Study On Stability Of Embankments Of Red Layers Subjected To Unsaturated Seepage

With the development of railway line for passenger traffic, in order to cater operation requirements of railway line for passenger traffic, Subgrade design compared with ordinary railway is needed a great deal of change, which embodies the point: Subgrade past is mainly on the strength to cater the requirements, but it is emphasized on strict control of embankment settlement in subgrade design of railway line for passenger traffic, and meanwhile the embankment slope stability is needed higher requirements. While most embankments are basically unsaturated soil, slope stability and deformation theories of embankment compared with saturated soil, are more complex, in view of the red layers easily collapsed and other characteristics, therefore evaluations of red layers fillers which can cater needs of railway line for passenger traffic or not become more complex. In this paper directly towards constructions of railway line for passenger traffic from Chongqing to Suining, Sichuan and double line from Dazhou to Chengdu Sichuan, which are across development zones of red layers mudstone, with study of red layers mudstone of Jurassic Suining Group detailed studies are carried out on engineering geology characteristics of red layers fillers, slope stability subjected to rainfall, unsaturated soil embankment settlement.With conventional chemical methods electron microscopy X-ray diffraction and mercury injection test, chemical mineral composition structural characteristics and physical parameters of red layers mudstone have been obtained; Hydrophysical properties of red lays fillers such as swelling and collapsion have been estimated by Laboratory testing of swelling and collapse indoor and outdoor;And at the same time through triaxial testing, penetration testing, CBR test and creep testing on different compactioning sample of the red layers, engineering characteristics of compressive strength shearing strength permeability bearing capacity After soaking and long-term strength have been analyzed.Based on FLAC^2d with its built-in fish language,coupling procedures of unsaturated water-gas two phase flow and runoff have been compiled. On the assumption that the slope surface is of impermeable border, with the analytic solution of the slope runoff, the numerical solution has been testified and with example analysises ,it is showed that in order to accurately assess rainfall influence on the slope stability, coupling borders are proposed , water-gas two phase flow taken into condider.In order to estimate seepage time of model test with different levels of parameters of red layers fillers of different compaction, FEM model of unsaturated water-gas two phase flow were established. With numerical simulation results for input targets different levels of parameters for output and simultaneously model test results for the input variables,unsaturated soil parameters of red layers fillers of different compaction were inversely deducted with RBF neural network model; and with the use of these different compaction parameters corresponding to the initial water saturation of model, numerical simulations on seepage of actual progress of model test were carried out , as a result seepages times of numerical simulation and model test are exactly the same which shows that it is feasible that unsaturated parameters are inversely deducted with RBF neural network model.Based on effective stress theory of single variable of unsaturated soil, unsaturated water-gas two phase fluid-solid coupling equations are established. In considering runoff-underground seepage and fluid-solid coupling of the two, with numerical simulation of engineering examlpe of slope in K240+10～70, railway line from Dazhou to Chengdu, Sichuan, caused damage under rainfall, corresponding characteristics of damage of numerical simulation and examlpe are exactly the same which proves numerical simmlation is feasible, and what's more, with numerical simulations, effects of kinds of factors to slope stability subjected to rainfall were analyzed, with its scope and depth of damage and infiltration depth of rainfall, from which it can be concluded that the intensity of rainfall and lasted time and Long-term strength will cause more effects on slope stability subjected rainfall.Based on results of uniaxial compression creep test of red layers and unsaturated soil single variable, theory of unsaturated soil embankment settlement of red layers is put forward; with numerical simulations of loading process of centrifugal tests, corresponding deformation characteristics are presented which are compared with result of centrifugal tests; and what's more through numerical simulation of embankment construction process of a worksite in Suining, railway line for passenger traffic from Chongqing to Suining, Deformation characteristics and predicted final settlement of numerical simulation and field measurements are exactly the same.