1. Earth pressure shield mainly focuses on improving control of earth pressure and plastic fluidity, supplemented by controlling soil flow and shield parameters. Mud shield mainly controls mud pressure and mud performance, supplemented by soil discharge control.
2. The control value of the earth pressure (mud pressure) on the excavation face is set according to the groundwater pressure (interstitial water pressure)+earth pressure+reserve pressure.
(1) The groundwater pressure can be correctly grasped from the borehole data, but the seasonal variation should be considered. Near rivers and other occasions, the influence of water level change should be considered.
(2) There are static earth pressure, active earth pressure and loose earth pressure, which should be used differently according to formation conditions. Setting and controlling the earth pressure according to the static earth pressure is the most ideal earth pressure value for the excavation face not to deform, but controlling the earth pressure is quite large, so it is necessary to increase the equipment capacity. Active earth pressure is the critical pressure for the excavation face not to collapse, and the control earth pressure is the minimum. When the geological conditions are good and the soil layer is deep, the soil arch can be formed, and the loosening pressure can be used.
(3) The reserve pressure is used to compensate the pressure loss in the construction process. Earth pressure shield generally takes 10 ~ 20kN/m2, and mud shield generally takes 20 ~ 50kN/m2.
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