Asymmetric pressure distribution in EPB shields : evaluation of measurements and numerical simulations

Measurements have shown that the pressure distribution at the front of an EPB shield drilling in saturated granular material is not symmetric with respect to the vertical plane. This was confirmed recently by computational simulations of the material flow within different EPB pressure chambers. The fluid pressure is higher in the part where the cutting wheel is moving upwards, compared to the pressure in the part where the movement is downward. This unbalance may influence both the steering of the TBM and the stability of the tunnel face. The pressure distribution as measured with pore pressure gauges at the cutting wheel are used to calculate the centre of gravity of the muck in an EPB and the measured pressure differences are compared with theoretical calculations. The pore pressure distribution in the mixing chamber along lines parallel to the tunnel axis is discussed