软岩三维弹黏塑性本构模型

为了有效地描述软岩的软化特征,首先推导了以压为正统一强度理论表达式,该理论可以考虑材料拉压强度不等及中间主应力效应,适合岩土工程界以压为正的使用习惯以及岩土材料拉压强度不等的特性;其次推导了以压为正统一强度理论π平面的极限线;第三,基于推导的π平面的极限线,结合Yin-Graham模型,推导了软岩的三维统一弹黏塑性本构模型表达式。根据针对取自日本石川县能登半岛端部的硅藻质泥岩所进行的不同围压、不同加载速率条件下的应变控制式和应力控制式固结不排水三轴试验资料确定了模型参数,进行了弹黏塑性数值模拟分析。并与三轴试验结果进行了对比分析,结果表明:本文建立的软岩三维统一弹黏塑性软化本构模型的数值模拟结果与试验结果非常接近,可以很好地模拟软岩的应变软化特征。

Three-dimensional nonlinear elastic viscoplastic constitutive model of soft rock

In order to depict the softening characteristics of soft rock effectively,firstly,a formula for the unified strength theory taking the compression as positive is established.This theory considers the strength difference of tension and compression and the mediate principal stress effect.So it is suitable for geotechnical materials.Secondly,the limit line in π plane of this theory is derived.Thirdly,a three-dimensional unified elastic viscoplastic softening constitutive model is derived based on the limit line in π plane and the model of Yin-Graham.Parameters of the model are determined with the relevant triaxial tests on a sort of diatom soft rock which is distributed in Nodo Peninsula in Japan,belonging to the late tertiary Miocene,and formed of debris diatom,clay and volcanic ash by depositing,and usually distributed in inshore regions.And finally,numerical simulation is done.The simulated results of the three-dimensional unified elastic viscoplastic softening constitutive model are very close to the experimental results,proving that the model can be used to accurately simulate the softening behaviors of soft rock.