Experimental study on seepage characteristics of rough fracture of limestone under loading-unloading of confining and osmotic pressures
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摘要: 裂隙面粗糙程度和加卸载环境对裂隙渗流特性的影响不可忽视。为研究不同裂隙面节理粗糙度系数(JRC)和围压、渗透压力(渗压)加卸载对石灰岩粗糙单裂隙渗流演化规律的影响,制备5组不同JRC石灰岩单裂隙试样,利用自研岩体裂隙渗流试验系统,开展了不同JRC裂隙试样在围压、渗压加卸载作用下的渗流试验研究。结果表明:不同JRC裂隙试样的渗流量和渗透率随围压增大而减小,加载时各试样渗透率均与围压呈幂函数关系,R2最小为0.9583,围压卸荷时存在明显滞回效应,卸载时JRC对滞回程度影响较大,与下降量和回升量呈对数关系;渗压加卸载过程,裂隙渗流量变化同渗压正相关,渗透率持续下降;一次渗压加卸载循环后的裂隙渗流量下降值与JRC相关性良好,提出了渗压加卸载后的裂隙渗流量预测模型。Abstract: The influences of the roughness of fracture surface and the loading-unloading environment on seepage characteristics of fracture cannot be ignored. To study the influences of the fracture surface with different joint roughness coefficients (JRC) and loading-unloading of confining and osmotic pressures on the seepage evolution laws of rough single fracture of limestone, five groups of limestone samples with a single fracture with different JRCs are prepared. The self-developed seepage test system for the fractured rock mass is used to conduct a seepage test of the fractured samples with different JRCs under loading-unloading of confining and osmotic pressures. The results show that the seepage flow and permeability of different fractured samples decrease with the increase of the confining pressure, and the permeability of each sample has a power function relationship with the confining pressure, with the minimum R2 of 0.9583. There is an obvious hysteretic effect during the unloading of the confining pressure. The JRC has a great influence on the hysteretic degree during unloading, which is logarithmic with the decline and recovery. During the process of loading-unloading of pressure, the change of seepage flow through the single fracture is positively correlated with the osmotic pressure, while the permeability decreases continuously. There is a good correlation between the decreased value of seepage flow through the single fracture and the JRC after a cycle of loading-unloading of pressure. A prediction model for seepage flow of fracture after loading-unloading of osmotic pressure is proposed.
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Keywords:
- limestone /
- rough fracture /
- confining pressure /
- osmotic pressure /
- loading-unloading /
- seepage test
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表 1 石灰岩物理性质
Table 1 Physical properties of limestone
物理量 计量单位 平均值 密度 g/cm3 2.70 吸水率 % 0.21 抗压强度 MPa 87.50 抗拉强度 MPa 8.20 抗弯强度 MPa 9.11 表 2 不同加卸载条件下渗流试验方案
Table 2 Schemes of seepage test under different loading and unloading conditions
试样编号 JRC 围压/MPa 渗压/MPa 加载速率/(MPa·s-1) M-1 2.64 2,3,4,6,8,10,8,6,4,3,2 0.5 0.005 M-2 7.78 M-3 11.40 M-4 15.47 M-5 19.51 H-1 2.64 3 0.2,0.5,0.8,1.0,1.2,1.5,1.2,1.0,0.8,0.5,0.2 0.001 H-2 7.78 H-3 11.40 H-4 15.47 H-5 19.51 -
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