喀斯特槽谷区土壤地上/下流/漏失过程与模拟研究

There are both overground and underground karst structure and typical consequent slope and reversed slope because of special lithology in karst trough valley area. Soil erosion occurred through ground soil loss and underground soil leakage.This caused severe rock desertification.Based on the special geological structure and special ground soil loss and underground soil leakage in karst trough valley area, the process and mechanism of soil loss and leakage in consequent slope and reversed slope of karst trough valley are illuminated by using full slope runoff plots combined with isotope tracer methods. Laboratory simulation facilities are established to investigate erosion process of consequent slope and reversed slope under concentration flow of different rainfall intensity and changing schist gradient, so as to understand soil erosion mechanism under impacts of concentration water flow. Process-based soil erosion model for ground soil loss and underground soil leakage in karst trough valley is developed based on the understanding of erosion process in consequent slope and reversed slope. Collected data of runoff and sediments in karst trough valley are used to estimate model parameters and to validate the runoff and sedimentation processes model. This study have contributed to the prediction of ground soil loss and underground soil leakage and the ecological restoration and inhabitant security in karst trough valley area .

喀斯特槽谷区由于其特殊的岩性，发育地表地下双层岩溶结构，岩石的倾向存在典型的顺/逆倾向，土壤侵蚀通过地表流失和地下漏失同时发生，石漠化程度严重。针对喀斯特槽谷区特殊地质构造与水土流/漏失的特殊性，通过全坡面径流场结合同位素示踪技术，阐明喀斯特槽谷区顺/逆层坡面土壤地上/下流/漏失过程与机理；室内模拟喀斯特槽谷区顺/逆层坡的自然形态，控制不同降雨强度和片岩倾斜度，定量确定降雨作用下顺/逆层坡面水土流/漏失规律，认识顺/逆层坡面侵蚀过程机理；在机理研究的基础上，建立顺/逆层坡面水土流/漏失模型，用现场调查和监测数据，获取模型参数并验证模型。研究将实现喀斯特槽谷区水土流/漏失预报，为喀斯特区生态环境恢复、生产生活安全等提供基础。

针对喀斯特槽谷区顺/逆层坡面水土流失剧烈等现状，通过地统计学、水文学、GIS等方法，结合野外调查和室内模拟，研究了顺/逆层坡土壤理化性质空间变异特征及其环境影响因子；探究了岩层倾角、雨强和地下孔隙度等的影响机制，揭示了槽谷区地上/下径流流/漏失及产沙过程的特征和水动力学特征及其侵蚀机理。主要结果如下： .1、揭示了喀斯特槽谷区顺/逆层坡土壤理化性质空间变异特征及其环境影响因子：（1）高斯模型是描述喀斯特槽谷区顺/逆层坡土壤理化性质空间分布特征的最优模型；（2）顺/逆层坡的土壤理化性质空间分布特征变异性极强；（3）自然因素的影响因子较大，坡位是最关键的环境因子。 .2、明确了雨强、地下孔隙度和岩层倾角的影响阈值，阐明了喀斯特槽谷区顺/逆层坡的径流泥沙流/漏失机制：（1）中雨强是地表产流的临界值，大雨强是地表径流超过地下径流的临界值；（2）在小雨强条件下，顺/逆层坡只有地下悬移质产生；（3）雨强0.75 mm/min是地表推移质产生的临界值。.3、厘清了雨强、地下裂隙度和岩层倾角对喀斯特槽谷区坡面水动力学参数与产流产沙的影响，并建立了水动力学模型：（1）顺/逆层坡平均水流流速、径流深、Re、Fr、径流剪切力和水流功率均随雨强增大而增大，f和曼宁糙率则减小；（2）f与Re呈负相关关系，f与弗汝德数Fr呈负相关关系，两者存在显著的幂函数关系；（3）各单一水动力学参数均和产流产沙呈二次函数关系。 .4、阐明了不同岩石与坡面夹角、坡度和流量组合下的坡面集中流水动力学及产流产沙特征：（1）Re随流量的增大而增大，随坡度变化规律不明显；（2）f随冲刷历时表现出增大的变化趋势，随坡度增大而增大，随流量增大而减小；（3）Re和岩层与坡面夹角关系均不显著，f 和岩层与坡面夹角间的关系在各流量和坡度组合下表现不同。.本项目从岩层倾角和地下裂隙度两个方向出发，创新了方法和技术，为喀斯特槽谷区土壤地上/地下/漏失过程和石漠化综合治理提供科技支撑。