An electrohydraulic system for synchronously jacked box tunneling in shallow saturated soft soil cover

Part of the Central Ring Fast Autoroad in Shanghai, Beihong Vehicular Undercrossing Tunnel is a two-way, eight-lane vehicular tunnel of 126-m long, 34.2-m wide, and 7.85-m high. An electrohydraulic control system for synchronously jacked box tunneling was developed in the project. Estimation of jacking force is essential prerequisite of design of electrohydraulic system. Volume speed-regulating hydraulic circuit rather than throttle circuit was used to adjust flow rate, and the rotating speed of driving motor of main pump is controlled by variable voltage variable frequency (VVVF) technology. Three-level structure of control system was employed. A “double-object synchronization” control scheme enables 112 cylinders to coordinate the extending action, and automatically achieve synchronous motion and posture control of box and uniform load distribution to each pump unit. Differences are controlled within ±40mm during the whole jacking process. ► We developed a new system for synchronously jacked box tunneling. ► Driving motor of hydraulic pump is controlled by variable-frequency technology. ► The system can work under the condition of non-artificial ground freezing. ► Three-level structure of control system was employed. ► A double-object synchronization control scheme can control the posture of box.