夏季南极固定冰单轴压缩强度及试样破碎规律研究

2012年11月—2013年4月中国第29次南极科学考察期间,针对南极夏季固定冰单轴压缩性质开展了研究。使用冰芯钻直接在平整冰层钻取力学试样,取样冰厚为149 cm,其中颗粒冰、柱状冰和片状冰分别占采样冰芯总长度的15.4%、72.5%和12.1%;单轴压缩试样只采用柱状冰部分,加工好的力学冰样尺寸为直径9 cm,长度为18 cm;共设置5个试验温度(-2、-4、-6、-8和-10℃),加载应变速率在10-6—10-2s-1。利用统计方法分析试验结果,建立了南极夏季海冰单轴压缩强度与孔隙率和应变速率的关系式,以及综合考虑应变速率和温度影响下的单轴压缩强度定量表达式;同时,基于分形理论对单轴压缩试样破碎块分布规律进行了分析,结果显示碎块长度分形维数随着温度和应变速率的降低有增大趋势。在特别低应变速率下海冰试样整体发生蠕变时,无法采用分形方法讨论海冰内部破碎程度。

Study on the uniaxial compressive strength and crushing regulation of the landfast Antarctic sea ice in austral summer

This paper presents the uniaxial compressive properties of landfast Antarctic sea ice in austral summer. The sea ice samples were collected during the 29th Chinese National Antarctic Research Expedition undertaken between November 2012 and April 2013. Specimens for mechanical testing were sampled using a Kovacs drill from 149-cm -thick ice. The sea ice comprised granular ice (15.4%), columnar ice (72.5%), and platelet ice (12.1%). For the mechanical tests, specimens 9 cm in diameter in cross section and 18 cm in length were cut from the columnar ice layer and then tested under different temperatures (–2, –4, –6, –8, and –10 °C) and strain rates ranging from 10^-6 to 10^-2 s^-1. Based on the experimental data, the uniaxial compressive strength of the sea ice was described as a function of porosity, and a quantitative expression of the uniaxial compressive strength, which comprehensively considers the influences of strain rate and temperature, was established. Moreover, the distribution of fragments from the uniaxial compression specimens was analyzed based on fractal theory. The results showed the fractal dimension of the fragment length increased steadily as the temperature and strain rate decreased. However, the fractal method could not be used to discuss the breaking degree of ice when creep-fatigue occurred at low strain rates.