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| Closed-form solution of excavation effects induced by shallow tunnel considering air pressure |
| ZHANG Zhiguo1，2，3，BAI Qiaomu2，ZHAO Qihua3，WANG Weidong4 |
| (1. Key Laboratory of Geohazard Prevention of Hilly Mountains，Ministry of Land and Resources，Fuzhou，Fujian 350002，China；2. School of Environment and Architecture，University of Shanghai for Science and Technology，Shanghai 200093，China；3. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection，Chengdu University of Technology，Chengdu，Sichuan 610059，China；4. East China Architecture Design Institute，Shanghai 200002，China) |
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Abstract A method to calculate the long-term and short-term soil displacements and liner stress affected by tunneling in saturated ground was proposed based on the oval deformation mode under two conditions of excavation with or without air pressure. It was observed that the soil deformation curves under the oval deformation mode are in good agreements with the measured values. The excavation under air pressure generates a larger soil deformation than under the non-pressure condition. The long-term settlements in saturated ground are larger than the short-term ones. The variation of the displacement of liner in saturated ground was investigated through parametric analysis. The results show that the maximum negative value of radial displacement of liner occurs at 90° while the minimum one at 270°，which reflects a significant oval deformation trend and overall subsidence. With the increase of the radius and the decrease of the soil moduli，the deformation trend becomes more obviously. The tangential displacement takes the axis of 90°/270° as the boundary axis，and the positive value is obtained at left semicircle while the negative value is obtained at right semicircle. Increasing the radius and decreasing the soil moduli raise the overall level of tangential displacement values. Investigations on the stress of liner through parametric analysis，indicate that the axial force is more likely to present a clear elliptical deformation trend when the tunnel gets stiffer ground or larger gap. The bending moment becomes smaller with the decrease of the depth，the radius and the weight of the soil. The bending moment becomes larger with the decrease of lateral earth pressure coefficient k. The increasing of air pressure results in the rise of the range of compression zone and the values of both positive and negative bending moments.
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2017, Vol. 36 
