九绵高速平武段泥石流运动参数特征与工程危害

泥石流特性及其工程危害分析是道路设计施工的重要依据。九寨沟至绵阳高速公路平武境内有7条沟道曾暴发泥石流,对公路安全造成潜在威胁。通过现场调查与高清遥感解译分析,计算了泥石流运动参数特征并分析了其危害模式,提出了相应的治理措施。研究表明:(1)该区域泥石流为低频沟谷降雨型中小规模稀性泥石流;泥石流容重为1.4~1.8 g/cm^3,流速为2.02~10.55 m/s,流量为2.91~581.33 m^3/s,冲击力为2 078~5 380 k N。(2)西南山区交通干线建设中泥石流对工程体的4种危害模式为冲击桥墩型、掏蚀岸坡型、冲刷顶板型、过流涵洞型;相对应的4类泥石流工程防护模式为桥墩防护、岸坡防护、顶板防护、路基防护。研究结果对九绵高速泥石流防治工程的规划设计具有一定参考作用,也可为西南山区重要交通干线的合理选线提供科学依据。

清平乡罗家沟泥石流基本特征调查及治理方案分析

本文通过对清平乡罗家沟泥石流的现场调查,从形成泥石流的基本要素——地形地貌、泥石流物源构成、水源进行研究,认为罗家沟地形、物源、水源均为泥石流的形成起到有利作用。使其灾害直接摧毁了下游沟道右侧2栋楼房及沿沟道4座桥涵及1.5km的道路,并将沟口10栋房屋全部或局部掩埋,同时大量的泥石流物质冲进绵远河,致使其改道约200m左右,河床平均淤积抬高3-5m。

冲沟堵塞系数对泥石流总量的影响分析

一次泥石流总量是泥石流的重要特征值,它反映了泥石流的规模、强度及流体性质,决定着防治工程建筑物的结构及尺寸,是泥石流研究的重要内容之一。泥石流流量计算方法有形态调查法和雨洪修正法,由于很多冲沟因多年未发生过泥石流,很难测得泥石流过流断面,因此雨洪法是泥石流流量计算的一种常见的实用方法,而雨洪修正法计算公式中堵塞系数Dc视冲沟沟谷堵塞情况而异,其取值具有很大的任意性和不确定性,本文通过对堵塞系数在不同取值下计算一次泥石流总量,经野外调查资料与计算结果校验,最终结果具有一定的可信度。

福建紫金山金矿特高台阶排土的控制研究

针对紫金山单台阶排土爆发泥石流工程现象进行了分析研究 ,计算出泥石流产生的特征参数 ,从而有效地实施了拦截工程 ,使得该排土场安全处于可控状态之中 ,节省了大量排岩运输费用 ,取得了巨大的经济效益。

The Optimal Cross-section Design of the “Trapezoid-V” Shaped Drainage Canal of Viscous Debris Flow

Debris flow drainage canal is one of the most widely used engineering measures to prevent and manage debris flow hazards.The shape and the sizes of the cross-section are important parameters when design debris flow drainage canal.Therefore,how to design the appropriate shape and sizes of the cross-section so that the drainage canal can have the optimal drainage capacity is very important and few researched at home and abroad.This study was conducted to analyze the hydraulic condition of a Trapezoid-V shaped drainage canal and optimize its cross-section.By assuming characteristic sizes of the cross-section,the paper deduced the configuration parameter of the cross-section of a Trapezoid-V shaped debris flow drainage canal.By theory analysis,it indicates that the optimal configuration parameter is only related to the side slope coefficient and the bottom transverse slope coefficient.For this study,the Heishui Gully,a first-order tributary of the lower Jinsha River,was used as an example to design the optimal cross-section of the drainage canal of debris flow.

Comparison of Rheometric Devices for Measuring the Rheological Parameters of Debris Flow Slurry

Soil samples with clay content ranging from 15% to 31%, were taken from three debris flow gullies in Southwest China. Three debris flow slurry samples were prepared and tested with four measuring systems of an Anton Paar Physica MCR301 rheometer, including the concentric cylinder system,the parallel-plate system, the vane geometry, and the ball measuring system. All systems were smoothwalled. Flow curves were plotted and yield stress was determined using the Herschel-Bulkley model,showing differences among the different systems.Flow curves from the concentric cylinder and parallelplate systems involved two distinct regions, the low shear and the high shear regions. Yield stresses determined by data fitting in the low shear region were significantly lower than the values from the inclined channel test which is a practical method for determining yield stress. Flow curves in the high shear region are close to those from the vane geometry and the ball measuring system. The fitted values of yield stress are comparable to the values from the inclined channel test. The differences are caused by wall-slip effects in the low shear region.Vane geometry can capture the stress overshoot phenomenon caused by the destruction of slurry structure, whereas end effects should be considered in the determination of yield stress. The ball measuring system can give reasonable results, and it is applicable for rheological testing of debris flow slurries.

The properties of dilute debris flow and hyper-concentrated flow in different flow regimes in open channels

Particle Image Velocimetry(PIV) technique was used to test the analogues of hyperconcentrated flow and dilute debris flow in an open flume. Flow fields, velocity profiles and turbulent parameters were obtained under different conditions. Results show that the flow regime depends on coarse grain concentration. Slurry with high fine grain concentration but lacking of coarse grains behaves as a laminar flow. Dilute debris flows containing coarse grains are generally turbulent flows. Streamlines are parallel and velocity values are large in laminar flows. However, in turbulent flows the velocity diminishes in line with the intense mixing of liquid and eddies occurring. The velocity profiles of laminar flow accord with the parabolic distribution law. When the flow is in a transitional regime, velocity profiles deviate slightly from the parabolic law. Turbulent flow has an approximately uniform distribution of velocity and turbulent kinetic energy. The ratio of turbulent kinetic energy to the kinetic energy of time-averaged flow is the internal cause determining the flow regime: laminar flow(k/K<0.1); transitional flow(0.1< k/K<1); and turbulent flow(k/K>1). Turbulent kinetic energy firstly increases with increasing coarse grain concentration and then decreases owing to the suppression of turbulence by the high concentration of coarse grains. This variation is also influenced by coarse grain size and channel slope. The results contribute to the modeling of debris flow and hyperconcentrated flow.

Numerical Investigation on the Initiation Mechanism of Debris-Flow under Rainfall

Rainfall is an important factor to trigger the debris flow.Numerical simulation on the responses of slopes and the initiation of debris flow under rainfall was processed by using the software FLAC2D based on the soil parameters in Weijia Gully,Beichuan County,Sichuan Province,China.The effects of the slope angle,rainfall intensity,soil parameters on the developments of the stress and pore pressure and deformation of the slope were studied.It indicates that large displacements of the slope are mainly located near the slope toe.With the increase of the rainfall intensity the stability of the slope decreases and so the debris-flow is easy to occur.

Rainfall,Landslide and Debris Flow Intergrowth Relationship in Jiangjia Ravine

Jiangjia Ravine is a world-famous debris flow valley in Dongchuan,Yunnan Province,China.Every year large numbers of landslides and collapses happened and caused enormous damages to people's properties and lives.With longtime observation and testing in Jiangjia Ravine we had found out one kind of special landslide which had the characteristics of landslide and collapse.Landslide and collapse supplied sufficient materials for debris flow.When a debris flow broke out,some kind of intergrowth existed among rainfall,landslide and debris flow.In order to study the intergrowth and some key parameters,we carried out artificial rainfall landslide tests and model experiments to observe the phenomena such as collapse,surface slide and surface flow.By observing the experimental phenomena and monitoring water contents,the transformation process among landslide deposits and debris flow under the condition of rainfall had been analyzed.Research results revealed the relationship of this kind of intergrowth among rainfall,landslide and debris flow in Jiangjia Ravine.Meanwhile,it was found that this kind of intergrowth relationship existed only when the moisture content was in a certain range.That is,the critical state seemed to be existed in the transformation process.