Science Technology and Engineering
1671-1815
2024
24
19
8193
8200
10.12404/j.issn.1671-1815.2303398
article
超固结黏土不排水剪切的屈服与临界状态
Yield and critical state of over-consolidated saturated clay under undrained shear
以研究超固结黏土的屈服与临界状态为目的，通过GDS三轴试验仪开展了一系列不同超固结状态的黏土不排水剪切试验。为了分析黏土的应力路径，选取了能描述超固结状态不同时土的屈服特性的ALPHA(α)模型。分析了黏土的偏应力/孔压-应变曲线变化趋势，并确定了孔压达到峰值时土体为破坏状态。根据应力破坏点拟合出临界状态线,提出了针对不同超固结比的不排水抗剪强度的计算公式。试验结果表明:不排水剪切试验中，前期固结压力相同时，超固结比越小，抗剪强度越高，但是屈服强度并非随超固结比的降低而单调递增变化；超固结比相同时，前期固结压力越大，抗剪强度越高，屈服强度也越高；正常固结和轻超固结土的破坏应变皆在5%左右，而重超固结土则呈现明显的剪胀现象和脆性破坏，破坏应变小于2.5%；正常固结和轻超固结土的应力路径呈“S”型，重超固结土的应力路径呈不断增长的趋势。根据破坏标准，重超固结土和轻超固结土、正常固结土共用一条临界状态线，不排水抗剪强度计算公式参数较少，易获取，易嵌入本构模型中，应用方便。
To study the yield and critical state of over-consolidated saturated clay, a series of undrained shear tests of saturated clay in different over-consolidated states were carried out by GDS triaxial tester. To analyze the stress path of saturated clay,and the ALPHA(α) model was selected to describe the yield characteristics of soils in different over-consolidation states. The variation trend of deviatoric stress/pore pressure - strain curves of saturated clay was analyzed , The failure state was identified when the pore pressure increased to the maximum value. The critical state line is fitted according to the stress failure points. The calculated formulas for the undrained shear strength with different over-consolidation ratios are presented. The results show that with the same preconsolidation pressure, the shear strength increases with the decrease of over-consolidation ratio. However, the yield stress do not monotonically increases with the decrease of over-consolidation ratio. With the same over-consolidation ratio, the shear strength increases with the increase of the preconsolidation pressure, and so dose the yield stress. The failure strain of normal consolidated soil and light over-consolidated soil is about 5%, while that of heavy over-consolidated soil is less than 2.5% with obvious dilatation and brittle failure. The stress paths of normal consolidated and light over-consolidated soils are "S" type, while the stress paths of heavy over-consolidated soils are in trend of increasing. According to the failure criterion, heavy over-consolidated soils share the same critical state line with light over-consolidated and normal consolidated soils. There are few formula parameters for calculating undrained shear strength, which is easy to be obtained and embedded in the constitutive models, and it is convenient for application.
黏土;超固结比;临界状态;α屈服面模型;不排水抗剪强度
Saturated clay ; Over-consolidation ratio ; Critical state ; α yield model ; Undrained shear strength
刘莹,朱圣焱,李艳,马少坤
Liu Ying, Zhu Shengyan, Li Yan, Ma Shaokun
jsygc/article/abstract/2303398