循环加载对沉积岩岩石Kaiser效应影响的试验研究

Experimental study on the influence of cyclic loading on Kaiser effect of sedimentary rocks

为获取不同沉积岩岩石更加合理的Kaiser效应点对应的应力值Kσ,采用声发射技术进行单轴循环加载试验,探讨加载循环峰值应力pσ、加载速率和含水率对Kaiser效应的影响,提出合理的多循环加载模式。试验结果表明:(1)随着加载速率或含水率的增加,细砂岩振铃计数和能量降低,Felicity比(FR)变化不明显;(2)pσ对砂岩Kaiser效应的影响显著于加载速率、含水率,当pσ较大于先前最大应力hmaxσ时,会使岩石损伤记忆进一步劣化,导致FR变化显著于当pσ小于或稍大于hmaxσ时;(3)采用循环加载KE试验时,粉砂岩、细砂岩、中砂岩、粗砂岩、砂质泥岩、泥岩、石灰岩等合理的首循环pσ分别小于岩石单轴抗压强度cσ的25.65%,21.66%,12.31%,11.31%,23.40%,3.61%,4.32%,之后循环pσ不超过cσ的59.39%~75.72%;(4)通过对σK/σc逐步回归分析发现,弹性模量、埋深、cσ能进入其回归方程,拟合度为0.556,随着埋深的增加,Kσ呈线性增加,相关系数R2为0.592。研究结果为Kaiser效应测试地应力提供理论依据和借鉴。

In order to get more reasonable corresponding stress value( K σ ) in Kaiser effect points of different sedimentary rocks,the uniaxial cyclic loading tests were conducted,combined with acoustic emission technology. The influence of the loading cycle peak stress( p σ ),the loading rate and the moisture content on Kaiser effect for rocks was discussed,and a reasonable multi-cyclic loading model was proposed. The results indicate that,as the loading rate or the water content increases,both the ringing count and the energy of fine sandstone decrease but Felicity ratio(FR) changes insignificantly,and that the impact of the loading cycle peak stress on sand Kaiser effect is more significant than the loading rate and the water content,and when p σ is greater than the previous maximum stress( hmax σ ),the damage memory of rock will be further deteriorated which results in that FR changes more significantly. It is also shown from cyclic loading KE tests that the reasonable values of first circulation p σ of various sedimentary rocks such as siltstone,fine sandstone,medium sandstone,coarse sandstone,sandy mudstone,mudstone and limestone are respectively less than 25.65%,21.66%,12.31%,11.31%,23.40%, 3.61% and 4.32% of the corresponding uniaxial compressive strengths( c σ ),and other cyclic p σ does not exceed 59.39% to 75.72% of c σ . Stepwise regression analysis ysis of σK/σc reveals that the elastic modulus,the buried depth and c σ can enter the regression equation with a fitting degree of 0.556. K σ is a linear function of the buried depth with a correlation coefficient of 0.592. The research results provide a theoretical basis and reference for measuring the in-situ stress by Kaiser effect.