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摘要:
溯源侵蚀是黄土丘陵区最强烈的动力地质作用。常导致沟头后退、坡脚掏蚀，进而引发崩塌灾害。文章通过对研究区崩塌灾害的统计分析，厘定出溯源侵蚀作用引发崩塌的典型类型为拉裂-倾倒型。该类型崩塌具有后壁陡直、粗糙、规模大、分布广、危害范围广，潜在危险性大等特点。分析认为溯源侵蚀引发拉裂-倾倒型崩塌是水力侵蚀和重力侵蚀耦合作用的结果。该类型崩塌的形成，主要是由于斜坡在地表水力侵蚀和重力作用下，坡体内拉应力分布区、剪应力分布区和强烈水力侵蚀区三个区发生了转化，经历了斜坡应力重新分布、拉应力的增大与范围扩大，剪应力状态改变与范围集中、坡顶拉张与孔隙水压力耦合作用下的崩塌体倾倒破坏三个阶段。控制和影响拉裂-倾倒型黄土崩塌稳定性主要因素包括：斜坡几何特征、土体物理力学参数及裂隙中的静水压力。随着土体含水率的上升，坡顶拉张裂缝深度加深，侵蚀凹槽深度加深，崩塌体稳定性逐渐降低。
Abstract:Tracing erosion is the strongest dynamic geological action in loess hilly areas. It often causes the head of the ditch to retreat and the toe of the slope to be eroded, which in turn leads to collapse. Based on the statistical analysis of collapse disasters in the study area, this paper determines that the typical type of collapse caused by the traceable erosion effect is tension-toppling type. This type of collapse is characterized by steep back wall, rough wall, large scale, widespread, wide damaging range, and high potential risk. The formation of this type of collapse is mainly due to the transformation of the three areas in horizontal direction such as the tensile stress distribution area, the shear stress distribution area and the strong hydraulic erosion area under the action of surface water erosion and gravity. the collapse of slope undergone three stages: the increase and scope expansion of the tensile stress, the change of the shear stress state and the concentration of the scope, and the collapse of the collapsed body under the coupling action of the slope top tension and pore water pressure. The stability analysis can be carried out by the moment balance method. The three factors that affect the stability of the tension-toppling loess collapse include: slope geometric characteristics, soil physical and mechanical parameters and water pressure in the cracks. Theoretical analysis illustrates that with the increase of soil moisture content, the depth of tensile cracks on the top of the slope deepens, the depth of erosion grooves deepens, and the collapse stability coefficient gradually decreases.
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表 1 溯源侵蚀引发典型黄土崩塌基本特征表
Table 1. Basic characteristics of typical loess falls caused by headward erosion
点号 名称 崩塌类型 高/m 宽/m 厚/m 地层岩性 XJG002 霍白湾村崩塌 淘蚀垮落 13 30 6 Q3黄土 XJG018 焉头村崩塌 拉裂倾倒 11 45 2 Q2黄土 XJG118 梨树塔村崩塌 拉裂倾倒 25 40 4 Q3黄土 XJG121 后坪村崩塌 拉裂倾倒 10 25 3 Q3黄土 XJG148 白家山村崩塌 淘蚀垮落 9 10 3 Q3黄土 XJG161 寺焉村以北崩塌 淘蚀垮落 12 20 3 Q3黄土 XJG200 畔畔山村崩塌 淘蚀垮落 22 13 3 Q3+Q2黄土 XJG208 马家渠村崩塌 淘蚀垮落 31 30 5 Q3+Q2黄土 XJG216 后焉村公路崩塌 拉裂倾倒 41 15 10 Q3黄土 XJG220 李家塌下山村崩塌 淘蚀垮落 33 10 3 Q3黄土 XJG223 尚家塬村崩塌 拉裂倾倒 24 10 3 Q3+Q2黄土 XJG231 冯家塬村崩塌 淘蚀垮落 31 45 12 Q3黄土 XJG232 田家塬村公路崩塌 拉裂倾倒 37 30 10 Q3黄土 XJG236 深砭墕村公路崩塌 拉裂倾倒 23 35 5 Q3黄土 XJG237 车家塬村西崩塌 拉裂倾倒 23 34 5 Q3黄土 XJG252 深砭墕村东崩塌 拉裂倾倒 15 20 3 Q3黄土 注：表中崩塌高、宽为崩塌后壁实测数据，厚度为估算或者实测裂缝距沟边距离。 
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