冻融循环作用下砂土粒组变化的分形特征及其与长期强度的相关性分析  

Fractal characteristics of sand grain group changes under freeze-thaw cycles and its correlation with long-term strength

作　　者：刘启 张泽 张圣嵘[1,2] 恽晴飞 付峻松 LIU Qi;ZHANG Ze;ZHANG Shengrong;YUN Qingfei;FU Junsong(School of Civil Engineering/Institute of Cold Region Science and Engineering/Permafrost Institute,Northeast Forestry University,Harbin 150040,China;Northeast-China Observatory and Research-Station of Permafrost Geo-Environment of the Ministry of Education/Collaborative Innovation Centre for Permafrost Environment and Road Construction and Maintenance in Northeast China(CIC-PERCM),Northeast Forestry University,Harbin 150040,China;State Key Laboratory of Frozen Soil Engineering,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,China;Shanghai Changkai Geotechnical Engineering Co.,Shanghai 200093,China)

机构地区：[1]东北林业大学土木工程学院/寒区科学与工程研究院/冻土研究所,黑龙江哈尔滨150040 [2]东北林业大学东北多年冻土区地质环境系统教育部野外科学观测研究站/东北多年冻土区环境、道路建设与养护协同创新中心,黑龙江哈尔滨150040 [3]中国科学院西北生态环境资源研究院冻土工程国家重点实验室,甘肃兰州730000 [4]上海长凯岩土工程有限公司,上海200093

出　　处：《冰川冻土》2022年第6期1820-1832,共13页Journal of Glaciology and Geocryology

基　　金：国家自然科学基金委员会(NSFC)与俄罗斯基础研究基金会(RFBR)合作交流项目(42011530083);国家自然科学基金项目(41771078);黑龙江省交通投资集团有限公司科研项目(JT-100000-ZC-FW-2021-0129);黑龙江省重点研发计划项目(指导类)(GZ20220095)资助。

摘　　要：在季节冻土区施工时,冷暖交替所产生的冻融循环作用是寒区工程破坏的主要原因之一,还原土体受冻融作用时的性质和状态尤为重要。制备了不同冻融循环次数的砂土试样,使用球形模板压入仪测试冻结砂土的长期强度,利用分形理论以及显著性分析的方法研究了不同冻融循环次数下两种冻结砂土的粒组与长期强度的变化规律。结果表明:对于细砂(FS),分形维数DB与长期强度变化呈极显著正相关,其中≥0.15~0.20 mm和≥0.25~0.40 mm粒组与长期强度的拟合优度较好,为FS的优势粒级;对于中砂(MS),分形维数DB与长期强度呈微正相关,变化呈“竖向N”趋势波动,其中≥0.30~0.40 mm和≥0.40 mm粒组与长期强度的拟合优度较好,为MS的优势粒级;其他粒组含量与长期强度变化并无明显关联。冻融作用改变了土体中粗、细颗粒粒组的含量配比。同时,随着整体粒径区间的增大,优势粒级也随之增大,表现为冻结砂土的长期强度会随着某些粒级含量的增加呈现先降低后升高的趋势。研究结果可为受冻融作用地区长期强度的测定提供理论参考。Seasonally frozen soils are widely distributed in China in terms of area, and the freeze-thaw cycle effect generated by the alternation of cold and warmth is one of the causes of engineering damage in cold areas during construction, and it is particularly important to restore the nature and state of the soil when it is subjected to freeze-thaw action. Therefore, sandy soil specimens with different numbers of freeze-thaw cycles were prepared, and the long-term strength of frozen sandy soil was tested using a spherical template indenter. Using fractal theory and the microstructure image processing software ImageJ, the change law of grain group and longterm strength of two frozen sandy soils under different numbers of freeze-thaw cycles were studied. The results show that: for fine sand(FS), the fractal dimension DB has a highly significant positive correlation with the long-term strength variation, among which ≥0.15~0.20 mm and ≥0.25~0.40 mm have the best fit with the longterm strength, and are the dominant grain classes of FS. For medium sand(MS), the fractal dimension DB is slightly positively correlated with the long-term strength, and the variation shows a “vertical N” trend, in which the grain size content of ≥0.30~0.40 mm and ≥0.40 mm fits better with the long-term strength, and is the dominant grain class for MS. The content of other grain groups did not correlate significantly with the long-term strength change. The freeze-thaw action changed the content ratios of coarse and fine grain agglomerates in the soil. With the increase of the overall particle size interval, the dominant particle size also increases, which shows that the long-term strength of frozen sandy soil tends to decrease and then increase with the increase of the content of some particle sizes. The results of the study can provide theoretical reference for the determination of long-term strength in areas subject to freeze-thaw action.

关 键 词：冻融循环 长期强度 冻结砂土 粒组 分形维数 

分 类 号：TU41[建筑科学—岩土工程] P642.14[建筑科学—土工工程]