The Treatment Of Collapsible Loess Foundation With Lime-soil Cushion And Impermeable Membrane

It is well known that the foundation is an important part of the building, its intensity, stability, reliability and security can affect the normal use of the building directly. To meet the request of upper structure bearing capacity and deformation, it is necessary to take appropriate counter-measures to reduce or eliminate the settlement caused by water and guarantee the use of substation. Combined with the national grid project in Gansu Province, as the collapsible loess, in Jiuzhoutai, Longxi, for the study, the foundation of substation handled with lime-soil cushion and impermeable membrane in the collapsible loess areas was first proposed in this paper.Based on the physical and mechanical properties of collapsible loess, lime-soil and impermeable membrane, two methods, including overall treatment and partial treatment, are proposed to handle the substation foundation, also analysis its performance through a series of measures, such as field research, laboratory experiments, theory and numerical simulation, reveals the mechanism of collaborative work and bearing characteristics. In addition, with the use of FLAC3D to research the stress and strain distribution and variation of lime-soil cushion and collapsible loess in substation foundation for the two proposed treatment programs, in the case of different sectional area, different cushion thickness, different upper load and different distance between foundation centers. The results show:the maximum vertical stress increases with the increase of cushion thickness, diffusion range of the stress expands with the increase of load; settlement decreases with the increase of cushion thickness and increases with the increase of the upper load, moreover, the closer foundation bottom the more obvious effects of settlement; in the same vertical plane, settlement decreases with the increase of the depth, in the same horizontal plane, settlement tends to increase from the edge to the center; in the same load, the foundation bearing capacity of the overall treatment is greater than the partial treatment, the settlement is the former less than the latter, but the difference is small. Therefore, for a project, the determination of what kind of foundation approach is more reasonable, site environmental, economic, construction, etc. should be taken into account. This method has many advantages, like, good impermeable effect, low cost, high construction feasibility and so on. It can not only reduce the settlement effectively and enhance the bearing capacity of foundation, but also provide theoretical and technical supports for the practice of substation and associated engineerings in collapsible loess area.