Soil pressures at the cutting wheel and the pressure bulkhead of an EPB-shield

摘要

Soil pressureswere measured on both sides of the cutterwheel of an EPB-shield during tunnellingrnin saturated sand, using foam for soil conditioning. The measured pressures are compared with the pressures atrnthe pressure bulkhead. The pressures are not purely hydrostatic but the results are also influenced by the yieldrnstrength of the foam mixture and the effective stresses. At the lowest positions, the sensors sometimes measuredrneffective stresses. This led to peaks in the pressures measured. It is shown that for the soil conditions present,rnthe pressures measured at the pressure bulkhead are comparable to the pressures measured at the rotor, but thernpressure gradients can differ significantly (around 30% difference in gradients is possible). The measurementsrnshow that the pressure distribution is asymmetric due to the rotation of the cutter head.