Stability analysis of different scale soil bunds on purple soil sloping farmlands
LI Jinlin, WEI Jie, HE Xiubin
1. Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Science, 610041, Chengdu, China;
2. College of Geography and Tourism Science, Chongqing Normal University, 401331, Chongqing, China;
3. University of Chinese Academy of Science, 100049, Beijing, China
摘要土坎稳定性对其发挥水土保持效益具有重要意义，分析紫色土坡耕地土坎规格对稳定性的影响可为三峡库区乃至长江上游紫色土区坡耕地整治、中低产田改造等工程中土坎规划设计和建造提供依据。根据野外调查结果，设定0.8、1.0、1.2和1.4 m 4种高度和50°、60°、70°和80° 4种外边坡坡度共组合成16种规格土坎。通过直剪试验获取紫色土埂坎土壤抗剪强度参数，利用极限平衡分析法计算稳定性系数、响应面分析法建立稳定性系数与高度和外边坡坡度响应模型。结果表明：土坎外边坡坡度一定时，稳定性系数随高度增加呈非线性衰减；高度一定时，稳定性系数随外边坡坡度变陡总体呈降低趋势。总体来看，土坎高度和外边坡坡度对其稳定性的影响极为显著（P<0.01），但二者的交互效应对稳定性的影响不显著。研究规格范围内，土坎潜在滑动面最不稳定的土体条块基底抗剪力均大于运动剪切力。土坎稳定性系数随着运动剪切力和右侧剪切力的增加呈降低趋势，而基底法向力和右侧法向力变化对土坎稳定性系数没有明显影响。结合紫色土坎的稳定性特征、三峡库区紫色土坡耕地的条件和农民耕作的便利性，土坎高为1.0~1.2 m，外边坡约60°较为适宜。
Abstract：[Background] Bunds are embankments constructed across the slope and along the contour, and play a key role in controlling soil erosion on sloping farmlands. Recently, it is unclear yet of the relationship between soil bund stability and scales. The aim of this work is to provide a basis for soil bund planning and design in the purple sloping farmland consolidation and lower-yield field reconstruction projects in the Three Gorges Reservoir area and even the upper Yangtze River, by revealing the purple soil bund stability response to scales.[Methods] We carried out field investigation, laboratory test, simulation and response surface analysis to reveal the stability of soil bunds under different height and slope conditions. We defined 4 levels of height (0.8, 1.0, 1.2, and 1.4 m at intervals of 0.2 m) and 4 levels of slope (50°, 60°, 70°, and 80° at intervals of 10°), a total of 16 soil bunds. The limit equilibrium analysis was adopted to calculate the stability coefficients, and the response surface analysis was adopted to build the model of purple soil bund stability responses to the bund size.[Results] The minimum of stability coefficient was 3.526, which indicated that all soil bunds defined in the present study were stable. When the outside slope was constant, the soil bund stability coefficients displayed a nonlinear reduction with the height increasing; however, when the height was constant, the soil bund stability coefficients decreased generally along with the outside slope, the average reduction was greater than 10% at each increasing interval under these two changing patterns. Overall, both the height and the outside slope had significant influences on the stability of soil bunds (P<0.01), while the interactive effect was not significant. Regression equation fitted by height, outside slope and their quadratic terms of soil bund can be used for describing the relationship between stability and scales perfectly, the adjustment determination coefficient and variation coefficient were 93% and 5.88, respectively. The potential sliding surface of soil bund was characterized by a shear resistance force greater than the moving shear force. With an increasing of the base shear mobility force and the right side normal force, the soil bund stability coefficient showed a decreasing trend, with no noticeable change trend along with the base normal force and the right side shear force change.[Conclusions] The reasonable scale is 1.0~1.2 m of height and 60° of outside slope while considering purple soil bund stability features, slopping farmland conditions and ease for farmers to cultivate.
韦杰, 史炳林, 李进林. 紫色土坡耕地埂坎土壤抗剪性能对含水率的响应[J]. 农业工程学报, 2016, 32(20):153. WEI Jie, SHI Binglin, LI Jinlin. Response of soil shear strength to soil water content in purple soil slope cropland bunds[J]. Transactions of the CSAE, 2016, 32(20):153.
[2]
WEI W, CHEN D, WANG L, et al. Global synthesis of the classifications, distributions, benefits and issues of terracing[J]. Earth-Science Reviews, 2016, 159:388.
[3]
薛萐, 刘国彬, 张超, 等. 黄土高原丘陵区坡改梯后的土壤质量效应[J]. 农业工程学报, 2011, 27(4):310. XUE Sha, LIU Guobin, ZHANG Chao, et al. Effects of terracing slope cropland on soil quality in Hilly Region of Loess Plateau[J]. Transactions of the CSAE, 2011, 27(4):310.
[4]
焦菊英, 王万中, 李靖. 黄土丘陵区不同降雨条件下水平梯田的减水减沙效益分析[J]. 水土保持学报, 1999, 5(3):59. JIAO Juying, WANG Wanzhong, LI Jing.Analysis on soil and water conservation benefit of level terrace under different rainfall condition in loess hilly region[J]. Journal of Soil and Water Conservation, 1999, 5(3):59.
[5]
GALLART F, LLORENS P, LATRON J, et al. Hydrological processes and their seasonal controls in a small Mediterranean mountain catchment in the Pyrenees[J]. Hydrology & Earth System Sciences, 2002, 6(3):527.
[6]
HAMMAD A A, HAUGEN L E, BORRESEN T. Effects of stonewalled terracing techniques on soil-water conservation and wheat production under Mediterranean conditions.[J]. Environmental Management, 2004, 34(5):701.
[7]
VANCAMPENHOUT K, NYSSEN J, GEBREMICHAEL D, et al. Stone bunds for soil conservation in the northern Ethiopian highlands:Impacts on soil fertility and crop yield[J]. Soil & Tillage Research, 2006, 90(1):1.
[8]
刘晓燕, 王富贵, 杨胜天, 等. 黄土丘陵沟壑区水平梯田减沙作用研究[J]. 水利学报, 2014, 45(7):793. LIU Xiaoyan, WANG Fugui, YANG Shengtian,et al. Sediment reduction effect of level terrace in the hilly-gully region in the Loess Plateau[J]. Journal of Hydraulic Engineering, 2014, 45(7):793.
[9]
ADIMASSU Z, MEKONNEN K, YIRGA C, et al. Effect of soil bunds on runoff, soil and nutrient losses and crop yield in the central highlands of Ethiopia[J]. Land Degradation & Development, 2012, 25(6):554.
[10]
AMARE T, ZEGEYE A D, YITAFERU B, et al. Combined effect of soil bund with biological soil and water conservation measures in the northwestern Ethiopian highlands[J]. Ecohydrology & Hydrobiology, 2014, 14(3):192.
[11]
MONSIEURS E, POESEN J, DESSIE M, et al. Effects of drainage ditches and stone bunds on topographical thresholds for gully head development in North Ethiopia[J]. Geomorphology, 2015, 234(104-105):193.
[12]
高霞, 李光录, 王新功. 陕南秦巴山区PP织物袋梯田筑坎土压力分布研究[J]. 水土保持通报, 2013, 33(6):37. GAO Xia, LI Guanglu, WANG Xingong.Soil pressure distribution on terraced field ridge of polypropylene bags in Qinba mountain of southern Shanxi province[J]. Bulletin of Soil and Water Conservation, 2013, 33(6):37.
[13]
葛逸群. 砂质山区土坎梯田埂坎稳定性分析[J]. 中国水土保持, 1999(7):30. GE Yiqun. Analysis of the stability of terrace soil edge in sandy mountains[J]. Soil and Water Conservation in China, 1999(7):30.
[14]
陈万铃, 谢宝文. 紫色砂泥岩区梯地土坎稳定性及利用效益研究[J]. 中国水土保持, 1994(9):28. CHEN Wanling, XIE Baowen. Stability analysis of earth banks of terraces in rocky area with sandy soil and the benefits of utilization of earth banks[J]. Soil and Water Conservation in China, 1994(9):28.
[15]
张宏, 高明, 王谊,等. 紫色土抗剪强度差异分析及土坎优化设计[J]. 西南大学学报(自然科学版), 2015, 37(5):31. ZHANG Hong, GAO Ming, WANG Yi,et al. Optimum engineering design of purple soil ridges based on an analysis of purple soil shearing strength[J]. Journal of Southwest University (Natural Science Edition), 2015, 37(5):31.
[16]
顾再柯, 王钰, 刘凤仙. 适合贵州非石质山区坡耕地整治的两种实用技术[J]. 中国水土保持, 2007(3):40. GU Zaike, WANG Yu, LIU Fengxian. Two techniques suitable for sloped cultivated land management of non-lithoid mountainous area in Guizhou and its main points for implementation[J]. Soil and Water Conservation in China, 2007(3):40.
[17]
邵龙潭, 郭莹. 新编土力学教程[M]. 北京:冶金工业出版社, 2013:192. SHAO Longtan, GUO Ying.New edition of soil mechanics course[M]. Beijing:Metallurgical Industry Press, 2013:192.
[18]
刘杰, 张学深, 褚世洪. 简单边坡的稳定性分析[J]. 岩土力学, 2002, 23(6):714. LIU Jie, ZHANG Xuesheng, CHU Shihong. Stability analysis of simple slopes[J]. Rock and Soil Mechanics, 2002, 23(6):714.
[19]
朱大勇, 邓建辉, 台佳佳. 简化Bishop法严格性的论证[J]. 岩石力学与工程学报, 2007, 26(3):455. ZHU Dayong, DENG Jianhui, TAI Jiajia. Theoretical verification of rigorous nature of simplified bishop method[J]. Chinese Journal of Rock Mechanics and Engineering, 2007, 26(3):455.
[20]
戴自航, 沈蒲生. 土坡稳定分析简化Bishop法的数值解[J]. 岩土力学, 2002, 23(6):760. DAI Zihang, SHEN Pusheng. Numerical solution of simplified Bishop method for stability analysis of soil slopes[J]. Rock and Soil Mechanics, 2002, 23(6):760.
[21]
文安邦, 齐永青, 汪阳春,等. 三峡地区侵蚀泥沙的137Cs法研究[J]. 水土保持学报, 2005, 19(2):33. WEN Anbang, QI Yongqing, WANG Yangchun, et al. Study on erosion and sedimentation in Yangtze Three Gorge Region[J]. Journal of Soil and Water Conservation, 2005, 19(2):33.
[22]
韦杰, 金慧芳, 贺秀斌,等. 三峡库区有限顺坡耕作坡耕地表土颗粒分形特征[J]. 中国水土保持科学, 2014, 12(3):23. WEI Jie, JIN Huifang, HE Xiubin, et al. Fractal features of soil particles on sloping farmland under downslope tillage system with limited slopelength in the Three Gorges Reservoir Area[J]. Science of Soil and Water Conservation, 2014, 12(3):23.
[23]
李进林, 韦杰. 三峡库区坡耕地埂坎类型、结构与利用状况[J]. 水土保持通报, 2017(1):229. LI Jinlin, WEI Jie.Types, structure and utilization pattern of field ridges on sloping farmland in Three Gorges Reservoir Region, China[J]. Bulletin of Soil and Water Conservation, 2017(1):229.
[24]
加拿大GEO-SLOPE国际有限公司. 边坡稳定性分析软件SLOPE/W用户指南[M]. 北京:冶金工业出版社, 2011:20. GEO-SLOPE International Limited. Stability modeling with SLOPE/W[M]. Beijing:Metallurgical Industry Press, 2011:20.
[25]
陈勋辉, 陈义涛, 黄耀英,等. 边坡稳定性分析的三种极限平衡法对比研究[J]. 人民黄河, 2016, 38(1):116. CHEN Xunhui, CHEN Yitao, HUANG Yaoying,et al. Comparative analysis of three different rigid body limit equilibrium methods[J]. Yellow River, 2016, 38(1):116.
[26]
李慧娟, 高建恩, 张元星,等. 延安极端降雨特性分析及对梯田侵蚀灾害影响[J]. 水土保持学报, 2016, 30(6):79. LI Huijuan, GAO Jianen, ZHANG Yuanxing, et al. Analysis of Yan'an extreme rainfall characteristics and impacts of erosion disasters on terraces[J]. Journal of Soil & Water Conservation, 2016, 30(6):79.
[27]
张信宝, 周萍, 严冬春. 梯田与植物篱的结构、功能与适用性[J]. 中国水土保持, 2010(10):16. ZHANG Xinbao, ZHOU Ping, YAN Dongchun. Structures, functions and applicability of terrace and living hedges[J]. Soil and Water Conservation in China, 2010(10):16.
2018, Vol. 16 
