Impact of biochar on the desiccation cracking behavior of silty clay and its mechanisms
Impact of biochar on the desiccation cracking behavior of silty clay and its mechanisms
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DOI：
10.1016/j.scitotenv.2021.148608
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发表时间：
2021-07-05
影响因子：
9.8
通讯作者：
Shi, Bin
中科院分区：
文献类型：
--
作者：
Lu, Yu;Gu, Kai;Shi, Bin
近年来，生物炭在环境岩土工程中得到了广泛的应用。然而，其对土壤开裂的影响尚未完全了解。研究了不同木质生物炭掺量对粉质粘土干燥开裂特性的影响，并结合图像和微观结构分析阐明了其机理。结果表明，生物炭对土壤干燥开裂特性的影响贯穿于水分蒸发和开裂发展的全过程。蒸发速率随着生物炭含量的增加而增加，但随着生物炭含量的增加而降低。在裂缝发展阶段，生物炭的加入增加了土壤的开裂含水量，诱发了土壤中环状裂缝的形成，改变了土壤裂缝的发展过程。定量分析结果表明，添加5%和10%的生物炭后，混凝土表面裂缝率分别降低了11.59%和34.32%，平均裂缝宽度分别降低了14.83%和34.51%。同时，生物炭改良土的单裂隙大多为细裂隙。此外，未添加生物炭的土壤表面裂纹率随着干湿循环次数的增加先增加后趋于稳定，而添加生物炭的土壤表面裂纹率略有下降。对比1次和5次循环后的裂缝网络，添加5%和10%生物炭的土样裂缝数量分别减少了-1.51%和19.24%和15.29%和36.92%，表明添加生物炭后，土样在循环过程中的抗裂性增强。总之，添加生物炭可以通过（1）降低土壤表面的张应力，（2）增加土壤颗粒之间的排斥力，（3）占据土壤颗粒之间的收缩空间，以及（4）降低土壤颗粒之间的拉伸强度来抑制干燥开裂。(c)2021爱思唯尔有限公司版权所有。
Biochar has recently been widely used in environmental geotechnical engineering. However, its impact on soil cracking is not fully understood. In this study, the influence of different wood biochar dosages on the desiccation cracking characteristics of silty clay was studied, and the mechanism was elucidated through a combination of image and microstructural analysis. The results indicate biochar affects the desiccation cracking characteristics of soil across the whole process of water evaporation and crack development. The evaporation rate decreased with low amounts of biochar, but increased as the biochar content increased. At the stage of crack development, the addition of biochar increased the soil cracking water content, induced the formation of annular cracks in soil, and changed the soil crack development process. Quantitative results of the stabilized cracks show the surface crack ratio was decreased by 11.59% and 34.32%, and the average crack width was decreased by 14.83%, and 34.51%, after 5% and 10% biochar addition, respectively. Meanwhile, most of the single cracks in biochar-amended soil are fine. In addition, the surface crack ratio of soil without biochar addition first increased and then stabilized with an increase in the number of wetting-drying (W-D) cycles, while that of the biochar-amended soil decreased slightly. Comparing the crack networks after one and five W-D cycles, the number of cracks formed with 5% and 10% biochar addition decreased by -1.51% and 19.24%, and 15.29%, and 36.92%, re-spectively, indicating that after the addition of biochar, the soil becomes more resistant to cracking under W-D cycles. In summary, the addition of biochar may have inhibited desiccation cracking by (1) reducing the tensile stress on the soil surface, (2) increasing the repulsive forces between soil particles, (3) occupying the shrinkage space between soil particles, and (4) reducing the tensile strength between soil particles. (c) 2021 Elsevier B.V. All rights reserved.