Gap_Analysis_Formatted_Report_with_Annexures_(1).pdf

IQC 391 – I – 11 – 00003

AID – 391 – 14 – 00001

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 1 of 16 AAA-TCI

Disclaimer:

This Project is made possible by the support of the American people through the United

States Agency for International Development (USAID). The opinion expressed herein are those of the author(s) and do not necessarily reflect the views of USAID,A. A. Associates or

Techno-Consult International.

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 2 of 16 AAA-TCI

Data Collection, Review and Preparation of

International Tender Document for the Diamer Basha Dam Project

IQC 391 – I – 11 – 00003

AID – 391 – 14 – 00001

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO

INTERNATIONAL BEST PRACTICES

Prepared by : Dr. Syed Abulkhair Masroor

Revised by : -

Approved by : Azher uddin Khan

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 3 of 16 AAA-TCI

Data Collection, Review and Preparation of

International Tender Document for the Diamer Basha Dam Project

IQC 391 – I – 11 – 00003

AID – 391 – 14 – 00001

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO

INTERNATIONAL BEST PRACTICES

Table of Content

1.0 BACKGROUND

2.0 ORGANISATION DOCUMENTS

3.0 CONFORMANCE TO CODE

4.0 DISCUSSION ON MAJOR SHORT COMING IN DESIGN

4.1 DAM TYPE SELECTION

4.2 OPTIMIZATION

4.3 DESIGN INADEQUACY

4.4 CONCRETE DESIGN

4.5 CONVOLUTED REASONING

4.5.1 Excerpts from the Design Report

5.0 CONCLUSION

6.0 RECOMMENDATIONS

7.0 REFERENCES

ANNEXURES:

ANNEXURE-1

STRUCTURAL DESIGN FOR CONCRETE DAMS AS PER ICOLD B126 .............................................. 20 to 27

ANNEXURE-2

ROCK FOUNDATION DESIGN INVESTIGATION AND PROCEDURES AS PER ICOLD B088...................... 29 to 35

ANNEXURE-3

DESIGN FEATURES OF DAM TO RESIST SEISMIC GROUND MOTION AS PER ICOLD B120.................. 37 to 40

ANNEXURE-4

SPECIFICATION AND QUALITY CONTROL OF CONCRETE FOR DAMS AS PER ICOLD B136.................. 42 to 55

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 4 of 16 AAA-TCI

1.0 BACKGROUND

The proposed Diamer Basha Dam was conceived in 1984 by the Montreal

Engineering Company Limited MONENCO as a part of Hydroelectric Inventory

Ranking for Pakistan under a grant from Canadian International Development

Agency CIDA. MONENCO also conducted a feasibility study for the construction of this project.

After a lapse of about eighteen year, the feasibility study was refined by a consortium of consultants led by NESPAK of Pakistan called NEAC. NEAC submitted their feasibility report to WAPDA in August 2004.

Review of the feasibility report and tender documents for the project were assigned to the Diamer Basha Consultants (DBC), a joint venture of Lahmeyer International

GmbH, Germany and National Development Consultants, Lahore with other consultants. The tender drawings and documents were completed in 2008.

The tender documents call for the construction of a 270m high roller compacted concrete dam founded on the bedrock.

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 5 of 16 AAA-TCI

2.0 ORGANISATION DOCUMENTS

Tender documents of the project are well organized. The work is divided into five lots to be separately tendered. Each tender set is accompanied by detailed drawings and specifications. Responsibilities of the contractors in each case are very clearly defined. The drawings are complete to the extent that work can be easily priced and scheduled by the contractor and advance procurement of materials can be ordered.

The drawings require very little effort for conversion to execution drawings. Civil and structural drawings show enough details for planning as well as construction.

Procurement of Mechanical and Electrical equipment is part of the tendering process and therefore E&M drawings at this stage are single line drawings to be fully detailed after equipment selection.

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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3.0 CONFORMANCE TO CODE

The following detailed due diligence forms are appended to this report:

1. STRUCTURAL DESIGN OF CONCRETE GRAVITY DAMS as per ICOLD B 126

2. SPECIFICATIONS AND QUALITY CONTROL OF CONCRETE FOR DAMS as per ICOLD

B136

3. DESIGN FEATURES OF DAMS TO RESIST SEISMIC GROUND MOTION as per ICOLD-

B120

4. ROCK FOUNDATIONS DESIGN INVESTIGATIONS AND PROCEDURES as per ICOLD-

B 088.

A cursory glance at these forms shows that the work has largely been done within the parameters of the code. There are only a few major non-conformances. These will be discussed further in this report. There are also a number of incomplete items in the above due diligence forms. These mostly stem from the fact that the design is still at a tender stage and not at the working drawing level.

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 7 of 16 AAA-TCI

4.0 DISCUSSION ON MAJOR SHORT COMING IN DESIGN

4.1 DAM TYPE SELECTION

The location for the dam was originally identified by the Montreal Engineering

Company MONENCO who conceived an Earth Core Rock fill Dam (ECRD) at the site.

The dam was to have a rock filled embankment with an impervious earth core and a cut off to the hard rock base.

The feasibility design stage was assigned to NEAC consortium led by National

Engineering Services Pakistan (NESPAK). The site was slightly shifted and the design at this stage was changed to a Roller Compacted Concrete Dam (RCCD) relying on gravity, thus completely changing the mechanics of design and cost considerations.

Initially, the designer had relied on the argument of “inherent superiority of concrete dam over an earthen dam”. However, when this view was rejected by the Panel of

Experts employed by WAPDA, the designer presented four main reasons were assigned to this major design change:

a. It was apprehended that the soil under the dam may be subject to liquefaction during a major once in a millennium earthquake.

b. The cutoff wall may not perform during such an earthquake because of negative friction from soil. The example of Manicougan -3 dam was cited as precedence for such an event.

c. It was feared that Differential Settlement caused by variable thickness of compressible strata may lead to cracks in the core which may later lead to piping and consequential weakening of the dam.

d. The fine grained material required for the core is not available in the vicinity.

Based on the above, the consultants re-designed the MONENCO ECRD section so that it would be founded on the bedrock. It was asserted that the redesigned section will be more expensive than RCCD and rejected.

The flaws in the above argument are quite obvious and they may be countered as below:

a. The calculations given for liquefaction potential assume a much softer soil than is shown by investigation. Moreover, no subsequent calculations were made to determine the actual submergence that may be caused by

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 8 of 16 AAA-TCI liquefaction if it does occur. The dam already has a good freeboard margin for subsidence and this could have been increased if required.

b. The designer could have proposed concrete soldier pile or steel sheet pile cutoff. This would probably still be cheaper than the rock treatment that is prescribed in the current design and which was probably not priced in the comparison stage.

c. Settlement of the dam substrata will continue through eight years of construction process and very little potential for further settlement will be left by the time the dam is completed. So the fear is probably unfounded.

d. A concrete faced rock fill dam (CFRD) could have overcome the shortage of fine grain material at the site. The same could also have resolved point C.

When the work of feasibility review and tender design was awarded to Diamer Basha

Consultants (DBC), a consortium of consulting firms led by Lahmeyer of Germany, the dam type was never reviewed.

At this most crucial stage, the designers should have re-evaluated the type of dam and conducted a comparative study to affirm if RCCD was the best option or if some other type of dam could be constructed more efficiently. Instead, DBC went ahead uncritically using the Roller Compacted Concrete design proposed by NEAC.

4.2 OPTIMIZATION

Such a large project cannot be designed without several iterations to arrive at the best design. DBC did not put in the effort to achieve the most efficient design. Three examples will illustrate this:

a. The consultants determined that an arch gravity dam will be the cheapest alternative, but as the independent Panel of Experts hired by the client insisted on construction of a gravity dam, the consultants agreed to this without any further discussion and went ahead with a gravity dam.

b. The designers started off with selection of a concrete section which would be stable in different load conditions and applied that section to all parts of the dam. When thermal and seismic analysis showed that although the overall section is stable, the tensile or shear capacity at certain levels is deficient, the

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 9 of 16 AAA-TCI designers responded by increasing the quantity of cementitious material, and thereby strength, in that particular section.

By altering concrete mixes, the designer has caused the cost of concrete to increase much beyond the original estimate. No effort is made to try out different sections and assess which section will be the most economical considering the lighter design mixes that will be needed for larger dam sections.

c. Similarly, the designer has used different proportions of cement and fly ash/GGBS in proposed mixes in tender design without considering if this will be the most economical solution. It is quite possible that a higher cement

(and lower fly ash) content concrete will be more cost effective if alternate cooling methods are used. However, no effort is made to determine if this can be achieved.

4.3 DESIGN INADEQUACY

At places, the designers adopt a complacent and a rather cavalier attitude toward design. Design inadequacies are explained away by philosophical discourses and committee decisions. Two examples of this slack reasoning are reported below:

a. The designers find that under Maximum Design Earthquake, the cracks will propagate to such an extent that in some parts, 80% of the section width will become de-bonded. In face of this result, the designers posit that this may not

“actually happen” because of shear keys. These shear keys are not modeled in the design and the transfer of forces through the keys if any, is neither estimated nor modeled. The following excerpt from the design report speaks for itself:

“…The block will be keyed in the upper elevations to the neighbouring blocks by the shear keys and in addition some load shedding will inevitably occur with instantaneous critical debonding thus tending to stabilise the block above the safety level indicated by the linear response analysis”

One would expect the designer after this statement to perform whatever extra analysis may be required to prove design adequacy but none is forthcoming.

b. The wedge analysis shows that the abutments are not capable of withstanding seismic loads for some slip surfaces. The designers surprisingly conclude that this is only an extreme case and such scenarios “may or may not” exist in reality as the rocks of the abutment are not fully investigated at the time of design.

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 10 of 16 AAA-TCI

They also postulated that the collapse is improbable because the dam body will resist the collapse of the abutment. But without modeling this situation, the designer left the “assessment” and possible re-design to a later stage.

4.4 CONCRETE DESIGN

The properties of concrete mixes that are proposed in design are not corroborated by experiments. In this large and costly project, it is surprising that the designers have based their design on assumptions and estimates of concrete property. It is noted by the designers that not much data is available on roller compacted concrete

RCC made with norite aggregate which is proposed for the dam concrete. Still, the reliance is made on “similar” mixes used in other RCC dams. These similar mixes are not identified by the designers and there is no way of knowing if these mixes are based on actual unpublished experience of the designers or other cases with entirely different set of materials.

In the absence of published resources for similar mixes, the designers should have tried to assess crucial concrete properties such as compressive and tensile strength and thermal properties through experimental work.

The project design report mentions the use of pozzolan which the designers claim is freely available in the vicinity. If this were the case, some trial mixes using this material could have been conducted. However, in the design specifications, no pozzolan is called for and the reliance is made on imported fly ash, with possibility of using a small proportion of ground granulated blast furnace slag GGBS.

Of course, the designers may have determined that it was better to use tried and tested materials instead of some minerals which may or may not produce the desired results. If this was the intention, the design report and executive summary should have made this determination obvious to all. Instead, the report creates an illusion that large quality “cheap” pozzolans will be used which can be mined near the project. This impression is carried through in the design report, but simply vanishes in project Bills of Quantities.

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 11 of 16 AAA-TCI

4.5 CONVOLUTED REASONING

At a number of places, the report follows a torturous language and complicated logical assertions to defend positions which appear untenable to a simple designers mind. Some examples are directly copied from the report without comments below:

4.5.1 EXCERPTS FROM THE DESIGN REPORT

“…Trial seismic loading evaluations determined that the MDE3 case gave results comparable and sometimes in excess of the MCE cases, even though the peak ground accelerations were lower than the MCE cases, due mainly to frequencies of this earthquake being ‘in-tune’ with the dam frequencies. The

MDE cases being chosen as intermediary loadings between OBE and MCE and for reasons that results for this MDE3 were not comparable with the other two MDE cases, it was decided after these preliminary analyses to treat

MDE3 as equivalent to an MCE case. Thus only MDE1 and MDE2 were considered under ‘MDE’ loading, but all MCE loadings included the so called

MDE3 case.

“..After extensive discussions, it was decided that the assumptions to make regarding joint strength on debonding as that the joint cohesion is retained to 100% of its un-debonded value, but that the frictional strength is decreased to a residual value, i.e. 450, provided that the joint does not debond across the complete horizontal plane, i.e. to say up to 80% of the planes total length. The safety analyses were made on this basis. However, numerical tests showed that this 100% factor could be reduced to say 70% or even 50% without much consequence in terms of safety factors reaching critical values, i.e. approaching 1.0. These assumptions are made on the basis that although debonding may have occurred, then the matching joint surfaces (on either side of the joint) will basically retain their roughness because debonding can only occur as a tension type strain if sufficient bonding length is still retained.

“..Under low reservoir conditions the reality to be expected under seismic motion will be other than that applied in this analysis where independent block motions are assumed:

a) even under early ages where creep may not have taken place to close lift joints, or under long-term conditions were internal temperatures will have

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 12 of 16 AAA-TCI reached steady-state conditions possible accompanied by some vertical contraction joint opening, these vertical joints will inevitably close under upstream motions during medium to strong seismic evens. This will lead to a stiffer solutions for upstream motions, because part of the seismic load will be carried by arch action, as well as some inter-block shear forces.

“Thus the assumptions made for low lake conditions may be regarded as conservative. Thus moderation of downstream motion will also influence upstream motions, as larger displacement excursions will inevitably be damped.

“.. The low instantaneous sliding safety is created by a combination of vertical as well as horizontal instantaneous seismic forces, but lift joint sliding is not expected during any of the analysed seismic events. Rather the block will be keyed in the upper elevations to the neighbouring blocks by the shear keys and in addition some load shedding will inevitably occur with instantaneous critical debonding thus tending to stabilise the block above the safety level indicated by the linear response analysis

“..However, it should be emphasised that the indicated debonding is shown to be in an area near the low level outlets, where in any case special reinforcement measures will be implemented

“..Although very large slide displacements are shown for certain seismic loadings, and even for some OBE loading conditions with mode-1 strengths, any potential hazard for the dam body, i.e. leading to possible dam body failure resulting from possible wedge movements against the dam, must be evaluated after specific failure scenarios have been actually identified from more extensive field tests prior to or during foundation excavation.

Necessary remedial measures will then have to be addressed once specific probable wedges have been identified in detail. At present, the wedges that are shown in this report are the most likely worst-case scenarios obtained from possible plane orientations, but are not as yet developed on precise field evidence. Even so, it can be seen from the results for these various wedge scenarios that only certain wedge geometries, if they exist, will pose a major threat to the dam body, such as wedge LL-1, and the likelihood of such

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 13 of 16 AAA-TCI a severe wedge scenario existing in practice, although to be treated with extreme caution, is quite unlikely.

“Wedge stability analyses have been conducted on the basis that the wedge is free to slide without any resistance being offered by the portion of the dam body which is not directly supported by the rock wedge (remaining dam body). Clearly, even small wedge displacements which are directed towards the remaining dam body will incur resistance from that remaining body, i.e. a resistance that will be dependant upon the said deformation, which can thus be modelled by an equivalent spring. In case relevant wedges are positively identified by further investigation, then it is recommended that this equivalent spring effect be introduced into the wedge stability analysis, coupled with an assessment of the effects on the remaining dam body of any load transferred by wedge movement. This means that the dam must also be investigated for potential failure resulting from any lateral wedge instabilities. This type of analysis should be conducted only when a detailed knowledge of actual potential sliding wedges has been obtained by further investigation, as the resulting analyses are complex and should be minimized by dealing with defined situations. These analyses should also be run in conjunction with details imposed by the specific remedial measures to be proposed at that time.”

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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5.0 CONCLUSION

Some major failings of design have been pointed out in the sections above. The project design suffers from acute problems which must be resolved before proceeding to construction.

Four Due Diligence Reports are annexed to this report with comments. A number of non-conformances and incomplete items have been identified. Some of the non-conformances are trivial, but work is needed to remove all these non-conformances.

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

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6.0 RECOMMENDATIONS

The work done so far is only up to the tender stage. The main purpose of the design at this stage is to invite bidding and not to proceed to construction. With this perspective in mind, the only crucial issue that afflicts the design is the decision to go by with an RCC dam instead of CFRD or ECRD. These alternatives must be decided upon before going to the final tendering phase. Alternately, the tender may be made sufficiently flexible to change the type of dam, once the construction design stage is completed.

GAP ANALYSIS OF DBDP DESIGN IN COMPARISON TO INTERNATIONAL BEST PRACTICES

Data Collection, Review and Preparation of International Tender document for the Diamer Bhasha Dam Project

Page 16 of 16 AAA-TCI

7.0 REFERENCES

ICOLD Bulletin 126 Roller Compacted Concrete Dams, State of the Art and Case

Histories, ICOLD Committee on Concrete for Dams, 2003

ICOLD Bulletin 136 The Specification and Quality Control of Concrete for Dams, ICOLD Technical Committee on Concrete for Dams, 2009

ICOLD Bulletin 53 Static Analysis of Embankment Dams, ICOLD Committee on the

Analysis and Design of Dams, 1986

ICOLD Bulletin 46 Seismicity and Dam Design, ICOLD Committee on Seismic Aspects of Dam Design, 1983

ICOLD Bulletin 52 Earthquake Analysis Procedures for Dams State of the Art, ICOLD

Committee on Analysis and Design of Dams, 1986

RESPONSE SPECTRUM ANALYSIS OF CONCRETE GRAVITY DAMS INCLUDING DAM-

WATER-FOUNDATION INTERACTION By Arnkjell Lokke and Anil K Chopra. Pacific

Earthquake Engineering Research Center July, 2013 (PEER 2013/17)

A PROBABLISTIC FRAMEWORK TO INCLUDE THE EFFECTS OF NEARFAULT DIRECTIVITY

IN SEISMIC HAZARD ASSESSMENT By S K Shahi and J W Baker. Pacific Earthquake

Engineering Research Center October, 2013 (PEER 2013/15)

CURRENT SEISMIC SAFETY REQUIREMENTS FOR LARGE DAMS AND THEIR

IMPLICATION ON EXISTING DAMS Paper by Martin Wieland and R. Peter Brenner

DAM SAFETY AND EARTHQUAKES, Position Paper of International Commission on

Large Dams (ICOLD) Prepared by ICOLD Committee on Seismic Aspects of Dam

Design, chaired by Dr. Martin Wieland

ICOLD Bulletin 72 Selecting Seismic Parameters for Large Dams, Guidelines, ICOLD

Committee on Seismic Aspects of Dam Design, 1988

ICOLD Bulletin 75 Roller Compacted Concrete for Gravity Dams, State of the Art, ICOLD Committee on Concrete for Dams, 1989 [Now superseded by Bulletin 126 above]

ICOLD Bulletin 88 Rock Foundations for Dams, prepared by P. Londe and Y. Le May, ACI 207.5R-99 Report on Roller Compacted Mass Concrete, American Concrete

Institute – Committee 207 1999.

Seismic Response of some Earth Dams: Some Recent Developments by George

Gazetas, Renselear Polytechnic Institute, Troy, NY, USA and National Technical

University, Athens, Greece.1987

Building Code of Pakistan (Seismic Provisions – 2007) GOP Min. of Housing and

Works, Islamabad

Geotechnical Earthquake Engineering by Steven L. Kramer. Prentice Hall/Pearson

Education Inc. 1996

Seismic response of earth dams: some recent

ANNEXURES

Due diligence on Design by DBC

CHECKLIST FOR EXAMINING

STRUCTURAL DESIGN FOR CONCRETE DAMS

AS PER ICOLD B126

STRUCTURAL DESIGN FOR CONCRETE DAMS

AS PER ICOLD B126

1.1 KEY

In this report, the items listed in the Due Diligence Format are marked OK, NG, NR, or IC in the design conformance section, followed by the comment number in the comments column. The markings reflect the following:

OK The item has been adequately and comprehensively addressed by the designer as per current practice.

NR The item is not required for the design method adopted by the designer for this particular site

IC The item is addressed by the designer but is deemed incomplete or needs minor adjustments or further work. This remark is invariably followed by comments.

NC The item has been either ignored or inadequately handled by the designer

S.No. Best Practice as per ICOLD Standards DBC Design Conformance

Remarks

1 Design Considerations Have the following properties of material been adequately evaluated?

-Elastic modulus

-Poisson’s ratio

-Coefficient of thermal expansion

-Unit weight

Has shear strength along the horizontal joints been evaluated?

Has temperature distributions and resulting thermal stresses in dam body evaluated

Has finite-element method (FEM) analysis carried out in assessing thermal induced stress behavior within dam body?

Has comparative Selection process undertaken between low-cementitious material content (i.e. 100 kg/m3 Portland cement and mineral admixtures) Vs.

RCC dam high-paste (high-cementitious content >

150kg/m3)?

Has use of upstream watertight membrane for low cement content option been evaluated?

Use of Bedding mixes for high cementitious content dam?

Has strength of lift joints been evaluated?

Has sliding on lift joints been checked?

Is full scale test proposed?

Were shear properties and permeability at lift surfaces worked out using following methods?

-In-situ direct shear tests in full-scale trials with full production equipment

-Drilled cores from full-scale trials for shear and direct tension

-Joint shear tests in large blocks

-Evaluation of joint maturity to confirm assumed criteria

-simulating joint conditions in lab in as far as possible

-Minimum cohesion higher 2.0 MPa

-Friction factor larger than 1.2

OK

OK

OK

OK

OK

IC

NC

OK

OK

NC

NC

NC

NC

NC

NC

OK

OK

OK

OK

NC

NC

OK

OK

IC

OK

Has two-dimensional analysis carried out using stress or FE analysis?

Has stability analyses for critical sections performed

Has the dam been analyzed using trial-load method or 3 D finite-element analysis?

Has stresses on abutments been evaluated?

Are methods prescribed for cooling the concrete are suitable?

Has contraction joints between blocks proposed for grouted before filling takes place

Has larger crack widths considered to increase distance between the preformed joints

Has a check been introduced for uncontrolled cracking?

Has “seeding” been proposed to induce cracking process and relieve stresses?

Use of heel-joints & water stops provided at U/S of dam to prevent tensile stress formation?

Prescribing of contraction joints & spacing especially in light of temperature rise expected as opposed to prevalent ambient temperatures?

Has tensile creep of concrete been considered?

Has checking of heat dissipation been made in the very high vertical section of the dam?

Have the followings elements been considered with respect to total economy of dam?

-Cementitious contents

-Simplicity of construction & lower unit costs

-durability in operational stages

-reduction of dam cross section by using high cement content

-Water-tightness at face

2 Seismic aspects Have seismic loading conditions been properly identified?

Have geometrical discontinuity, if any, in dam structure been evaluated?

Have tensile and shear strength of horizontal lift joints been examined for seismic loading as opposed to normal static loading?

3 Adequacy of Selection Process of Type of Dam :

In selecting Gravity Arch RCC type dam proposed for

Bhasha, have following aspects been thoroughly examined?

-Production methods

-Weather seasons for construction

-Speed of construction

-Types of mixtures

-Structural designs

-No special requirement for dam construction and use of conventional equipment (trucks, dozers, vibratory rollers, etc.)

-Reduced Cost of Construction

-Thinner layer lift and increased safety

-Safety as no formwork required

-Lesser environment impact

-Spillway within the dam body

-Less complicated river diversions

-Reduced flood risks

-Shorter penstocks and conduits

-Intake tower against dam face

-Passing floods during construction conveniently by over-topping & reduced damage potential

-Longer seasons for construction

OK/IC

4 Thermal Considerations

Has cracks control in mass concrete been thoroughly evaluated?

Has design been checked for temperature and crack control?

Has volumetric change been computed due to gradients in temperature over life of structure?

Has drying shrinkage been examined?

Has restraints to actual concrete bond at foundation and abutments levels been worked out?

Variations in changes and resulting strains in concrete within the body and exterior of dam?

Have following parameters been examined?

OK

OK

OK

-peak internal temperatures

-uncontrolled cracking

-Average outside temperatures and response to dam mass concrete against cooling

-modulus of elasticity

-degree of restraints at foundation and abutment levels

-prediction of cracks propagation especially into body of dam

5 Temperature control

Does design account to prevent cracking due to temperature drop i.e. from hydration condition to final stabilized temperature?

Are following factors accounted for?

-adequacy in block size of mass concrete

-geometry of structure

-distance from foundation

-stiffness of concrete vs. foundation rock

-tensile strength and creep behavior of concrete

-rate of temperature drop

-beneficial effects of sequential and rapid placement of lift layers

-Lowering the thickness of layers

-Maximum contraction joint spacing

-have studies been made on maximum tensile stress generated in body of dam

-Have depths for cracks been calculated from face of dam

-finite-element analysis to evaluate thermal stresses / crack potential

-time based numerical simulation predicting temperature variations in body of dam from placing to final stabilized temperatures

Do the modeling and design criteria / specs allow for following factors?

-placing temperature of the RCC, -adiabatic temperature rise and heat of hydration, -construction schedule

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

-loss of heat to environment

–heat gain by solar radiation, –heat loss by radiation

-heat loss via convection

-evaporation of curing water

-loss of heat to foundation

–heat losses to reservoir

–heat loss through the galleries.

-effects of aggregates on temperature rise

-placement time

-weather conditions

-Have sufficient site specific meteorological data collected and used in analysis

-Calculations for allowable temperature drop for dam body structure

-maximum allowable peak temperature at placement

-maximum placing temperature

-Concrete cooling systems such as mix proportions combinations, Pre-cooling, cooling of aggregates by spraying, Shading of stockpiles, use of chilled air

Use of chilled water, Evaporative cooling

Post-cooling

OK

OK

OK

OK

OK

OK

OK

NR

6 Contraction Joints

Are following factors accounted for in prescribing vertical contraction joints?

-volume change

-foundation restrain

-foundation irregularities

Has any philosophy provided for selection, location and optimization of type of contraction joints?

-Post-formed

-Formed joints

-Induced joints

Has numerical modeling been done to determine stress induced within dams using results of thermal analysis Also if stress prediction has been made in the whole body of dam as a consequence of temperature changes?

1.2 COMMENTS

1 The process of selection is not described in enough detail to determine whether a previous iteration was done to check this.

2 The design at this stage is not sufficiently detailed for this process to take place.

3 Only 2-D analysis has been performed

Has changes to concrete stress-strain, thermal and creep properties been considered over time?

Have aggregate properties been considered for and concrete properties and thermal expansion characteristics of dam body

7 Seepage Considerations

Assessment of coefficient of permeability and seepage through the dam body?

8 Galleries within Dam

Any inserts in dam body be minimum such that effect on rates of concrete placement is minimal

Have adequate inspection and safety assessment galleries and adits provided in dam body

9 Spillways

Type shape and size of spill way provided

10 Appurtenant structures and inserts

Delays or interference to dam construction?

11 Instrumentation

Adequate justification and sufficiency in range of equipment for thermal conditions for both construction and operational stages especially safety?

Geodetic & collimation survey instruments, 2 or 3 dimensional joint meters, strain meters, thermocouples and piezometers

12 MATERIALS

This section is DELETED A separate DD analysis is appended for

RCC

4 Wedge Method is used for analysis and factor of safety was found less than 1 for some conditions.

5 Post cooling is not recommended in design and stresses due to heat of hydration have been accounted for

6 The overall section is determined by minimum requirements of stability and other factors are forced by this decision. No alternatives were tested for calculating “total economy”

7 These items were addressed in design but not shown to have been considered in comparative evaluation with respect to overall economy of system.

8 Formed joints are used.

ANNEXURE-2

ROCK FOUNDATIONS DESIGN INVESTIGATIONS

AND PROCEDURES

AS PER ICOLD B088

ANNEXURE-2

ROCK FOUNDATIONS DESIGN INVESTIGATIONS

AND PROCEDURES- AS PER ICOLD B088

2.1 KEY

column. The markings reflect the following:

OK The item has been adequately and comprehensively addressed by the designer as per current practice.

NR The item is not required for the design method adopted by the designer for this particular site

IC The item is addressed by the designer but is deemed incomplete or needs minor

NC The item has been either ignored or inadequately handled by the designer.

Remarks

1. Methods/Procedures used in Rock Classification

1.1 Is the rock mass classification made according to

International Society for Rock Mechanics and reflects weathering conditions of the rock?

OK

1.2 Has the foundation rock mass been classified

according to following parameters?

-layer thicknesses observed?

-discontinuity intercepts?

-uniaxial compressive strength of rock?

-angle of friction of the discontinuities

1.3 During site comparison and selection of final

foundation / dam axis has rock mass classification been applied in examining merits and demerits of a site with above parameters?

OK

1.4 Does the geological criteria adapted account for

following factors concerning presence of shear faults in the dam foundation?

-length of intersection with ground surface

-width of fault zone

-nature of infilling

-total throw of fault

-faults position with respect to regional tectonics

-fault’s time of last movement

1.5 Has seismic refraction techniques been used to

confirm thickness of weathered rock / soil cover and in comparative evaluation of dams sites?

OK

1.6 Has any seismic logging techniques been employed in

assessing fracture density of rock?

OK

1.7 Has deeper (sub-surface) cross-hole seismic paneling

methods been used to examine following aspects of rock mass:?

-details in rock fracture zones

-identification of local rock structures and patterns

OK

1.8 Has any advanced gravimetric methods been

employed to study the underlying rock integrity?

1.9 In case resistivity profiling conducted has the derived IC 2 rock type, depth of water table, and faults, cavities, seepage paths and rock features been compared / correlated with drilled information?

1.10 Has rock RQD documented fracture frequency and

record of colored indented photographs of core boxes been kept?

OK

1.11 Has the drilling parameters been properly recorded as

permanent project record?

OK

1.12 Do permeability tests inferences on foundation rock

mass include degree of fracture and spacing and opening of discontinuities?

OK

1.13 Has the foundation rock mass properly examined for

following key characteristics:?

-strength and safety against failure

-deformation characteristics

-effects of deformation on rock mass structure

-effects of seepage on the rock mass

OK

1.14 Has modulus of elasticity of foundation rock

(deformability potential) been properly determined using Jacking Tests?

OK

1.15 Have residual stresses been assessed for locations

such as abutment rock or toe of hills?

OK

1.16 Has the identification and analysis of rock foundations

included following tests:?

-compression tests

-radial permeability

-shear strength of joints

2. Foundation Design

2.1 Has flow nets, patterns of hydraulic gradients, been

studied to determine changes in permeability or its cross distribution in the rock mass systems?

OK

2.2 Have impervious zones been identified wherein

highest seepage stresses are likely to occur?

IC 3

2.3 Has the damaging effects of seeping water (main

cause of internal erosion) been assessed?

OK

2.4 Has foundation rock been classified and approved to

be free from internal erosions?

OK

2.5 Does design on rock foundation account for following

modes and design conditions:?

-possible modes of failure due to geological and applied loads

-stability from equilibrium conditions

2.6 Has designers prepared a model for expected rock

mechanics in DBDP foundations:?

OK

2.7 Does the rock model account for:?

-randomness in rock properties in the rock mass structure?

-inaccuracies and errors in measurements

-uncertainty in loads & their variability

-conditions in analyzed in 3 D

OK

2.8 Has the rock mechanics modeled been verified or

validated during design or future stages of implementation of DBDP?

OK

2.9 Does the rock mechanics model proposed has helped

visualize the static (equilibrium) or instability conditions in the rock mass?

OK

2.10 Does design documents include proposals for

subsequent interpretation of instrument observed

(monitoring) data?

OK

2.11 (Most Important) Has proper estimation of shearing strength values of material (on large scale) been utilized in to study jointed rock masses?

OK

2.12 Has slope stability in rock masses (over ground) been

assessed using shear strength derived from effective normal stress on weak planes and also using Mohr failure envelopes?

OK

2.13 Does stability analysis of underground excavations

account for response of the rock masses to principal stresses acting upon each individual blocks?

OK

3. Factor of Safety

3.1 What is FOS (1.50 pass) determined for stability

analyses of geotechnical materials, soils or rocks?

OK

4. Failure Analysis

4.1 As both FOS and probabilistic failure analysis is not

entirely recommended by ICOLD for rock stability, in contrast has a parametric analysis been conducted considering the limit state conditions for critical parameters been estimated for following scenarios:?

-first filling of reservoir when first loading of rock foundation takes place

-failure due to overtopping

-failure dues to piping

-sliding failure

5. Deformation of Rock Foundations

5.1 Has rock mass deformation separately and

independently been conducted from simple conventional surface movement analysis?

NC

5.2 Has the actual deformations of rock at required depth

been studied using numerical models?

NC

5.3 In modeling and analyzing has rock mass been

assumed to behave as an elastic system?

NC 4

5.4 Has in situ jacking tests for deformation studies been

proposed or executed?

OK

5.5 In case jacking test not used then what acceptable

method with justification has been used in determining deformation modulus for the rock foundation design for DBDP?

NR 5

5.6 Has the effect of rock deformations on Dam body

been evaluated in detail?

OK

5.7 Has irrecoverable deformations as formed by closing

of cracks / shearing been estimated and considered in design?

IC 6

6. Effects of Seepage

6.1 Are seepage effects as caused by hydraulic gradient

examined for stability of dam structure and foundation?

OK

6.2 Has seepage flows and resulting system of forces been

computed ?

OK

6.3 Has following aspects within rock system considered in

estimating flows and seepage forces?0

-geological discontinuities

-flow boundary conditions

-variations in flow conditions due to rock deformation

OK

7. Foundation Treatment

7.1 Has design consultants considered following modes of

improvements?

-deformation reducing measures

NR 7

-strength improvements

-control of impinging hydraulic forces

7.2 While prescribing measures for foundation treatment, has DBC identified following measures to improve properties of the rock foundation?

-excavation treatment

-foundation strengthening

-seepage control and drainage

8. Excavation Treatment

8.1 In design documents has effects of large scale bastings

duly considered impacts such as increased deformability, permeability, grout volumes, loss in stability of excavated slopes?

OK

8.2 Has pre-splitting measures been considered to avert

major blasting issues?

IC 8

8.3 Are excavated slopes been analyzed for safety and any

measures proposed to improve safety?

OK

8.4 Has following surface treatment measures been

considered to stabilize decompression effects on the newly exposed ‘stress relieved rock’ (condition after excavation)?

-use of buttresses

-soil coverings

-reshaping of slopes

-substitution with roller compacted concrete (for very poor rock conditions)

-consolidation grouting

OK

9. Foundation Strengthening

9.1 Treatment of Faults NR 1

9.2 Has procedures taken into account in design and spec

regarding treatment of fault by cleaning them and backfill concreting?

NR 1

9.3 Has reinforcement of rock masses considered by steel

reinforcement and if so what justifications provided in contrast with other measures available?

NR 1

10. Seepage Control & Drainage

10.1 Has grout and drainage curtains been considered to

curb seepage flows?

10.2 Has any shallow drainage system provided in the rock OK

2.2 COMMENTS

1 No faults are found under the dam and the mass is composed of solid Norite rock.

Hence these points do not apply.

2 Profiling is not conducted.

3 Random samples have been tested and an overall prevalence and severity of pervious zones has been assessed, but the zones are not identified clearly or mapped on a drawing.

4 The foundation is assumed as fixed

5 Jacking tests have been performed in adits

6 Shearing and closing of cracks are not expected

7 Grouting the rock surface and drainage curtains near both faces of the dam have been used to effectively control seepage through any cracks that may exist in the system

8 The blasting procedures are left at the discretion of contractor. These are to be designed by contractor and submitted for approval by engineer.

9 The designers considers grouting to be sufficient.

contact zone?

10.3 For foundation of DBDP has both conditions of

homogenous impervious rock and fissured rock been evaluated to relieve seepage flows though drainage?

OK

10.4 Has grout curtains or drainage curtains considered as

appropriate for the foundation conditions encountered?

OK

10.5 Drainage of Preferential Channels and Faults NR

10.6 Has drainage (relief) holes been provided over whole

foundation in addition to preferential channels?

NR

10.7 Have galleries been provided for execution of grout

and drainage curtains?

OK

10.8 For areas where grouting considered insufficient, has

concrete diaphragms walls proposed to act as positive cut-off?

NR 9

ANNEXURE-3

DESIGN FEATURES OF DAMS TO RESIST

SEISMIC GROUND MOTION

AS PER ICOLD-B120

ANNEXURE-3

DESIGN FEATURES OF DAMS TO RESIST

SEISMIC GROUND MOTION

AS PER ICOLD-B120

3.1 KEY

column. The markings reflect the following:

OK The item has been adequately and comprehensively addressed by the designer as per current practice.

NR The item is not required for the design method adopted by the designer for this particular site

Remarks

1.0 GENERAL

Has DBC evaluated performance of Diamer Bhasha Dam giving due cognizance to seismic requirements and structural considerations to resist seismic induced ground motions?

Has failure modes been laid out and discussed in detail?

Considerations for earthquake occurring at a distance from DB dam site?

What are expected movements of fault systems if identified?

Has seismic input parameters been compiled while conforming to ICOLD Bulletins No.72 and seismic loading in accordance with Bulletin no. 52 – an essential ICOLD requirement ?

2.0 Seismic Consideration in evolving Dam Structure

Has structural integrity of Bhasha Dam been checked by making a comparison of seismic theoretical analysis of Bhasha dam with actual seismic behavior of similar existing dams?

Have the seismic shaking loads been determined and applied in the 3-D Model tests?

Have predictions / estimates been made for type and magnitude of seismic induced residual deformations, observed cracking and damage to main dam or foundation structures?

Has a sufficiently comprehensive seismic investigation campaign been conducted as part of general design process?

Have Topographic effects of the valley and geology of two abutments been taken into account in assessing seismic concerns?

Have geotechnical properties of shear zones and those of alluvial foundations been assessed from seismic point of view and treatments prescribed?

Have seismic response of DB dam main body, its foundation and reservoir water been interactively and integrally been assessed?

3.0 Dam Site Shape & Geology Related

Has amplifications due to topographic formation / shape of a canyon been examined for seismic induced vibration – either qualitatively or by 3 D simulation models?

Has adequate measures adapted in optimizing dam cross section such as stress and strain concentrations as consequence of river valley configuration, foundation geology, direction and intensity of shaking at site?

Has any sharp changes in geologic conditions been identified for e.g. change in formations across gorge ?

Has effect of shaking joint between dam foundation to foundation rock assessed and counter measures provided?

Any treatments given to naturally occurring foundation shear zones?

Has inspection galleries been provided to assess future expected damages?

Does the 3 dimensional modeling account for non-uniform and out-of-phase vibrations expected across the alignment of dam?

4.0 Seismic Concerns in Selecting of Arch Type RCC Dam

Type for Diamer Bhasha

(Deleted)

5.0 Structural Features Adapted for Diamer Bhasha Dam

Have factors such as following been accounted for in determining cross section of the dam?

-Smooth Geometry and Symmetry -Shaping of foundation to ensure continuous compressive loading -Limiting crest length to height ratio to prevent distortion during shaking -Adequate prevision of Contraction joints with interlocking -Foundation consolidation improvements such as soil replacement by concrete, filling of cavities, grouting etc.?

-Improving quality of bonds between lift surfaces -Crest width widening to avoid local cracking

OK

OK

OK

OK

3.2 COMMENTS

1 Fault movements have not been used to determine seismic loads e.g. as per A

PROBABLISTIC FRAMEWORK TO INCLUDE THE EFFECTS OF NEARFAULT DIRECTIVITY

IN SEISMIC HAZARD ASSESSMENT By S K Shahi and J W Baker. (PEER 2013/15)

2 See separate report on seismic hazard assessment

3 Only 2D finite element models have been checked

4 There is no alluvium under the dam as it rests on the rock foundation

5 No assessment is made e.g. as per Lokke and Chopra to modify response by including foundation and reservoir in the model

6 Arch type dam is not selected. Instead a gravity dam with a large radius is designed.

The section is therefore omitted.

7 The philosophy behind width of deck is not discussed.

8 The work is not detailed to this level at this stage.

-Minimizing mass in higher section of dam -Low concrete placing temperatures to minimize heat-induced tensile stresses and shrinkage cracking -Effective drainage system -Use of shear keys in joints -Minimizing discontinuities in dam body -Avoid breaks in slope on D/S slopes to reduce local stress concentrations

Have dynamic interaction & displacements been worked out for structures adjoining dam body due to different dynamic responses of each component?

Have effects of earthquake triggered landslides been accounted for in the reservoir body?

Is freeboard sufficiently provided to prevent earthquake induced (large) water wave loadings?

OK

OK

OK

6.0 Dam Instrumentation

-Has sufficient dam instrumentations provided to monitor effects of strong motion?

SPECIFICATIONS AND QUALITY CONTROL OF

CONCRETE FOR DAMS

AS PER ICOLD B136

SPECIFICATIONS AND QUALITY CONTROL OF

CONCRETE FOR DAMS

AS PER ICOLD B136

4.1 KEY

the design conformance section, followed by the comment number in the comments column. The markings reflect the following:

OK The item has been adequately and comprehensively addressed by the designer as per current practice.

NR The item is not required for the design method adopted by the designer for this particular site

Remarks

1.0

General What type of specification has been used ? Is it Method based Specification or Performance based Specification ?

Has scope of entire Bhasha RCC Mega project clearly and in detailed form been defined in the design and specification documents for entire process of mass manufacture, transportation, placement, finishing, repair and curing of RCC concrete?