橄榄岩蠕变特性及本构模型研究

Study on creep characteristics and constitutive model of peridotite

为了研究橄榄岩的蠕变力学特性,对取自中老铁路玉磨线安定隧道的橄榄岩开展常规压缩和不同围压下的蠕变试验。试验结果表明,饱和橄榄岩试件与干燥试件弹性模量的比值和其软化系数较为接近,而饱和试件的泊松比略大于干燥试件;橄榄岩加载后产生的瞬时应变以弹性应变为主,且其存在蠕变启动阈值;当轴向偏应力低于蠕变启动阈值时,橄榄岩仅产生瞬时应变,而无蠕变应变;当轴向偏应力高于蠕变启动阈值时,橄榄岩才会产生蠕变现象;随围压增大,橄榄岩的蠕变启动阈值和加速蠕变阈值有呈线性增大的趋势。在此基础上,根据橄榄岩的蠕变特点,建立一个7元件的非线性黏弹塑性蠕变模型来描述橄榄岩的蠕变行为,并利用蠕变试验结果对模型的合理性进行了验证。结果表明,所建模型能较好地反映该类岩石的蠕变力学行为。

In order to research the creep mechanical property of peridotite which was taken from the Anding Tunnel of the Yumo Line of the China-Laos Railway,creep test under different confining pressures and conventional compression test were carried out.The test results show that the ratio of the elastic modulus of saturated peridotite specimens to that of dry specimens is close to the softening coefficient peridotite.Meanwhile,the Poisson's ratio of the saturated peridotite specimens is slightly larger than that of the dry specimens.The instantaneous strain produced after peridotite loading is mainly elastic strain,and peridotite has a creep initiation threshold.When the axial deviatoric stress is lower than the creep initiation threshold,the peridotite only has instantaneous strain without creep strain.Only if the axial deviatoric stress is larger than the creep initiation threshold,creep phenomenon occurs in peridotite.As the surrounding rock pressure increases,the creep initiation threshold and accelerated creep threshold of peridotite have a linear increasing trend.Based on the creep mechanical property of peridotite above,a creeping model of 7-element nonlinear viscoelastic-plastic was established to describe the creep behavior of peridotite.At the same time,the rationality of the model was verified by the creep test results.The results show that the established model can better reflect the creep mechanical behavior of this kind of rock.