Abstract
The surrounding ground settlement and displacement control of an underground diaphragm wall during the excavation of a foundation pit are the main challenges for engineering safety. These factors are also an obstacle to the controllable and sustainable development of foundation-pit projects. In this study, monitoring data were analyzed to identify the deformation law and other characteristics of the support structure. A three-dimensional numerical simulation of the foundation-pit excavation process was performed in Midas/GTS NX. To overcome the theoretical shortcomings of parameter selection for finite-element simulation, a key data self-verification method was used. Results showed that the settlement of the surface surrounding the circular underground continuous wall was mainly affected by the depth of the foundation-pit excavation. In addition, wall deformation for each working condition showed linearity with clear staged characteristics. In particular, the deformation curve had obvious inflection points, most of which were located deeper than 2/3 of the overall excavation depth. The characteristics of the cantilever pile were not obvious in Working Conditions 3–9, but the distribution of the wall body offset in a D-shaped curve was evident. Deviation between the monitoring value of the maximal wall offset and the simulated value was only 4.31 %. The appropriate physical and mechanical parameters for key data self-verification were proposed. The concept of the circular-wall offset inflection point is proposed to determine the distribution of inflection-point positions and offset curves. The method provides new opportunities for the safety control and sustainable research of foundation-pit excavations.
Highlights
Underground continuous walls have been widely applied as foundation-pit supports due to their high stability, rigidity, and impermeability, in addition to their predictable deformation characteristics
Results showed that the bending moment of the underground continuous wall was largely generated due to the cracking of the wall, and that the lateral displacement of the wall was not affected by this factor
It was determined that the surface settlement of a circular underground continuous wall is mainly controlled by the depth of foundation-pit excavation
Summary
Underground continuous walls have been widely applied as foundation-pit supports due to their high stability, rigidity, and impermeability, in addition to their predictable deformation characteristics. For circular anchor foundation pits with underground continuous walls as the predominant retaining structure, monitoring and predicting wall displacement and surface settlement around the foundation pit remain challenges. Bolton and Powriet [1] carried out various laboratory tests to study the deformation characteristics of an underground continuous wall under different soil conditions and foundation-pit parameters They calculated the deformation and failure conditions of the foundation pit. To better analyze foundation-pit support systems, Kishnani and Borja [5] conducted detailed analysis of the soil structure and seepage into the foundation pit, and analyzed the impact of these two factors on the support system They determined that the seepage affected earth pressure behind the wall and caused the surrounding ground to settle. There was no analysis of ground settlement around the foundation pit and the deformation of the supporting structure, and the validity of the parameters in the simulation process was not verified
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