鄂东南崩壁不同深度土层微形态特征及稳定性评价

为了深入认识崩壁不同深度土层微观结构特征和稳定性状况,选取鄂东南通城县一处发育完整的崩壁为研究对象,通过观察土壤薄片,定量和定性分析了崩壁6个不同深度土层的微形态特征,在此基础上,采用主成分分析对崩壁稳定性进行评价,并构建了崩壁稳定性评价体系的微形态指标最小数据集(MDS)。结果表明:(1)崩壁不同深度土层微形态差异显著。表土层土壤基质颜色呈现暗红色,基质比较高(0.91),团聚体和孔隙状况发育成熟,孔隙连通性较好。红土层基质颜色以红色为基调,随深度增加逐渐变浅,基质比为0.69(平均值),土壤团聚体结构弱发育,孔隙类型以囊孔和裂隙为主,连通性较差。砂土层主要以未风化完全的矿物颗粒为主,基质比极低(0.25),孔隙类型以矿物颗粒间隙为主。(2)各土层稳定性微形态评价得分从大到小排序为:表土层(TC₁)>红土层(TC₂>TC₃>TC₄)>砂土层(TC₅>TC₆),与多数土壤微形态指标间呈现显著正相关(p<0.05)。(3)崩壁土体稳定性微形态评价的最小数据集(MDS)由土壤基质颜色、土壤基质类型、土壤基质比、土壤团聚体、土壤微结构、总孔隙百分比和有机质含量7个指标构成。综上,不同深度土层微形态特征差异是崩壁土体稳定性具有层次分异性的重要因素之一。基于土壤微形态分析及建立的最小数据集评价体系,可以对崩壁土体的稳定性进行初步的监测。

Micromorphological Characteristics and Stability of Different Soil Layers of Collapsed Wall in Southeastern Hubei Province

In order to gain a deeper understanding of the microstructural characteristics and stability conditions of the soil layers at different depths of the crumbling wall, a well-developed crumbling wall in Tongcheng County in southeast of Hubei was selected as the research object, and the micromorphological characteristics of the soil layers at six different depths of the crumbling wall were quantitatively and qualitatively analyzed by observing the soil thin sections, and on this basis, the stability of the crumbling wall was evaluated by using principal component analysis, and the minimum micromorphological indexes of the crumbling wall stability evaluation system were constructed. The results showed that:(1)the micromorphology of soil layers at different depths of the crumbling wall differs significantly; the soil matrix color of the topsoil layer shows dark red color, high matrix ratio(0.91), mature development of agglomerates and pore condition, and good pore connectivity; the tone of matrix color of the laterite layer is red, and gradually becomes lighter with increasing depth, the red soil layer has a matrix ratio of 0.69(mean), a weakly developed soil aggregate structure, pore type dominated by cystic pores and fissures, and poor connectivity; the sandy soil layer is mainly composed of mineral particles that have not weathered completely, with a very low matrix ratio(0.25), and the pore type is mainly the interstitial space between the mineral particles;(2)the evaluation scores of stability micromorphology of each soil layer decrease in the order: topsoil layer(TC₁)>laterite layer(TC₂>TC₃>TC₄)>sandy soil layer(TC₅>TC₆), which shows the significantly positive correlation with most soil micromorphology indicators(p<0.05);(3)the minimum data set(MDS)for microform evaluation of crumbling wall soil stability consists of seven indicators: soil matrix color, soil matrix type, soil matrix ratio, soil agglomerates, soil structural body, total pore percentage and organic matter content. From what has been discussed above, the difference in micro-morphological characteristics of soil layers at different depths is one of the important factors for the stability of crumbling wall soils with hierarchical differentiation. Based on the soil micromorphology analysis and the established minimum data set evaluation system, the stability of different soil layers of the crumbling wall can be preliminarily monitored.