Analysis Of Response Of The Deep Soil And Existing Tunnel Adjacent To Deep Excavation

The horizontal displacements of the retaining piles were monitored through thewhole processes of a deep excavation project. It is found that, due to the differences ofhorizontal bracing stiffness, and the influence of asymmetry of excavation, thedeformation modes of the retaining piles at different locations are different, and themaximal horizontal displacements also have significant difference.Through sophisticated FEM modeling, the characteristics of the displacementfields caused by four deformation modes of retaining structure were analyzed. And theresults show that under the situations of different deformation modes of retainingstructure with the same maximal horizontal displacement, the deep soil displacementfields outside of the excavations can be considerably different, and therefore theimpacts on environment may vary hugely.When the retaining structure exhibits convex or composite deformation mode,the deep soil settlement field can be divided into concave settlement area, triangledeformation area and heave area; for cantilever deformation of retaining structure, thesettlement only can be divided into triangle deformation area and heave area; and thearea of concave settlement caused by the kick-in deformation of retaining structurespreads deeper. Similarly, the horizontal soil displacement induced by convex orcomposite deformation of retaining structure also can be divided into three parts:bow-shape deformation area, transition area and cantilever deformation area; forcantilever deformation of retaining structure, the horizontal soil displacement onlyshow cantilever deformation mode, and range of horizontal displacement induced bythe kick-in deformation of retaining structure is deeper and further.Further, the characteristics of the deformation and internal forces of the existingtunnel adjacent to excavation caused by four deformation modes of retaining structurewere analyzed. And on this basis, combining with the displacement control standardsof existing tunnel, influence areas of excessive displacement of four deformationmodes on the existing tunnel outside the excavation were analyzed and compared.According to the vertical deformation characteristics of the vault and invert ofthe tunnel, the soil layer outside the excavation can be divided into three areas, i.e.,settlement area, transition area and heave area. For the convex and composite deformation of retaining structure, the range and characteristics of each area arealmost the same; the cantilever deformation of retaining structure has less influenceon the vertical deformation of tunnel, leading to the shrink of settlement area; whenthe retaining structure exhibits kick-in deformation mode, the settlement area becomeslarger, and transition area and heave area are considerably compressed.The influenced range of the deformation of existing tunnel caused by thecantilever deformation of retaining structure is the smallest; for the convex andcomposite deformation mode, the ranges are similar and larger than that of thecantilever deformation mode; the influenced range caused by the kick-in deformationmode is the largest among these four modes.In practical engineering, besides the control of the maximal horizontaldisplacements of the retaining structure, the deformation mode of retaining structurealso should be designed according to the surrounding environment, and the kick-indeformation of retaining structure should be avoided.