complex slope because this method canget the global optimal solution of optimization problems.Accelerating hybrid genetic algorithm (AHGA) and FLAC softwareare used to analyse how underground mined-out area of different size andlocation influence the slope stability in Jia Gou Aluminium Mine ofAluminium Company in China. According to the variation of the stress,displacement and safety factor of slope, Author synthetically analyse theinfluencing degree of every influencing factor.The least safety thickness of the vacant area roof is the necessarycondition that the surface of slope cann't collapse. Strength reduction technique and dichotomy principle are adopted, and the through cuttingof plasticity zone is regarded to be the destructive criterion, then, the leastsafety thicknesses are calculated by FLAC in Jia Gou Aluminium Mine.The main factors that influence the least safety thickness of the vacantarea roof are gained, and the variation laws that the safety factors of slopefollow the thickness of the vacant area roofs are studied.After the synthetical analysis of the slope stability influenced byundergroud vacant area, the main reasons of slope slip and collapse in JiaGou aluminium mine are obtained. In order to judge if the slope happento slide or collapse, the treatment standard of underground vacant area isput forward.The displacements of slope surface are measured during the shallowburying tunnel is dug in Guankouya, and the variation law is obtainedthrough data treatment and analysis. The displacements of slope surfaceare nearly relative to the location of cutting surface of tunnel. Thedisplacements of slope surface are divided into 4 phases: tinydisplacement phase, faster increase phase, lower increase phase andsteady phase.Based on the after-exploited technology of FLAC^3D, the 3D modelis set up to calculate the displacement of slope surface in the defferentphase of shallow burying tunnel cutting, at the same time, the stress fieldand safety factor are obtained, and the influencing laws that every workcondition of tunnel cutting influence to the slope are concluded. Thecalculation results and the measure data are compared, and we can knowthat calculation result answer the measure data very well, so the resultscan be used to guide construction.Standing at the front of science research, the influence thatunderground vacant area acts to the slope is studied by the author of thedissertation using newly numerical methods and means in the course ofresearch work. It shows a high theoretical and practical value.