双圆盾构隧道施工偏转角对地表变形影响研究

INFLUENCE OF TILTING ANGLE ON SURFACE DEFORMATION DURING DOUBLE-O-TUBE SHIELD TUNNEL CONSTRUCTION

双圆盾构隧道施工中土体变形控制和纠偏控制是其主要的技术难点。在分析双圆盾构隧道施工中盾构机偏转特性的基础上,基于随机介质理论,采用坐标变换和分区域积分,推导双圆盾构隧道施工中偏转角与地表沉降和水平变形的函数关系式。通过实例计算,分析偏转角对地表变形的影响规律。结果表明:偏转将导致地表产生附加变形,使地表变形曲线由对称变为非对称;地表沉降曲线存在3个焦点(V_1,V_2和V_3),水平变形曲线存在4个焦点(H_1,H_2,H_3和H_4),每个焦点左右两边土体的附加变形方向相反。对于逆时针偏转,V_1左边和V_2,V_3之间的土体附加竖向变形为隆起,V_3右边和V_1,V_2之间的土体附加竖向变形为沉降;H_1与H_2之间、H_3与H_4之间的土体产生正的附加水平变形,而H_2与H_3之间、H_1以左和H_4以右的土体产生负的附加水平变形。最大地表沉降随偏转角增大呈非线性增加,且其位置向左移动;最大右向水平地表变形呈线性增加,最大左向水平地表变形先减小后增加;水平地表变形的平衡点逐渐向左移动。对于顺时针偏转,焦点两边土体的附加变形方向与逆时针偏转相反,且最大右向水平地表变形随偏转角增大而减小,最大地表沉降位置和平衡点逐渐向右移动。

The control of soil deformation and the rectification of shield machine tilting are the major technical difficulties in double-O-tube(DOT) tunnel constructions. In this paper, the tilting characteristics of a DOT shield machine during construction were analyzed. Based on the theory of stochastic medium, the relationship between tilt angle and surface subsidence and horizontal deformation was derived by transformation of the coordinate system and integration over several partitioned areas. The relationship was then applied in the analysis of two case studies: anticlockwise and clockwise tilting. As demonstrated, the tilting of the DOT shield causes additional surface deformation and results in asymmetric surface deformation curves compared with symmetric profiles when there is no tilting. There are three focal points(V1, V2and V3) on the surface subsidence curve and four focal points(H1, H2, H3and H4) on the horizontal surface deformation curve, where surface deformation increments of soils occur in opposite directions on either side of any focal point. For anticlockwise tilting of the DOT shield, the additional vertical deformation of soils on the left side of V1and between V2and V3is upward while that on the right side of V3and between V1and V2is downward. The additional horizontal deformation of soils between H1and H2and between H3and H4is positive while that between H2and H3, on the left side of H1and on the right side of H4is negative. The maximum surface settlement increases nonlinearly as the tilting angle increases and its position moves left. The maximum horizontal surface deformation to the right increases linearly while the maximum horizontal surface deformation to the left decreases slightly first and then increases, while the point with no horizontal deformation gradually moves left. For clockwise tilting, additional surface deformation of soils on both sides of any focal point is in the opposite direction to that of the anticlockwise case. The maximum horizontal surface deformation to the right decreases as the tilt angle increases and both the position of the maximum surface settlement and the point with no horizontal deformation gradually move right. © 2015, Science Press. All right reserved.