松散土坡结构特征与滑坡堰塞体堆积特征之间的关系试验研究

EXPERIMENTAL STUDY ON RELATIONSHIP BETWEEN STRUCTURAL CHARACTERISTICS OF LOOSE SOIL SLOPE AND ACCUMULATION CHARACTERISTICS OF LANDSLIDE DAM

通过模型实验,探讨了松散土坡3种不同结构特征条件下(均匀坡体(坡体物料均匀混合)、平行坡体(土层成层且层面与滑面平行)和斜交坡体(土层成层且层面与滑面斜交))形成滑坡堰塞体的动力过程和堆积特征,通过分区域取样及三维扫描技术研究了堰塞体的物质分布规律与形态特征。研究结果表明:堰塞体堆积特征与坡体特征存在紧密联系,堰塞体纵向(沿主沟道方向)和横向(沿滑坡运动方向)上的物质分布与坡体纵向和横向的物质分布特征基本对应;在垂向(表层到底部)上,由于不同坡体条件下滑坡的动力过程和机理不同,从而导致堰塞体堆积特征存在一定区别。均匀坡体和平行坡体呈整体启动模式,运动过程中物料间存在垂向渗透和交换作用,导致堰塞体物质在垂向上呈明显的上粗下细反粒序分布特征,堰塞体横剖面多呈平坦型和倾斜型。斜交坡体呈分层启动模式,运动堆积过程中保持原有层序,粗、细颗粒先后启动条件下颗粒间存在推挤、爬升和水平渗透作用,使得堰塞体更加密实且垂向上也呈现反粒序分布特征,横剖面多呈起伏型。本研究为滑坡堰塞体稳定性快速评估和复原滑坡初始状态提供依据。

According to physical model tests,we discuss the dynamic process and accumulation characteristics of landslide dams formed under three different slope features including uniform slope(slope compositions mixed uniformly,parallel slope(soil layer surface parallel to the sliding surface)and intersecting slope(soil layer surface intersecting with the sliding surface).The material distribution and morphological characteristics of the landslide dams are studied by sub-regional sampling and 3D scanning technology.The results demonstrate that the accumulation characteristics of landslide dam are closely related with the slope body.The material distribution in the longitudinal direction(along the main river)and cross-sectional direction(along the sliding direction)of the dam are basically corresponded with that of the slope body,but different in vertical direction due to the differences in dynamic process and accumulation mechanism of the landslide dam under different slope conditions.The uniform slope and parallel slopes are initiated in an overall-starting mode.Obvious vertical infiltration effect and material exchange are present during the movement process,leading to the inverse grading distribution of sediment in the vertical direction of the dams.And the cross-sectional shapes of the dam are mostly flat and inclined.The intersecting slopes present a layered-starting mode.The original sequences are maintained during the movement and accumulation process.The pushing-climbing effect and horizontal infiltration can occur under some conditions,accounting for the inverse grading characteristic of sediment distribution in the vertical direction and undulating cross-sectional shape of the dam.This study promotes a better understanding of the relationship between slope body and landslide dam and provides a basis for rapid assessment of the stability of landslide dam and restoration of the initial state of the slope.