scholarly journals Influence of Internal Structure on Breaking Process of Short-Lived Landslide Dams

2021 ◽  
Vol 9 ◽  
Author(s):  
Chu-Ke Meng ◽  
Kun-Ting Chen ◽  
Zhi-Pan Niu ◽  
Bao-Feng Di ◽  
Yu-Jian Ye
Keyword(s):  
Growth Rate ◽  
Failure Process ◽  
Landslide Dam ◽  
Storage Process ◽  
Dam Breach ◽  
Landslide Dams ◽  
Evolution Characteristics ◽  
Breaking Mechanism ◽  
The Difference ◽  
The Stability

The diversity of the landslide dam structure will result in the difference in the dam body’s seepage. In this paper, based on two kinds of soil bodies of different particle gradations, fourteen groups of structures of the landslide dam are designed to generalize different seepage developments and breaking processes. The study shows that the saturation and seepage evolution characteristics of the landslide dam's seepage have a considerable influence on the landslide dam’s breaking characteristics. An empirical formula is fitted according to the time-seepage degree curve of the landslide dams of different breaking processes to predict the breaking forms of the landslide dams before the dam break. During the water storage process of the landslide dam, the seepage's saturation process inside the dam body reduces the stability of the landslide dam, thus affecting the evolution of the failure process after it has started. In the experiment, it is found that the growth rate of the seepage degree of the landslide dam is inversely proportional to the growth rate of the dam breach area. Although the internal penetration of landslide dams is usually undervalued, the result verifies that the study on the seepage process before the breaking of landslide dam is conductive for further understanding the breaking mechanism of the landslide dam.

Comparison on the failure process and mechanism between a debris flow and a landslide dam

2020 ◽  
Author(s):  
Huayong Chen ◽  
Chunran Cao ◽  
Xiaoqing Chen ◽  
Jiangang Chen
Keyword(s):  
Debris Flow ◽  
Water Content ◽  
Failure Process ◽  
Landslide Dam ◽  
Clay Content ◽  
Peak Discharge ◽  
Initial Water Content ◽  
Dam Breach ◽  
Initial Water ◽  
Landslide Dams

<p>Besides the numerous artificial dams, there are some other kind of dams distribute such as the glacier dams, moraine dams, landslide dams, and the debris flow dams in China. Especially, the landslide dams and debris flow ones widely distribute in southwest of China after the M8.0 Wenchuan earthquake. Much attention has been paid to the formation, stability, breach process, and the peak discharge prediction of a landslide dam. However few achievements are obtained on the debris flow dams even if the failure of a debris flow dam has posed great threat to the property and life of residents downstream. In this paper, based on the main difference between a landslide and debris flow dam, experiments were conducted by considering different clay content, the initial water content, and incoming water flow. It indicated that the failure duration of a debris flow dam was about 1.60 times as long as that than that of a landslide dam. The peak discharge at the debris flow dam breach was 5.38 L/s. However, the peak discharge at the landslide dam was 7.50 L/s, which was 1.39 times as big as that of a debris flow dam. Finally, by modifying the existing critical initialization condition for the landslide dams, the critical initialization condition for a debris flow dam was proposed.</p>

scholarly journals Resistivity and AE Response Characteristics in the Failure Process of CGB under Uniaxial Loading

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Tingye Qi ◽  
Guorui Feng
Keyword(s):  
Failure Process ◽  
Peak Stress ◽  
Uniaxial Loading ◽  
Energy Curve ◽  
Cumulative Energy ◽  
Response Characteristics ◽  
Before And After ◽  
The Difference ◽  
Linear Slope ◽  
The Stability

To understand the characteristics of the acoustic emission (AE) and electrical resistivity of cemented coal gangue backfill (CGB) under uniaxial compression, the variations in these characteristics at 1 day, 3 days, and 7 days are analyzed by means of a stress-strain-resistivity-AE test, and the microperformances are investigated. The research results indicate that the AE can reflect the initiation and propagation of cracks and later explain the variation of the resistivity of the specimens under the uniaxial loading. The cumulative energy curve of AE is approximately two straight lines corresponding to the peak stress, and the difference in the linear slope gradually decreased with the increasing curing time due to the lower pore solution content and the compact pore structure. The relationships between the stress and resistivity and the loading condition before and after the peak stress at different curing times were established. Therefore, it is of great significance to predict the stability of the filling body by monitoring the AE and resistivity variations of the filling body. In addition, it is possible to calculate the roof stress using the relation equation between the resistivity and stress.

The effect of geometry on the gravitational instability of a buoyant region of viscous fluid

1989 ◽  
Vol 202 ◽  
pp. 577-594 ◽  
Author(s):  
John R. Lister ◽  
Ross C. Kerr
Keyword(s):  
Growth Rate ◽  
Stokes Equations ◽  
Gravitational Instability ◽  
Cube Root ◽  
Scaling Analysis ◽  
Island Arcs ◽  
Layered Systems ◽  
Ocean Ridges ◽  
The Difference ◽  
The Stability

The low-Reynolds-number stability of a region of buoyant fluid surrounded by denser fluid is analysed in two situations. In the first study, the buoyant fluid lies in a thin layer sandwiched between two denser and much deeper layers. The growth rate and wavelength of the most unstable sinusoidal perturbation are calculated and the effects of the viscosity ratios and density differences between the fluids are investigated. It is found that if the buoyant fluid is much less viscous than the overlying fluid then, in quite general circumstances, both the most unstable wavelength and the corresponding growth rate are inversely proportional to the cube root of the viscosity of the buoyant fluid. A physical explanation of this result is given by scaling analysis of the total dissipation. In the second study, the buoyant fluid takes the form of a cylinder rising through a uniform environment. The eigenmodes of small perturbation about this state of motion are found for each axial wavenumber in terms of Fourier series of separable solutions to the Stokes equations. In contrast to the first study, it is found that the most unstable wavelength and growth rate are asymptotically independent of the viscosity of the buoyant fluid when this viscosity is small.The difference between the results of the two studies is of importance, particularly for geophysical applications in which viscosity ratios are very large. Previous models of linear regions of volcanism at mid-ocean ridges and at island arcs have assumed that results obtained in simple two-layered systems can be generalized to other geometries. The conclusions of these models are discussed in the light of the stability results for a cylindrical (and hence linea.

scholarly journals Numerical Simulation on the Longitudinal Breach Process of Landslide Dams Using an Improved Coupled DEM-CFD Method

2021 ◽  
Vol 9 ◽  
Author(s):  
Dong-yang Li ◽  
De-feng Zheng ◽  
Hao Wu ◽  
Yue-qiang Shen ◽  
Ting-kai Nian
Keyword(s):  
Coupling Effect ◽  
Morphological Evolution ◽  
Landslide Dam ◽  
Mesh Size ◽  
Surface Flow ◽  
Erosion Process ◽  
Dam Breach ◽  
Particle Sedimentation ◽  
Landslide Dams ◽  
Cfd Method

An accurate investigation of the landslide dam breach process is crucial for the understanding the breach mechanism and disaster prediction. However, the numerical research on the landslide dam breach process to date is rarely reported, especially regarding the soil-water flow coupling effect incorporated in the erosion process. This paper presents a numerical investigation on the longitudinal breach process of landslide dams via a coupled discrete element method (DEM) and computational fluid dynamics (CFD) with the volume of fluid (VOF). Moreover, a virtual sphere model is proposed to overcome the computational instability caused by the particle size approaching the mesh size. The accuracy and validity of the improved coupled method are verified using a series of single particle sedimentation cases. By employing this method, the longitudinal breach process of landslide dams featuring different materials and hydrodynamic conditions has been simulated. It is found to satisfactorily reproduce the longitudinal breach process of landslide dams including surface flow erosion, backward erosion, head-cut erosion, and water and sediment rebalance or complete breach. The effects of the inflow discharges and dam materials on the erosion process are systematically resolved. The breach flow can cause the rotation trend of particles and lead to the increase of tangential contact force at the initial stage of the dam breaching. During the breach process, both the strength and density of the force chain continue to attenuate. The results obtained from the improved coupled DEM-CFD simulations can reasonably explain the particle-fluid interaction mechanisms, physical and morphological evolution and breach process at both macroscopic and mesoscopic scales.

scholarly journals A Preliminary Study of the Failure Modes and Process of Landslide Dams Due to Upstream Flow

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1115 ◽  
Author(s):  
Xinghua Zhu ◽  
Jianbing Peng ◽  
Cheng Jiang ◽  
Weilong Guo
Keyword(s):  
Large Scale ◽  
Failure Modes ◽  
Mine Waste ◽  
Failure Process ◽  
Landslide Dam ◽  
Experimental Tests ◽  
Field Investigation ◽  
Dam Failure ◽  
Experimental Conditions ◽  
Landslide Dams

In the process of mineral development, large-scale flash floods (or debris flows) can be induced by the failure of landslide dams formed by the disorganized stacking of mine waste. In this study, the modes and processes of mine waste dam failures were explored using 13 experimental tests based on the field investigation of landslide dams in the Xiaoqinling gold mining area in China. Our 13 mine waste dam experiments exhibited three failure modes: (i) Piping, overtopping, and erosion; (ii) overtopping and soil collapse; and (iii) overtopping and erosion. In addition, the failure processes of the landslide dams included impoundment, seepage, overtopping, and soil erosion. Different experimental conditions would inevitably lead to different failure processes and modes, with the failure modes being primarily determined by the seepage characteristics. Overtopping was the triggering condition for dam failure. The landslide dam failure process was determined based on the particle size of the mine waste and the shape of the dam. These findings will provide a scientific reference for the prevention and mitigation of natural hazards in mining areas.

scholarly journals Effects of Grain Size Distribution on Landslide Dam Breaching—Insights From Recent Cases in China

2021 ◽  
Vol 9 ◽  
Author(s):  
Shengyao Mei ◽  
Shengshui Chen ◽  
Qiming Zhong ◽  
Yibo Shan
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Emergency Response ◽  
Landslide Dam ◽  
Dam Breach ◽  
Response Planning ◽  
Landslide Dams ◽  
Emergency Response Planning ◽  
Dam Breaching

Landslide dams are common geological features in mountainous areas, which may have serious consequences due to sudden breaching of the dam. An effective emergency response requires rapid and accurate forecasts regarding the landslide dam breach process. However, most existing models use physical, mechanical, and erosion properties of the mean or characteristic grain sizes to represent the landslide deposits. The grain size distribution and variations in soil erodibility with the depth in the landslide dam are not considered, resulting in an incorrect estimation of the breach flow hydrograph. In this paper, a simplified landslide dam classification is presented based on the formation mechanism and grain size distribution of landslide dams. Additionally, the influences of grain size distribution on the residual dam height and breach process of landslide dams are analyzed. This paper proposes a numerical method to rapidly obtain the breach hydrographs and breach morphology evolution of landslide dams. The new method can quickly classify landslide dams according to geological survey data and predict the landslide dam breach process. Three types of representative landslide dams in China are simulated to validate the proposed method. The breach flow discharge is significantly affected by spillway excavation. This contribution can provide rapid prediction of the landslide dam breach process and can be used for the emergency response planning before dam breaching.

Breach of a naturally embanked dam on Yalong River

1992 ◽  
Vol 19 (5) ◽  
pp. 811-818 ◽  
Author(s):  
Y. J. Chen ◽  
F. Zhou ◽  
Y. Feng ◽  
Y. C. Xia
Keyword(s):  
Key Words ◽  
Failure Process ◽  
Landslide Dam ◽  
Sichuan Province ◽  
Dam Breach ◽  
Flood Discharge ◽  
Flood Hydrograph ◽  
The Right ◽  
Yalong River

A huge slide involving 68 × 106 m3 of soils occurred along the right bank of Yalong River in Sichuan Province, China. The sliding materials blocked the river and formed a dam-like structure having a height of 175 m and creating a reservoir with a capacity of approximately 680 × 106 m3. The dam breach which was caused by overtopping lasted 13 h and resulted in an estimated maximum flood discharge of 53 000 m3/s. Based on the hydrograph created by measuring the flows downstream of the dam, the process of dam breach was roughly estimated. Key words: landslide dam, cohesionless material, overtopping, breach, flood, hydrograph, failure process.

scholarly journals Recent Advances in Stability and Failure Mechanisms of Landslide Dams

2021 ◽  
Vol 9 ◽  
Author(s):  
Hongchao Zheng ◽  
Zhenming Shi ◽  
Danyi Shen ◽  
Ming Peng ◽  
Kevin J. Hanley ◽  
...  
Keyword(s):  
Failure Modes ◽  
Risk Mitigation ◽  
Failure Mechanisms ◽  
Landslide Dam ◽  
Evaluation Indexes ◽  
Landslide Dams ◽  
Recent Advances ◽  
Engineering Measures ◽  
Dam Stability ◽  
The Stability

Numerous landslide dams have been induced in recent years as a result of frequent earthquakes and extreme climate hazards. Landslide dams present serious threats to lives and properties downstream due to potentially breaching floods from the impounded lakes. To investigate the factors influencing the stability of landslide dams, a large database has been established based on an in-depth investigation of 1,737 landslide dam cases. The effects of triggers, dam materials, and geomorphic characteristics of landslide dams on dam stability are comprehensively analyzed. Various evaluation indexes of landslide dam stability are assessed based on this database, and stability evaluation can be further improved by considering the dam materials. Stability analyses of aftershocks, surges, and artificial engineering measures on landslide dams are summarized. Overtopping and seepage failures are the most common failure modes of landslide dams. The failure processes and mechanisms of landslide dams caused by overtopping and seepage are reviewed from the perspective of model experiments and numerical analyses. Finally, the research gaps are highlighted, and pathways to achieve a more complete understanding of landslide dam stability are suggested. This comprehensive review of the recent advances in stability and failure mechanisms of landslide dams can serve as a key reference for stability prediction and emergency risk mitigation.

Use of a Lyophilized Reference Plasma to Compare Coagulation Test Procedures

1975 ◽  
Vol 34 (02) ◽  
pp. 426-444 ◽  
Author(s):  
J Kahan ◽  
I Nohén
Keyword(s):  
Oral Anticoagulant Therapy ◽  
Repeated Measurements ◽  
Test Procedures ◽  
Coagulation Activity ◽  
Close Relationship ◽  
Measured Activity ◽  
Test Materials ◽  
The Difference ◽  
The Stability ◽  
The One

SummaryIn 4 collaborative trials, involving a varying number of hospital laboratories in the Stockholm area, the coagulation activity of different test materials was estimated with the one-stage prothrombin tests routinely used in the laboratories, viz. Normotest, Simplastin-A and Thrombotest. The test materials included different batches of a lyophilized reference plasma, deep-frozen specimens of diluted and undiluted normal plasmas, and fresh and deep-frozen specimens from patients on long-term oral anticoagulant therapy.Although a close relationship was found between different methods, Simplastin-A gave consistently lower values than Normotest, the difference being proportional to the estimated activity. The discrepancy was of about the same magnitude on all the test materials, and was probably due to a divergence between the manufacturers’ procedures used to set “normal percentage activity”, as well as to a varying ratio of measured activity to plasma concentration. The extent of discrepancy may vary with the batch-to-batch variation of thromboplastin reagents.The close agreement between results obtained on different test materials suggests that the investigated reference plasma could be used to calibrate the examined thromboplastin reagents, and to compare the degree of hypocoagulability estimated by the examined PIVKA-insensitive thromboplastin reagents.The assigned coagulation activity of different batches of the reference plasma agreed closely with experimentally obtained values. The stability of supplied batches was satisfactory as judged from the reproducibility of repeated measurements. The variability of test procedures was approximately the same on different test materials.

In the stability of paints and varnishes for protective and decorative wood finish

2016 ◽  
Author(s):  
Ю.И. Цой
Keyword(s):  
Organic Solvents ◽  
Evaluation Criteria ◽  
Ternary Systems ◽  
Solubility Parameters ◽  
Formaldehyde Resin ◽  
Film Forming ◽  
The Difference ◽  
Molecular Forces ◽  
The Stability ◽  
Thermodynamic Interaction

Задача получения однородного состава ЛКМ сводится к правильному выбору пленкообразователей и соответствующих растворителей и, в случае необходимости, разбавителей и добавок. На основе положений теории растворимости была проведена оценка совместимости компонентов и стабильности таких систем. Критериями оценки были приняты параметры растворимости и термодинамического взаимодействия. Исследовали совместимость алкидных лаков с аминоформальдегидными смолами в бутаноле, и результаты этих исследований представлены в треугольной фазовой диаграмме. Для оценки совместимости смол по результатам расчета параметров термодинамического взаимодействия были построены спинодали для тройных систем. Как показывает анализ результатов проведенных исследований, даже при большой разности ?? = |?12 – ?13| = 0,2 наблюдается небольшая область несовместимости. С уменьшением разности ?? область несовместимости сужается. При ?23 > ?с область несовместимости расширяется как для ? = 0,2, так и для ?? = 0,1 и ?? = 0. Таким образом, для таких систем на совместимость компонентов, в первую очередь, влияет их взаимодействие между собой – чем оно больше, тем лучше они совместимы. Проведенные исследования показали, что парциальные параметры растворимости, учитывающие природу когезионных сил, более объективно характеризуют растворимость пленкообразующих смол в органических растворителях, чем их общий параметр растворимости. Растворимость пленкообразующих алкидных и этерифицированных аминоформальдегидных смол в органических растворителях обусловлена термодинамическим взаимодействием молекулярных сил различной природы. Стабильность смеси алкидной и этерифицированной аминоформальдегидной смолы в бутаноле обусловлена в большей степени термодинамическим взаимодействием молекулярных сил; при этом степень бутанолизации меламиноформальдегидной смолы оказывает наибольшее влияние на стабильность cистемы. Проведенные исследования по стабильности лакокрасочных смесей из различных пленкообразующих смол на основе рассмотренных критериев оценки могут быть использованы для совершенствования технологии защитно-декоративной отделки древесины. The problem of obtaining a homogeneous composition of the coatings is reduced to the proper selection of film-forming agents, and diluent and, if appropriate, diluents and additives. On the basis of the theory of solubility, we have carried out the assessment of the compatibility of the components and stability of such systems. The evaluation criteria were adopted the parameters of the solubility and thermodynamic interaction. Researched the compatibility with alkyd varnishes aminoformaldehyde resin in butanol, and the results of these studies are presented in the triangular phase diagram. To evaluate the compatibility of the resins according to the results of calculation of thermodynamic parameters of interaction were built spinodal for ternary systems. As the analysis of the results of the studies, even when the difference ??|?12 – ?13| = 0,2 there is a small area of incompatibility. With the decrease of the difference ? ? region incompatibility narrows. When ?23> ?с region incompatibility extends to ?? = 0,2, and for ?? = 0.1 and ?? = 0. Thus, for such systems, compatibility of components, primarily, affects their interaction with each other – the further away it is, the better they are compatible. Studies have shown that the partial solubility parameters, which take into account the nature of cohesive forces, more objectively characterize the solubility of film-forming resins in organic solvents than their total solubility parameter. The solubility and film-forming aminoformaldehyde esterified alkyd resins in organic solvents due to thermodynamic interaction of molecular forces of different nature. Тhe stability of the mixture and aminoformaldehyde esterified alkyd resin in butanol is generated largely by thermodynamic forces of molecular interaction; the degree of butanolate melamine-formaldehyde resin has the greatest effect on the stability of the system. Conducted research on the stability of the paint mixtures of various film-forming resins on the basis of the evaluation criteria can be used to improve the technology of protective and decorative wood finish.

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