Tectonic Landform Conditions And Its Hazard Effect In Heifangtai Area

In recent years, a large number of landslides and collapses and debris flows were induced by pumping irrigation in HeiFangtai area where is the Liujiaxia reservoir settlements. The geological disasters cause great economic losses and seriously threaten the life safety or properties of the local residents. So the disasters caused wide attention. Therefore prevention and the study of the disaster are imminent. However, tectonic geomorphic conditions to a certain extent control the development of disaster. In this paper, analysis the impact of disasters by tectonic geomorphic conditions such as, attitude of rock bed, characteristics of pebble bed, and characteristics of clay layer distribution. For a more comprehensive understand the mechanism of the occurrence of disasters and evolution process of platform. For deeply discuss the method on topographical features to analyze the platform-margin slope stability. In this paper, through field investigation include tectonic phenomena (faults, folds, joints, rock profile and so on), pebble bed development characteristics (thickness, site, pebble occurrence, shape size, lithology and the like) and landslide main scarp features. Combining with the DEM data and geological map information, then analyze the evolution process of tableland slope using superposition calculation method, analyze the distribution and development of disasters using the method of terrain gallery band, analyze the morphological characteristics of 38 landslides around platform using the fractal dimension method, and analyze the groundwater runoff and ancient river environment based on the characteristics and arrangement of pebble shape. The results show that:(1) About 7 faults developed around the terrace, in the majority with reverse faults. Hulanggou fault (FH) and Jiaojia fault (FJ) have occurred small dislocation since the quaternary period, are active. These two faults have a deeply effect on underground clay layer in Heifangtai platform. The local stress fields where faults outcrop distribution reflected by the development characteristics of Fault plane and joints are similary to the modern tectonic stress field. Loess landslides are smaller, the slip is longer, and the average fractal dimension value is 1.75. Loess bedrock landslides are larger and the average fractal dimension value is 1.82.(2) There are two kinds of langslides developed around Heifangtai platform. They have subsection characteristics on the spatial distribution, the landslides developed in different sections have different sizes, different hazard degrees.(3) The direction of Ancient River when the Ⅳ level terraces formed was similarly to the direction of Yellow River now. The paleochannel of Ancient River has a deep effect on the runoff discharge characteristics of groundwater. Due to clay layer has weak water permeability, after the irrigation water infiltration to the top of the clay layer, it easy assembles and flows along the top surface where elevation lower such as northeast.(4) Recede and sink phenomenon happened obviously on Heiftai geographical edge and front part are piled up, maximum subsidence range of 35 m, accumulation is the thickest place to 37 m. Moreover, from 1977 to 2010,33 years, ground subsidence reach to about 1.5 m in Heitai area. The quantity of platform-margin high slope (main scarp) is decrease, especially the slope which degree more than 55°.