围压作用下盐岩损伤恢复研究

Study of Damage Recovery of Salt Rock Under Confining Pressures

为了解在围压作用下盐岩损伤恢复特性和盐岩损伤与强度之间的联系,设计了盐岩在不同围压、不同稳压时间之后的盐岩强度测试试验。结果表明:加载初期,盐岩弹性模量随着稳压时间的增加而逐渐增大,且随着稳压时间的增加,盐岩峰值应力对应的轴向应变和横向应变均逐渐增大;盐岩损伤与强度之间存在负相关联系;随着稳围压时间的增加,盐岩强度逐渐增大,最后保持在趋于相对稳定的状态。在围压作用下盐岩损伤愈合可以分为损伤快速恢复阶段和损伤缓慢恢复阶段,对于不同稳压大小,盐岩损伤恢复2个阶段有明显的时间节点,其中在损伤快速恢复阶段盐岩强度增幅比较明显;在损伤缓慢恢复阶段,盐岩强度增幅较小。在一定范围内,盐岩损伤快速恢复阶段的时间长短随着稳压阶段围压的增大而逐渐减小,当σ_3=5 MPa时,所需时间T=12 h;当σ_3=30 MPa时,所需时间T=4 h;当σ_3=50 MPa时,所需时间T=2 h。增加稳围压阶段的围压可以一定程度上缩短盐岩损伤快速恢复阶段时间,但是增大围压可能会对盐岩造成新的损伤。

In order to understand the salt rock damage recovery characteristics and the connection of damage and strength under the effect of confining pressure,different test was designed for salt rock with different confining pressure and different holding time of confining pressure. The results showed that at early loading,the salt rock elastic modulus increased gradually along with the increase of the pressure holding time,and the increase of pressure holding time,the corresponding axial strain and lateral strain of salt rock peak stress increased gradually. There was a negative correlation between salt rock damage and strength. With the increase of holding time of confining pressure the intensity of salt rock gradually increased,and finally tended to maintain a relatively stable state. The damage recovery of salt rock could be divided into rapid damage recovery phase and slow damage recovery phase under the effect of confining pressure,and there was a distinct time node for different salt rock damage recovery phase. In the rapid recovery stage,the strength of salt rock increased obviously,but in the slow recovery stage,the intensity of salt rock increased little. Within a certain range,with the increase of the strength of confining pressure in the stage of holding confining pressure,the duration of salt rock rapid damage recovery phase was gradually reduced. When σ_3 were 5,30,and 50 MPa the time required 12,4,and 2 hours,respectively. The duration of salt rock rapid damage recovery phase can be shorten with the increase of the strength of confining pressure in the stage of holding confining pressure.However,with the increase of the strength of confining pressure,new damage may be caused in the salt rock.