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以地铁隧道穿越西安三类勘察场地的地裂缝为研究原型,分析了地裂缝的发育特征;运用数值模拟方法,研究了三类场地地裂缝不同活动量值引起的地层应力场、破坏区域和位移场的变化特征,计算了地裂缝的影响区域范围,解析了地裂缝带活动对地铁隧道结构产生的破坏特征,并提出了相应的工程对策。研究结果表明:地裂缝活动造成其两侧地层的竖向应力呈近似反对称的分布形态,地层应力的变化增量随上盘沉降的增加而增大;通过综合分析位于地铁隧道拱顶和拱底埋深处地层的竖向应力变化特征,得到三类场地地裂缝上盘和下盘的主要影响范围分别为0~20m和0~15m,经对比验证,与物理模型试验结果一致;下盘靠近地裂缝的区域发生剪切破坏,且破裂逐渐向上扩展,最终形成一条与地裂缝呈18°夹角的剪切破坏包线,其中间包含的范围为剪切破坏的集中区域;地裂缝活动导致两侧土体发生位移突变,形成2个类似“活动楔体”的变形区域,且该区域范围逐渐扩大;上、下盘隧道的差异沉降随着地裂缝错动量的增加而增大,当地裂缝活动量达到20cm时,造成整体式地铁隧道呈“S”破坏形态;为适应三类场地地裂缝活动引起的大变形,建议地铁隧道结构采用分段设置特殊变形缝加柔性接头处理等措施进行设防。
Taking the subway tunnel crossing the ground fissures of the three types of surveyed sites in Xi’an as prototypes, the developmental characteristics of ground fissures are analyzed. By using numerical simulation methods, the formation stress field, the damage area and the displacement caused by different activities of ground fissures Field characteristics of changes in the calculation of the scope of the impact of regional fissures, ground fissure activity analysis of the subway tunnel structure damage characteristics, and put forward the corresponding engineering measures. The results show that the vertical stress of the strata on both sides of the ground fissure is approximately antisymmetric distribution, and the increment of formation stress increases with the increase of the settlement of the upper plate. The main influence range of the upper and lower plates of the ground fissures in the three types of sites is 0 ~ 20m and 0 ~ 15m, respectively. The results of the tests are consistent with those of the physical model test. The lower plate Shear failure occurs in the area close to the ground fissure, and the fracture gradually expands upwards to form a shearing and destructible wire at an angle of 18 ° with the ground fissure, which contains the concentrated area of shear failure. The ground fissure activity Resulting in the displacement of soil on both sides of the sudden change in the formation of two similar “active wedge ” deformation area, and the area gradually expanded; the differential settlement of the upper and lower tunnel increases with the increase of the ground fissure, When the local crack activity reaches 20cm, the monolithic subway tunnel is destroyed by “S”. In order to adapt to the large deformation caused by the ground fissure activity in the three types of sites, it is suggested that the subway tunnel structure be provided with special deformation joints Sexual joints and other measures to deal with fortification.