自然与饱水状态下深部斜长角闪岩蠕变特性

通过金川深部斜长角闪岩单轴压缩蠕变实验,选取典型蠕变曲线,发现该岩石黏弹性、黏塑性变形较瞬时变形偏小,卸载后弹性后效不显著。在5.1 MPa轴向应力下,自然状态的岩样近似纯弹性特征。饱水状态下岩样瞬时强度σ′b和长期强度σ′∞总体低于自然状态,且σ′∞已接近深部高地应力,因此,对于深部节理、裂隙很发育的岩体,应特别注意巷道排水,防止围岩因长期强度降低而导致巷道变形和破坏。自然与饱水状态下岩样瞬时弹性应变εme、瞬时塑性应变εmp随应力增大而增加,但增速逐渐放缓,饱水状态下塑性变形更显著;相同应力下,饱水状态岩样蠕变量大于自然状态,应变速率也总体快于自然状态,2种状态的蠕变速率在20~30 h时都逐渐稳定,且速率曲线随应力增大,微裂隙压密,彼此逐渐靠近,岩样处于相对硬化阶段;当轴向应力达到66.3 MPa后,饱水状态蠕变速率有相对加速趋势,速率曲线随应力增大先往左下移动,再朝右上移动,而自然状态蠕变速率曲线总体向右上移动。最后,通过蠕变数据分析,推导γ=ασk型经验方程,对蠕变试验数据进行回归拟合,拟合结果证明该蠕变经验模型的正确性。金川矿区斜长角闪岩蠕变实验研究为分析深部巷道该类围岩流变稳定性及支护方案优化等提供有效帮助。

基于三维离散元的沥青砂浆蠕变研究

本文基于单轴压缩试验和单轴蠕变试验,获取不同温度和加载强度情况下沥青砂浆蠕变的荷载-位移曲线,采用1stopt软件对蠕变柔量进行拟合,获取其广义Burgers模型参数,并利用该参数进行单轴蠕变三维离散元虚拟试验。将得到的数值模拟结果和室内试验结果进行对比,对比显示在初始蠕变阶段试验结果和模拟结果有一定差异,但在稳定蠕变阶段两者趋势相同并且数值相差在一定范围值内。因此通过运用PFC模拟沥青胶浆的蠕变试验是可行的。

Integrated identification method of rheological model of sandstone in Sanmenxia bauxite

Based on the uniaxial compression creep experiments conducted on bauxite sandstone obtained from Sanmenxia,typical creep experiment curves were obtained.From the characteristics of strain component of creep curves,the creep strain is composed of instantaneous elastic strain,ε（me）,instantaneous plastic strain,ε（mp）,viscoelastic strain,ε（ce）,and viscoplastic strain,ε（cp）.Based on the characteristics of instantaneous plastic strain,a new element of instantaneous plastic rheology was introduced,instantaneous plastic modulus was defined,and the modified Burgers model was established.Then identification of direct screening method in this model was completed.According to the mechanical properties of rheological elements,one- and three-dimensional creep equations in different stress levels were obtained.One-dimensional model parameters were identified by the method of least squares,and in the process of computation,Gauss-Newton iteration method was applied.Finally,by fitting the experimental curves,the correctness of direct method model was verified,then the examination of posterior exclusive method of the model was accomplished.The results showed that in the improved Burgers models,the rheological characteristics of sandstone are embodied properly,microscopic analysis of creep curves is also achieved,and the correctness of comprehensive identification method of rheological model is verified.