Study On The Moisture Infiltration Law And Collapse Deformation Of Loess Subgrade

In the expressway construction engineering, the loess is the main padding of expressway subgrade. Under the interaction of water and upside load, soil bring about collapse deformation, as time goes on, the subgrade sometimes come forth various hazards. The study on collapsible loess of the highway engineering is basically to adopt the criterion and experiment rules of architecture to investigate and design, have not fully considered a good many of characteristics about the expressway. Due to the working circumstance and mechanics condition different to architecture foundation widely, so applying criterion and experiment rules of architecture directly to collapsibility evaluation and calculation on loess expressway is blindness and inconsequence ,the more important is lacks pertinence.Through moisture infiltration simulation and test in situ of subgrade in area of loess, combine with seepage and collapsility data , has proposed collapsibility evaluate method and principle, set up collapsibility evaluate model which suit for practicality engineering and more accurate moistening deformation theory model. The main content is:First of all, according to unsaturated soil mechanics theory, combine liquid phase and gas phase continuity conditions on moisture seepage with Darcy law, strike up two-dimentional uncoupling solution about steady state and unsteady state flow, its finite element equation is obtained through Galerkin weighted residuals principle, via various border conditions and initial conditions, adopt iterated convergence law to all nodal water head and permeability coefficient, which can procure subordinate items such as pore water pressure, hydraulic gradient, flow velocity, etc.Secondly, under the circumstances of rainfall infiltration and soak infiltration, through the finite element analytical method on unsteady state flow, distribution rule of moisture infiltration and permeating depth about saturated and unsaturated area can be analyzed, which under before and after treatment of subgrade,different road embankment height in loess area, at the same time, through rainfall infiltration and soak infiltration test in situ and other relational moisture infiltration data to confirm the accurately about numerical simulation, obtain the normal rainfall infiltration depth distributing law table in seventh loess subarea in case of largest rainfall, offer the reference basis for the collapsibility evaluation and treatment measures on loess subgrade.Finally, consider different actual water source,stress state,the initial wet-sink pressure conditions of loess subgrade, synthesize result of rainfall infiltration,soak infiltration numerical simulation and the test in situ which systemic bring forward loess subgrade collapsility evaluation principles and methods. At the base of that, utilize unsaturated soil mechanics theory and effective stress analysis, according moisture infiltration slug flow model to establish collapsibility evaluation model which suit for practical engineering. At the same time, establish rainfall infiltration and soak infiltration moistening model, research the application secant modulus law to the expressway loess subgrade moistening deformation in theory method.