控制混凝土沉井开裂的施工控制关键技术研究

发布时间：2018-10-11 10:58

【摘要】：沪通长江大桥主航道桥为主跨1 092m的双塔钢桁梁斜拉桥,桥塔墩采用86.9 m(长)×58.7m(宽)×105m(高)的沉井基础,针对超长超宽混凝土沉井易发生早期裂纹的情况,研究控制混凝土沉井开裂的施工关键技术。考虑造成混凝土沉井开裂的因素——混凝土水化热、混凝土收缩、温度梯度,确定采用分节分块浇筑混凝土、设置后浇段以及局部抗裂钢筋相结合的裂纹控制措施。在上游段设置后浇段+增设抗裂钢筋、留2处不设置后浇段的措施,中间段设置后浇段、不设抗裂钢筋的措施,下游段设置后浇段+增设抗裂钢筋,并布置测量元件监测结构应变和应力。结果证明,设置抗裂钢筋使混凝土收缩应力沿钢筋轴向均匀分布,避免在截断处出现应力集中,设置后浇段可使后浇段两侧一定范围的混凝土自由变形,释放混凝土收缩产生的拉应力,提高了混凝土的抗裂性能,避免了混凝土沉井出现裂纹。
[Abstract]:The main waterway bridge of the Hutong Yangtze River Bridge is a cable-stayed bridge with steel truss girder with a main span of 109.2 m. The tower pier of the bridge adopts a caisson foundation of 86.9 m (length) 脳 58.7 m (width) 脳 10 5m (high), aiming at the early cracks in ultra-long and ultra-wide concrete caisson. The key construction technology to control the cracking of concrete caisson is studied. Considering the factors causing cracking in concrete caisson, such as hydration heat of concrete, shrinkage of concrete and temperature gradient, the crack control measures are determined, which are divided into sections, set up post-pouring section and local anti-crack steel bar. In the upstream section, the anti-cracking steel bar is added in the post-pouring section, the measures of not setting the post-pouring section in 2 places, the measures of setting the post-pouring section in the middle section, and the anti-crack steel bar in the downstream section are set up, and the anti-crack reinforcement is added in the downstream section. And the measuring elements are arranged to monitor the strain and stress of the structure. The results show that the shrinkage stress of concrete is uniformly distributed along the axial direction of the steel bar, and stress concentration is avoided at the truncation point. The free deformation of concrete on both sides of the post-pouring section can be achieved by setting the post-pouring section. By releasing the tensile stress caused by concrete shrinkage, the crack resistance of concrete is improved, and cracks in concrete caisson are avoided.
【作者单位】：中铁大桥局集团有限公司;
【分类号】：U445.557

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