中文摘要：

三峡库区万州区侏罗纪红层中发育了许多近水平地层滑坡，目前对这些滑坡的成因机制存在争议，滑带土特性研究是滑坡成因机制研究的重要途径。为了认识滑带土的松弛特性，采用GDS非饱和土三轴试验系统对万州安乐寺滑坡滑带土进行了松弛试验研究。试验结果表明，滑带土应力松弛速率与初始应变具有线性关系，而围压对应力松弛速率影响不明显；在松弛过程中，土体体变几乎可以忽略不计。根据松弛试验数据，推导了滑带土的应力-应变-时间松弛模型，该松弛模型假定了应力-应变满足双曲线关系，应力-时间满足对数关系，模型可以较好的反映滑带土的应力松弛规律。研究结果为探讨三峡库区近水平地层滑坡的力学机制提供了模型和参数。松弛模型表明，安乐寺滑坡滑带土的松弛应力可以持续到零，这对近水平地层滑坡的成因机制研究及防治具有重要意义。

英文摘要：

There are many approximately horizontal slip surface landslides in Jurassic red strata in Wanzhou city of the Three Gorges Reservoir area. However, the formation mechanisms of these landslides are not clear. In order to explore the mechanism of these landslides, triaxial stress relaxation experiments with GDS unsaturated triaxial testing systems are carried out to investigate the stress relaxation properties of the sliding zone soil of Anlesi landslide. Test results show that the stress relaxation speed changes linearly with initial strain variation. However, it is independent of confining pressure. The soil volume changes little; and it can almost be ignored during the relaxation tests. Based on the stress relaxation tests, a new constitutive model for the stress-strain-time behavior of the sliding zone clay is introduced by assuming a hyperbolic stress-strain relationship and a logarithmic time-tress relationship. The comparison between the rheological model and experimental results reveals that the new rheological model presents the relaxation characteristics of the sliding zone clay nicely. And that also provides the model and parameters for the further researches on approximately horizontal slip surface landslides existing in Jurassic red strata in the Three Gorges Reservoir area. The new relaxation model indicates that the shear stress of the sliding zone clay will decrease to zero. The result is significant for researching and controlling the approximately horizontal slip surface landslides.