Abstract
Shield tunneling is becoming the preferred construction scheme for metro construction because of its advantages of fast construction speed and small disturbance. However, limited by process defects, the stratum movements induced by the construction of shield tunnels still affects the safety of nearby underground structures and aboveground buildings. Therefore, the reliable prediction of stratum movements is important. Described in this paper is an analysis method of the Greenfield stratum movements (Greenfield is an area of land that has not yet had buildings on it, stratum movements means the movement of various soil layers) caused by shield tunnel construction combining an elastic half-space model of mirror source–sink method with the use of modified analytical method. Based on the theoretical formula in this paper, not only can the curve of surface settlement trough be calculated, but also the three-dimensional displacement field of deep soil can be obtained. By comparing vertical and horizontal contour maps of Greenfield stratum movements, good consistency between theoretical formula results and centrifugal test results are shown. This solves the defects and limitations of existing two-dimensional formulas; furthermore, based on this, it is convenient to evaluate the effect on the other skewed underground structures through the elastic foundation beam and other similar methods; therefore, this paper can provide a wide guidance and service for the design and construction of underground engineering in the future.
Highlights
Since the 21st century, tunnel and underground engineering in China have made great progress [1,2,3,4,5,6,7]
This paper studies the Greenfield stratum movements caused by shield tunnel construction combining an elastic half-space model of mirror source–sink method with the use of modified analytical method
Compared with the effect of the gap, the stratum movements caused by the additional force on the shield working face and the frictional force between the outer surface of the shield and the surrounding soil during tunnel construction is very small [67]
Summary
Since the 21st century, tunnel and underground engineering in China have made great progress [1,2,3,4,5,6,7]. Yang, et al [32,33,34] introduced this theory into the prediction of stratum displacement caused by the excavation of geotechnical tunnels These studies have the advantages of concise calculation formula and convenient use, they lack a clear theoretical basis of mechanics. Based on field monitoring data, Loganathan, Jiang, and other researchers [44,45,46,47,48,49,50,51] modified the stratum displacement pattern by exponential function and deduced the prediction formula of surface subsidence under non-equivalent radial movement pattern Most of these methods are only suitable for three-dimensional orthogonal plane or two-dimensional cases, which have great defects and need to be improved urgently. Based on this improved solution, it is convenient to evaluate the effect on the other skewed underground structures through the elastic foundation beam and other similar methods; this paper can provide a wide guidance and service for the design and construction of underground engineering in the future
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