砾石对石灰土表面干缩裂隙发育特征的影响

Effects of Rock Fragments on Characteristics of Surface Shrinkage Cracks in Calcareous Soil

[目的]研究砾石粒径及含量对石灰土表面干缩裂隙发育特征的影响,为探索喀斯特地区的水土流失机理提供参考依据。[方法]通过室内模拟试验和数字图像处理技术,研究了砾石粒径(2.0~5.0 mm和5.0~12.5 mm)和砾石含量(0%,10%,20%,30%,40%)条件下的石灰土表面干缩裂隙特征。[结果]①无砾石石灰土平均表面裂隙率仅为3.03%,含砾石石灰土具有更大的表面裂隙率,在大粒径(5.0~12.5 mm)高含量(40%)条件下,表面裂隙率最大,达到8.66%;②当砾石含量增加时,裂隙的形态变得细小且密集,小粒径砾石会使裂隙网络更复杂;③大粒径(5.0~12.5 mm)条件下的土壤表面裂隙率与砾石含量成正线性相关,而小粒径(2.0~5.0 mm)条件下的裂隙率与砾石含量成负线性相关;④砾石会成为裂隙发育的基点,每个砾石颗粒周围都有可能产生围绕砾石或是向外延伸的裂隙。且在砾石形态的棱角处,容易产生向外延伸的裂隙。[结论]石灰土中存在砾石会导致表面裂隙率提高,弱化土体的抗侵蚀能力,是石漠化治理不容忽视的问题。

[Objective]The effects of rock fragment(RF)size and content on the development characteristics of surface shrinkage cracks in calcareous soil were studied to provide a reference basis for exploring the mechanism of soil erosion in karst areas.[Methods]RF size(2~5 and 5~12.5 mm)and RF content(0%,10%,20%,30%,and 40%)were controlled,and digital-image-processing technology was used to study the effect of RFs on surface crack development in calcareous soil.[Results]①The surface crack rate(SCR)of the calcareous soil without RFs was only 3.03%,whereas the samples with added RFs had a larger SCR.The maximum SCR of sample(5~12.5 mm,40%)reached 8.66%.②When RF content increased,the morphology of the crack network became small and dense,and small RFs made the crack network more complex.③The SCR of 5~12.5 mm RFs was positively correlated with the RF content,whereas the SCR of 2~5 mm RFs was negatively correlated with the RF content.④RFs can become the basis of fracture development,and each RF probably produce fracture around the RF or extend the crack network.Moreover,at the corner of an RF,it was easy to produce cracks extending outward.[Conclusion]The existence of RFs in calcareous soil could lead to the increase of the SCR and weaken the resistance of soil to erosion.