Landslide hazard analysis of Liyuan Town based on effective rainfall threshold
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摘要: 以湖南省澧源镇为例,利用证据权模型和灰色关联度模型分别计算了坡度、地层岩性、斜坡形态、土地利用类型、人类工程活动5个因子二级状态证据权值和一级因子权重;综合2种模型确定全区滑坡易发性指数后,完成基于斜坡单元的全区滑坡易发性区划;根据研究区岩土体类型(碎屑岩类、碳酸盐岩夹碎屑岩类、碳酸盐岩类和松散岩土体类)分组研究不同滑坡发生概率下的有效降雨阈值曲线(I-D曲线)。研究降雨时间为3日、有效强度为22.4 mm/d的降雨工况下各岩土体类型滑坡发生的时间概率。综合时间概率和易发性结果得到澧源镇基于有效降雨阈值的滑坡灾害危险性区划图。研究结果表明:澧源镇滑坡灾害高和极高易发区占研究区总面积的25%,主要沿澧河分布;极高危险区和高危险区占研究区总面积的14%,主要分布在澧河北侧。Abstract: This paper takes Liyuan Town of Hunan Province as an example, and used the weight of evidence model and the grey relational degree model to calculate separately the weights of the five factors of slope, formation lithology, shape of slope, land use type and human engineering activity in secondary states and in first states. After defining the landslide susceptibility index of the whole region by combining two models, the susceptibility zoning based on the slope unit is completed. According to the geotechnical geological type of the rock and soil in the study area (clastic rocks, carbonate nip clastic rocks, carbonate rocks and loose rock soils), the effective rainfall threshold curves (I-D curve) under different landslides occurrence probability are determined by grouping. The time probability of landslides in different rock and soil types under 3-day duration and effective intensity of 22.4mm/d is studied. Finally, the landslide hazard zoning map of Liyuan Town based on effective rainfall threshold is obtained through. combining time probability and susceptibility results. The results show that the high-susceptible areas and extremely high-susceptible areas account for 25% of the total study area and distributed mainly along the river. The extremely high-hazard areas account for 14% of the total study area and are mainly distributed in the north of the river.
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Key words:
- hazard /
- effective rainfall threshold /
- time probability /
- grey relational degree /
- landslide
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表 1 评价因子信息
Table 1. Information of index factors
一级影响因子 二级影响因子 频率比 证据权重 排序 坡度/(°) [0, 10) 0.199 8 -2.029 29 19 [10, 20) 1.790 4 0.550 79 7 [20, 30) 1.359 1 0.165 23 11 [30, 40) 0.605 2 -0.860 37 15 > 40 0.139 5 -0.157 67 13 岩土体工程地质类型 碎屑岩类 0.008 9 0.169 56 10 碳酸盐岩夹碎屑岩类 0.007 3 0.215 11 9 碳酸盐岩类 0.000 0 -0.289 81 16 松散岩土体类 0.587 3 0.671 95 5 土地利用类型 林地 0.440 1 -1.247 84 18 农业用地 1.881 0 0.932 29 4 建设用地 1.835 6 0.992 22 3 果园地 1.451 7 0.572 68 6 斜坡形态 凸形坡 1.036 4 0.257 06 8 直线坡 0.543 9 -0.772 05 14 凹形坡 1.189 5 0.008 06 12 人类工程活动 道路切坡 1.252 5 1.441 11 2 建房切坡 5.400 2 3.079 03 1 非切坡区 0.848 9 -0.325 08 17 表 2 指标因子权重值
Table 2. Weighting of index factors
坡度 岩土体工程地质类型 土地利用类型 斜坡形态 人类工程活动 0.177 41 0.179 09 0.201 96 0.174 62 0.266 92 表 3 澧源镇易发性等级分区与滑坡频次
Table 3. Classification of landslide susceptibility and landslide occurrences in each class
易发性等级 分级栅格数(A) 分级栅格占比/% 滑坡栅格数(B) 滑坡栅格占比/% 滑坡频次(B/A) 极低易发区 113 860 25 0 0 0.00 低易发区 118 859 26 0 0 0.00 中易发区 106 269 24 471 16 0.00 高易发区 91 231 20 977 34 0.01 极高易发区 21 775 5 1 440 5 0.07 表 4 桑植县1996年7月18日-22日降雨信息
Table 4. Rainfall information of Sangzhi County from July 18 to July 22, 1996
时间 18日 19日 20日 21日 22日 降雨量/mm 0.1 14.1 117.2 78.5 0.1 表 5 各岩土体类型中不同滑坡发生频率对应的有效降雨阈值曲线
Table 5. Effective rainfall threshold corresponding to the frequency of occurrence of different landslides in each rock and soil types
岩土体工程地质类型 降雨滑坡发生频率/% 降雨阈值曲线 碎屑岩类 10 I=20.093D-1.099 8 20 I=27.647D-1.099 8 50 I=48.692D-1.099 8 碳酸盐岩夹碎屑岩类 10 I=15.371D-0.593 07 20 I=19.971D-0.593 07 50 I=54.981D-0.593 07 碳酸盐岩类 10 I=25.905D-0.645 76 20 I=32.931D-0.645 76 50 I=74.815D-0.645 76 松散岩土体类 10 I=19.0124D-0.896 7 20 I=26.830D-0.896 7 50 I=37.85D-0.896 7 表 6 研究工况下各岩土体类型滑坡的有效降雨阈值及时间概率
Table 6. Effective rainfall threshold and time probability ofeach rock and soil type under research conditions
岩土体工程地质类型 降雨阈值曲线 降雨滑坡发生概率P[B|A] 降雨发生概率P[A] 时间概率P 碎屑岩类 I=74.961D-1.099 8 0.644 4 1 0.644 4 碎屑岩夹碳酸盐岩类 I=43.571D-0.593 07 0.428 6 1 0.428 6 碳酸盐岩类 I=45.920D-0.645 76 0.218 4 1 0.218 4 松散岩土体类 I=60.171D-0.896 7 0.750 0 1 0.750 0 表 7 危险性分区与历史滑坡频次
Table 7. Hazard zoning and historical landslide frequency
危险性等级 分级栅格数(A) 分级栅格占比/% 滑坡栅格数(B) 滑坡栅格占比/% 滑坡频次(B/A) 极低危险区 154 342 34 0 0 0.00 低危险区 114 804 25 178 2 0.00 中危险区 122 047 27 1 258 45 0.01 高危险区 48 125 11 610 21 0.01 极高危险区 12 676 3 842 32 0.07 表 8 危险性验证案例信息及结果
Table 8. Information and results of hazard verification case
滑坡名称 发生日期 所属岩土体工程地质类型 易发性等级及空间概率范围 时间概率 危险性概率值 危险性分区结果 验证结论 朱家坪四组滑坡 2012-07-23 碎屑岩类 极高易发区(> 0.7) 0.644 4 0.45~0.64 极高危险区(> 0.55) 符合 卢家湾滑坡 2012-05-01 碎屑岩夹碳酸盐岩类 高易发区(0.5~0.7) 0.428 6 0.21~0.30 中危险区(0.25~0.40) 符合 朱家台苏桥滑坡 2012-04-05 松散岩土体类 高易发区(0.5~0.7) 0.750 0 0.37~0.53 高危险区(0.40~0.55) 符合 -
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