Study On The Deformation Of TRD Enclosure Structure Deep Foundation Pit Construction

Since the1990s, a large number of public facilities such as high-rise buildings, roads,bridges and subway stations are built in China. The development of deep foundationpit engineering can be described with the following words “deeper, larger, tighter andcloser”, which increases the difficulty in the design, construction and monitoring tosome extent. As a newly developed underground supporting form, the TRD enclosurestructure, with its advantages of uniform wall, nice water-stop, regular thickness,smooth surface, and flexible H-beam setting, draws more and more attention. In thisthesis, based on a deep foundation pit engineering in Nanchang Green Central Square,the deformation of TRD enclosure structure in the process of deep excavation isstudied through on-site measurement, theoretical analysis and numerical simulation.The main work and conclusions are listed as follows:1. The characteristics of deep foundation pit engineering as well as thecharacteristics of TRD method （Trench-Cutting Re-mixing Deep Wall Method）and its applications are introduced.2. The monitoring scheme and on-site measurement data of the deep foundationpit is analyzed in detail. The variations of surrounding road settlement, thedisplacement of the top of the TRD enclosure wall, the horizontaldisplacement of TRD enclosure wall, the groundwater level outside the pitand the axial force of the reinforced concrete braces are summarized. It’sfound that the TRD enclosure poses excellent property of water-stop and soilretaining and is well worthy of further application. The present results can beserved as a reference in the design, construction and monitoring of similarprogram.3. By virtue of the finite element software PLAXIS, combining the practicalexcavation steps, the above mentioned pit engineering is modeled. Thesimulated deformation of enclosure structure and settlement of surroundingroads during the process of deep excavation are compared with the on-sitemonitoring data. The comparing study reveals that numerical and measuredresults agree well with each other and are smaller than the threshold ofengineering design, which infers that the TRD enclosure structure poses high strength and rigidity and the design of foundation pit is conservative. In thiscase, the design should be further optimized so that both the safety and theeconomy can be assured. Our investigation also displays that the numericalmodel as well as the selected parameters are reliable.4. Using the above validated method, the effect of TRD enclosure embedmentdepth, the thickness of wall, the support rigidity and the soil property of onthe deformation of TRD enclosure structure is further investigated. Thepresent results can provide theoretical foundation and optimization target forthe optimal design of enclosure structure and may level up the design of deepfoundation pit engineering.