Damage to the Microstructure and Strength of Altered Granite under Wet-Dry Cycles
Damage to the Microstructure and Strength of Altered Granite under Wet-Dry Cycles
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DOI：
10.3390/sym10120716
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发表时间：
2018-12-01
期刊：
影响因子：
2.7
通讯作者：
Qin, Zhe
中科院分区：
文献类型：
--
作者：
Chen, Xuxin;He, Ping;Qin, Zhe
本文提出了一种具有一定时间内地下水对称上升和下降的对称形隧道或巷道围岩的分析方法。研究了水库水位对干湿循环的影响。通过力学试验和扫描电镜（SEM）研究了蚀变花岗岩的微观结构和强度变化及其演化过程。结果表明：(1)干湿循环削弱了蚀变花岗岩的强度。随着循环次数的增加，单轴抗压强度、弹性模量、黏聚力和内摩擦角均呈下降趋势，最大降幅分别为50.22%、63.84%、93.76%和53.90%。(2)干湿循环破坏了蚀变花岗岩的微观结构。SEM分析表明，在干湿循环作用下，蚀变花岗岩的内部结构由光滑、完整的内部结构转变为孔隙和裂纹的萌生、发育和扩展。利用扫描电镜测量了岩石的孔隙度和分形维数。定量分析了干湿循环作用下蚀变花岗岩的损伤程度。(3)通过岩石力学强度试验和扫描电镜、x射线衍射分析，探讨了蚀变花岗岩干湿循环损伤机理。研究结果为对称形状隧道的稳定性分析提供了依据，特别是在富水地区建造的对称圆形隧道和对称马蹄形隧道。
This paper presents an analytical method for surrounding rocks in symmetrically shaped tunnels or roadways, with the symmetrical rise and fall of groundwater over a certain period. The influence of reservoir water level on wet-dry cycles were studied. The changes in the microstructure and strength of altered granite and its evolution were explored using mechanical tests and scanning electron microscopy (SEM). The results showed that: (1) the wet-dry cycles weakened the strength of altered granite. Furthermore, the uniaxial compressive strength, elastic modulus, cohesion, and internal friction angle decreased with the increase of the number of cycles, while the maximum reduction in these parameters reached 50.22%, 63.84%, 93.76%, and 53.90%, respectively. (2) The wet-dry cycles damaged the microstructure of altered granite. The SEM analysis showed that, under wet-dry cycles, the structure of altered granite changed from a smooth and integrated internal structure to the initiation, development, and expansion of pores and cracks. The porosity and fractal dimension of rock were determined using the SEM results. The degree of damage to altered granite under wet-dry cycles was quantitatively analyzed. (3) According to the rock mechanics strength tests and SEM and X-ray diffraction analyses, the damage mechanism of altered granite subjected to wet-dry cycles was discussed. The results provide the basis for a stability analysis of symmetrically shaped tunnels, especially symmetrical tunnels constructed in water-rich areas such as symmetric circular tunnels and symmetric horseshoe tunnels.