scholarly journals Flume tests on the hydraulic/mechanical behavior of the Tangjiashan landslide dam considering the influences of the different debris materials in heterogeneous strata

2021 ◽  
Author(s):  
Xi Xiong ◽  
Tatsunori Matsumoto ◽  
Zhenming Shi ◽  
Feng Zhang
Keyword(s):  
Landslide Dam ◽  
Model Design ◽  
Finite Element Analyses ◽  
Mechanical Behaviors ◽  
Test Program ◽  
Drainage Tunnel ◽  
Flume Tests ◽  
Dam Breaching ◽  
Dam Stability ◽  
The Stability

Abstract Landslide dams (LDs) usually form from natural debris materials and exhibit heterogeneous strata along both the depth and run-out directions. In addition, an LD usually has a weaker structure than that of undisturbed ground and is more vulnerable to seepage loading. Considering that the surface layer of naturally packed LD materials is generally in an unsaturated state, it is undoubtedly important to investigate the stability of the unsaturated debris materials in the heterogeneous strata of LDs. In this paper, a systematic flume test program was first conducted, in which the Tangjiashan LD was carefully referenced for model design. Three water level rising rates and two stratal arrangements were considered in the flume tests. Then, soil-water-air coupled finite element analyses were conducted to simulate the flume tests, and all the material parameters of the LD materials were carefully determined based on the results of the element tests. A comparison of the test and calculated results shows the possibility of using the proposed numerical method to estimate the occurrence of dam breaching and the risk of LD failure. Moreover, the hydraulic/mechanical behaviors of the LD materials and the heterogeneous strata of the LD were very important to the stability of the Tangjiashan LD. Finally, from an engineering viewpoint, the possibility of utilizing a naturally formed LD and thus not destroying it when it forms is also discussed, e.g., dam breaching risk can be reduced by excavation of a drainage tunnel, and the dam stability can be carefully estimated based on accurate geological data.

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.

scholarly journals Hydroxypropylsulfonation/Caproylation of Cornstarch to Enhance Its Adhesion to PLA Fibers for PLA Sizing

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1197 ◽  
Author(s):  
Wei Li ◽  
Jie Wu ◽  
Xingui Cheng ◽  
Lanjuan Wu ◽  
Zhi Liu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Internal Stress ◽  
Mechanical Behaviors ◽  
Cohesive Failure ◽  
Adhesive Layers ◽  
Adhesion Measurement ◽  
Acid Sodium Salt ◽  
The Stability ◽  
The Impact ◽  
Scanning Electron

The impact of hydroxypropylsulfonation/caproylation on the adhesion of cornstarch to polylactic acid (PLA) fibers was investigated for ameliorating the applications such as PLA sizing. The hydroxypropylsulfonated and caproylated cornstarch (HCS) samples with different degrees of substitution (DS) were synthesized by a hydroxypropylsulfonation of acid-converted cornstarch (ACS) with 3-chloro-2-hydroxy-1-propanesulfonic acid sodium salt (CHPS-Na) and subsequently a caproylation with caproic anhydride (CA). The HCS granules were characterized by Fourier transform infrared spectroscopic and scanning electron microscopy. The adhesion was evaluated by measuring the bonding forces of the PLA roving impregnated. The mechanical behaviors of the adhesive layers were estimated by determining the properties of the films. The results of adhesion measurement were also analyzed especially through the wetting and spreading of the paste on the fiber surfaces, as well as the failure type, internal stress and mechanical behaviors of the adhesive layers among fibers. Additionally, apparent viscosity and its stability of the pastes were also determined. It was found that hydroxypropylsulfonation/caproylation was not only able to obviously improve the adhesion of ACS to PLA fibers, but also capable of further improving the adhesion of hydroxypropylsulfonated starch (HS) to the fibers. With the rise in the total DS, the adhesion gradually increased. The two substituents improved the wetting and spreading, reduced the internal stress, lowered the probabilities of interfacial failure and cohesive failure, decreased the film brittleness, and increased the van der Waals force at the interfaces. Moreover, the HCS samples with a stability of above 85% could meet the demand on the stability for sizing. Considering the experimental results of the adhesion and the analysis of the results, HCS showed potential in the application of PLA sizing.

Study on the Capacity Increasing and Dam Heighten of Plain Reservoirs

2013 ◽  
Vol 353-356 ◽  
pp. 2531-2536
Author(s):  
Xiu Guang Song ◽  
Zhi Dong Zhou ◽  
Hong Bo Zhang ◽  
Hong Ya Yue
Keyword(s):  
Numerical Simulation ◽  
Comparative Analysis ◽  
Site Investigation ◽  
Seepage Flow ◽  
Differential Settlement ◽  
Construction Technology ◽  
Dam Stability ◽  
The Stability ◽  
Design Construction

In order to solve the problem of differential settlement, seepage flow and stability between the new and old dam boundary in capacity increasing of the plain reservoirs, the comparative analysis on the stability of the dam slope with different methods on dealing with the new and old dam boundary was performed by numerical simulation with FLAC3D. The result shows that combining the new and old dam by using geogrid indicates superiority for reducing differential settlement, improving the dam stability and safety, etc. In the meantime, on the basis of actual site investigation and theoretical analysis, combined with the requirements of design, construction and management in capacity increasing of the plain reservoirs, the key construction technology was put forward and widely applied foreground, which can improve the quality of the construction, reduce engineering disease and provide references for capacity increasing engineering of in plain reservoirs.

scholarly journals A large landslide in Zigui County, Three Gorges area

2004 ◽  
Vol 41 (6) ◽  
pp. 1233-1240 ◽  
Author(s):  
F C Dai ◽  
J H Deng ◽  
L G Tham ◽  
K T Law ◽  
C F Lee
Keyword(s):  
Clayey Soil ◽  
Landslide Dam ◽  
Bedding Plane ◽  
Raw Material ◽  
Left Bank ◽  
Three Gorges ◽  
Shear Surface ◽  
Three Gorges Area ◽  
Dam Breaching ◽  
Large Landslide

On 13 July 2003, a landslide with a volume of approximately 20 × 106 m3 occurred on the left bank of the Qinggan River, Zigui County, Hubei Province, China. As a result, 14 people died and 10 people are missing. A landslide dam was formed, blocking the Qinggan River. A channelized diversion was constructed for prevention of upstream flooding and damage downstream caused by dam breaching. The landslide was a typical translational rockslide in weathered shale and sandstone, a block of which slipped down along the bedding plane. It is estimated that the landslide was caused by the combined effect of the following factors: (i) a bedding plane between incompetent weathered shale and competent sandstone that daylights at or is shallowly buried at the bottom of the Qinggan River; (ii) a thin layer of clayey soil acting as the slip plane that is likely a preexisting shear surface; (iii) excavation of the shale as raw material for brick fabricating on the slope; and (iv) a combination of prolonged rainfall and reservoir impounding.Key words: landslide, landslide dam, rainfall, impounding, Three Gorges area.

An Examination of the Stability of an Earthquake-Induced Landslide and Landslide Dam

2012 ◽  
pp. 93-100
Author(s):  
Ryoichi Ohno ◽  
Satoshi Niwa ◽  
Hideya Iwata ◽  
Sachihiko Ozawa
Keyword(s):  
Landslide Dam ◽  
The Stability

scholarly journals Stability Evaluation of Overtopped Concrete Hydraulic Structures Using Computational Fluid Dynamics

2020 ◽  
Author(s):  
Mario Freitas ◽  
Etienne Favre ◽  
Pierre Léger ◽  
Lineu José Pedroso
Keyword(s):  
Water Pressure ◽  
Back Analysis ◽  
Hydrodynamic Pressure ◽  
Flow Conditions ◽  
Gravity Dams ◽  
Pressure Fields ◽  
Dam Stability ◽  
The Stability ◽  
Resultant Forces ◽  
Safety Guidelines

A particularly challenging aspect in gravity dam stability assessment is the estimation of the induced hydrodynamic water pressure when water with significant velocity is overtopping gravity dams and flowing in or over spillway components. The water flow conditions, including the related pressure fields and resultant forces, are difficult to quantify accurately. Herein, existing dam safety guidelines to estimate the weight of the overflowing water nappe on gravity dams with rectangular crests are first reviewed. Then, a CFD methodology is developed to improve the simplified estimation of hydrodynamic pressure fields acting on the rectangular crests of submerged gravity dams. The CFD pressures are used as input data to classical structural stability analyses based on the gravity method to more adequately quantify the dam stability during overtopping. A back analysis is also performed on the stability of an existing gated spillway that was overtopped during the 1996 Saguenay flood in Québec.

scholarly journals Influences of Spillway Section Morphologies on Landslide Dam Breaching

2021 ◽  
Vol 9 ◽  
Author(s):  
Meng Yang ◽  
Qiming Zhong ◽  
Shengyao Mei ◽  
Yibo Shan
Keyword(s):  
Cross Section ◽  
Landslide Dam ◽  
Longitudinal Section ◽  
Disaster Mitigation ◽  
Slope Ratio ◽  
Dam Breach ◽  
Time To Peak ◽  
Dam Breaching ◽  
Bottom Width ◽  
The Cross

Spillway excavation is often adopted as a precautionary engineering measure for disaster mitigation before landslide dam breaching. Based on the landslide dam breach mechanisms, this paper focuses on developing a numerical model to comprehensively discuss the issue based on three documented landslide dam failures, such as Tangjiashan, Xiaogangjian, and Baige landslide dams. The spillway cross section morphologies were modeled with different sizes under common shape (i.e., an inverted trapezoid) and slope conditions. The influence of cross section on dam breach processes was analyzed under conditions of different depth, bottom width, slope ratio in the cross and longitudinal sections, with/without spillway. The following conclusions can be drawn: 1) excavation of a spillway can effectively reduce the peak breach flow, therefore delay the time to peak; 2) the peak breach flow dramatically decreases and the time to peak delays as the spillway depth increases; 3) the peak breach flow changes little and the time to peak occurs earlier with the increment in spillway bottom width; 4) the peak breach flow decreases and the time to peak delays with the decrease of slope ratio in cross section in the spillway; 5) the slope ratio in the longitudinal section has little influence on the breach process. Hence, if conditions permit, the spillway with large spillway depth, small bottom width, and gentle slope ratio in the cross section is the preferable section morphology for the emergency disposal of the landslide dam.

Formation and Stablity of the Sky Pond Landslide Dam, China

2011 ◽  
Vol 243-249 ◽  
pp. 3189-3200 ◽  
Author(s):  
Yan Hui Song
Keyword(s):  
Yellow River ◽  
Limit Equilibrium ◽  
Landslide Dam ◽  
Equilibrium Analysis ◽  
Qualitative Assessment ◽  
Hydropower Station ◽  
The Yellow River ◽  
Geological Conditions ◽  
Dammed Lake ◽  
The Stability

The Sky Pond landslide dam is located in Muchang valley, a branch of the Yellow River branches. From this point it is about 6Km to the mouth of the valley from where the Yellow River flows 0.8Km downwards to the planned Jishi gorge hydropower station. The Sky Pond landslide dam is actually formed by two landslides from both the left and right bank slopes and completely blocks the seasonal river channel. The volume of the landslide dam is about 14 millions m3 with 2.37 millions m3 water stored in the dammed lake under the condition of perennial mean water level. Because (1) the dam body is large in width and thickness; (2) the dammed lake water is small both in volume and weight compared to the landslide dam; (3) recharge to the dammed lake is basically the same as the discharge every year; and (4) there is a natural spillway in the dam body, the landslide dam is present at least 750 years after its formation. Although landslide dams which have existed for several hundreds to thousands of years are generally considered as stable, there are remains which may fail catastrophically. In order to analyze the stability of the Sky Pond landslide dam and provide justification for the future engineering decisions, this paper describes the engineering geological conditions near the landslide dam and the characteristics of the dam body, and a detailed discussion of the formation mechanism of the landslide. Based on engineering geology investigation, a qualitative assessment of the stability of the dam and an analysis of the probability of dam overtopping and piping is carried out. Limit equilibrium analysis has been used to calculate the stability of the dam slope under various operational conditions. Results of the stability analyses indicate that the Sky Pond landslide dam should remain stable and does not present a potential theat to the planned hydropower station.

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