SMALL DAMS PETITS BARRAGES

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Fig. 3.4 – Nix Lake dam failure in Texas, in 1989 (ASDSO, 2007). Fig. 3.5 – Consequences of the failure of Bear Foot Lake dam, in 1994 (ASDSO, 2007) 3.3.3 Internal Erosion Internal erosion and piping in embankments and their foundations is the second cause of failures and accidents at embankment dams. For new dams, the potential for internal erosion and piping can be controlled by good design and construction of the dam and provision of filters to intercept seepage through the embankment and the foundations. However many existing dams were not provided with filters and are susceptible to internal erosion failure, with a likelihood increasing with ageing. The ICOLD Bulletin on “Internal erosion of dams and their foundations” (to be completed soon) and Feel & Fry [2] describe the four types of internal erosion: erosion at concentrated leaks, erosion at contacts between coarse and fine materials, backward erosion in which erosion at the toe of structures from erosion pipes under them, 36
and suffusion or internal instability, which may occur in gap-graded materials where the soil fabric is such that small particles can be eroded out between larger particles. In any case, internal erosion is due to non controlled seepage through the embankment, through the foundation or at a transition between the embankment (or foundation) and a rigid structure (spillway, bottom outlet, etc). Illustrations are given with the following pictures. Fig. 3.6 - Cavern in the dam body as a result of wooden bottom outlet decay and internal erosion (Czech Republic) Fig. 3.7 – A sinkhole above failed bottom outlet concrete pipes, in a small dam. 37
Page 1 and 2: SMALL DAMS Design, Surveillance and
Page 3 and 4: FOREWORD The ICOLD - International
Page 5 and 6: ACKNOWLEDGEMENT The Ad Hoc Committe
Page 7 and 8: FOREWORD ACKNOWLEDGEMENT SUMMARY TA
Page 9 and 10: 5.5.5 Compaction in confined areas
Page 11 and 12: 7.2.1 Introduction 7.2.2 Spillway c
Page 13 and 14: 1. SMALL DAMS DEFINITION AND CLASSI
Page 15 and 16: 2 Fig. 1.2 - Relationship H . V wit
Page 17 and 18: 1.3 REFERENCES [1] French Committe
Page 19 and 20: 2.3 ZONED EARTHFILL DAMS In arid pa
Page 21 and 22: sloping core guarantees water impou
Page 23 and 24: Fig. 2.11 - Hlinky Concrete Gravity
Page 25 and 26: Fig. 2.13 - Photograph of Neusberg
Page 27 and 28: The gabion dam as the gabion retain
Page 29 and 30: Some inflatable dams are operated b
Page 31 and 32: 3.1 INTRODUCTION 3. SAFETY OF SMALL
Page 33 and 34: Condition Effect on safety 13. Dama
Page 35: Fig. 3.2 - Massive dam break overto
Page 39 and 40: downstream part of the embankment m
Page 41 and 42: small dam impounding a lot of water
Page 43 and 44: Whenever the Supervising Authority
Page 45 and 46: emergency management organizations
Page 47 and 48: c) The decommissioning plan should
Page 49 and 50: 5.1 INTRODUCTION 5. FEATURES OF THE
Page 51 and 52: 5.2 DESIGN FLOODS Inadequate flood
Page 53 and 54: downstream slope will show seepage
Page 55 and 56: Fig. 5.2 - Design Freeboard 5.4.3 F
Page 57 and 58: 2 U f Fe S 1400 D Where Uf is the d
Page 59 and 60: Maximum compaction is obtained at c
Page 61 and 62: characteristic must be determined.
Page 63 and 64: 5.6.1 Foundation Watertightness The
Page 65 and 66: � A continuous vertical chimney d
Page 67 and 68: Thickness of pervious layer Thick D
Page 69 and 70: t 5.7.1.4 Practical Considerations
Page 71 and 72: It is generally accepted that cohes
Page 73 and 74: � Simple Bishop (1955) � Spence
Page 75 and 76: � The elements for surface draina
Page 77 and 78: The supporting layer for the rip-ra
Page 79 and 80: For very small reservoirs (fetch of
Page 81 and 82: The junction of the downstream slop
Page 83 and 84: Fig. 5.14 - Hongshiyan homogenous d
Page 85 and 86: material has been left in place or
Page 87 and 88:
The homogeneous dam is recommended
Page 89 and 90:
[3] OL and OH soils are not recomme
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part (core) lies in the zone (Fig.
Page 93 and 94:
6. GUIDELINES ON SURVEILLANCE OF SM
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cases the owner may retain the serv
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Surface displacement on an embankme
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Fig. 6.1 - Leakage measurement usin
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Water Level Sounder - Details of th
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pressure) Left abutment 2 5 Weir ga
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Fig. 6.9 - Recommended standpipe pi
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the others weir gauges need to be i
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� Earthquakes sensible at the dam
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APPENDIX INSPECTION CHECKLIST FOR S
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Exposed reinforcement � The condu
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These spillways can be lined or unl
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flowing water. Flowing water with h
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Fig. 7.3 - Installation of the arti
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Fig. 7.7 - Dam overtopping protecti
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complete construction was in 2001,
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In some cases, the downstream face
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Tube-a-manchettes injection system
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7.3.5 Slope Protection Measures 7.3
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Pipe Rehabilitation SLIPLINING MODI
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Conditions Pros Cons Comments types
Page 135 and 136:
Embankment dams that have properly
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and minimize erosion. Design of sui
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[20] SMEC- “Draft Guidelines for
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present visual information. It must
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Fig. 8.1 - Three small dams in casc
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Social Disruption low (rural area)
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Fig. 8.4 - Flood water level after
Page 149:
8.9 REFERENCES [1] BURREC (1994) -
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SMALL DAMS PETITS BARRAGES

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