冻融诱发岩石-混凝土界面损伤脱粘机理研究

The damage and debonding of interface between rock and concrete induced by the freeze-thaw cycles have occurred commonly and resulted in some typical project disasters, which have became one of the fundamental scientific problems for the cold regions and artificial freezing projects. It is important to study the damage characteristics and debonding process of the interface of rock and concrete, the interface damage model of the "one-body, two-element" structure and debonding criterion caused by the freeze-thaw cycles. All of these are the key works to carry out the further study of prevent frost and control crack of the interface of rock and concrete. The aim of this subject is to reveal the damage and debonding mechanism of the interface of rock and concrete. Some macro-mesoscopic test experiments reflecting different freeze-thaw parameters and interface properties of rock and concrete were carried out, the degradation process and strength damage characteristics during freeze-thaw cycles were systematically observed with acoustic emission(AE), splitting tensile test, fracture morphology scanning and nuclear magnetic resonance (NMR) technology. It is cleared to establish the relationship between interface degradation response and freeze-thaw characteristics threshold, which is helpful to provide the distinguish threshold of the damage model and interface debonding criterion. The rock-concrete interfacial damage model reflected the freeze-thaw index, interfacial properties and their coupling effect was established using the interface nonlinear damping element representation. And the hybrid-modal freeze-thaw debonding criterion represented by tensile and shear stress critical factors was also put forward based on the interface stress intensity index theory. Lastly, the XFEM program is simulated and verified to the interface degradation and the rationality of damage model. This study results should provide some fundamentality references to know of the rock-concrete interface bonding degradation mechanism during the freeze-thaw processes and its latter prevention technology development.

冻融诱发岩石-混凝土界面处损伤、脱粘进而引起工程灾害，是寒区及人工冻结施工亟待解决的科学难题之一。研究“岩-砼”界面损伤特性及脱粘演化规律，构建一体二介质界面冻融损伤模型及脱粘判别准则，是实现“岩-砼”二元体界面防冻止裂的关键基础。现开展不同冻融参数、界面性状的界面损伤脱粘宏细观试验，基于声发射、劈裂抗拉测试、断口形貌扫描及核磁共振（NMR）等多元测试指标信息辨识，分析冻融过程中界面损伤脱粘过程及强度劣化规律，明确界面劣化响应与冻融特征阈值内在关联，为界面损伤模型及脱粘判据提供试验支持；基于试验结果及界面力学基础理论，提出反映冻融、界面性状及互馈效应的界面损伤模型；采用界面临界应力强度因子表示法，建立多模态冻融脱粘判别准则；应用扩展有限元数值验证冻融界面劣化规律及理论模型合理性。研究成果可为系统认知“岩-砼”二元体界面冻融脱粘机制及防控技术发展提供基础参考。

冻融易诱发岩石-混凝土界面处损伤脱粘问题，是寒区工程亟待解决的关键科学难题之一。据此，本项目开展不同冻融参数、界面性状的界面损伤脱粘宏-细-微观试验，研究冻融作用下岩石-混凝土二元体界面脱粘演化规律及强度劣化机制，以期为寒区岩体工程防护提供科学基础依据。经四年期持续攻关研究，本课题取得了以下成果：.①开展了冻融对岩石-混凝土界面的宏观强度劣化特性试验；制备不同粗糙度、亲疏水界面的岩石-混凝土二元体试样，并进行不同冻融参数的循环试验；同时采用变角剪切试验测定界面剪切强度，剖析了界面强度劣化与影响因素之间的内在关联；并对破坏后界面形貌进行精细化测定，获得了岩石-混凝土剪切后的破坏断面形态特征及主控因素。.②建立了冻融作用下岩石-混凝土界面强度劣化模型；基于岩石-混凝土界面强度劣化影响指标试验分析，构建了一体二介质界面黏结强度冻融劣化模型，并验证了模型的可靠性。此外，开展了界面黏结性能冻融劣化机制分析，为认知岩石-混凝土界面强度劣化特征提供了理论依据。.③明确了冻融过程中岩石-混凝土界面损伤脱粘细观特性；基于核磁共振T2谱开展砂岩-混凝土二元体含水率变化分析，获得不同空间位置的核磁信号强度演化，确定了岩石-混凝土界面影响区（IIZ）范围。同时，结合IIZ范围冻胀静水压力、水分迁移、冻结速率等分析，明确了岩石-混凝土IIZ细观损伤特性及演化机制。.④揭示了冻融作用下岩石-混凝土界面过渡区损伤脱粘微观机制；通过开展冻融条件下砂岩-混凝土界面过渡区（ITZ）微观结构、微观力学及脱黏微观试验，研究了不同冻融梯度、冻融次数下ITZ微观力学性能、形貌及裂纹演化特征，揭示了冻融诱发岩石-混凝土界面脱黏微观机制。.⑤建立了冻融诱发岩石-混凝土界面脱黏启裂判据；通过断裂力学及冻胀力演化分析，对砂岩-混凝土二元体界面脱粘过程进行精细捕捉，提出了适宜评价岩石-混凝土界面影响区启裂判据方法，为后期开展针对性防控技术研发提供了基础依据。