hcmc vietnam deriner arch dam

SEISMIC SAFETY EVALUATION OF THE 250 M HIGH DERINER

ARCH DAMM. WIELAND

Chairman, ICOLD Committee on Seismic Aspects of Dam DesignPöyry Energy Ltd., Zurich, Switzerland

Location of Deriner Dam Site, Turkey

Deriner

Layout Deriner HPP

1. arch dam,

2. diversion tunnel,

3. surface spillway

4. power intake

5. upstream cofferdam

6. cable crane

Dam Site, view from downstreamHangsicherung:

2300 vorgespannte Anker

Arch dam crest el. 397Batching plant, cement silos

Cofferdam

Cable cranesloading platform

Switchyard

Diversion tunnel outlet

Dam Site, view from upstream

Technical Project DataHydrology• Catchment area 18,839 km²• Mean annual flow at dam site 4,847 million m³• Mean annual discharge at dam site 154 m³/s• Design flood 10,110 m³/s

Reservoir storage• Total 1,969 million m³• Active 963 million m³

Diversion Tunnel• Horseshoe tunnel, diameter 11.70 m, 876 m long• Number1 Design discharge 1,804 m³/s

Dam Type• Double curvature arch dam• Max. height 250 m• Length at crest 740 m

Technical Project DataOverflow spillways• Type: Tunnel, diameter 8.00 m, with frontal inlet• Number: 2 Design discharge 2 x 1,125 = 2,250 m³/sOrifice spillways• Type: 8 Orifices in the dam body: size (W x H) 2.80 x 5.60 m• Design discharge 8 x 875 = 7,000 m³/sPowerhouse: Underground, concrete lined• Size (W x H x L) 20 m x 45 m x 126 mTurbines: 4 Francis vertical• Gross head 206 m• Design discharge 4 x 90 = 360 m³/s• Installed capacity 4 x 167.5 = 670 MWTotal annual energy production 2,118 GWh• Firm 1,212 GWh• Secondary 906 GWh

Crushing and sieving plant 2 x 1000 m3/h

Betonierarbeiten

Cable Cranes

• Capacity 3 x 9 m3 buckets• Supplier: KRUPP, Germany

Loading platform

Batching plant• Capacity 360 m3/h

Arch Dam – Site installations

Cement Silos

Batching Plant

Concrete Lab

Arch Dam - Batching plant loading station

Arch Dam – Formwork

Arch Dam – Battery of vibrators

…

Arch Dam – Start of concreting Dec. 2005

Arch Dam – Concreting

Arch Dam

Nov 2003Nov 2003Nov 2003

Arch Dam – Post cooling system

Arch Dam - Concreting

Toe gallery

Post-cooling pipes

Joint grouting system

Arch Dam – Grouting tests from gallery

Deriner Dam & HEPP: > 2000 rock anchors

Overflow Spillway RB - Excavation

Power Cavern

Tailrace Tunnels

Nov 2003Nov 2003Nov 2003

SEISMIC ASPECTS OF

DAM DESIGN

Seismic hazard – multiple hazard• ground shaking: vibrations in dams,

appurtenant structures, equipment and foundations

• fault movements in dam foundation

• fault displacement in reservoir bottom: water waves in reservoir or loss of freeboard

• mass movements into reservoir: impulse waves in reservoir

Ground shakingEarthquakes affect all components of a

dam project at the same time:dam

foundation safety devices

pressure systemunderground works

appurtenant structures hydro-mechanical equipment

electro-mechanical equipment etc.

Seismic design criteriaDam and safety-relevant elements:Operating basis earthquake, OBE (145 years) Safety evaluation earthquake, SEE/MCE (ca. 10,000 years) Appurtenant structures Use of seismic building codes (ca. 475 years)

Temporary structures:Use of seismic building codes (< 475 years)

Design Earthquake Title Element / Component

CE DBE OBE/ SEE

Diversion Facilities - Civil Intake/outlet structures X Tunnel, tunnel liner X - Geotechnical Rock slopes X Underground facilities X Cofferdams X - Electrical/Mechanical Gate equipment X

Dam: Dam Body Dam body X

- Individual Blocks OBE Crest bridge X Crest spillway cantilevers X X Bottom Outlet cantilevers X Foundation/Abutments Abutment wedges X X Bottom Outlet Main gates, Valves X X Guard gate X Operating equipment X X Dam: Electrical/Mechanical Essential parts X

Design Earthquake Title Element / Component

CE DBE OBE/ SEE

Underground powerhouse

- Excavation and Rock Support Rock slopes X - Service Bay Civil Design Substructure X Superstructure X Surface powerhouse - Civil Excavation, foundation X Substructure X Superstructure X - Architectural Layout and Finishes X - Cranes and Lifting Devices Cranes X Support structures X - Generators & Exciting System Stationary components X Rotating components X - Turbine X - Transformers and other components X

SEISMIC STABILITY ANALYSIS OF

DETACHED CONCRETE BLOCKS

SEE/MCE analysis of Deriner arch dam

Dam-foundation model MCE (horizontal PGA: 0.35 g)

Results of linear-elastic dynamic analysis

Large dynamic responses in central upper portion of dam

– Very high accelerations– Large tensile stresses

(exceeding dynamic tensile strength of mass concrete)

Consequences– Contraction joints open – Horizontal cracks develop

along lift joints

Crest deflection under different MCE’s

Selection of detached concrete blocks

Simplified dynamic stability analysis of cracked dam

Step 1: Linear-elastic 3D analysis assuming incompressible (or compressible) reservoir and massless foundation;

Step 2: Nonlinear 2D rocking-sliding analysis of detached concrete blocks

Simplified dynamic stability analysis of concrete blocks: Methodology

1.Linear-elastic dynamic time history analysis;2.Selection of detached concrete blocks;3.Calculation of absolute acceleration response at

base of each block;4.Dynamic rocking-sliding analysis of detached

concrete blocks using 2D FE models; and5.Calculation of the maximum sliding and crack

opening displacements.

Main assumptions

1.Cracks are assumed to form along the vertical contraction joints and horizontal lift joints only.

2.Damping ratio for MCE: 7%. 3.The acceleration response in the central upper

portion of the dam can be obtained from a linear-elastic dynamic analysis.

4.Detached concrete blocks can slide only towards the upstream due to the geometry of the arch dam.

5.Effect of shear keys in contraction joints ignored.

Selection of detached concrete blocks

Finite element model for dynamic stability (rocking-sliding) analysis of 20 m high block

Rocking-sliding analysis of 20 m high block

Initial state During earthquake shaking

Final state

Typical results of rocking-sliding analysis

Horizontal displacement(sliding)

Crack opening displacement at downstream face (rocking)

Results of dynamic stability analysis

• MCE1* reversed MCE1 etc.

Input ground motion

Max. sliding displacement along

crack at lift joint (mm)

Max. crack opening displacement at upstream edge

(mm)

Max. crack opening displacement at

downstream edge (mm)

A) Empty reservoir MCE1 272 129 58

MCE1* 580 154 47

MCE2 525 149 40

MCE2* 622 110 55

MCE3 708 142 76 MCE3* 1045 179 66

B) Full reservoir MCE1 346 136 96 MCE1* 193 65 36

MCE2 307 143 86

MCE2* 233 93 39

MCE3 280 110 30

MCE3* 284 144 47

15 s

25 s

32 s

Results of dynamic stability analysis

Final displacement towards upstream(sliding response)– Empty reservoir: max. 1045 mm– Full reservoir: max. 346 mm– A sliding displacement of about 1 m is

acceptable (dam thickness: 17 m).

Results of dynamic stability analysis

Maximum crack opening displacement (rocking response)– Empty reservoir condition:

Upstream: max. 179 mmDownstream: 76 mm

– Full reservoir condition: Upstream: 144 mmDownstream: 96 mm

– Weaker rocking towards upstream

Discussion of results

•Full resevoir: final sliding displacement is small due to the restoring effect of the water pressure.

•Empty reservoir: The sliding movement towards the upstream tends to be cumulative.

Discussion of results

•The dynamic impulse is shared by a combination of rocking and sliding motions. Thus, smaller rocking response towards the upstream is accompanied by a larger sliding response.

•For a symmetrical concrete block, the final sliding movement of the block towards the upstream would be considerably smaller.

Sensitivity analyses: 20 m block, empty reservoir

Input ground motion

Max. sliding displacement

(mm)

Max. crack opening displacement at upstream edge

(mm)

A) Friction coefficient: 0.7

MCE2 (PGA: 0.35 g) 525 149

2 × MCE2 (PGA: 0.70 g) 1067 336

3 × MCE2 (PGA: 1.05 g) 2648 588

B) Friction coefficient: 0.5

MCE2 (PGA: 0.35 g) 437 18

2 × MCE2 (PGA: 0.70 g) 1691 168

3 × MCE2 (PGA: 1.05 g) 2339 515

Sensitivity analyses: 20 m block, empty reservoir

Effects of lower friction coefficient

• Higher sliding response, and smaller rocking response

• However, not necessarily higher maximum sliding displacement (as lower friction also increases likelihood of reversed sliding)

Conclusions1.Maximum sliding and rocking displacements can

vary considerably. Dynamic stability analyses shall be carried out for several statistically independent input earthquakes.

2.As the effect of the shear keys in the vertical contraction joints has been neglected, the results of simplified rocking-sliding analysis are conservative.

3.The computation of the inelastic response of detached concrete blocks needs careful checks, because the results are sensitive to several numerical integration parameters.