Abstract: The pea gravel backfilling and grouting layer is an important part of the shield TBM tunnel lining system, and it is of great theoretical and practical significance in studying the impact of different defects in the pea gravel backfilling and grouting layer on construction works. In this paper, common defect types and its distribution law in the pea gravel backfilling and grouting layer are summarized on the basis of a diversion tunnel constructed by the double shield TBM. Then, the effects of different defect types on segment stress and displacement under different engineering conditions are systematically simulated and analyzed. The results show that common defect types mainly include cavity, non-dense grouting, plain cement and high rock powder content in cemented grouts; among others,cavity has the greatest impact, and the fully filling should be performed as much as possible; the vertical displacement of segments is sensitive to construction defects, the difference between horizontal and vertical displacements of segments might decrease under the action of internal water pressure in the pressurized tunnel; under the condition of Class Ⅱ surrounding rock, the influence of various defects is small, while that of other defects might be ignored ex? cept that cavity should be avoided as far as possible; in the Class Ⅳ surrounding rock the displacement and stress of segments are governed by the geological conditions, which would amplify the effect of defects, so that countermeasures should be taken accordingly; interaction of the internal water pressure and geological conditions would further amplify the influence of construction defects, the displacement of segments in Class Ⅳ surrounding rock is about 2~ 3 times of that in the Class Ⅱ surrounding rock, with especially prominent influence effect of cavity defect.