施工期深大立井内壁混凝土开裂机理

In recent years, concrete cracks are generally appear on inner wall of deep-large shaft lining during construction period, water-leakage damage is worsening after frozen wall thawing which has caused great security threat and economic loss, what is more, the concrete cracking mechanism is not clear. To reveal cracking mechanism of new pouring concrete is a prerequisite for scientific prevention of shaft lining water-leakage damage. On the basis of previous works, firstly, in order to provide some basic data for further research, simulating actual temperature of the new pouring concrete, and researching the thermal physical and mechanical parameters evolution laws of high strength concrete with its age and temperature. Secondly, assuming concrete as heterogeneous material, a microscopic thermo-mechanical coupling numerical computation model of aggregate random distribution is built, the thermal physical and mechanical parameters of concrete change with its age and temperature. Based on the numerical computation model, researching the change laws of stress field and crack propagation of inner wall with different thickness, different concrete strength grade and different constraint condition. Thirdly, an electrical conductive concrete similar material is developed to solve the temperature field dissimilar problem of concrete scale model, and then adopting some advanced test technologies including digital shoot and distributed Fiber Bragg Grating to carry out concrete restrained shrinkage physical simulation study on the change laws of deformation field and crack propagation of inner wall. Finally, comprehensively analyzing these results to revealing concrete cracking mechanism during construction period and proposing crack prevention technologies of inner wall of deep-large shaft lining. The results of this research for concrete cracking mechanism have important theoretical and practical value for freezing shaft lining and underground structure support technology.

近年来，随立井深度和直径增大，冻结井筒内壁开裂、漏水日益严重，机理不明，造成重大安全威胁和经济损失。揭示施工期新筑内壁混凝土开裂机理是科学防治冻结井筒渗漏水害的前提。基于前期工作，首先，模拟新筑内壁真实的温度条件，研究高强混凝土热物理、力学参数随龄期和温度的演化规律，为后续研究提供基础数据。第二，将混凝土视为非均质材料，建立热物理、力学参数随龄期和温度变化以及骨料随机分布的新筑内壁三维细观损伤计算模型，开展细观尺度热力耦合数值计算，研究不同厚度、不同强度等级和约束条件下内壁应力场及裂缝演化规律。第三，研制可突破水泥水化放热相似模拟难题的导电混凝土相似材料，采用数字照相、分布式光纤光栅等先进测试技术，开展约束状态下新筑内壁变形场和裂缝演化规律物理模拟试验。最后，分析揭示施工期深大冻结井筒内壁混凝土开裂机理，提出防裂技术路线。研究成果对发展冻结井壁和地下空间支护技术具有重要理论意义和应用价值。

近年来，随立井深度和直径增大，冻结井筒内壁开裂、漏水日益严重，机理不明，造成重大安全威胁和经济损失。揭示施工期新筑内壁混凝土开裂机理是科学防治冻结井筒渗漏水害的前提。首先，本课题模拟新筑内壁真实的温度条件，研究了内壁混凝土热物理、力学参数随龄期和温度的演化规律，为后续研究提供基础数据；第二，基于电热原理，研制了可以突破水泥水化放热相似模拟难题的导电混凝土相似材料，研究获得了导电混凝土内壁的电热特性；第三，将内壁混凝土视为非均质材料，开展细观尺度热力耦合数值计算，通过分层游走法建立了基于随机骨料随机参数的混凝土内壁细观数值模型，构建了内壁细观结构损伤破坏与其宏观力学响应之间的联系，研究了不同厚度、不同强度等级和约束条件下的内壁应力场及裂缝演化规律；第四，成功研制适用于井壁等筒状结构的温度—应力试验机，为开展变约束条件下新筑内壁温度—应力模拟试验提供了仪器支撑；第五，采用导电混凝土相似材料浇筑混凝土内壁相似模型，真实模拟新筑内壁的水化升温与降温过程，采用分布式光纤光栅等先进测试技术，研究获得了不同厚度、不同强度等级和约束度条件下的新筑内壁变形场、应力场及裂缝演化规律。最后，分析揭示了温度梯度与边界约束协同作用致裂深大冻结井筒新筑混凝土内壁的机理，并提出了内壁防裂技术路线。研究成果对发展冻结井壁和地下空间支护技术具有重要理论意义和应用价值。