新疆某渠道边坡填料的剪胀特性与变形失稳研究

The dilatancy and instability of an infilled material in a channel slope in Xinjiang

近年来,新疆基础工程建设数量剧增,迫切需要深入揭示重塑黄土力学特性,指导工程实践。研究采用新疆某引水渠道边坡的黄土填料进行试验,研究压实度对土料剪胀特性与变形失稳的影响规律。研究中,首先采用扫描电镜技术与CT技术分别检视土料的微、细观组构。在宏观力学试验中,一共考虑3个压实度水平和3个应力水平,首先进行不排水条件下饱和土的应力变形、剪胀特性和路径分析,然后在排水条件下进行比较验证。结果表明:介于松散土的剪缩行为与密实土的剪缩-剪胀行为2种典型现象之间,该土料还存在一种剪缩-剪胀-剪缩的体变现象,且不受排水条件的影响;该土料在应力平面上具有唯一的临界状态线,但其临界状态在压缩平面上受初始孔隙比影响,分布于一个带状区间内;该土料的失稳线斜率随压实度而增加,土体的应力状态需要达到较高的应力比才能进入失稳区,工程扰动导致渠坡失稳的可能性降低。

The amount and scale of engineering construction in Xinjiang develop greatly in recent years. Engineering practice necessitates that a comprehensive understanding on the reconstituted loess's mechanical behavior to provide theoretical support. In this research,laboratory tests were performed using an infilled loess material from a channel slope in Xinjiang,to investigate the dilatancy and instability of the material which are affected by the degree of compaction. Scanning electron microscope technique and CT technique were used firstly to examine the microscopic and mesoscopic compositions firstly. The stress-strain relationship,the dilatancy and the experienced paths were then analyzed under saturated undrained condition,with consideration of three levels of degree of compaction and three stress levels. Thereafter,the results are compared and verified under drained condition. The findings are below. Firstly,the material could demonstrate contraction-dilation-contraction behavior,between the contractive behavior at loose state and the dilative behavior at dense state. Secondly,the material has a unique critical state line in the stress plane,while its critical states are affected by initial void ratio,suggesting a belt region in the compression plane. Third,the slope of instability line increases with the degree of compaction,indicating a higher stress ratio to achieve instability region. Therefore potential instability led by engineering disturbance reduces at a higher degree of compaction.