Abstract
Combined with the soft clay layer of Foshan metro, a back-analysis method combining model test and numerical simulation is developed. First, the similitude criterion for the model used in this study was derived from similarity theory and elasticity mechanics equations. Artificial clay is prepared by mixing kaolin, bentonite, loess, and river sand in proportions of 4 : 2: 3 : 1. Gypsum, water, and borax are mixed in proportions of 1 : 0.7 : 0.015 to simulate the tunnel lining. The model tests were carried out based on four load modes: the combination of mode 1, vertical load distribution and horizontal load linear distribution, mode 2, vertical load distribution and horizontal load parabolic distribution, mode 3, vertical load parabolic distribution and horizontal load linear distribution, and mode 4, vertical and horizontal load parabolic distribution. Then, the calculation model corresponding to the four load modes is established using ABAQUS, and the measured data is back-analyzed as the known quantity. The specific load values obtained were 359 kPa, 380 kPa, 361 kPa, and 368 kPa by the load-internal force curve. The bending moment and axial force are calculated by substituting the back-analysis load values back into the model and comparing the results with the measured values; it was found that the internal forces under the back-calculation load still deviated by varying degrees. By using the comprehensive error function E to evaluate the advantages and disadvantages of the four distribution modes, the comprehensive errors are 4.3%, 1.7%, 6.5%, and 5.9%, respectively. That is, the error of load distribution of mode 2 (the combination of vertical load distribution and horizontal load parabolic distribution) is the lowest and is highly consistent with the measured value, which is the closest to the characteristics of the load pattern of the stratum.
Highlights
Driven by the strong economic development of China, the urbanization process has continued to grow, especially in coastal cities
E specific load values obtained were 359 kPa, 380 kPa, 361 kPa, and 368 kPa by the load-internal force curve. e bending moment and axial force are calculated by substituting the back-analysis load values back into the model and comparing the results with the measured values; it was found that the internal forces under the back-calculation load still deviated by varying degrees
In this paper, based on the typical water-rich soft clay layer present in the Foshan area, a 1 : 30 similarity model test is designed by using similarity theory, and the ABAQUS finite element software is used to carry out an inversion analysis
Summary
Driven by the strong economic development of China, the urbanization process has continued to grow, especially in coastal cities. E construction of urban subways can relieve traffic pressure and improve productivity. Efficiency promotes urban economic development and further accelerates the pace of modernization [1,2,3]. Rail transit construction can be divided into civil engineering construction and mechanical-electrical equipment construction, primarily including locomotive purchase and signal system construction, of which civil engineering costs account for 70% of the total subway construction costs. Beijing Metro Line 4 represents a construction investment of 15.4 billion RMB, of which 10.7 billion RMB is slated for the construction of civil engineering projects, and the cost of the subway segment accounts for 40% of the total cost [4, 5]. Beijing Metro Line 4 represents a construction investment of 15.4 billion RMB, of which 10.7 billion RMB is slated for the construction of civil engineering projects, and the cost of the subway segment accounts for 40% of the total cost [4, 5]. erefore, how to simplify segment design and reduce material costs has become a pressing issue in current research and how to determine the distribution law of water and soil pressure around segments and the size of external loads has become the first crucial link in accomplishing material reductions
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