渗透压与围压对粉砂质泥岩流变特性的影响

为了研究渗透压及围压对岩体蠕变特性的影响,对三峡库区巴东组二段粉砂质泥岩进行了不同围压和渗透压下的三轴蠕变实验。根据试验结果,在分析粉砂质泥岩蠕变特性曲线的基础上,探讨了围压和渗透压对岩体蠕变特性的影响过程和机理。最后,采用等时应力-应变曲线法和稳态蠕变速率法求得了粉砂质泥岩在不同围压和渗透压下的蠕变长期强度。结果表明:①粉砂质泥岩瞬时弹性模量随着偏应力等级的增加而减小;②孔隙水压在蠕变初期能够减小轴向应变,但在蠕变后期由于其有利于裂纹扩展而增大了轴向应变;③渗透压缩短了岩石蠕变破坏的时间,使蠕变破坏呈现出一定的脆性特点;④渗透压的存在有利于岩石裂隙的扩展和贯通,因而降低了岩石蠕变的长期强度,但是围压的存在增大了蠕变长期强度。研究成果为深入认识和了解三峡库区粉砂质泥岩的流变力学特性提供了重要的试验和理论依据。

Effects of Osmotic Pressure and Confining Pressure onthe Rheological Properties of Silty Mudstone

Triaxial rheology tests under different confining pressures and osmotic pressures were carried out on the silty mudstone from the Badong formation in Three Gorges Reservoir area to study the effect of osmotic pressure and confining pressure on the rheological properties of rock mass.The collection and preparation of rock specimens as well as the test scheme are introduced in detail.Through analyzing the creep curves of silty mudstone,the osmotic pressure and confining pressure's influences on the rheological process and mechanism of silty mudstone are discussed.Furthermore,creep long-term strength of silty mudstone under different confining pressures and osmotic pressures is obtained according to the stress-strain isochronal curves and the steady-state creep rate.Results show that: 1) the instantaneous elastic modulus of silty mudstone decreases as the stress level increases;2) pore water pressure could reduce the axial strain in the initial stage of creep,but increase the axial strain in the later stage of creep because of crack extension;3) osmotic pressure shortens the time of creep damage and causes some characteristics of brittle failure;4) osmotic pressure is conducive to the expansion and coalescence of rock fissures,which yields the reduction of the creep long-term strength of rock;whereas confining pressure increases the creep long-term strength.The results provide important experimental and theoretical references to understanding the creep characteristics of silty mudstone in the Three Gorges Reservoir area.