Abstract The upper and lower limits of support pressure are key for determining the reasonable support pressure of slurry shields. Based on an analysis of the stability mechanism of the working face during slurry shield operation, it is determined that there are three necessary conditions for ground breakdown failure in shallow-buried sand strata: 1) severe slurry dehydration or slurry penetration directly into the ground, causing a drastic increase of the extra-static pore water pressure; 2) good directionality of the slurry with a great pressure difference compared with that of static water pressure in the ground due to higher support pressure; and 3) a permeability coefficient of the overburden that is too small to cause slurry directly seeps and diffuses into the ground, creating an extremely high water pressure gradient at the contact site of the soil particles, which means that the extra-static pore water pressure increases along with the high-pressure slurry permeating directly into the ground, and seepage failure occurs thereafter due to large water head difference. Accordingly, a practical calculation method of maximum support pressure, which is convenient and requires fewer parameters, is proposed. The maximum support pressure is calculated and a comparison with a practice case is carried out based on a certain river-crossing tunnel project, verifying the rationality and effectiveness of the method.
Abstract：
The upper and lower limits of support pressure are key for determining the reasonable support pressure of slurry shields. Based on an analysis of the stability mechanism of the working face during slurry shield operation, it is determined that there are three necessary conditions for ground breakdown failure in shallow-buried sand strata: 1) severe slurry dehydration or slurry penetration directly into the ground, causing a drastic increase of the extra-static pore water pressure; 2) good directionality of the slurry with a great pressure difference compared with that of static water pressure in the ground due to higher support pressure; and 3) a permeability coefficient of the overburden that is too small to cause slurry directly seeps and diffuses into the ground, creating an extremely high water pressure gradient at the contact site of the soil particles, which means that the extra-static pore water pressure increases along with the high-pressure slurry permeating directly into the ground, and seepage failure occurs thereafter due to large water head difference. Accordingly, a practical calculation method of maximum support pressure, which is convenient and requires fewer parameters, is proposed. The maximum support pressure is calculated and a comparison with a practice case is carried out based on a certain river-crossing tunnel project, verifying the rationality and effectiveness of the method.
.Discussion of a Practical Calculation Method for the Maximum Support Pressure of Slurry Shield Tunnels in Sand Strata[J] MODERN TUNNELLING TECHNOLOGY, 2015,V52(4): 158-164
2015, Vol. 52 