Abstract: Shield constructions usually have significant influences on adjacent piles due to soil disturbing, not grouting in time and shortfall grouting, which changes inner force and induces deformation and displacement. Orthogonal test is an effective and fast method to find major and minor factors on certain parameters. Based on the mode of elastoplastic FEM induced in the process of shield construction, combined with orthogonal tests and variance analysis, magnitude of shield construction influence factors on adjacent piles is got. The results show that magnitude of influence factors from large to small is distance between pile and tunnel, load applied on pile top, stress loss and properties of soil. Piles are not affected by shield construction beyond 2.5-3.0 times diameter of tunnel; and there is obvious relationship between pile settlement and pile loading which reflects state of initial stresses. Adjacent pile degree and formula are proposed according to results of significance testing of variance analysis, based on which, piles are classified into four categories: very near pile, adjacent pile, distant pile and very far away pile. The results show that there will have major impacts on first and second category piles that will be protected and strengthened, while third piles are taken measures regarding situations and the fourth piles needn′t be dealt with.

Key words: shield, orthogonal test, pile, adjacent pile degree