跨江海隧道功能梯度混凝土管片的收缩开裂研究

Shrinkage Cracking of Functionally Gradient Concrete Segment Used in River-crossing or Sea-crossing Tunnels

引入梯度功能设计思路，进行功能梯度混凝土管片（functionally gradient concrete segment，简称FGCS）的结构与材料设计。无细观界面过渡区水泥基材料（meso—interfacial transition zone-free cement—based materials，简称MIF）中由于掺入了能显著改善收缩开裂趋势的减缩组分和细微化裂纹的抗裂组分，降低了MIF的收缩值，提高了MIF的抗裂能力，有利于提高MIF的抗渗性能，进而可以提高FGCS的抗渗性能。混凝土两次浇注成型时，采用界面强化工艺——压印工艺，可以提高混凝土功能层之间界面粘结强度10％-35％，产生界面强化效应。采用ANSYS计算的FGCS中界面最大拉应力的计算值远小于界面劈裂抗拉强度试验测试值，FGCS中界面由于收缩引起的应力不会引起FGCS产生相对的滑移而导致开裂。用于武汉长江隧道工程的FGCS的外弧面裂缝宽度〈0．1mm，Cl^-扩散系数为4．9×10^-13m^2／s。

Gradient function design thought is introduced in structure and material design of functionally gradient concrete segment （FGCS）. Owing to blending a shrinkage reducing ingredient that can decrease shrinkage, and an anti-cracking ingredient that can fine cracks in meso-interfacial transition zone-free cement-based materials（ MIF）, the shrinkage of MIF is decreased, and the ability to anti-cracking is improved. Because of the above mentioned cause, the impermeability of MIF and FGCS can be improved. When the concrete is cast twice, interface bond strength between two functional layers is increased by 10% to 35% by means of imprinting process as compared to the control without imprinting process. Imprinting process can result in the effect of interface strengthening. The maximum interface tensile stress due to shrinkage in interface is calculated by ANSYS software （finite element analysis tool）, whose value is less than the test value of interface splitting tensile strength. Interface tensile stress due to shrinkage in interface doesn＇t result in cracking of FGCS, and the sliding deformation of interface layers would not generate. FGCS has been used in Wuhan Yangtze River Tunnel Engineering, whose width of crack is less than 0. 1 mm on the outside arc surface, and whose chloride diffusion coefficient is 4.9× 10 ^- 13 m^2/s.