Study On Calculating Model And Parameters Of Ground Fissure

Ground fissure is a kind of special macro structural planes develop ing in soil. As aunique urban disaster geological phenomenon, it has a great influence both on the groundand underground engineering. It caused the extensive concern of the Chinese and foreigngeologists, and obtained a series of research results. Detail study of the calculation model ofground fissures and method for the determination of parameters and the influence ofparameter change on the ground fissure mechanics behavior has important theoreticalsignificance and practical value. Macroscopic structural planes in the soil，which just likerocks, perform control functions on soil deformation and failure. At present, the macrostructure in soil is lack of systematic study. This paper will taking ground fissure as aspecial macroscopic structural plane, and from aspects of the interface constitutive model,the fissure-plane parameters determination test and the numerical simulation,ect.to studymechanical behavior of ground fissures and its parameters. Here mainly includes thefollowing contents:(1) In this paper, the element type and the constitutive model for describing theinterface problems are summarized and the applicability, advantages and disadvantages,determination method of parameters of each model are discussed;(2) Measure the fissure-plane parameters by repeated direct shear test of remoldingloess and meanwhile study its mechanical behavior. Analyzed the interface shear strengthparameters’ change disciplinarian along with shear times (namely microscopic particles’cumulative displacement) and the change disciplinarian along with soil moisture content.Make a dynamic modification to the direct shear test when analysis the test result, whicheffectively conquers some defects of direct shear test and more ideal results are obtained.The loess fissure-plane tangential stiffness and normal stiffness be measured experimentallyin testing, and then study its regularity along with the change of moisture content;(3) Regard the ground fissures as a contact problem, and conduct numerical simulationanalysis on the ground fissure applying the interface element in FLAC3D. Because the mainactivity of ground fissure is vertical dislocation between hanging wall and footwall, applyvertical displacement boundary conditions on hanging wall’s bottom to simulated practical activity of ground fissure. Study shape parameters、 strength and deformation parameters’impact on surface subsidence. The sensitivity of each parameter of the surface subsidence isobtained by analysis.