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The sufficient bond between concrete and rock is an important prerequisite to ensure the effect of shotcrete support. However, in cold regions engineering protection system, the bond condition of rock and concrete surface is easily affected by freeze-thaw cycles, resulting in interface damage, debonding and even supporting failure. Understanding the micromechanisms of the damage and debonding of the rock-concrete interface is essential for improving the interface protection.Therefore, the micromorphology, micromechanical properties, and microdebonding evolution of the sandstone-concrete interface transition zone(ITZ) under varying freeze-thaw cycles(0, 5, 10, 15, 20) were studied using scanning electron microscope, stereoscopic microscope, and nano-indentation. Furthermore, the distribution range and evolution process of ITZ affected by freeze-thaw cycles were defined. Major findings of this study are as follows:(1) The microdamage evolution law of the ITZ under increasing freeze-thaw cycles is clarified, and the relationship between the number of cracks in the ITZ and freeze-thaw cycles is established;(2) As the number of freeze-thaw cycles increases, the ITZ's micromechanical strength decreases, and its development width tends to increase;(3) The damage and debonding evolution mechanisms of sandstone-concrete ITZ under freeze-thaw cycles is revealed, and its micromechanical evolution model induced by freeze-thaw cycles is proposed. 相似文献
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页岩力学各向异性特征是地应力、井壁稳定、水力裂缝扩展相关研究的重要基础参数。针对页岩力学各向异性宏观测试中存在样品制取困难、制样成功率低的特点,采用来源丰富的钻井岩屑或破碎岩块,通过研究纳米压痕实验原理、实验方法和数据解释方法,采用连续刚度测试方法对平行层理和垂直层理的页岩试样进行纳米压痕测试;基于硬度的分类准则将纳米压痕数据分为三类主要矿物基质进行合理解释,采用接触刚度法计算硬度、杨氏模量,采用能量法计算断裂韧性,得出了页岩粘土基质的杨氏模量、硬度和断裂韧性。测试结果表明这种基于硬度的分类准则处理纳米压痕数据是方便合理的。页岩粘土基质力学特性在纳米尺度上具有各向异性,纳米尺度力学参数与层理方向相关。页岩不同力学参数的各向异性表现不同,杨氏模量各向异性较弱,断裂韧性各向异性较强。平行层理方向断裂韧性为垂直层理方向断裂韧性的80%。 相似文献
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随着温度的升高,花岗岩宏观力学参数往往经历略升高、小幅降低、大幅降低几个阶段。利用纳米压痕测试仪器,对热处理后的花岗岩中主要矿物成分进行纳米压痕试验,揭示花岗岩宏观力学参数随温度演化的微观机理,（1）温度在 300 ℃以内微观结构没有显著变化,基本上没有微裂纹产生,在300～500 ℃之间时岩体内部开始产生微裂隙,温度超过500 ℃时岩体内部产生大量微裂隙,并逐渐扩展增大;（2）石英在300 ℃以内弹性模量和硬度略有增加,超过300 ℃弹性模量和硬度开始下降。超过500 ℃晶体结构发生 相到 相转变,弹性模量和硬度急剧下降,长石在400～500 ℃之间时,弹性模量和硬度开始下降,超过800 ℃弹性模量和硬度急剧下降,云母在800 ℃以内弹性模量和硬度有所增加;超过800℃时弹性模量和硬度开始下降;（3）花岗岩宏观力学性能与主要矿物成分的力学性能和微观结构均相关,室温～300 ℃范围内主要受到前者控制,300～500 ℃范围内时受到两者联合控制,超过500 ℃后主要受到后者控制。研究结果可为研究花岗岩和其他岩石的温度效应提供实验数据和理论支持。 相似文献
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