Abstract
Foundation pit envelope and foundation pit excavation solution design is a multidisciplinary problem that could be linked to a series of safety issues in the geotechnical engineering of an actual construction project. Moreover, the construction of large deep foundation pit in soft soil often faces greater risks and challenges as the support structure deforms more easily and unpredictably. In order to improve the deformation prediction of deep foundation pit engineering precision and efficiency and to ensure that the construction of deep foundation pit engineering is safe and efficient, in this article the traditional MSD (mobilizable strength design) theory research and analysis, combined with the Jinan formation characteristics of a tunnel in JInan, and new parameters were introduced to the original MSD method theory: the wall itself within the bending strain energy U and support compression elastic potential energy of V. A new law of conservation of energy is constructed, and finally, an optimized MSD method has been proposed, this method is shown in the article. Finally, the results of foundation pit deformation calculation were compared among the optimized MSD method, finite element calculation method, and field monitoring data analysis method, so as to demonstrate the reliability of the prediction system of optimized MSD method and finite element analysis method. The results show that, by optimizing the MSD calculation method, the horizontal displacement of the retaining wall varies depending on the excavation depth of the foundation pit and the form of internal support with the overall peak value of displacement between 0∼0.2% H (H being the excavation depth); the deformation of retaining wall increases gradually with the increase of excavation depth of the foundation pit, and the peak position of deformation gradually moves down with the excavation of foundation pit. The trend of these changes is consistent with the results of the finite element method and field data analysis method, proving that the optimized MSD method is reliable in predicting the deformation of the foundation pit under specific stratum conditions.
Highlights
Constructing a large deep foundation pit in soft soil strata is risky [1,2,3], and the retaining structure of the foundation pit is prone to deformation [4,5]. erefore, it is very important to have a deep understanding of the deformation law of the foundation pit in soft soil strata
MSD is a common method for foundation pit deformation prediction proposed by Osman and Bolton [7] based on the plastic deformation mechanism of cantilever foundation pit excavation and the principle of energy conservation in the foundation pit system. e equation for ground subsidence of retaining wall with internal support was derived, and the practicability of the MSD method was verified
By summarizing the measured data of Hangzhou typical long and narrow soft soil foundation pit, Ma et al [15] concluded the lateral movement law of typical section support of foundation with the MSD method of modified strength analysis and prediction theory. e measured data were analyzed, and the results proved the effectiveness of the MSD method
Summary
Constructing a large deep foundation pit in soft soil strata is risky [1,2,3], and the retaining structure of the foundation pit is prone to deformation [4,5]. erefore, it is very important to have a deep understanding of the deformation law of the foundation pit in soft soil strata. Bolton et al [9,10] calculated the deformation of the foundation pit with internal support using the MSD method, which combines two basic theories of deformation increment method and energy conservation principle and includes the anisotropy and undrained shear strength. By summarizing the measured data of Hangzhou typical long and narrow soft soil foundation pit, Ma et al [15] concluded the lateral movement law of typical section support of foundation with the MSD method of modified strength analysis and prediction theory. Erefore, this powder-clay foundation pit is not completely applicable to the conditions in Jinan In this case, this paper took the actual stratigraphic conditions in Jinan into consideration and introduced new deformation parameters to the traditional MSD theory, namely, the bending strain energy U of the wall itself and the compressive elastic potential energy V of the inner support. Finite element analysis was used as an auxiliary approach to further improve the deformation prediction system of soft soil foundation pit [16]
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