Influence of sand density and retaining wall stiffness on three-dimensional responses of tunnel to basement excavation

Abstract

Basement excavation inevitably causes stress changes in the ground leading to 38 soil movements which may affect the serviceability and safety of adjacent tunnels. Despite 39 paying much attention to the basement-tunnel interaction, previous research has mainly 40 focused on the influence of tunnel location in relation to the basement, tunnel stiffness and 41 excavation geometry. The effects of sand density and basement wall stiffness on nearby 42 tunnels due to excavation, however, have so far been neglected. A series of three-dimensional 43 centrifuge tests were thus carried out in this study to investigate these effects on the complex 44 basement-tunnel interaction. Moreover, three-dimensional numerical analyses and a 45 parametric study by adopting hypoplastic sand model were conducted to improve the 46 fundamental understanding of this complex problem and calculation charts were developed as 47 a design tool. When the basement was constructed directly above the existing tunnel, 48 excavation-induced heave and strain were more sensitive to a change in soil density in the 49 transverse direction than that in the longitudinal direction of the tunnel. Because a looser sand 50 possesses smaller soil stiffness around the tunnel, the maximum tunnel elongation and 51 transverse tensile strain increased by more than 20% as the relative sand density decreased by 52 25%. Moreover, the tensile strain induced along the longitudinal direction was insensitive to 53 the stiffness of the retaining wall, but that induced along the transverse direction was 54 significantly reduced by a stiff wall. When the basement was constructed at the side of the 55 existing tunnel, the use of a diaphragm wall reduced the maximum settlements and tensile 56 strains induced in the tunnel by up to 22% and 58%, respectively, compared with the use of a 57 sheet pile wall. Under the same soil density and wall stiffness, excavation induced maximum 58 movement and tensile strains in the tunnel located at a side of basement were about 30% of 59 the measured values in the tunnel located directly beneath basement centre. 60

A Precise Prediction of Tunnel Deformation Caused by Circular Foundation Pit Excavation

“…Many research results have been obtained with regard to the effect of tetragonal excavation on the deformation of an adjacent metro tunnel. The main contents of this study are as follows: geometry of the excavation [1,2]; relative position of tunnel and excavation [3][4][5][6][7]; excavation conditions and reinforcement method [8][9][10][11]; tunnel lining stiffness [4] and diameter of tunnel lining [1]; different soil constitutive models [12]; soil relative density and retaining wall stiffness [13]; influence zone [14] and calculation methods [15][16][17].…”

Effect of Soil Reinforcement on Tunnel Deformation as a Result of Stress Relief

“…If the induced tunnel deformation and internal forces exceed the capacity of the tunnel structures, segment cracking, leakage, and even longitudinal distortion of the railway track may occur and seriously threaten the smooth travel and safety of the trains in operation. Many studies have investigated the effects of adjacent excavation on existing shield tunnels using various methods, including in situ monitoring [1][2][3], centrifuge model tests [4][5][6], numerical analysis [7][8][9][10][11][12][13][14][15], and semi-analytical methods [16][17][18][19]. For example, the main objects of investigation have been the excavation dimension [13,15], relative distance between the tunnel and excavation [4,8,9,11,13], construction and reinforcement methods [10,12], tunnel dimension and physical parameters [9,13], soil density and wall stiffness [6], different constitutive models [14], and influence zone [20].…”

Sequential Measurement and Analysis of Large Underground Retaining Structures by Diaphragm Wall Anchor for the Spring Area

“…Meanwhile, the supporting structures and adjacent facilities security are a challenge due to deep excavations construction. erefore, field monitoring of structure deformations and ground movements plays a vital role in excavation process [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Based on the reported field monitoring data, empirical and semiempirical methods have been identified as an appropriate approaches for the prediction of the excavation deformations [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”