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RESEARCH OF UNLOADING RATES OF CONFINING PRESSURE UNDER PORE WATER PRESSURE CYCLES ON MECHANICAL PROPERTIES OF SANDSTONE
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摘要: 针对三峡库区消落带边坡岩体的开挖，通过室内三轴卸荷试验，研究在不同孔隙水压循环次数和围压不同卸荷速率下砂岩的力学特性。结果表明：1）水岩作用对砂岩的偏应力峰值强度和变形模量均产生显著影响，随着孔隙水压升降循环次数的增加，偏应力峰值强度和变形模量逐渐减小；随着围压卸载速率的加快，偏应力峰值强度和变形模量增大；2）随着围压卸荷速率的加快和孔压循环次数的增加，砂岩破坏时的轴向和环向应变围压柔量及峰值围压均不断降低，对环向应变围压柔量的影响比对轴向应变柔量更大；3）在0.3 MPa的孔隙水压循环作用下，砂岩破坏时的破裂角与卸荷速率没有明显的线性关系。Abstract: Considering the actual excavation conditions of the water-level fluctuation zone in the Three Gorges reservoir area, the effects of different pore water pressure cycles and unloading rates of confining pressure on the mechanical properties of sandstone were studied by the indoor triaxial unloading experiment. The results were as follows:1) the effect of the pore water pressure cycles and unloading rates of confining pressure on peak intensity of deviator stress and deformation modulus of sandstone was significant. The more the cycles, the smaller the peak intensity and deformation modulus; the faster the unloading rates, the larger the peak intensity and deformation modulus; 2) when destroyed, axial and circumferential rates of strain variations or peak confining pressure all increased with the increase of pore water pressure cycles and decreased with the increase of unloading rates of confining pressure, however, the impact on the circumferential was more obvious than the axial; 3)the rupture angles of the sandstone under 0.3 MPa pore water pressure were not relevant to the unloading rates of pore water pressure.
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Key words:
- confining pressure /
- unloading rate /
- pore water pressure cycle /
- sandstone /
- strength deterioration
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