本项目具有基础性、实用性和前沿性，因为准脆材料（混凝土、岩石等）尺寸效应和应变率效应的关联性目前还无人研究，还缺乏考虑上述两种效应的统一材料模型。申请者的初步研究表明，准脆性材料I型确定性尺寸效应和应变率效应具有紧密的内在联系。现在需要解决的问题是：1）II型确定性尺寸效应与应变率效应是否具有关联；2）两种效应关联性的理论基础是什么；3）能否建立外载作用下准脆材料破坏的时间-构造准则；4）能否建立考虑材料内部构造和热涨落的材料寿命预测公式；5）能否建立准脆材料的热活化-构造-统计变形破坏模型。将考虑材料的结构层次，利用固体力学、固体物理学等学科的基础理论，结合试验研究和数值模拟等方法进行研究。这些问题的研究与解决对于理解两种效应及其联系，对于受不同加载速度的不同尺度的岩体和结构的强度计算和寿命预测具有重大的理论意义，同时对于提高设计精度，提高大型工程的安全性和可靠性具有重大的现实意义。

This program has fundamental, practical and frontier characteristic, because the intrinsic relation between size effect and strain rate effect of quasi-brittle materials (concrete, rock etc) has not been studied so far, there is a lack of unified model for this two effects. The preliminary investigation of the applicant shows that the type I deterministic size effect and strain rate effect of brittle materials has close intrinsic relation. The problems to be solved are: 1) whether the type II deterministic size effect has relationship with strain rate effect; 2) what is the theoretical basis for the relation between them; 3) whether the temporal-structural failure criterion under loading can be developed; 4) whether the equation for prediction of lifetime of materials with the consideration of internal structure and thermal fluctuation can be developed; 5) whether quantum thermal activational-structural-statistical failure model can be developed. This program will use solid mechanics and physics theories with combination of experimental studies and numerical modeling to study these problems. The study will be helpful for the undestanding of these 2 effects and their nature, and has important theoretical meaning for the prediction of the strength and lifetime of structures of different sizes under different loading rates, and has imporatnt practical meaning for improving the calculation accuracy and the safety and reliability of large scale engineering projects.