Research On The Long-term Deformation Of Soil-rock Mixtures In Mountainous Airports

High-fill projects in mountainous areas usually face complex geological conditions,in which local soil-rock mixtures with complicated physical characteristics are frequently used.In order to ensure the operation of the airport,special attention should be paid to the deformation and stability of the filling body.In this thesis,the mechanical properties of the filling materials used in the high fills are studied.The compression properties of filling materials under the influence of various factors are discussed.The time-dependent mechanical characteristics of the materials are studied and a constitutive model considering the shear creep and compression creep is proposed.Moreover,the shear creep behavior of the interface between the filling and bedrock is studied using a newly invented large-scale shearing apparatus.Based on the experimental results,a constitutive model for the interface based on the critical state framework is put forward.The main contents of this thesis are as follows:1.Experimental study on the long-term mechanics of soil-rock mixture is carried out.The compression creep characteristics of soil-rock mixture under different stress were studied by using the large-scale oedometer compression apparatus.An apparatus for the shear creep test of the interface between the filling material and the bedrock is invented,with which several shear tests of different loading paths are conducted.The deformation laws of compression creep and shear creep in these tests are then summarized.2.A three-parameter model describing the compression of the filling material is proposed.The model assumes that samples with the same particle size distribution and grain matter and different initial void ratios will approach the same limit compression line in oedometer compression.Within the framework of this model,the model is capable of describing compression creep,size effect and wetting collapse by introducing three more parameters.3.An elastic-viscoplastic double-yield-surface model is proposed for describing time-dependent behaviors of the filling materials with consid eration of the mechanical characteristics induced by particle breakage.The stress-dependence of the strength,dilatancy/contractibility and creep is carefully considered based on recent experimental findings.Verifications with various experimental results demonstrate that the model is capable of predicting creep in various stress states satisfactorily.Based on this model,a simplified method to predict the post-construction settlement of large-area high fills is suggested.4.An interface creep model is proposed with the concept of critical state soil mechanics,in which the influence of the bedrock roughness on the strength is considered.The model can reflect the short-term and long-term deformation regularities of the interface.