Research On Detection And Stability Of Goafs Under Expressways

The goaf is a huge potential threat to expressways, due to it’s residual deformation has the characteristics of concealment and complexity, the sudden and long-term. At present, studies on the goaf under expressways are weighted too heavily toward construction experience and examples, and theoretical research is neglectesd so that the detection, monitoring, stability studies and governance are lack of sufficient theoretical support. So, researches on detection and stability of goafs under expressways have important practical significance.Rheological mechanics model of goaf roof-pillar system under complex loading is established through the theoretical analysis. Goaf detection-authentication system is set up according to the characteristics of goafs under expressways. and traditional displacement monitoring instruments are improved in order to enhance the applicability of the instrument. The numerical simulation analysis about interactions goafs and expressways reveal the influences that mining depth, mining thickness, dip angle and the size of the cavity on expressways. Then relevant test and numerical simulation researches are carried out to verify the government effect of fly ash foamed concrete for bashing. The results show that:(1) A rheological mechanics model of goaf roof-pillar system under complex loads is established and it’s reliability for forecasting the time of goaf stability is verified by engineering examples.(2) The detection-authentication system about goafs under expressways is established. The results of drilling and sampling at characteristic locations, acoustic detection and imaging technology Inside the hole verify the reliability of detecting goafs by multi-electrode resistivity method, then the detection-authentication system is amended by adjustment method and finally determine positions and status of goafs under expressways.(3) Traditional monitoring instruments improved are more applicative and the steel pipe-piston sealing technology is reliable to bottom seal and avoid grout runout.(4) The residual settlement and range when expressways and goafs space intersecting is smaller than when expressways and goafs have a same trend, and the residual settlement, horizontal displacement and deformation band of expressways are small when angle of goaf tilt is small, but the height of inbreak and fracture region is a definite value coupling with a certain mining thick, and a larger mining thick make a greater bending thickness and the boundary of subsidence curve is more Smooth.(5) A prediction program of maximum residual deformation is established according to the multi-dimensional interpolation of deformation of expressways influenced by deep- thickness ratio, dip Angle and filling effect.(6) The compressive strength of fly ash foamed concrete used to fill goafs is 0.4-2.8 MPa. And tests and numerical simulations verify that the filling body reducing subsidence of expressways is above 70%.