Experimental and numerical study of upstream slope stability in an earth dam reservoir under rapid drawdown conditions

The rapid ‎drawdown of the dam reservoir is one of the most common situations occurring in the lifetime of a dam. For this reason, one of the main factors in the design of the upstream slope is the rapid drainage of the reservoir. In this case, the upstream slope is in a critical condition and the slope may be unstable. When the water surface in the reservoir is drawdown suddenly, the water level in the dam body does not decrease at the same time as the reservoir water level. The analysis of seepage from the earth dam body and calculation of the water loss play an important role in calculating the amount of pore water pressure, and, consequently, the stability analysis of the dam body. In addition, any seepage analysis is dependent on the hydraulic properties of the dam materials. In order to investigate the effect of hydraulic conductivity on the rapid drawdown of water level and the seepage, an experimental model was constructed of an earth dam. By accurate measurement of hydraulic parameters of the materials in saturated and unsaturated media, the flow through this model was modeled using a disk penetrometer by seep/w software. The results were then compared with the observed data.

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Slope Stability of an Earth Dam during Drawdown Conditions (KHASA-CHAI Dam) as a Case Study

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i4.37.23605 ◽

2018 ◽

Vol 7 (4.37) ◽

pp. 17

Author(s):

Adnan Jayed Zedan ◽

Mariwan Ridha Faris ◽

Ahmed Amer Abdulsattar

Keyword(s):

Slope Stability ◽

Factor Of Safety ◽

Slip Surface ◽

Earth Dam ◽

Downstream Face ◽

Upstream Slope ◽

Maximum Water Level ◽

Water Drawdown ◽

Action Taking ◽

Safe Condition

Aiming in this research was to have a clear view about the behavior of Khasa-Chai Dam during the draw down action taking into consideration the newly built of this dam which was filling during the time of this article, the upstream slope was investigated by taking drawdown of the water from the reservoir. This dam is consists of the zoned embankment with a total length of (2.36 km) with an upstream slope (1v:3h) and downstream slope (1v:2h). Slope stability was investigated during the drawdown of the water from the reservoir by considering the water in the reservoir to be at maximum water level and by taking two cases during the rapid and slow drawdown. SLOPE/W which is a sub program from Geo-Slope software was used in association with SEEP/W software to find the factor of safety of the upstream slip surface during the drawdown conditions. It was noticed from the drawdown conditions that the phreatic line falls almost at the same position for both cases. Also for both cases the factor of safety of the upstream slip surface falls above the value of (1.0) and that is mean the upstream slope is in a safe condition when the water drawdown. The exit gradient and the rate of flow at the downstream face decrease with time as the water in the reservoir drawdown which means the factor of safety against boiling increases with time.

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Rapid Drawdown in Homogeneous Earth Dam Considering Transient Flow and Suction

Ingeniería e Investigación ◽

10.15446/ing.investig.v40n1.80002 ◽

2020 ◽

Vol 40 (1) ◽

pp. 17-26

Author(s):

Grover Romer Llanque Ayala ◽

Francisco Chagas da Silva Filho ◽

Rosiel Ferreira Leme ◽

Maria Do Carmo Reis Cavalcanti ◽

Claudio Fernando Mahler

Keyword(s):

Stability Analysis ◽

Slope Stability ◽

Safety Factor ◽

Transient Flow ◽

Flow Analysis ◽

Analysis Data ◽

Earth Dam ◽

Maximum Height ◽

Upstream Slope ◽

Transient Flow Analysis

The present work intends to demonstrate the advantages of considering transient flow regime in the stability analysis of the upstream slope for the rapid drawdown situation of a homogeneous earth dam. Upstream slope stability evaluations were carried out, considering pore pressure and suction from transient flow analysis while simulating rapid drawdown of the reservoir. The evaluations comprised different geometries of the upstream slope (from 1V:1.1H to 1V:2.5H) and heights varying from 10 m to 50 m, as well as several low permeability materials (SM, SM-SC, SC, ML, ML-CL, CL, MH and CH). In addition, equations relating the safety factor to such slopes or dam height were adjusted to the analysis data, in order to define the minimum slope for a certain dam height or the maximum height for a given upstream slope. The results have shown that, considering the transient flow condition, including suction, within the slope stability analysis of the rapid drawdown situation, increases the safety factor in relation to the simplified analysis that is usually adopted. This also results in much steeper slopes (for a safety factor of 1.1) than the ones recommended by the U.S. Bureau of Reclamation (USBR), suggesting the importance of performing transient flow analysis for rapid drawdown situations and considering its results instability analysis.

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Engineering geology characteristics and geometry of slope stability of Tukul Dam reservoir in Karanggede Village, Pacitan Regency, East Java Province, Indonesia

10.1063/5.0062458 ◽

2021 ◽

Author(s):

Novita Fadriana ◽

I. Gde Budi Indrawan ◽

I. Wayan Warmada

Keyword(s):

Slope Stability ◽

Engineering Geology ◽

Dam Reservoir

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Efficient reliability analysis of earth dam slope stability using extreme gradient boosting method

Acta Geotechnica ◽

10.1007/s11440-020-00962-4 ◽

2020 ◽

Vol 15 (11) ◽

pp. 3135-3150 ◽

Cited By ~ 5

Author(s):

Lin Wang ◽

Chongzhi Wu ◽

Libin Tang ◽

Wengang Zhang ◽

Suzanne Lacasse ◽

...

Keyword(s):

Slope Stability ◽

Reliability Analysis ◽

Earth Dam ◽

Gradient Boosting ◽

Extreme Gradient Boosting ◽

Boosting Method

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A numerical study of pumping effects on flow velocity distributions in Mosul Dam reservoir using the HEC-RAS model

Lakes & Reservoirs Research & Management ◽

10.1111/lre.12306 ◽

2020 ◽

Vol 25 (1) ◽

pp. 72-83

Author(s):

Mohammad E. Mohammad ◽

Nadhir Al-Ansari ◽

Sven Knutsson ◽

Jan Laue

Keyword(s):

Flow Velocity ◽

Numerical Study ◽

Dam Reservoir

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Submarine slope failure due to gas hydrate dissociation: a preliminary quantification

Canadian Geotechnical Journal ◽

10.1139/t06-121 ◽

2007 ◽

Vol 44 (3) ◽

pp. 314-325 ◽

Cited By ~ 85

Author(s):

M F Nixon ◽

J LH Grozic

Keyword(s):

Slope Stability ◽

Gas Hydrates ◽

Gas Hydrate ◽

Numerical Study ◽

Fluid Pressure ◽

Slope Failures ◽

Case Histories ◽

Hydrate Dissociation ◽

Methane Gas ◽

Submarine Slope

Gas hydrates are icelike compounds composed of water and methane gas in very compact form. There is substantial evidence from case histories that links gas hydrate dissociation to submarine slope failures and other geohazards. Theoretical analyses have also shown that upon dissociation gas hydrates will cause an increase in fluid pressure and a reduction in effective stress and thus result in loss of the soil strength. This paper presents a preliminary quantification of the effects of gas hydrate dissociation through development of a pore-pressure model that was incorporated into one- and two-dimensional slope stability analyses. The ensuing numerical study investigated submarine slope stability through parametric studies and application to two important case histories and found that dissociation of even small amounts of hydrate can have a significant destabilizing effect. Yet whether gas hydrate dissociation can alone cause large-scale slope failures has still to be demonstrated as there are often many destabilizing processes; however, this research highlights the importance of assessing the effects of gas hydrate dissociation on the behaviour of submarine slopes.Key words: gas hydrates, slope stability, marine, offshore, methane gas, instability.

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