考虑中主应力变化的原状黄土变形特性研究

Deformation characteristics of undisturbed loess considering the change of intermediate principal stress

为研究在高围压条件下考虑中主应力变化的原状黄土变形特性,利用西安理工大学真三轴仪对原状黄土进行了控制固结围压和中主应力b值的等b等p(p为球应力)剪切试验,试验给出了高围压条件下各主应变之间的关系,得到了不同高围压条件下的破坏应变与不同b值阶段的影响规律。结果表明:高围压条件下,所有b值阶段的ε3均为膨胀变形;b=0.2为中主应变变形临界点,0≤b<0.2为中主应变膨胀变形,0.2<b≤1.0为中主应变压缩变形。在高围压状态下,b值对应变的影响要远远大于围压对应变的影响。将b值增量对应变的影响程度定义为b值敏感度K(ε),中主应变的b值敏感度K(ε_(2))、小主应变的b值敏感度K(ε_(3))和广义应变的b值敏感度K(ε_(s))在b值为0~0.7之间均增长,0.7~0.9之间受b值变化影响减弱,0.9~1.0受b值变化影响最大。K(ε_(v))基本在0~5范围内,说明在不同中主应力阶段破坏体应变受b值变化的影响程度较小。

In order to study the deformation characteristics of the undisturbed loess considering the change of the intermediate principal stress under high confining pressure conditions,equal b and equal p(p is the spherical stress)shear tests with controlled consolidation confining pressure and medium principal b values were conducted on undisturbed loess using a true triaxial instrument of Xi’an University of Technology.The relationships between the principal strains under high confining pressure were given,and the influence law of the failure strain and different b-value stages was revealed under different high confining pressure conditions.The results show that under the condition of high confining pressure,e3 of all b-value stages is expansion deformation,b=0.2 is the critical point of intermediate principal strain deformation;0≤b<0.2 is the intermediate principal strain expansion deformation,and 0.2<b≤1.0 is the intermediate principal strain compression deformation.In the high confining pressure state,the influence of the b value on the strain is much greater than the influence of the confining pressure on the strain.The degree of influence of b-value increment on strain is defined as b-value sensitivity K(_(ε)),and b-value sensitivities K(ε_(2)),K(ε_(3))and K(ε_(s))all present an increasing trend when b-value lies between 0 and 0.7,are less affected by change in b-value between 0.7 and 0.9,and most affected by change in b-value between 0.9 and 1.0.K(ε_(v))mostly falls in the range of 0 to 5,indicating that the failure volumetric strains in intermediate principal stress stages are less affected by the change of b-value.