层状盐岩力学特性研究进展

ADVANCES IN RESEARCHES OF THE MECHANICAL BEHAVIORS OF BEDDED SALT ROCKS

盐岩具有孔隙度低,渗透率小,损伤自恢复和塑性变形能力大等特性.本文着眼于深部盐岩能源地下储备,在简要介绍国内外盐岩力学特性研究现状基础上,着重综述了近期关于层状沉积型盐岩工程力学特性研究的进展.层状盐岩压缩试验表明泥质硬石膏夹层对盐岩体的变形和破坏特性有明显的影响,揭示了复合岩体的变形和破坏机制;层状盐岩流变试验表明层状盐岩的蠕变主要由盐岩层控制,硬夹层的存在对溶腔围岩的长期蠕变起到抑制作用;为了深入了解界面的力学特性,开展了层状盐岩直接剪切试验、间接拉伸试验和界面微观分析试验,试验表明层状盐岩体中盐岩夹层界面具有较强的黏结力,这十分有利于盐岩溶腔的密闭性和稳定性;针对特殊的层状岩体提出了复合岩体Cosserat介质扩展本构模型,并应用于层状盐岩构造中能源储库稳定性分析中.最后指出了层状盐岩工程力学特性研究中值得关注的几个重点研究方向.

The engineering mechanical properties of bedded salt rocks are investigated for the purpose of understanding energy storage in a deeply bedded salt rocks formation. Compression tests show that the presence of anhydrite interlayers affects strongly the deformation and failure of the bedded salt rocks. A ＇stress drop＇ phenomenon of stress-strain curves is observed in low confining pressure cases and it denotes that the anhydrite layers fracture prior to the salt rocks. Creep tests on the salt rocks, the anhydrites and the composite rocks imply that creep deformation of surrounding rocks of a storage cavern is controlled by the salt rock layer, and long-term volume shrinkage is restricted by the anhydrite layers. Direct shear tests, Brazilian disk tests and TEM tests are carried out to investigate the mechanical properties of the interfaces between the anhydrites and the salt rocks. These experiments show that the interfaces are bonded perfectly and are strong, which results in good sealability and stability of the energy storage caverns in the bedded salt rocks. Also in this paper, the Cosserat constitutive theory is extended in special cases and is applied to stability analyses of the salt caverns in the bedded salt rock formation. Finally, several important future research directions on the mechanical properties of the bedded salt rocks are pointed out.