Abstract
Accurately evaluating the ground pressure on the tunnel lining greatly helps the structure design of a tunnel. In this study, the earth pressure and water pressure on the tunnel lining of four cross sections of a metro tunnel were measured and analyzed and then compared with the theoretical values. Results show that the values and distribution of observed ground pressure acting on the lining are different for different overburden depths. The water pressure measured on-site is approximately equal to the theoretical hydrostatic pressure. The water pressure acting on the shield tunnel lining does not fluctuate with the shield tunnel excavation. The maximum ground pressure was measured in the process of backfill grouting, and the maximum values are approximately larger than 30% of the stable value of the measured pressure. For a shield tunnel under a river with deep water, the water pressure on the lining is dominant and the observed total ground pressure is nearly equal to the water pressure. The findings presented in this paper can provide a reference for the structure design of similar tunnel projects.
Highlights
In recent decades, there has been an increase in applications of shield machines for the excavation of tunnels in large cities, especially under severe conditions, such as highdensity utilization of urban space, because shield tunnelling can effectively control and minimize ground settlement
When the cross section of the tunnel is below the Yangtze river and the H/D ratio ranges from 1.0 to 1.5, the observed ground pressure is much closer to the theoretical hydrostatic pressure, the soil pressure acting on the shield lining is very small, and only the hydrostatic pressure acts on the shield tunnel lining according to the field measurements. ese results matched previous examinations [3]. erefore, the river level above the shield tunnel should be considered for use as the design value of the ground pressure with high water pressure
Based on the field results and analyses, the following conclusions can be drawn: (1) e pressure observed acting on the lining demonstrated that the total ground pressure distribution and the ground pressure amount are different for different overburden depths. e distributions are uneven due to construction reasons
Summary
There has been an increase in applications of shield machines for the excavation of tunnels in large cities, especially under severe conditions, such as highdensity utilization of urban space, because shield tunnelling can effectively control and minimize ground settlement. Multiple factors influencing the earth pressure around the tunnel lining, including the engineering geology, the depth of the overburden, the ground water level, the excavation method, interactions between the lining and soil and the construction behaviour, operational parameters, and grouting parameters, have been indicated by many scholars [4,5,6]. Some previous field measurements have shown that the actual load acting on the shield tunnel lining could be much smaller than that adopted for the designs, especially for good ground conditions [7,8,9,10]. The observed ground pressure on a large-diameter shield tunnel lining at different depths is presented in-field, and the relationship between the earth pressure and time is demonstrated. The observed ground pressure on a large-diameter shield tunnel lining at different depths is presented in-field, and the relationship between the earth pressure and time is demonstrated. e measured earth pressures and water pressures are compared to the theoretical value adopted in the tunnel lining design. e factors influencing the earth pressure are discussed
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