超固结度对超固结饱和黏土不排水蠕变特性的影响研究

Influences of overconsolidation ratio on undrained creep behavior of overconsolidated saturated clay

以具有不同超固结度的重塑黏土试样为研究对象,在加载应力比等同于临界状态线斜率的应力条件下开展了一系列不排水蠕变试验,研究了超固结饱和黏土的蠕变特性。试验结果表明,对强超固结度黏土试样,随着蠕变时间的增加,孔压一直降低,并从正孔压降到负孔压。强超固结度试样的初始应力路径虽然都到达了正常固结土试验获得的临界状态线,但强超固结度的试样在蠕变阶段并不破坏。在蠕变初始阶段,对于不同强超固结度轴应变速率与对数蠕变时间的关系线是相互平行的直线。整个蠕变过程中,强超固结度试样都处于剪胀状态中,且超固结度越大,到达最大剪胀状态的蠕变时间越长。在相同的应力比下,超固结度是影响超固结试样不排水蠕变破坏与否的重要因素。

The results from creep tests on reconstituted clay are presented and used to develop a preliminary framework of undrained creep behavior of overconsolidated clay. Based on the results of undrained creep tests on the samples with different OCRs under the same stress ratio close to the slope of CSL, as the creep time increases, the pore pressure decreases to the end of creep, from a positive value to a negative one. The stress paths of the specimens with different OCRs all reach the critical state line. However, the highly overconsolidated specimens do not fail. At the beginning of creep, there are parallel lines for the relationship between the axial strain rate and the creep time for different OCRs. The specimens with higher OCRs are all in the state of stress dilatancy during the undrained creep. The higher the value of OCR is, the much more creep time the specimen reaching the greatest dilatancy state needs. Under the same stress ratio, the OCR is the important factor influencing the specimens to fail or not.