The Analysis Of Stress And Deformation In Expressway Widening Engineering Used Foamed Lightweight Soil On Soft Soil Foundation

Aiming at the expressway widening engineering on soft soil foundation in the southeast coastal area, the treatment view of widening subgrade should be changed by analyzing disease mechanism of it and the control of uncoordinated deformation, as well as the combination of lightweight material which is used currently and extended widely. This implies that the view of improving bearing capacity and consolidation degree of soft-soil foundation should be transformed into the thought of decreasing the overlying additional load. The purpose of the transformation is to reduce treatment intensity of soft-soil foundation and optimize design of retaining wall structure rationally by controlling properties of the widening subgrade filler.Combining practical monitoring of earth pressure with numerical simulation analysis by finite element method, the study is started mainly in the following three aspects by taking the widening subgrade project from tianjin to tangshan as research object, which is used foamed lightweight soil as filler.Firstly, the main physico-mechanical parameters characteristics and engineering application mechanisms of foamed lightweight soil is summarized. Moreover, the control measures concerning consolidation settlement of soft-soil foundation are analyzed on principle based on the effective stress principle and the influence of hard crust, the mechanical mechanism of foamed lightweight soil is analyzed emphasisly when it is applied to widening subgrade on soft-soil foundation. Simultaneously the significant factors of earthwork synthetic material are put forward explicitly when it is used for cohesion in widening subgrade which is filled with lightweight soil plate body.Secondly, the elastic-plastic theory of geotechnical materials is studied from the perspective of internal mechanism of plastic deformation produced by it, which is different from metal materials. In addition, it is pointed out that the applicabilities of foamed lightweight soil to DP ideal elastic-plastic model according to the mechanical properties of it. Furthermore, in combination with the construction characteristics of foamed lightweight soil and the influence of construction stage, non-linear structural analysis of stress response in widening subgrade construction process and different section size is carried out by the technique of initial stress field which is applied by the gravity of old subgrade and foundation, as well as element birth-death technique of old slope excavation and layer pouring of lightweight soil. At the same time, the force-transferring mechanism of lightweight soil plate body on the pouring interlayer and basement is put forward which is considered to be similar to rigid foundation. Combining the hard crust effect with load distribution characteristic of lightweight soil, the tendency of displacement development at different widening subgrade locations is also explored, thus clarifying the stress weakness region and concentration region of displacement development in the widening subgrade filled with lightweight soil.Finally, the global stability of widening subgrade filled with foamed lightweight soil is analyzed according to strength reduction principle, the influence of three factors on the development of plastic zone and horizontal displacement are also explored. The factors include material parameters of foamed lightweight soil, shear strength parameters of soft-soil foundation and the existence of hard crust. Furthermore, the high-narrow model and low-wide model of widening subgrade are compared emphasisly in aspect of the formation characteristics of plastic zone and unstable failure mechanism, thus providing guidance for adjusting material parameters of foamed lightweight soil, determining the important position of cohesion treatment by earthwork synthetic materials and raising the reinforcement pertinence of soft-soil foundation.