Establishment of fracture mechanics based design method for SFRC tunnel lining

通过数值计算结果与试验数据的比较，验证了所提出的混凝土裂缝扩展分析方法的有效性。主要关注的是检查分布的裂缝局部是否可以复制成一个主要裂缝。进行了钢纤维混凝土的单轴拉伸试验和弯曲试验。用激光散斑法测量了隧道的表面位移，得到了裂缝和裂缝张开位移的分布，通过测量的裂缝张开位移和拉伸软化曲线估算了穿过裂纹表面的传递应力。由单轴拉伸试验和弯曲试验得到的拉伸软化曲线与反分析方法得到的拉伸软化曲线是一致的。这表明拉伸软化曲线是一种与试验方法无关的材料特性。将得到的拉伸软化曲线用于有限元分析，讨论了设计方法。根据混凝土的断裂力学，估算了混凝土的正截面承载力。验证了设计方法的有效性。将估算的截面承载力与现有的试验结果进行了比较。

The validity of the developed analysis method for crack growth in concrete is clarified by comparing numerical results with experimental data. The main concern is to check weather the localization of distributed cracks into one major crack can be reproduced or not.Uniaxial tension tests and bending tests of steel fiber reinforced concrete are conducted. The surface displacements are measured with laser speckle method, and the distribution of cracks and crack opening displacements are obtained.The transmitted stress across the crack surface is estimated through the measured crack opening displacement and tension-softening curve.The tension-softening curves obtained from uniaxial tension tests and bending tests with back analysis method are in agreement.This implies that the tension-softening curve is a material property which does not depend on the testing method.The obtained tension-softening curve is used in FEM analysis in discussions for the design method.A design method of tunnel lining with SFRC (steel fiber reinforced concrete) is proposed. The cross-sectional capacity is estimated based on fracture mechanics of concrete. To show the validity of the design method. the estimated cross-sectional capacity is compared with the existing experimental results.