Modeling And Coordinated Optimal Control Method Of Shield Capsule’s Earth Pressure

With the rapid development of urbanization process, the developable space on the ground becomes less and less, and the valuable resource of underground space is paid increasingly attention to day by day. The development and utilization of underground space becomes more and more frequent. Earth pressure balance shield has been widely applied in tunnel excavation of underground construction because of its fast construction speed and extensive applicability of stratum.During construction process, the capsule’s earth pressure is controlled to keep dynamic balance with earth pressure and water pressure of excavation face in order to maintain the stability of tunnel face. If the pressure is unbalanced, surface subsidence or uplift is likely to occur that causes casualties and property losses. So the earth pressure balance is very important for shield tunneling security. For the tunneling condition of shield is usually complex and changeable and the operation parameters are coupled, the capsule’s earth pressure control model is established mostly based on neural network, fuzzy algorithms and other intelligent methods or the low of mass conservation of the capsule’s earth, ignoring the cutter-head soil-compacting effects on the capsule’s earth pressure. Earth pressure balance can be kept only by controlling the amount of earth into and out of the capsule. However, according to the monitoring data in tunneling process, the soil-compacting effects of shield are stronger than commonly believed. If the soil-compacting effects on the capsule’s earth pressure are ignored, the control effect of earth pressure balance must become worse, even lead to abnormal condition. In view of the above questions, the following research is done in this paper:In this paper, after considering the influence of cutter system, propulsion system and soil discharging system on the capsule’s earth pressure, a coordinated optimization control strategy for earth pressure balance is proposed. At first, the impact of cutter-head soil-compacting effects on the soil deformation is analyzed, and then a new control model of earth pressure is established combined with the soil deformation caused by shield imbalance tunneling. The earth pressure in this model is decided by the three subsystems. In order to make the earth pressure follow its set value fast and stably, a coordinated optimization control method for cutter system, propulsion system and soil discharging system is proposed. The method remains the set value of cutter speed unchanged and then coordinates to control advance speed and screw conveyor speed. Finally, simulation results show that:the earth pressure balance control strategy proposed in this paper can realize the target that capsule’s earth pressure follows its set value fast and stably, so it can provide a guide for actual excavation process.