云南红土型滑坡室内试验研究

【作者】 石崇喜；

【导师】 黄英；

【作者基本信息】 昆明理工大学 ， 水利水电工程， 2011， 硕士

【摘要】 本文在综合分析国内外关于边坡稳定、滑坡试验、降雨型滑坡等研究现状的基础上,明确了滑坡研究中存在的问题,并结合云南大量存在的红土型边坡和降雨集中的特点,提出了“云南红土型滑坡室内试验研究”这一课题。针对云南典型红土,开展了室内滑坡试验研究。研究内容主要包括滑坡试验装置的研制、降雨量的率定、滑坡试验的开展、物理特性与抗剪强度特性的研究以及滑坡机理分析等方面,这对于深入研究红土型滑坡的滑动机制以及开展红土型滑坡的防治具有重要的理论意义和现实意义。室内滑坡试验装置主要由降雨系统、模型槽和集水槽三部分构成。降雨系统的降雨特性通过降雨量的率定试验来确定,其率定方法包括降雨量实测法和能量修正法。率定结果表明,水龙头开度一定时的室内降雨量、实际降雨量均与水龙头关闭时刻呈线性关系,但室内实测降雨量大于进行能量法修正的实际降雨量,二者之间存在一个能量折减系数。在研制完成室内滑坡试验装置的基础上,针对云南典型红土,考虑坡角、坡高、含水率、干密度等不同影响因素,通过水平分层击实、竖直分层击实和堆积法制作边坡,控制降雨等级为暴雨,开展了一系列的滑坡试验研究。结果表明：产生滑坡的成功率很低；发生滑坡的条件为堆积法成型、干密度偏小、含水偏高、坡顶面长度偏长、坡高偏高、坡角偏大等情况；红土型滑坡的滑动面近似圆弧；边坡滑动时,可观测到裂缝、滑动面、滑带、滑动位置、滑壁高度、滑动历时、滑动方式、滑前征兆等滑动特征；不管边坡是否滑动,降雨过程中,都呈现出“溅蚀”、“结皮”、细颗粒运移和坡脚破坏等典型现象。滑坡红土的物理特性包括含水、密度及颗粒组成三个方面。不管边坡是否发生滑动,其含水特性表现为红土的含水率随坡高的降低逐渐增大,密度特性表现为密度随坡高的降低逐渐减小,颗粒组成特性表现为粉粒含量随坡高的降低均有不同程度的增加,粘粒含量均有不同程度的减少；边坡发生滑动时,坡高位置相同,滑带土的含水率最高,滑床土的含水率次之,滑体土的含水率最小。滑坡红土物理特性的变化就是降雨在坡体表面发生击打、入渗、产流等共同作用的结果。红土的抗剪强度特性表现为：干密度相同,其抗剪强度和内摩擦角随含水率的增加逐渐降低,粘聚力随含水率的增加出现最大值；含水率相同,其抗剪强度和粘聚力随干密度的减小逐渐降低,内摩擦角随干密度的减小有增大的趋势。红土抗剪强度的变化主要取决于红土颗粒的大小、颗粒之间的联结以及颗粒之间的排列所构成的复杂的土体结构和土中基质吸力的变化。降雨过程中,边坡呈现出的“溅蚀”、“结皮”、细颗粒运移和坡脚破坏等典型现象可以从雨滴对坡面土颗粒的击打、雨水渗入坡体、坡面产流以及坡体中产生的孔隙水压力等作用来解释。降雨作用下红土型滑坡的发生机理实际上就是雨水对边坡土体的增重、软化和润滑三个方面综合作用的结果。更多还原

【Abstract】 On the basis of the comprehensive analysis of the slope stability,the landslide test and the rainfall-induced landslide from home and abroad,the substantial problems of the landslide research are defined.Combining with the characteristics of a large number of the laterite-type slopes existed and rainfall concentration in Yunnan province,the research subject,which is named as "laboratory test research on laterite-type landslide in Yunnan province",is presented.Aiming to the typical laterite in Yunnan province,laboratory landslide tests were carried out with contents such as manufacture of laboratory landslide test apparatus,calibration of rainfall capacity,development of landslide test,research of physical characteristics and shear strength characteristic of laterite and analysis of rainfall-induced landslides mechanism.The acquisitive research-fruits are of great theory and realization significance for the sliding mechanism and prevention of laterite-type landslides.The laboratory landslide test apparatus mainly includes rainfall system,model slot and water collecter.Rainfall characteristics of rainfall system can be confirmed by the rainfall capacity calibration tests.There are practical measurement method and energy modification method to confirm the rainfall of rainfall system.Under the condition that the tap is keeping certain opening,the relationships of both laboratory rainfall capacity and actual rainfall capacity to the tap closed-timing are linear, but actual rainfall capacity is larger than laboratory rainfall capacity, and there is an energy fold reduction factor between them.After finishing the manufacture of landslide test apparatus,aiming to the typical laterite in Yunnan province,under different conditions such as angle of slope,height of slope,moisture content,dry density and molding method including layered-bumping method in horizontal direction, layered-bumping method in vertical direction and packing method,a series of landslide tests were carried out while rainfall grade is rainstorm.The rate of success for laterite-type slope is very low.The occurrence conditions of landslide were as follows:laterite-type landslides are made by packing method,the dry density is smaller,the moisture content and heights of slope are higher.the roof length of slope is longer.and the angle of slope is larger.The sliding surface of the laterite-type landslide is approximate arc shape. when laterite-type slope is sliding.sliding characteristics,such as crack,sliding surface,sliding zone.sliding position,height of slippery wall.sliding lasted-time, sliding way and sign before sliding,can be observated.Whether laterite-type slope is sliding or not,there are several typical phenomenons during rainfall,which include"splash erosion","crust",particles migration and slope destruction.Physical characteristics of the landslide laterite include containing water, density and grain composition.Whether laterite-type slope is sliding or not, with the decrease of the slope height, whose moisture content is growing and density is reducing gradually, whose silt content is increased and clay content is reduced by different degrees.Under the condition of the same position for slope height, moisture content of slide-zone soils is maximum,moisture content of slide-part soils is next,moisture content of slide-bed soils is minimum.The variation mechanism of physical properties is the consequence of a combination of strike action,infiltration action and runoff action on slope surface caused by rainfall.Shear strength characteristic of the laterite which was prepared in different moisture contents and densities, was determined by direct shear tests.With the increase of the moisture content, shear strength and friction angle are reduced gradually in the same dry density, but there is an maxima for cohesion.In the same moisture content, as dry density reduced, shearing strength and cohesion are decreased gradually, but friction angle trends towands enlarger. The variation mechanism of shear strength characteristic depends on the size of the laterite particles, the link between laterite particles, soil structure by the way of arranging among particles and soil suction.In rainfall process, typical phenomenons, such as "splash erosion", "crust", particles migration and slope destruction, can be explained from strike action, infiltration action, runoff action and pore water pressure action on slope surface. Under the action of rainfall, laterite-type landslide mechanism is clarified with weight increase action, soften action and lubrication action.更多还原