峰丛洼地岩溶裂隙水土漏失过程室内模拟试验

Laboratory Simulation on Process of Soil and Water Leakage from Fissures in Karst Peak-cluster Depression

[目的]水土漏失控制是喀斯特地区石漠化防治的关键,因此对水土漏失机理及其影响因素进行探究。[方法]通过室内模拟试验,研究水压力(0.3,1.3,2.3,5.5 m水头)、岩溶裂隙宽度(0.25,0.50,0.75,1.00 cm)和土壤团聚体粒径(0~1.0,1.0~2.0,2.0~5.0,0~5.0 mm)对峰丛洼地水土漏失过程的影响。[结果]水压力和裂隙宽度越大、团聚体粒径越小或粒组缺失的土壤,上覆土层越易被击穿。土层被击穿时间约需2~20 min。在土层被击穿后,水漏失速率迅速增大并逐渐趋于稳定,土壤漏失速率则急剧增大至峰值后减小并趋于其稳定值,且水土漏失速率及其累积漏失量显著大于未击穿土层。水土漏失量随着水压力或裂隙宽度的增大而增大。当裂隙宽度为0.25,0.50,0.75,1.00 cm时,1.3~5.5 m水压力时的累积水漏失量分别比0.3 m水压力时增大1.2~13.2,2.4~131.0,2.1~167.3,75.8~141.9倍。累积土壤漏失量随团聚体粒径的增大而显著减小。在大团聚体缺失时土壤漏失量随着裂隙宽度的增大而减小,而在小团聚体缺失时则随之增大。当裂隙宽度为0.25,0.5,0.75,1.0 cm时,1.0~2.0,2.0~5.0 mm团聚体粒组的土壤漏失量分别比0~1.0 mm粒组减小98.4%和99.1%,46.3%和83.7%,43.2%和74.0%及41.1%和27.1%。[结论]上覆土层的稳定状况决定峰丛洼地水土漏失过程,水力条件、土壤性质及岩溶裂隙发育程度是影响其稳定的关键因素。

[Objective]Soil and water loss control is the key to the prevention and control of rocky desertification in karst areas,so the mechanism of soil and water loss and its influencing factors are explored.[Methods]The effects of water pressure(0.3,1.3,2.3,and 5.5 m water head height),karst fissure width(0.25,0.5,0.75,and 1.0 cm),and soil aggregate size(0~1.0,1.0~2.0,2.0~5.0,and 0~5.0 mm)on the process of soil and water leakage in the karst peak-cluster depression were studied through laboratory simulation experiment.[Results]The greater the water pressure and the fissure width were,the smaller the soil aggregate size was,or the absence of certain soil particle groups,the more easily the overlying soil layer was broken down taking approximately 2 to 20 minutes.After the soil layer was broken down,the water leakage rate surged rapidly before stabilizing,while the soil leakage rate peaked and then settled.The rates and cumulative amounts of soil and water leakage from the disrupted soil layer were significantly greater than that of the unbroken one.The cumulative amounts of water and soil leakage increased with the increased water pressure or fissure width.When fissure width was 0.25,0.50,0.75,and 1.00 cm,the cumulative amount of water leakage at 1.3 to 5.5 m water pressures was 1.2 to 13.2,2.4 to 131.0,2.1 to 167.3,and 75.8 to 141.9 times greater than that at 0.3 m one,respectively.The cumulative soil leakage diminished notably with larger soil aggregate sizes.The absence of larger aggregates led to the decrease of soil leakage with the increase of fissure width but the opposite was true for soils lacking smaller aggregates.When fissure width was 0.25,0.50,0.75,and 1.00 cm,the cumulative amounts of soil leakage from 1.0 to 2.0 and 2.0 to 5.0 mm aggregate particle groups were decreased by 98.4%and 99.1%,46.3%and 83.7%,43.2%and 74.0%as well as 41.1%and 27.1%,respectively,compared with that of 0 to 1.0 mm one.[Conclusion]The stability of the overlying soil layer plays a pivotal role on the process of soil and water loss in peak-cluster depression,and hydraulic conditions,soil properties,and the degree of karst fissure development critically influence this stability.