土壤风蚀抗蚀性与抗剪强度研究

Soil wind erosion-antierodibility is the mechanical properties of soil particles to resist wind erosion force. The study on soil wind erosion-antierodibility is the key process to understand wind erosion dynamic process deeply. The current studies on the expression of the soil wind erosion-antierodibility, the relationship between soil wind erosion rate and soil wind erosion-antierodibility are still relatively weak. The factors that affecting soil wind erosion can be classified into wind erosivity factors, soil wind erosion-antierodibility, and roughness interference factors. In order to establish a soil wind erosion-antierodibility index with clear dynamic mechanical meaning, soil shear strength which can describe the ability of soil to resist external damage, is introduced to the study. The implementation of the project will be carried out only considering the wind erosivity factors and soil wind erosion-antierodibility without considering roughness interference factors. In order to establish the relationship between soil wind erosion-antierodibility and soil shear strength, soil wind erosion rate and soil wind erosion-antierodibility, soil shear strength direct shear test, soil wind erosion wind tunnel simulation experiment and field soil wind erosion observation will be introduced to this program. This program will choose soil samples according to land use types and soil texture to carry out following works. 1) Measurement of different soil samples shear strength by using an unsaturated soil strain-controlled direct shear apparatus, the influence mechanism of soil physical and chemical properties and plant root condition on shear strength, the quantitative relationship between soil shear strength and main influencing factors, establishment of non-dimensional soil cohesion force prediction model. 2) Clarification of the change law between wind erosion characteristics and wind speed of different soil samples with different land use types and soil texture, determination of the wind erosion shear stress and soil antierodibility stress to wind erosion of topsoil particles during the wind erosion process, establishment of soil wind erosion-antierodibility based on soil antierodibility stress to wind erosion, which is represented by the non-dimensional soil cohesive force. 3) The establishment and verification of the quantitative relationship between soil wind erosion rate, wind erosion shear stress and soil wind erosion-antierodibility combining with the field soil wind erosion observation data. These studies will provide scientific support for the construction of soil erosion model based on the theory of wind erosion dynamics.

土壤风蚀抗蚀性是土壤抵抗风力侵蚀而呈现的力学属性，对土壤风蚀抗蚀性的研究是深入理解风蚀动力过程的关键环节。当前对土壤风蚀抗蚀性的表达及风蚀速率与土壤风蚀抗蚀性的关系研究还较为薄弱。本项目在不考虑粗糙干扰因子情况下，针对风力侵蚀因子和土壤抗蚀因子，聚焦于描述土壤抵抗外应力破坏能力的抗剪强度指标与土壤风蚀抗蚀性的转换、土壤风蚀速率与风蚀抗蚀性关系研究，通过不同利用类型和不同质地土壤样品的抗剪强度直剪试验、风蚀风洞控制性实验以及野外风蚀观测，研究土壤理化性质和植物根系状况等因素对土壤抗剪强度的影响机制，明确抗剪强度与主要影响因子的定量关系，建立无量纲土壤内聚力预测模型；确定土壤风蚀过程中表层颗粒所受的侵蚀剪应力和土壤抗风蚀剪应力，利用无量纲内聚力表征土壤抗风蚀剪应力，发展土壤风蚀抗蚀性指标；建立并验证土壤风蚀速率与风侵蚀力和土壤风蚀抗蚀性的定量关系，为构建土壤风蚀动力学模型提供科学支持。

土壤抗剪强度作为土壤力学性质的关键指标，表征了土壤在外力剪切作用下产生的抵抗力，代表了土壤抗剪力的强度极限。土壤抵抗风蚀能力与土壤抗剪强度密切相关，本项目聚焦于土壤抗剪强度与土壤抗蚀性研究，研究土壤理化性质对土壤抗将强度的影响机制，明确抗剪强度与主要影响影子的定量关系，基于土壤抗剪强度构建土壤风蚀抗蚀性指标。按照研究计划，项目开展了翻耕地、退耕地、草地等不同土地利用类型及不同理化性质土壤的抗剪强度直剪试验，不同筛分次数土壤样品抗剪强度直剪试验，在风蚀事件及风蚀季不同时间尺度，分别对翻耕地、退耕地、天然草地等不同地类的地表土壤抗剪强度变化及风蚀量进行野外监测，利用土壤风蚀风洞模拟实验，进行了不同土壤样品的土壤风蚀风洞模拟实验，测定了不同土壤样品在不同风速等级下的风蚀速率及床面不同位置的表层土壤抗剪强度，对比了不同时空分辨率及插值方法下，不同抗风蚀能力土壤在不同风力条件下的风蚀状况，评估了风速处理方法及风速数据时空分辨率对模型模拟结果的影响。基于以上研究，构建了包括土壤含水率、粒径分布、颗粒形状及养分含量等因素对土壤抗剪强度的综合影响表达，在影响土壤抗剪强度的诸多因子中，土壤粒径分布是影响土壤抗剪强度的主要因子；提出了基于土壤应力-应变过程中的能量累积过程构建基于抗剪强度的土壤风蚀抗蚀性指标；土壤风蚀导致的理化性质变化直接影响了风蚀抗蚀性的变化，土壤风蚀抗蚀性随土壤团聚体稳定性的降低而降低，随着土壤风蚀过程的持续而增大，在固定的吹蚀时间内，较高的风速可导致土壤风蚀抗蚀性增大约10%，翻耕地土壤样品抗蚀性在风蚀过程中的变化要较退耕地及草地更为敏感；不同风速处理方法及时空分辨率风速数据对不同抗风蚀能力土壤在不同土壤风蚀模型中的土壤风蚀模数计算结果存在差异，在风蚀模数计算过程中，应充分考虑风蚀数据的类型及处理方法。相关成果可为未来构建土壤风蚀动力学模型提供科学支持。