损伤岩盐高温再结晶剪切特性的试验研究

EXPERIMENTAL STUDY ON HEATING RECRYSTALLIZATION EFFECT ON SHEAR CHARACTERISTICS OF DAMAGED ROCK SALT

岩盐矿床目前被公认为放射性核废料地质处置的理想场所。核废物的放射作用能使储库围岩温度极大升高,同时在岩盐晶体内部会发生高温再结晶作用。因此,研究高温再结晶对岩盐、特别是损伤岩盐的力学特性的影响,对处置库内核废料与外界生物圈的安全隔离具有十分重要的意义。通过试验,对无水芒硝岩盐试件60℃时剪切损伤、120℃时加热再结晶的剪切力学特性进行了研究。研究发现:(1)120℃下加热10h的损伤再结晶岩盐试件,其剪切峰值强度降低为原完好试件的82%,相应的变形模量为原来的1.5倍;(2)高温再结晶之后损伤岩盐试件仍具有完好试件的基本变形特征;(3)随温度由60℃升高到120℃,完好岩盐试件的剪切强度得到了一定提高,其中内摩擦角增幅较大;(4)高温再结晶可以恢复岩盐的内摩擦角,但是对于粘聚力的恢复表现不明显。

Salt deposit is commonly regarded as an ideal host for geologic disposal of radioactive nuclear wastes. The radiation of the wastes can significantly increase the ambient temperature of the waste repositories,so that heating recrystallization of the crystal of rock salt takes place simultaneously. The study of heating recrystallization effect on mechanical characteristics of rock salt,especially of damaged rock salt,is meaningful for the safe isolation of the nuclear wastes inside repositories from outside biosphere. The angle-changed shear tests for intact and damaged rock salt samples were carried out in the laboratory,respectively. The rock salt samples were loaded to peak shear strength and damaged at 60 ℃,and then heated and recrystallized at 120 ℃. The test results of heating recrystallization effect on shear characteristics of damaged rock salt samples are introduced in this paper. The test results indicate that the 120 ℃ heating recrystallization effect on damaged rock salt can recover the peak shear strength to 82% of that of original intact samples at 60 ℃,meanwhile the deformation modulus of the samples increase to 1.5 times of that of the original ones. Through tests,it is also found that the damaged rock salt samples suffering from heating recrystallization are still of the basic deformation characteristics as the same as intact samples,and the shear strengths of intact rock salt samples are improved with the temperature increasing from 60 ℃ to 120 ℃. It is concluded that 120 ℃ heating recrystallization can recover the inner friction angle of rock salt sample to some extent,but has little effect on the recovery of the cohesion.