为提高地铁盾构隧道施工效率和管片拼装精度，提出用等腰楔形环拼装圆弧形盾构隧道的新的理论与算法。主要结论如下： 1）从理论上证明当等腰楔形环依次向相反方向旋转相同角度θ时，隧道轴线在一个平面上，隧道半径R=L/(2sin α/2· cos θ/2)，其中L是环宽，α是楔形角； 2）提出一种采用容许旋转角拼装楔形环的算法，确定整个盾构隧道上每个衬砌管片环的位置和方位； 3）根据楔形环的方位可以确定隧道上的第几环是左转弯环，第几环是右转弯环，使封顶块的位置在隧道上部，从而确定整个盾构线路所需左、右转弯环的数量。

A new theory and algorithm for assembling a circular metro shield tunnel segment by using isosceles wedged rings are proposed to improve the tunnel construction efficiency and segment assembling precision. Main conclusions are drawn as follows: 1) It is theoretically proved that the tunnel axis is on a plane when rings are alternately rotated about the same angle θ and the tunnel radius R=L/(2 sin α/2 cos θ/2) where L is the ring′s width and α is wedged angle. 2) An algorithm, using allowable rotation angle method, is given to compute the position and orientation of every lining ring in the whole circular shield tunnel. 3) Every isosceles wedged ring can be identified as a left bend ring or a right bend one according to its orientation where the Ksegment is on the top of the tunnel, which means that the amounts of left and right bend rings can be respectively foreknown before constructing a shield tunnel.