摘要
2020年3月30日四川省西昌市森林火灾发生后,该地区的地质灾害显著增多,火灾对表层土壤产生一定影响,但目前对火灾影响土壤的物理力学性质的机制及致灾特征研究尚浅。以未遭受火灾区域和遭受火灾区域的表层土样为研究对象,进行了总有机碳、颗粒级配和X射线衍射分析,并结合室内相关力学试验研究了火灾前后土样的黏土矿物含量及力学强度特性。试验结果表明:①火灾发生后土壤有机质含量降低,导致不稳定的无机土壤裸露;土壤团粒结构稳定性降低,土壤中细小颗粒含量增高,细小颗粒容易阻塞土壤表层孔隙,不利于雨水或地面径流的下渗;②火灾的高温过程使得土壤中黏土矿物含量变化,高岭石(Kao)相对含量减少了10%,伊利石/蛭石混层增加了1%,伊利石(It)减少了20%,蛭石(V)增加了29%,变化最为明显;③火灾发生后土壤黏聚力(c)、内摩擦角(Φ)明显衰减,应变软化现象更为明显,这是土壤黏土矿物含量的变化,即蛭石矿物含量增高导致的。森林火灾会从颗粒粒径,矿物含量和强度参数3个方面显著影响土壤的物理力学性质,从而导致火烧迹地遭受泥石流、滑坡等地质灾害的风险增加。
After the forest fire in Xichang city of Sichuan province on March 30th,2020,the geological disasters in the burned areas increase.At present,the research on the physical and mechanical properties of the burned soil and the disaster-causing mechanism is not in-depth.The organic carbon content,particle size and X-ray diffraction analysis were carried out on the surface soil samples in the areas covered by fire and the areas uncovered by fire,and the clay mineral content and mechanical strength characteristics of the soil samples before and after fire were studied in combination with related laboratory mechanical tests.The results show that:①the content of soil organic matter decreases after the fire,resulting in the exposure of unstable inorganic soil;the stability of soil aggregate structure decreases,and the content of fine particles in soil increases;fine particles tend to block the pores in the surface layer of soil,which is not conducive to the infiltration of rainwater or surface runoff.②The high temperature process of the fire causes the content of clay minerals in the soil to change,with kaolinite(Kao)relative content decreasing by 10%,illite/vermiculite mixed layer increasing by 1%,illite(It)decreasing by 20%and vermiculite(V)increasing by 29%,and the increase of vermiculite is most obvious.③After the fire,the cohesion c value and internal friction angleφvalue of soil decrease obviously,and the shear strength of soil samples with high vermiculite mineral content decreases obviously,and the strain softening phenomenon becomes more obvious.The occurrence of forest fire will significantly affect the basic physical and mechanical properties of soil,and the burned area has great development risk of geological disasters such as debris flow and landslide.
作者
王瑞
兰恒星
刘世杰
伍宇明
WANG Rui;LAN Heng-xing;LIU Shi-jie;WU Yu-ming(School of Geological Engineering and Geomatics,Chang an University,Xi an 710054,Shaanxi,China;State Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Beijing 100101,China)
出处
《地球科学与环境学报》
CAS
北大核心
2022年第1期114-123,共10页
Journal of Earth Sciences and Environment
基金
中国科学院战略性先导科技专项(A类)项目(XDA23090301)
国家自然科学基金项目(42041006,41927806)。
关键词
地质灾害
森林火灾
有机碳
粒径级配
黏土矿物
力学性质
蛭石
应变软化
geological disaster
forest fire
organic carbon
particle size distribution
clay mineral
mechanical property
vermiculite
strain softening
