Stability Reserch On The Guocun Goaf Area Of South To North Water Diversion Middle Route PhaseⅠproject

Goaf stability is one of the major engineering problems for Mid-route South-to-North Water Transfer Project in Yuzhou segment. Factors affecting the goaf stability is very complex, channel construction, channel working and leakage during working will lead to further deformation of goaf, and thus threaten the safe of channel. This paper introduces the domestic and foreign research status about goaf stability and residual settlement prediction achievements, then summed up the basic movement form of goaf strata, introduce the history and treatment measure of guocun goaf, then ultilize qualitative methods, analytical methods, monitoring methods and numerical methods to research the stability of South-to-North Water Transfer Project in Guocun goaf, the residual deformation and the stability in seepage conditions, the specific work is as follow:(1) According to goaf research results in various industries, the main factors affecting the goaf stability underlying South-to-North Water Transfer Project are mining method, top management method, the mechanical properties of the overlying rock and coal seam conditions and mining time; guocun goaf is in residual deformation period and basically in stable condition, but because of the backward of mining methods, top management methods and the influence of channel construction, channel working, potential residual deformation is large.(2) Based on probability integral method subsidence theory, deduce goaf residual deformation formula under gravity effect, calculate the vertical and horizontal terminal residual deformation in guocun goaf which are 331 mm and 82.8mm. Based on profile 4 of guocun goaf, utilize the software FLAC3 D to build two-dimensional model, simulate the construction and working of channel without grouting to study deformation of the field area. The results show that the maximum horizontal displacement locates the ground above both edge of goaf, its value is small; the maximum vertical displacement is 9.32 cm, surface displacement decreases with increasing depth of goaf, with increasing horizontal distance from the channel; channel working has limited impact on the surface deformation.(3) Analysis surface settlement during the construction of channels, the results show: before construction, goaf residual deformation is small and goaf is basically stable; grouting and excavation led to the residual deformation of goaf increased than before, but obviously grouting measure mitigates deformation, total value of surface deformation in field area is small and integral stable.(4) Utilize software FLAC3 D to build three-dimensional model of guocun goaf, weaken the mechanical parameters of Q3 and Q2 strata to simulate three leakage working conditions of channel as follows: no leakage, general leakage and serious leakage. The results show that the values of surface settlement in grouting area is 1-2cm smaller than no grouting area, grouting can significantly reduce residual deformation; vertical displacement mainly distributes in Q3 and Q2 strata, and its maximum, influence range and depth all increase with increasing of leakage level, surface subsidence increment caused in initial stage is greater than the late, the maximum vertical displacement is up to 5.46 cm, while the surrounding rock and the goaf almost no vertical deformation; at the bottom of channel, differential settlement is remarkable, at leakage working conditions, the differential settlement maximum value is 4.2cm and inclination is 2-3mm/m, which can destroy concrete plate of channel; maximum horizontal displacement is 1.24 cm, the effect is relatively small.