摘要
为了研究大坂山隧道围岩的抗冻特性，将采自隧道 Ｋ１０６＋４００截面处的岩样加工成 ２４块样品，样品的高度和直径均为 ５０ ｍｍ。将样品分成 ４组，每组 ６个样品、根据《公路工程石料试验规程》中的岩石抗冻性试验方法进行了隧道围岩试样的冻融损伤试验。４组样品分别进行了０次，７次， １４次和 ２５次冻融．试样冻融后的抗压强度分别为 ７７．７１， ６８．９５， ６３．７７和 ５０．７７ ＭＰａ．实验结果表明，该隧道围岩抗冻性能良好，不会由于冻融产生过快的风化，力学性能较稳定．此外，还利用ＣＴ对冻融前后的试样进行了检测，检测结果表明，冻融使试样的强度、密度和ＣＴ均值降低，ＣＴ的均方值增大、这种现象说明冻融损伤使试样的物理性能分布变得更加不均匀．冻融对试样的表层损伤较大。
In order to study the properties of the surrounding rocks of a tunnel in the Daban Mountain, rocks sampled from the Section K106+400 of the tunnel were machined into 24 pieces, whose height and diameter were 50 mm and 50 mm, respectively. These samples were arranged in 4 groups. There were 6 pieces of samples in every group. According to the rock material experimental standard, the anti-frost property of a rock is good when its strength after15 freezing-thawing cycles is larger than 75% of the strength before frost for the rock located at a site where the annual mean temperature is higher than -15℃. The rocks were sampled from the tunnel where the annual mean temperature is -3℃. The experiment was conducted between 20℃ and -15℃. Four groups of samples were experimented for 0, 7. 14 and 25 freezing-tha wing cycles, respectively. The final strengths of them are 77.71, 68.95, 63.77 and 50.77 MPa for the 4 groups. respectively. The anti-frost coefficients are 0.887, 0.820 and 0.653 for 7, 14 and 25 cycles, showing that the sampled rocks have a good anti-frost property. A CT detection of these samples were made in the State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, CAS. The thickness of CT scanning layer, 10 mm in interval, was 5 mm. The bandwidth of CT scanning was 3 mm. From Layers 1, 2, 5 and 6 in Picture 2, it could be seen that there is quartz within the rock. and the interior structure of the rock is inhomogeneity. The pre-frosted CT images are whiter than the post-frosted ones. Because frost damage lowers rock strength. the result as shown in CT images is that CT images get darker, i.e.. white area decreases and dark area increases. From the CT detection of the samples before and after frost. it is found that the strength, density. and CT value of the samples after frost decrease in comparison with those samples before frost. From the CT values it can be seen that their mean value gets lower and their variance gets larger after frost. This phenomenon indicates that frost enlarges the difference in properties within a sample, also enlarges rock inhomogeneity. Especially. CT values at both ends of the samples, 46.4 and 42.0, have largely decreased, indicating that the frost damage at both ends of a sample is larger than that at the middle of a sample.
出处
《冰川冻土》
CSCD
北大核心
2000年第3期206-210,共5页
Journal of Glaciology and Geocryology
基金
中国科学院"百人计划"基金!项目资助
