基于教实结合的泥石流实验教学改革模式探讨

为促进传统实验教学模式的改革,以适应当今社会对泥石流防灾减灾人才的需求。针对泥石流实验教学的目标,将室内泥石流自主设计实验与课堂教学相融合的方式,从教学模式和教学成果展示途径来探讨泥石流实验教学方式的改革。提出通过开课宣讲、实例引导、理论解析、自主实验、结果反馈5个教学步骤和"以赛促学""以分促学"两种成果展示途径来实现泥石流实验教学模式的改革,达到促进学科交叉融合、培养学生创新与实践能力的目的。实践表明,提出的教学模式在泥石流实验教学课程中成功实践并取得良好教学成果。

泥石流模拟实验装置及虚拟仿真平台设计与应用

针对泥石流实验教学需求,该文设计了泥石流室内模拟实验装置用于模拟泥石流的启动、运移和堆积,基于数值模拟软件对实验数值建模和模拟分析,构建泥石流虚拟仿真平台。使用该实验平台对实际泥石流问题进行分析,验证了其实用性。该实验平台可用于地质工程专业学生的课程实验、课程设计、开放性创新实验和毕业设计,培养学生自主设计实验的创新能力和独立完成实验的动手能力。

实验教学方法在土力学课程中的实践探索

为解决土力学教学中存在的理论与实际应用脱节等问题,以实验教学为手段,将水槽泥石流实验和三轴实验作为两个典型实验对象,使学生能够直观地观察和操作,加深对土体力学行为的认识,提高对土力学理论的理解和应用能力。水槽泥石流实验强调了土体在水动力作用下的变形和运动特性,有助于学生将土力学理论与地质灾害防治结合。而三轴实验则通过模拟不同地下工程条件,加深学生对土体强度和变形特性的理解。理论与实验相结合的教学模式有助于学生培养解决实际问题的能力,为学生从事土木工程等实际工作做好准备,更好地培养学生的综合素养和实用技能。

基于科学核心素养改进“泥石流模拟实验”

浙教版科学七年级上册第三章第五节“泥石流”中关于泥石流的形成和预防模拟实验存在操作烦琐、取材不易、实验现象不明显等问题。为此,利用身边简易的器材改进实验装置,增强了实验的可视性、稳定性和操作性,同时在教学中渗透了控制变量法这一科学方法,符合科学核心素养的培养要求。

Influence of Fine Sediment on the Fluidity of Debris Flows

Debris flows include a great diversity of grain sizes with inherent features such as inverse grading, particle size segregation, and liquefaction of fine sediment. The liquefaction of fine sediment affects the fluidity of debris flows, although the behavior and influence of fine sediment in debris flows have not been examined sufficiently. This study used flume tests to detect the effect of fine sediment on the fluidity of laboratory debris flows consisting of particles with various diameters. From the experiments, the greatest sediment concentration and flow depth were observed in the debris flows mixed with fine sediment indicating increased flow resistance. The experimental friction coefficient was then compared with the theoretical friction coefficient derived by substituting the experimental values into the constitutive equations for debris flow. The theoretical friction coefficient was obtained from two models with different fine-sediment treatments： assuming that all of the fine sediments were solid particles or that the particles consisted of a fluid phase involving pore water liquefaction. From the comparison of the friction coefficients, a fully liquefaction state was detected for the fine particle mixture. When the mixing ratio and particle size of the fine sediment were different, some other eases were considered to be in a partially liquefied transition state. These results imply that the liquefaction of fine sediment in debris flows was induced not only by the geometric conditions such as particle sizes, but also by the flow conditions.

Experimental Studies on Debris Flow with Logs Focusing on Specific Weight Difference of Log Species

There are many experimental approaches,field investigations and numerical calculations for movements of woods in a clear water and debris flow.However,kinematic conditions for accumulated logs and the interactions between a main flow and logs have not been fully evaluated.Mitigations for woods need taking into account the characteristics of tree species such as conifer and broad-leaf trees and of shapes such as root swells and crown.In the present study,we focus on the differences in specific weight of conifer and broad-leaf trees with some moisture in a sediment-water mixture flow with narrow flow width,and consider that conifer and broad-leaf tree are floating and submerged solid phase,respectively.Flume tests are conducted in steady flow of clear and debris flow over a rigid bed in order to evaluate conifer and broad-leaf tree movement in clear water and debris flow.Experimental data indicates that dimensionless transverse diffusion coefficient can be 0.1 to 0.4 and 0.3 to 0.9 in flow direction.Those diffusive characteristics seem to be independent of Reynolds number and Froude number,but dependent of bed slope,i.e.,gravity,though detailed considerations are needed to discuss about flow characteristics such as spatial eddy structures,momentum transfer induced by interactions of logs and so on.

Experimental Study on the Viscoelastic Behaviors of Debris Flow Slurry

The rheological properties of most liquid in nature are between liquids and solids, including both elastic changes and viscosity changes, that is socalled ＂viscoelastic＂. Dynamic oscillatory test was used to quantitatively study the distinct viscoelastic behaviors of debris flow slurry in the shear stress conditions for the first time in this study. The debris flow slurry samples were from Jiangjiagou Ravine, Yunnan Province, China. The experimental results were found that at the low and middle stages of shearing, when the angular velocity 09〈72.46 s-1, the loss modulus （G was greater than the storage modulus （G3, i.e. G＂〉G＇. At the late stage of shearing, when the angular velocity co-72.46 s-x, the storage modulus was greater than or equal to the loss G = G, tan -〈 1 （where phase-shift modulus, i.e. ＇ 〉 ＂ angle 5=G＂,/G3, and the debris flow slurry was in a gel state. Therefore, the progress of this experimental study further reveals the mechanism of hyperconcentrated debris flows with a high velocity on low-gradient ravines.

Experimental study of entrainment behavior of debris flow over channel inflexion points

On-spot observation and field reconnaissance of debris flows have revealed that inflexion points in the longitudinal profile of a movable channel may easily become unstable points that significantly affect their entrainment behavior.In this study,small-scale flume experiments were performed to investigate the entrainment characteristics of debris flows over two types of inflexion points,namely,a convex point,which has an upslope gradient that is less than the downslope gradient,and a concave point,which has an upslope gradient that is greater than the downslope gradient.It was observed that when debris flowed over a convex point,the entrainment developed gradually and progressively from the convex point in the downstream direction,and the primary control factors were the slope gradient and friction angle.Conversely,when debris flowed over a concave point,the entrainment was characterized by impacting and impinging erosion rather than traditional hydraulic erosion,and the impingement angle of the flow significantly determined the maximum erosion depth and outflow exit angle.An empirical relationship between the topography change and the control factors was obtained from the experimental data.

Experimental study on the energy dissipation characteristics of debris flow deceleration baffles

Debris flow can cause serious damages to roads, bridges, buildings and other infrastructures.Arranging several rows of deceleration baffles in the significant influence on the mobility and deposition characteristic of debris flow. The deposit amount first increased then decreased when the flow density rises,flow path can reduce the flow velocity and ensure better protection of life and property. In debris flow prevention projects, deceleration baffles can effectively reduce the erosion of the debris flow and prolong the running time of the drainage channel.This study investigated the degree to which a 6 m long flume and three rows of deceleration baffles reduce the debris flow velocity and affect the energy dissipation characteristics. The influential variables include channel slope, debris flow density, and spacing between baffle rows. The experimental results demonstrated that the typical flow pattern was a sudden increase in flow depth and vertical proliferation when debris flow flows through the baffles. Strong turbulence between debris flow and baffles can contribute to energy dissipation and decrease the kinematic velocity considerably. The results showed that the reduction ratio of velocity increased with the increase in debris flow density,channel slope and spacing between rows. Tests phenomena also indicated that debris flow density hasand the deposit amount of debris flow density of 1500kg/m^3 reached the maximum when the experimental flume slope is 12°.

Influence of Housing and Urban Development on Debris Flow Flooding and Deposition

Debris flows form deposits when they reach an alluvial fan until they eventually stop.However,houses located in the alluvial fan might affect the debris flow flooding and deposition processes.Few previous studies have considered the effects of houses on debris flow flooding and deposition.This study conducted model experiments and numerical simulations using the Kanako2D debris flow simulator to determine the influence of houses on debris flow flooding and deposition.The model experiments showed that when houses are present,the debris flow spreads widely in the cross direction immediately upstream of the houses,especially when the flow discharge is large or the grain size is small.Houses located in the alluvial fan also influence the deposition area.The presence of houses led to flooding and deposition damage in some places and reduced the damage in others.The simulation also demonstrated the influence of houses.Both the model experiment and the simulation showed that houses change the flooding and deposition areas.