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Prediction and Analysis of Ground Displacement and Stress Caused by the Excavation of a Shallow-Buried Shield Tunnel in a Compound Stratum
(1 School of Civil Engineering, Central South University, Changsha 410075; 2 National Engineering Laboratory for Construction Technology of High Speed Railway, Central South University, Changsha 410075)
Abstract To reveal the distribution of ground displacement and stress caused by the excavation of a shallow-bur? ied shield tunnel in a compound stratum, the Покровский equivalent layer method was applied to simplify the problem into a solution for the displacement and stress distribution in a homogeneous formation. Using the modified Loganathan′s formula, the expressions of ground displacement and strain component and stress component were deduced, and a displacement field distribution prediction model was established. Based on a theoretical prediction model, the predicted and measured values were compared, and the effects of elasticity modulus ratio n of the upper and lower soil layers, the depth of tunnel z and the Poisson ratio μ on tunnel excavation are also discussed. As for a tunnel excavation in a soft interbed stratum, the equivalent thickness K of the soft interbed stratum is introduced.The research results show that: 1) with an increase of the n value, the maximum surface settlement Smax, maximum additional horizontal stress σx and vertical stress σz decrease; 2) with an increase of the z value, the maximum settle? ment increases; 3) with an increase of the μ value, the Smax value decreases and the maximum additional horizontal stress and vertical stress increase; 4) with an increase of the K value, the Smax value increases; and 5) during tunnel construction, displacement and stress diffusion occur in the stratum that is hard at the upper part and soft at the lower part, while displacement and stress concentration occur in the stratum that is soft at the upper part and hard at the lower part.
Abstract：
To reveal the distribution of ground displacement and stress caused by the excavation of a shallow-bur? ied shield tunnel in a compound stratum, the Покровский equivalent layer method was applied to simplify the problem into a solution for the displacement and stress distribution in a homogeneous formation. Using the modified Loganathan′s formula, the expressions of ground displacement and strain component and stress component were deduced, and a displacement field distribution prediction model was established. Based on a theoretical prediction model, the predicted and measured values were compared, and the effects of elasticity modulus ratio n of the upper and lower soil layers, the depth of tunnel z and the Poisson ratio μ on tunnel excavation are also discussed. As for a tunnel excavation in a soft interbed stratum, the equivalent thickness K of the soft interbed stratum is introduced.The research results show that: 1) with an increase of the n value, the maximum surface settlement Smax, maximum additional horizontal stress σx and vertical stress σz decrease; 2) with an increase of the z value, the maximum settle? ment increases; 3) with an increase of the μ value, the Smax value decreases and the maximum additional horizontal stress and vertical stress increase; 4) with an increase of the K value, the Smax value increases; and 5) during tunnel construction, displacement and stress diffusion occur in the stratum that is hard at the upper part and soft at the lower part, while displacement and stress concentration occur in the stratum that is soft at the upper part and hard at the lower part.
.Prediction and Analysis of Ground Displacement and Stress Caused by the Excavation of a Shallow-Buried Shield Tunnel in a Compound Stratum[J] MODERN TUNNELLING TECHNOLOGY, 2017,V54(4): 97-106
2017, Vol. 54 