Abstract Serious accidents involving front collapse and water bursting are mostly attributed to the excessively thin overburden of shield tunnels. In this paper, the existing problems with the current calculation theory for the minimum buried depth of an underwater shield tunnel are analyzed and an improved calculation formula for minimum depth is given considering such factors as the anti-floating safety coefficient, soil shear strength, and grouting pressure behind the segment. Meanwhile, by using the orthogonal test analysis method without null columns, the range analysis and variance analysis of various factors that affect the determination of the tunnel buried depth, such as tunnel radius, segment thickness, grouting pressure, effective unit weight and effective internal friction angle of the overlaying soil, and soil viscosity, are carried out, and the significant influential factors for the minimum buried depth and its tendency to vary with various factors are derived. The study shows that segment thickness and effective internal friction angle have minimal influence on the variation of buried depth but grouting pressure greatly influences it. The order of influence of the factors related to the given formula is: grouting pressure, soil viscosity, effective unit weight of the soil, tunnel radius, effective internal friction angle of the soil, and segment thickness.
Abstract：
Serious accidents involving front collapse and water bursting are mostly attributed to the excessively thin overburden of shield tunnels. In this paper, the existing problems with the current calculation theory for the minimum buried depth of an underwater shield tunnel are analyzed and an improved calculation formula for minimum depth is given considering such factors as the anti-floating safety coefficient, soil shear strength, and grouting pressure behind the segment. Meanwhile, by using the orthogonal test analysis method without null columns, the range analysis and variance analysis of various factors that affect the determination of the tunnel buried depth, such as tunnel radius, segment thickness, grouting pressure, effective unit weight and effective internal friction angle of the overlaying soil, and soil viscosity, are carried out, and the significant influential factors for the minimum buried depth and its tendency to vary with various factors are derived. The study shows that segment thickness and effective internal friction angle have minimal influence on the variation of buried depth but grouting pressure greatly influences it. The order of influence of the factors related to the given formula is: grouting pressure, soil viscosity, effective unit weight of the soil, tunnel radius, effective internal friction angle of the soil, and segment thickness.
JIAO Jian-Wei,
Wang-Kong-Qian
.The Orthogonal Test Analysis of the Minimum Buried Depth of a Shallow Shield Tunnel[J] MODERN TUNNELLING TECHNOLOGY, 2014,V51(3): 138-142
2014, Vol. 51 