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针对白鹤滩地下厂房开挖过程中所揭露的力学响应行为十分复杂的错动带,为研究其在高应力条件下的加卸荷力学特性,开展一系列不同应力水平和应力路径下的不排水三轴常规加、卸荷试验。研究结果表明:(1)卸荷过程中,错动带卸荷应力–应变曲线特征与初始围压相关性很大,错动带向卸荷方向回弹变形显著,从卸围压开始即表现出强烈的剪胀现象;卸轴压卸围压方案比增轴压卸围压方案的侧向扩展变形表现更为显著;且在试样表面都出现了张/张剪裂纹。(2)卸荷应力路径下,错动带变形模量劣化效应十分明显,随围压的减小而逐渐降低,基本呈三次多项式递减;体积模量随体积应变的增加而减小,整体呈负指数形式降低;泊松比则随体积应变逐渐增加,整体呈近似抛物线形式递增。(3)相同初始围压条件下,相较于加荷条件,卸荷条件下错动带的破坏应力有所降低,内摩擦角明显增大,而黏聚力则明显降低;卸轴压卸围压方案下的破坏应力劣化更显著。试验所采用的应力水平和应力路径基本涵盖和反映了错动带在洞室开挖过程中所经历的复杂的应力重分布过程,具有一定的代表性,地下厂房开挖后高边墙错动带黏聚力和内摩擦角取值基本可参考卸轴压卸围压应力路径下天然含水率错动带的试验结果,为后续进一步讨论错动带强度特征并建立错动带本构模型提供了有效依据。
In order to study the loading-unloading mechanical properties under the high-stress conditions, a series of undrained zones under different stress levels and stress paths are proposed to deal with the complicated dynamic displacement zone revealed during the excavation of the underground plant in Baihetan. Three-axis conventional plus, unloading test. The results show that: (1) During the unloading process, the characteristics of unloading stress-strain curve are greatly correlated with the initial confining pressure, and the deformation direction of the unloading zone is remarkable, starting from the unloading confining pressure A strong dilatancy phenomenon was observed. The unloading of shaft unloading and confining pressure program was more significant than that of the unconfined confining pressure program. The sheet / sheet shear cracks appeared on the specimen surface. (2) Under the unloading stress path, the degenerated modulus of staggered zone is obviously degraded, and decreases gradually with the decrease of confining pressure, and decreases by cubic polynomial. The bulk modulus decreases with the increase of volumetric strain, The negative exponent decreases; the Poisson’s ratio increases gradually with the volumetric strain, and the overall parabola increases. (3) Under the same initial confining pressure, compared with the loading condition, the failure stress of the moving belt under the unloading condition is decreased, the internal friction angle obviously increases, and the cohesion is obviously reduced; Under the confining pressure scheme, the failure stress is more obvious. The stress level and stress path adopted in the experiment basically covered and reflected the complex stress redistribution process of the dislocation belt during the excavation of the cavern, which was representative. The displacement of the high side wall after excavation of underground powerhouse The results of cohesion and internal friction angle can basically refer to the test results of the natural moisture content zone under unloading and unloading confining pressure path. For the further discussion of the characteristics of the staggered zone strength and the establishment of the structure model of the staggered zone, A valid basis.