矿井环境中混凝土材料腐蚀损伤演化与机理分析

通过试验模拟地下复杂环境中混凝土在硫酸盐腐蚀和干湿循环耦合作用下混凝土受力特点和损伤演化，测试和分析了不同腐蚀时期混凝土的抗压强度、劈裂抗拉强度、抗折强度、质量和超声波速的变化及加载受荷过程中应力应变曲线变化，运用损伤力学，对腐蚀损伤进行多指标全面评价。分析受荷过程中腐蚀损伤对混凝土应力-应变关系的影响。结合腐蚀时间和应变对混凝土损伤扩展的影响，建立受蚀混凝土的受荷损伤模型。采用环境扫描电镜（ESEM）和X射线衍射（XRD）分析受蚀混凝土的微观结构演化。试验结果表明：① 混凝土受到硫酸盐侵蚀和干湿循环耦合作用，抗压强度、劈裂抗拉强度和抗折强度的经时变化规律大致相同，均呈现先增大后减小，其中劈拉强度和抗折强度对侵蚀引起的损伤更加敏感，劣化更加明显。通过数据回归得到以各性能指标为损伤变量的混凝土腐蚀损伤演化方程，得到不同损伤因子之间的线性函数关系；② 随着腐蚀环境的长期作用，腐蚀损伤混凝土试件峰值应力减小，峰值应变增加，弹性模量和峰值变形模量均有所降低。通过数学模型将腐蚀损伤和受荷损伤统一起来，表征混凝土受到的环境腐蚀、荷载及损伤之间的作用关系；③ 腐蚀产物钙矾石和石膏的膨胀作用和硫酸钠的结晶压在试件内部形成微破裂，随着腐蚀的加剧，微破裂逐渐增多和扩展。

Damage evolution and mechanism of concrete erosion at sulfate environment in underground mine

Some experiments were conducted to simulate the mechanical characteristics and deterioration of concrete under sulfate and wet-dry cycle environment.The parameters were tested and analyzed，including compressive strength，splitting tensile strength，bending strength，the variation of mass and ultrasonic velocity and stress-strain curves over attacked time.The damage development was evaluated by multi-index of attacked concrete based on damage mechanical theory.The relationship between the corrosion damage and stress-strain characteristics was analyzed.The damage model of corroded concrete was established considering the effects of the parameters such as corrosion time and strain on the damage evolution.According to the ESEM images and XRD results，the damage mechanism was obtained by analyzing the microstructures of concretes at different erosion periods.The research results show that：① Under the coupling action of sulphate attack and drying-wetting cycles，the parameters，including the compressive strength，splitting tensile strength，bending strength and ultrasonic velocity，increase first and then decrease with erosion time，and especially the splitting tensile strength and bending strength signature are more sensitive to damage and deteriorate more seriously.According to data regression，the corrosion damage evolution equations were developed.In the equations these performance indicators were regarded as damage variables.Linear functional relationship exists among different damage factors.② In the long term，with corrosion time the peak stress decreased while peak strain increased.Elastic modulus and deformation modulus also decreased.The damage caused by corrosion and the one caused by load were unified by means of mathematical model，which revealed the relationship between and among sulphate attack，load and damage to concrete in complex underground environments.③ During the erosion time，the combined expansions of ettringite，gypsum and the crystal of sodium sulfate decahydrate cause micro fractures.With the increase of corrosion time，the micro-cracks developed and their number increased.