Development of theory and analysis method for localization and progressive failure

提出了裂纹局部化的理论和分析方法。通过考虑弹簧-裂纹单元模型，给出了判断局部化解的方法和局部解的求解方法。证明了该问题可归结为约束条件下的极小化问题。将该理论推广应用于混凝土裂缝局部化问题。该方法可以在四点弯曲试验中将初始分布的裂纹局部化再现为单个裂纹。结果表明，为了获得结构的极限强度，在很多情况下需要对裂纹或剪切破坏面局部化进行处理，约束条件下的极小化问题是需要解决的问题。结果表明，该方法能够捕捉到混凝土坝在大地震激励下的裂缝扩展和局部化，并考虑了软岩的渐进破坏，提出了一种软岩渐进破坏的分析方法。对人造软岩进行了平面应变双轴压缩试验，模拟了峰值前的本构关系、破坏条件和破坏面上的行为。对软岩的渐进破坏进行了分析，并与软岩模型试验结果进行了比较。

A theory and an analysis method for cracking localization are presented. The method to judge the initiation of localization and to find the localized is solution is presented through consideration of spring-crack element models. It is shown that the problem is reduced to a minimization problem under constraint conditions. The theory is generalized and applied to problems of cracking localization in concrete. The proposed method can reproduce the localization of initially distributed cracks into a single crack in a four-point bending test. It is shown that to capture the ultimate strength of structures treatment of the localization of cracks or shear failure planes is necessary in many cases, and minimization problems under constraint conditions are the problems to be solved.A finite element with displacement discontinuities is developed and finite element analysis for cracking localization is carried out using the proposed theory of cracking localization. It is demonstrated that crack growth and localization in concrete dam under large earthquake excitation is captured by the present method.The progressive failure in soft rock is also considered, and an analysis method for progressive failure in soft rock is presented. Plane strain biaxial compression tests on artificial soft rock are carried out and the pre-peak constitutive relationship, the failure condition and the behavior of failure plane are modeled. Analysis of progressive failure in soft rock are carried out and results are compared with that of model tests with soft rock.