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To improve the measurement precision of the shield΄s pose, the factors which influence the measurement results are studied in this paper. Coordinate transformation formula is applied to calculate the shield΄s pose by transforming the relative coordinate of the shield΄s cutter head center in the laser target coordinate system to the world coordinate. The relative coordinate of the cutter head center is calibrated by transforming the formula inversely. The calibration error of the relative coordinate caused by the measurement error of the attitude angle is analyzed detailedly. The position measurement error of the cutter head center is deduced based on the principle of error transfer. Finally, the impact of each attitude angle΄s measurement error on the cutter head center is obtained by traversal algorithm in the variation range of attitude angle. According to the different influence degree, the measurement error of each attitude angle is proportionally allocated. [ABSTRACT FROM AUTHOR]

With the development of the urban construction, the shield machine becomes more and more important as the main equipment to extend the underground space for the human being. In this paper, we investigate the dynamic mechanism of the shield machine in the vertical plane. Through this analysis, the basic requirement maintained balance of the shield machine while excavating is given. Meanwhile, the key rectification techniques about the deviation from the desired trajectory in vertical plane are discussed. This study is developed based on the engineering problems from which are frequently met in construction, and we hope to provide useful guidance to the actual excavating process. [ABSTRACT FROM AUTHOR]

In this paper, the load transmission model of the shield thrust system is established taking into account the variable boundary constraints between the shield skin and the surrounding strata, which is obtained based on the finite element methods. The results show that the resisting moment on the shield skin from the geologic layer has a nonlinear relationship with the bending moment loads on the cutterhead when the material behavior of the strata is modeled by an elasto-plastic Mohr-Coulomb model. The dynamic load behavior of the shield thrust system is significantly influenced by the variable shield-strata boundary constraints, which may cause incorrect load predictions of the hydraulic thrust system and consequent snake-like motions of the shield machine. [ABSTRACT FROM AUTHOR]

On the basis of brittle tensile fracture theory, assuming the destruction of rock was due to tensile failure, a cutting-tool loading calculation model was established, considering the compact core impact in front of cutting-tool, then the mechanism of cutter-rock, as well as the process of brittle fracture of rock were analyzed and the expressions of horizontal cutting force and vertical propulsive force for the shield cutter were obtained. At the same time, three kinds of cutters with different rake angle were designed, and the cutting experiments on a linear cutting performance testing station were carried out. By comparing, the results of experiments were basically in accordance with those of mechanical model, error rate of horizontal cutting force was below 7% and that of vertical propulsive force was in the scope of 9%. At last, the experiments proved that the force of cutter would increase along with the increasing depth, or decreasing rake angle. [ABSTRACT FROM AUTHOR]

Taking the shield machine tunneling in a railway section as the research object, the discrete element numerical model for analyzing the chamber pressure is established. Comparing the numerical simulation results of the observed pressure on the chamber board with the field construction data, the validity and the feasibility of the simulation method is testified. Then the pressure distribution rules on the chamber board in different opening ratios of the cutting wheel and tunnel axis depth are studied, and the mathematical model of the pressure distribution is proposed. The mapping relation between the excavation face pressure and the chamber board pressure is advanced. The results provide basis for the design and control of the earth pressure balance shield machine. [ABSTRACT FROM AUTHOR]

In the shield tunneling construction, the inclinometer is usually utilized to measure the pitching angle and rolling angle of the shield machine in real-time. However, the nonlinearity and the temperature characteristic of the inclinometer always result in large measurement error. In order to improve its measurement accuracy, the research on compensating the nonlinear error and the temperature drift error based on BP neural network is presented in this paper. The characteristic of the inclinometer is studied by experiment at first and then its inverse model is built using BP neural network and trained with an amount of experimental data; finally the trained model is used to compensate the measurement error. The experimental results verify that the proposed compensation method can improve the measurement accuracy of the inclinometer greatly by correcting the nonlinearity and eliminating the influence of temperature. [ABSTRACT FROM AUTHOR]

The rolling phenomenon of the shield body occurs frequently in the process of practice construction, which could lead to the derivation of the shield machine and increase the difficulties of the excavation control. It is mainly caused by the rotation of the cutter head. Based on this practical problem, we investigate the forces around the shield body and the cutter head. Meanwhile, the positive and negative rotary controlling techniques are developed to regulate the deviated rolling angle. These studies would provide theoretical basis to the further research about the whole postures rectification of the shield machine. [ABSTRACT FROM AUTHOR]

The shield machine is a heavy construction machine for tunnel excavation. The segment erector is an important subsystem of the shield machine. The 2DOF five-bar radial mechanism in the 6DOF erector is hard to implement the precise synchronization control. Hence, this paper proposes a redundantly actuated PRPRP radial mechanism for the segment erector. When the redundant actuator is locked or produces enough pretightening stretching force, the PRPRP mechanism can ensure the synchronization of the two driving hydraulic cylinders based on the mechanical structure. The redundant actuator can also make the two flexural torques applied at the hydraulic cylinders be the same, which avoids the overload of the single cylinder. [ABSTRACT FROM AUTHOR]