中文摘要：

元谋干热河谷区的土桥地貌是当地常见的一种潜蚀地貌，是区域地貌的重要组成部分。元谋土桥是造成当地水土流失的重要原因之一，研究其形态特征及演化过程对于认识区域地貌演化及生态地质环境的治理具有重要的现实意义。2009-2013年，通过多次对土桥形态特征、分布区域的地形地貌的现场测定，对土层进行了分析。结果表明：1）元谋土桥大部分分布于冲沟中上游的沟底，少部分分布于冲沟边缘的峭壁下，有连续出现，也有单独出现；2）土桥发育的土层具有层间差异性，即桥洞所在土层较其顶部土层抗崩解性弱，易受侵蚀；3）地层构造节理及冲沟坡度的变化等因素对土桥的形成具有一定的影响作用；4）元谋土桥的形态、结构与一般天生桥或人工桥梁具有相同的桥体结构，形态规模一般都不大；5）演化过程遵循一般事物的发展规律，分为萌芽期、年轻期、成熟期、消亡期4个阶段；6）元谋土桥与陷穴、冲沟等地貌具有一定的耦合关系。

英文摘要：

Soil bridge isone of thecommon erosional landforms in Yuanmou Dry-hot Valley. It is alsoan importantreasoncausinglocalwaterand soilloss,studyingthemorphologicalcharacteristics and evolution process of soil bridgewouldhave important practical significanceforbetterunderstandingof the evolution of regional landforms andmanagement of localeco-geological environment.From 2009 to 2013the authors made field investigationsonthe morphological characteristics,microtopography of the soil bridge, the soil bridge position, and the shape of the longitudinal profile of the gully. And thepropertiesof soil layerswere analyzed. The resultsshowed： 1） Soil bridge mainly developedatthe bottomin upper and middle reachesof the gully,less at the bottom of cliffat the edge of gully. Somesoil bridgesoccurred continuously and some lonely. 2） Therewas differenceamongsoil layers ofthebridge,the resistance of thesoil layer of bridge holeagainstdisintegration and erosionwas weakerthanthat ofthe top layer ofthebridge. 3） Therewas some influence of structure joints and gully slope on the formation of soil bridge. 4） The shape and structure of soil bridgeweresimilar to those ofthe naturalbridge or the artificial bridge. The scaleof soil bridge was generally little. Theshapeofthebridge hole was mainlysimilarto triangle andsometimes to arc. The top of the hole mainly developed along the vertical joint and collapsewasmorefrequentlyobserved. The influencing factors of thesoil bridgedevelopmentweremainly the climate environment, the tectonic setting, the formation joint and the slope of gully, etc. 5） Theevolution processof soil bridgefollowed the general law of thing development, whichcould bedivided into four stages：germination stage, young stage, mature stage and withered stage. 6） Therewascertaincoupling relationship between soil bridge and sink hole and gully in Yuanmou.