异向性岩芯冰的反复压缩-退火实验研究

在蠕变试验机上完成了三组(6块样品)单轴反复压缩-退火实验,试验机载荷精度为1％,实验温度为-2±0.2℃。实验样品取自南极洛多姆冰帽BHQ钻孔的冰岩芯。三组试样的受压方向分别与冰岩芯的轴向平行、成45°角和垂直。试验前试样的C轴组构为单极大型或大致为单极大型,晶粒大小不一。用0.8MPa的初始轴向应力对样品进行压缩,达到10％应变后卸载退火72小时。每组实验如此反复进行6次。结果表明,在较高的温度和大载荷下,样品经反复压缩-退火,其初始组构特征消失,代之以小环状组构和细的、等粒的晶体,某些情况下发展为多极大型组构。结构和组构分析表明,新组构的形成机制主要是再结晶作用。随着压缩-退火反复进行,六块样品在组构上的差异减少,它们的流变特性趋于一致,晶粒尺寸逐渐减少而趋于一个稳定值。

REPEATED COMPRESSION-ANNEALING EXPERIMENTS ON ANISOTROPIC CORE ICE

Three runs (6 samples) of repeated uniaxial compression-annealing experiments were conducted on a creep testing machine with a loading accuracy of 1 % at-2±0.2℃. The tested samples were cut from BHQ, ice core. Compression axes were parallel, at an angle of 45 and normal to the vertical of them core respectively. The initial orientation fabrics of samples were single-maximum pattern or approximate single-maximum pattern with different mean grain size. The sample was compressed with an initial axial stress of 0.8 MPa, until 10% axial strain was obtained, and then annealed for 72 hours. Such compression-annealing procedure was repeated 6 times for a run. The experimental result shows that under a warm temperature and large load, the initial features of structure and fabric disappear finally, and a small circle girdle fabric with fine equigranular grains appears, and a mult-maxima fabric developes to some extent. Analysis of structure and fabric shows that the formation mechanism of new fabrics in these experiments is principally recrystallization. With the repetition of compression-annealing,the difference in the fabric of the six samples is reducing, their rheological behavior tends to be uniform, and their grain size decreases towards a steady state value.