Abstract:

System of Laser Steering (SLS) is widely employed in shield boring. The boring trend is very important in shield tunneling, which determines the oncoming boring alignment. When the trend value is in the reasonable range, the boring alignment can be guaranteed; otherwise the shield will deviate from the alignment seriously. The deviation rectification ability of Herrenknecht shield used in Chengdu Metro is poor. In the paper, the concept of shield boring trend, the calculation of the boring trend in curved sections, the statistics of the actual deviation rectification ability of the shield, the deduction of the allowable trend deviation formula, the determination of the trend deviation alarm value and the determination of the final alarm value for the shield boring are presented. The research results have been applied in the boring practices to control the alignment and no center line deviation accidents have occurred.