BAUERGlobal Dam Services

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ContentRehabilitation and Upgrade Dams

• Center Hill Dam, USA ............................................... 4

• Sylvenstein Dam, Germany ....................................... 6

• Hinze Dam Upgrade, Australia .................................. 7

New Dams

• Peribonka Hydroelectric Development, Canada ........ 8

• Punatsangchhu-I Dam, Bhutan ............................... 10

• New Assiut Barrage, Egypt ..................................... 11

Competences

• Construction Methods ............................................ 12

• Equipment and Techniques ..................................... 14

• Design .................................................................... 16

• Concrete ................................................................. 17

Responsibility

• Quality Management ............................................... 18

• HSE Management System ...................................... 19

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BAUER Spezialtiefbau GmbH, together with its sub-sidiaries, has over 30 years experience in designing and executing cut-off walls for dam rehabilitation,

upgrading of dams and new dams including their coffer-dams. Our core competencies include different types of concrete barrier walls to depths of more than 150 mthrough alluvium and embedded into fresh rock as wellas grouting and ground improvement to meet the pro-ject requirements. Dam safety is our utmost priority. Bauer’s technological developments and experience in

barrier wall installation facilitate the preparation of de-signs. Our highly professional staff is available to en-hance planning in the emerging hydro energy market.

BAUER Spezialtiefbau GmbH provides excellent service, experience and innovation in ground engineering tech-niques necessary for dam construction. The strength of our company are our in-house resources facilitating world-class solutions for projects around the globe, with the goal to deliver safely, on time and on budget.

4 Rehabilitation and Upgrade Dams

Center Hill Dam is located in the State of Tennessee, just east of Nashville. The Dam was

designed and built in the 1940s with concrete and embankment sections founded on karst limestone. Being res-ponsible for the Center Hill Dam from its Nashville District, the US Corps of Engineers identifi ed that seepage through the karst limestone beneath Center Hill Dam’s foundation was suffi ciently severe to warrant a large scale remediation project. This re-mediation requires the construction of positive cut-off walls in the foundation of the embankment dam section, into the left abutment of the embankment dam and a connection to the concrete dam section to address the seepage situation.Bauer was awarded the contract as main contractor to install a concrete barrier wall through the earthen por-tion of the dam and into the rock to depths of about 100 m.After complex preparatory works, including obtaining required permits and approvals, the widening of the embankment dam crest and the in-stallation of a heavy-duty concrete working platform for Bauer’s equip-ment and site-setup was built. The platform had to provide a stable work area for equipment with individual weights of up to 330 tons each.After completing the remarkable site installation required for the works including traffi c management of the highway along the site, the concrete seepage cut-off wall is constructed in two phases.The fi rst phase is the installation of a concrete encasement wall to protect the dam embankment during the con-struction of the permanent barrier wall. The encasement wall, a diaphragm

wall installed by a BAUER trench cutter MC 50 on an MC 128 base carrier, is set into the underlying bedrock. The high-performance MC 50, equipped with two powerful slurry pumps, is the largest hydrocutter excavating an area of 3.2 m x 2.25 m at once. The BAUER BC 50 trench cutter excavates the panels under slurry to allow concrete placement using the tremie method. The encasement wall is completed fi rst with suffi cient overlap between the pri-mary and secondary panels to ensure the continuous wall protecting the em-bankment in case of unexpected slurry loss into an undetected cavity.Inside the concrete encasement wall the designed barrier wall is installed into the karst foundation rock. This hy-brid barrier wall consists of primary piles installed by a BAUER BG 50 rotary drilling rig and secondary rec-tangular panels installed by two Bauer trench cutters, the BC 50 and an addi-tional BC 40, intersecting the primary piles to form a continuous barrier wall.

Center Hill Dam, USA

Layout and section of the walls

5Rehabilitation and Upgrade Dams

A part of the barrier wall towards the left abutment is executed as a secant pile wall with bored piles partly cased into rock. These piles are also con-structed with the BAUER BG 50 rig.All of the elements are installed with very tight tolerances; verticality is required to be within 0.25 % – to a maximum deviation of 0.25 m at 100 m depth.Working with the hydrocutter in the clay-silty embankment an extremely complex slurry treatment plant and a downstream water treatment plant are required to protect the environment including the Caney Fork River. The treatment plants are constantly com-puter-aided and monitored to ensure protection of the ecosystem and the area at the project.

The construction process, the qualitycontrol and the verifi cation of the works is provided in real-time with monitoring data being available on-line via a visualization software likeWallTracker™. The client’s quality in-spectors as well as Bauer Quality Con-trol Management are equipped with a tablet computer providing data while walking the site ensuring verifi cation

of the works being carried out as spe-cifi ed. To ensure safety on the work site, a rigorous HSE system is imple-mented on the project to safeguard all personnel and the installation during the execution of the works.Bauer with the experience of working on impounded dams for decades ensures high quality work and dam safety throughout the project.

6 Rehabilitation and Upgrade Dams

Sylvenstein Dam, GermanyIn the course of 2012 – within a

construction period of eight months from spring to autumn – BAUER

Spezialtiefbau GmbH installed a dia-phragm wall with a depth of 70 m and a thickness of 1 m. The installation of the concrete cut-off wall was the fi rst step in a three-phase measure to retrofi t the dam. The client, Bayeri-sches Staatsministerium für Umwelt und Gesundheit (Bavarian Ministry for the Environment), was represented by the Water Management Offi ce Weil-heim which had the responsibility for the execution. The Sylvenstein Dam, built between 1954 and 1959, has now been reinforced by the cut-off wall and further with a state-of-the-art reporting and controlling system for leakage water after having run for more than 50 years. Originally, the main task of the dam was to correct the low water level of the Isar, mean-while the focus has turned on mitiga-ting strong fl oods.

Bernhard Lederer, Bauoberrat (Respon-sible Authority) from the Bayerisches

Staatsministerium für Umwelt und Gesundheit (Bavarian Ministry for the

Environment)

“Following the successful completion

of Bauer´s part of the project, we would

like to express our perfect satisfaction

with the means and methods in which

Bauer has performed on the project.”

lamellas embedded in rock approximately0.3 m

Thus, the rehabilitation was also a precaution against the follow-up of possible climate changes and has proven during the fl oods of 2013 to be a major key to preventing fl ooding in Bad Tölz and Greater Munich. Syl-venstein Dam being 42 m of height and 180 m of length is based on a 100 m deep erosion trench in the main dolomite fi lled with detrital of the river.

This trench was sealed by several rows of injection grouting using clay-cement during the construction of the dam. The slim central sealing core consists of a soil-concrete (gravel, fi ne sand, silt with bentonite) with up and downstream fi lters of moraine gravel. Now, a two-phase diaphragm wall was installed as new sealing ele-ment. Its position in the core is shifted slightly downstream of the dam axis. By executing several investigation drillings up to a depth of 140 m into the dam subsoil it was determined how deep the diaphragm wall had to be. The diaphragm wall had to reach a depth of up to approximately 70 m below the dam crest (suffusion sta-bility) as there are alternating layers of gravel and rock sediments and the highly varying permeability of the old underground sealing. Starting from the 180 m long dam crest Bauer Spezial-tiefbau installed the concrete cut-off wall having a total area of 10,000 m². Preparation works were executed with a grab in the upper part of the trench. Then, the diaphragm wall was installed, deploying a BAUER trench cutter BC 40 with a base carrier MC 128, up to a depth of 70 m also embedding the wall laterally into very hard rock.

B13 to Lenggries B307 to Tegernsee

7Rehabilitation and Upgrade Dams

Hinze Dam Upgrade, AustraliaThe Hinze Dam is located on the

Nerang River, 15 km south-west of Nerang in South East Queens-

land and provides the major part of the Gold Coast region’s water supply. The Hinze Dam was built in 1975 and raised in 1985 up to a level of 93.5 m. During stage 3 the dam was raised once again, this time by 15 m to 108 m,thus doubling water capacity and signifi cantly elevating fl ood storage capacity. The project also provides greater fl ood mitigation for properties downstream of the dam and adjusts the structures to current dam safety de-sign guidelines and standards. During the design stage of the Hinze Dam upgrade the permeability of the dam and the foundation were evaluated. It was found that the increased water pressure would have an impact on the right abutment, due to the presence of highly permeable chert and greenstone with a discrete series of defects as well as continuous defects in geolo-gical contact zones. This unfavorable geological formation infl uences the seepage through the structure, which

causes increased leakage through the foundation, internal erosion and pi-ping. The client’s design team, which was supported by Bauer, concluded that only a plastic concrete wall which stops seepage through the hard rock strata (UCS up to 150 MPa) would meet all the requirements, providing a reliable and sustainable seepage bar-rier. The cut-off wall of 220 m length, a depth of more than 50 m and a thick-ness of 0.8 m constructed by Bauer begins within the existing saddle dam, extends through the section of the central core and fi nally reaches into a 5,000 m² hard bedrock area below the core where seepage is being decreased to a minimum.

Peter Kinsella, Construction Manager from Thiess Pty Ltd

“I congratulate you and your team on

the completion of a successful and

very professionally run project.”

8 New Dams

Peribonka Hydroelectric Development, Canada

The Peribonka dam is located in the heart of the province of Qué-bec, Canada. The project involves

the construction of a main earth dam across a main and secondary valley, two main dykes and a hydroelectric generating Run-Of-River station with an estimated capacity of 385 mega-watts.Under the main dam body, the con-struction of an exceptionally deep cut-off wall was required, to create a seepage barrier in highly permeable riverbed alluvia.Bauer was awarded the contract on the basis of an alternative design: the plastic concrete cut-off wall to be completely embedded in the bedrock, a design which avoided any potenti-ally hazardous areas to be sealed by cement grouting.The cut-off wall was exceptional by its depth, reaching almost 116 m, and being surrounded by complex geo-technical ground conditions.Bauer commissioned a hydraulic cutter, the CBS CBC 135, the biggest ever manufactured, which included new features and was designed spe-cifi cally for the construction of the Peribonka dam cut-off wall. Beside the extreme depth of the bed rock, the design was further complicated by the presence of hard rock including gra-nite, with strengths at times in excess of 200 MPa, quasi vertical rock cliffs, rock overhangs, and gullies fi lled with coarse alluvia, including boulders.

Fill/moraine

Boulder layers

Alluvium without bouldersRock

9New Dams

In addition to the cut-off wall con-struction Bauer provided a complete construction package comprising soil improvement of alluvium and man-made fi ll material by vibro densifi cation down to depths of 48 m – rock con-solidation and contact grouting as well as construction of a grout curtain to depths of up to 150 m by drilling and grouting, and the installation of permanent and temporary dewatering systems.The plastic cut-off wall constructed in Peribonka has shown that this tech-nique provides solutions for dams in ground conditions which are beyond the limits of other techniques such as cement grouted cut-offs.

Richard Boudreau, Principal Director from Production Projects,

Hydro-Québec Equipment and SEBJ

“It means a lot to me to say thank

you to the teams of Hydro-Québec,

SNC Lavalin and Bauer. Because

of the fusion of their energy, know-

how and skills the works were com-

pleted in excellent quality within the

given time frame. After completion

of this successful phase now, we

can begin with the construction of

the dam so that the fi lling of the

basin can be started as planned in

autumn 2007.

Congratulations!”

10 New Dams

Punatsangchhu-I Dam, BhutanThe Punatsangchhu-I Hydroelectric

Powerplant project is located in the Southern Himalayas, about

80 km east of Bhutan’s capital Thim-phu. The new dam reaches across the Punatsangchhu River, delimited by steep hills on both sides. For the excavation of the pit for the main dam construction, two temporary cofferdams were required upstream and downstream of the pit across the Punatsangchhu River bed, to seal off ground and river water ingress. The V-shaped river gorge is fi lled with he-terogeneous river deposits, predomi-nantly consisting of highly permeable sand-gravel packages, intercalated by cohesive layers. Boulders in sizes up to few meters also frequently occur. Bedrock reaches from exposed sur-face down to as deep as 93 m below actual working platform elevation, with a UCS strength of occasionally more than 100 MPa. These highly permea-ble non-cohesive soil layers needed to be sealed for the purpose of creating a seepage barrier underneath the upstream cofferdam. After evaluation of different sealing methods, a two-phase cutter excavated cut-off wall (COW) was selected as the most appropriate and reliable methodology for the construction of the sealing ele-ment. Pretreatment works were carried out by means of gravity grouting and tube-à-manchette grouting, to tempora-rily seal the open void soil layers and to fi x boulders and big cobbles, thus mitigating the risk of localised collapses of excavated COW trenches, and to mi-nimize material overconsumption. Pre-treatment reached down to as deep as 96 m below working platform. The cut-off wall was constructed using one BAUER DHG-C hydraulic grab, and two BAUER BC 40 trench cutter units.

The nominal width of the COW is 1.2 m with panel length of 2.8 m and depth down to a maximum of 93 m, always embedding a minimum of 0.6 m into the solid bedrock. The biggest challenges hereby were cut-ting through the numerous boulders, and the embedment of the COW into the steeply inclined, partially vertically dipping bedrock contour. Amongst the technical challenges for con-structing a COW under such diffi cult geotechnical conditions, the site logi-stics were one of the most signifi cant issues: All machineries, equipment and tools had to be shipped to Kolkata/India, and then by road to the site, over narrow mountainous roads into a quite remote area. Despite all the challenges, Bauer managed to com-plete the project on time and to the full satisfaction of the client.

V. Mahadevan, Project Manager from Larsen & Toubro Limited

The project has been completed

“as per subcontract agreement with

good safety and quality standards.”

11New Dams

New Assiut Barrage, EgyptThe Assiut Barrage is a damming

structure across the river Nile in the vicinity of the city of Assiut in

Upper Egypt (400 km south of Cairo). The Assiut Barrage was constructed between 1898 and 1903 across the Nile, about 560 km downstream of the Aswan Dam. Its purpose was to divert the river fl ow during low water levels into Egypt‘s largest irrigation canal, the Ibrahimiya Canal.

Along with the old Aswan Dam, the Assiut Barrage today remains in ser-vice as the oldest barrier on the Nile in Upper Egypt. Naga Hammadi (with the contribution of Bauer) and Isna Dams were already replaced with new dam structures in the 1990s. Between 2000 and 2005, the Egyptian government commissioned an extended feasibility study fi nanced by the German govern-ment to investigate the options of re-habilitation or upgrade of the existing Assiut Dam and the Ibrahimiya Canal. The study evaluated the practicality of rehabilitation in comparison to a replacement with a new hydropower barrier. German consultants fi nanced by the Kreditanstalt für Wiederaufbau (KfW) conducted the study and con-cluded that a new barrier with power generating capabilities would be the most economic solution. This new retaining structure would provide an increase in the allowed pool levels, permitting more water to discharge into the Ibrahimiya Canal and improve navigation conditions. The new barrage will also include a low head hydro-power plant.Based on the results of the feasibility study the decision was made to pro-ceed with the project of constructing a new dam structure approximately200-300 m downstream of the existing

Permanent cut-off wallTemporary slurry wall

Sheet pile wallDiaphragm wall

0.8 m to create a cut-off under the fu-ture barrage. In addition to these cut-off wall works for the dam, Bauer also installed 18,000 m² foundation barrettes with 0.8 m thickness and depths up to 23 m to allow a construction of the barrage piers with low settlement.

dam. The main works for the project were awarded to the Egyptian – French New Assiut Barrage Joint Venture which consisted of the three interna-tional companies Vinci, Arab Contractor and Orascom. Due to the vast experi-ence in both, cut-off wall construction and previous dam projects on the Nile, Bauer was awarded the sub-contract for specialist foundation engineering works, comprising of different work packages ranging from cut-off walls for temporary purposes to the con-struction of dewatering wells, as well as the foundation barrettes and per-manent cut-off wall works. The spe-cialist foundation engineering works were designed by the German design company Lahmayer International with strong input from Bauer on the design properties of the cut-off wall and the cut-off wall material. In a fi rst step Bauer constructed 60,000 m² of tem-porary single-phase cut-off wall for the ring dam with 38.2 m in depth and 0.8 m thickness, using state-of-the-art BC 40 cutter equipment. Within the dry excavation pit of the temporary ring dam Bauer then constructed about 12,000 m² of permanent double-phase cut-off wall with varying depths be-tween 20 and 30 m and a thickness of

12 Competences

Construction Methods

Secant Pile Wall – Concrete

Hybrid Wall – Concrete

These types of concrete cut-off walls are executed by drilling rigs and hydro cutter – primary elements are bored piles with large diameter whereas secondaries are relatively slim rec-tangular elements. Put together these elements form a continuous wall still

limiting the number of joints compared to the secant pile wall. Wall depths reached are up to 100 m with special high precision pile installation. Execu-tion of the individual element type will take place as explained above.

The classical type of positive cut-off wall for deep barriers in all types of geology is excavated by grab and hy-dro cutter to reach depths of 150 m and more and is embedded in bed rock as designed. The walls are constructed using primary and secondary elements with element length depending on

safety, trench stability of the slurry supported excavations and given geo-logy. The continuous walls are formed by overcut of primaries while construc-ting the secondary elements. The limited number of joints are serrated and cleaned as required for optimum interlocking.

Diaphragm Wall – Concrete

Grout Curtains – Grout

Grout curtains are intended to reduce the seepage through discontinuities in the foundation rock (ICOLD Bulle-tin 119–2000). Different techniques of grouting are provided and chosen by experienced engineers to provide

seepage mitigation in the foundation. Whether jet grouting or permeation low pressure grouting is used depends on a number of factors to be discussed for the individual project based on speci-fi ed tasks and the existent geology.

Mixed-in-Place (MIP) Wall – Cement-Bentonite

Positive cut-off walls constructed by overlapping/interlocking circular primary and secondary elements are being executed by drilling rigs. The open boreholes are supported by either special segmental steel casings or by slurry. The number of joints is to

be considered for these generally eco-nomical types of walls. The relatively small size of equipment is predestined for smaller working platforms. The continuous walls are being installed in all types of geology including embed-ment into rock.

Mixed-in-Place (MIP) walls are formed by mixing the existent soils with ce-ment or cement-bentonite slurry to form a durable continuous cut-off wall. Available techniques are triple-auger Mixed-in-Place and Cutter-Soil-Mixing. Depths reached by these techniques depend on the base carrier

size and range between 20 m to 30 m. Execution sequence with primary elements and overcutting secondary elements are typical and similar to diaphragm wall. The very economic Mixed-in-Place walls are typically used to improve existing levees and dykes.

13Competences

New Dams - Greenfi eld Projects

Bauer cut-off walls provide new op-portunities for investors and designersinvolved in Water Resource Develop-ment projects. When planning a newWater Resource Development project,one of the major obstacles is fi nding alocation with suitable geological andhydrological formations for the projectwhich also has appropriate environ-mental and social aspects. Bauer cut-off walls can be installed in any type of ground condition to provide a reliable, durable and impermeable (approxi-mately 1x10-8 m/sec.) system which ensures effi ciency, durability, stability and safety for your project. Thus, the Bauer cut-off wall makes selection of the project site that bit easier. Bauercut-off walls convert the existing ground conditions to meet your design requirements, at a location of your choice. The ability to install the walls in remote areas enables you to meet the environmental and social require-ments of dams.

Design and ConstructionStage 1

temporary diversiontemporary diversion

new dam

new dam

foundation treatment if required

proposed permanentcut-off wall

proposedcut-off wall

proposedcut-off wall

permanentcut-off wall

if required if required

Design and ConstructionStage 1

Cut-off wall in operationStage 2

Excavation in operationStage 2

Cofferdams for New Embankment Dam founded on alluvium

Cofferdams for excavation pits for New Concrete Dam founded on rock

Existing Dams - Upgrade, Rehabilitation and Repair Projects

Upgrade Design and ConstructionStage 1

Rehabilitation Design and ConstructionStage 1

Upgrade in operation“Increased dam safety and storage capacity”

Stage 2

Rehabilitation in operation“Increased dam safety and storage capacity”

Stage 2

Upgrade of Existing Dam(heightening)

Mitigate Seepages bydurable Concrete Barriers

As part of dam safety programme, dam owners, municipal and state au-thorities and private parties conduct regular reviews of all their dams. Al-though the condition of a dam has not changed since it was built, reviews of the purpose or the design identify a need for upgrades to increase capacity or to enhance life span and dam safety which may be compromised due to hydraulic conditions or during major earthquakes.

Other existing barrier systems, forexample those constructed with con-ventional grouting methods, often failto meet the degree of effi ciency anddurability, as well as other performance specifi cations over the life of the struc-ture as required by the design.

temporarycofferdam

temporarycofferdam

temporarycofferdam temporary

cofferdam

upstream

downstream

temporarycofferdam

temporarycofferdam

proposed permanentcut-off wall

proposed permanentcut-off wall

permanentcut-off wall

permanentcut-off wall

14 Competences

Cutter and Grab

Bauer rotary drilling rigs on large dams are used to construct a secant pile wall or – in combination with dia-phragm wall elements – a hybrid wall. The BG drilling rigs like BG 28 or BG 40 are ideally suited for drilling cased or slurry-supported boreholes

with the kelly-system and special drilling tools as demanded by the in-dividual geology on the project. The segmental steel casings for cased boreholes are installed by rotary drive or optionally by hydraulic oscillator powered by the drilling rig.

Rotary Drilling Rig

Bauer trench cutters and Bauer hy-draulic grabs are typically the lead equipment for the panel excavation for the execution of concrete cut-off walls.The centrepiece of the Bauer trench cutter system consists of a steel frame with two gearboxes attached at its base, which rotate in opposite direc-tion around a horizontal axis. Cutter wheels suitable for the pre-vailing ground conditions are mounted on the gearboxes. Selecting the most suitable type of cutter wheels (standard cutter wheel, round shank chisel-cutter wheel or roller bit-cutter wheel) is essential for cutter progress which mainly depends on the soil conditions (particle size, density, abrasiveness, compressive strength, etc.). The ac-curate determination on the trench cutter for your project depends on ground conditions, the required trench width and wall depth. The ideal base machines for Bauer trench cutter and mechanical or hydraulic grab equip-ment are BAUER foundation cranes MC 64, MC 96 and MC 128. The entire hydraulic power supply of the attached cutter/hydraulic grab is provided by the hydraulic systems of the MC craw-ler cranes which have been specially designed for those applications.

Equipment and Techniques

15Competences

The open trenches of diaphragm wall elements are supported by slurry. Du-ring the preparation of bentonite slurry, the bentonite powder has to be mixed intensively with water. This can be achieved by pump mixers or colloidal mixers of the SCW/SK-series. Single-phase slurry mixes for cut-off walls consisting of multiple components, such as rock powder, cement, bento-nite and water, are produced by Bauer mixers as well.Bauer desanding plants are developed specifi cally for the use with trench cut-ters to separate the cuttings from the slurry used to support the open trench and to transport the cuttings. The plants are characterized by the following features: modular construc-tion throughout the entire plant unit and, therefore, the ability to match treatment capacity to soil type and cutter output capacity. Advantages: secondary circulation with desilter or centrifuge possible, short setting up and dismantling times and containerized transport dimensions.

Small Diameter Drilling Rig

Mixed-in-Place

Bauer Mixed-in-Place (MIP) is devel-oped specifi cally for use in the overbur-den (granular, slightly cohesive soils). The entire hydraulic power for the rota-ry drives of the attached triple augers is provided by the hydraulic system of the base carrier which have been spe-cially modifi ed for those applications. Base carriers like BAUER RG 18, RG 22,RG 25 or BG 40 are chosen as per the fi nal depth to be reached.

Mixing and Desanding Unit

The main equipment for the drilling & grouting method on large dams are the Bauer hydraulic drilling rigs of the KLEMM KR 800-series. These modern and extremely compact rigs are parti-cularly suitable for the different drilling applications:

• Rotary-, • Rotary drilling with down-the-hole hammer, • Rotary percussion-, • Overburden-, • Double head drilling rotary/rotary and

• Double head drilling rotary/rotary percussion

The drilling rigs will be fi tted with hydraulic drifters of the Eurodrill HD-series, with different types of drill rods and drill tools to suit the geology and depth required for the individual project. After state-of-the-art controls over borehole deviation the grouting process will be executed. The accu-rate determination on grouting equip-ment (pump-type, mixer, packer type, etc.) depends on soil conditions and the required grouting material.

16 Competences

Bauer Spezialtiefbau supports the designer in different stages of project development regarding

relevant foundation engineering tech-niques. State-of-the-art foundation

engineering methods together with re-liable software is used by experienced in-house designers to support clients and their engineers during preliminary stages and for the execution design.

To carry out special foundation works, complete designs with all details are needed to ensure safe and smooth execution. Not only specifi c design calculations such as trench stability designs are provided, but also com-plete geotechnical project designs to

establish the execution parameters of the various foundation engineering techniques in accordance with the client’s requirements. For dam rehabi-litation projects the safety of the exist-ing structure is considered to be of utmost importance for such designs.

Execution and Final Design

In addition to the standard design calculations such as the stability of the open trench during construction of a cut-off wall or slope stability con-

sidering the working loads during the execution of works on existing dams, special tasks are also performed re-gularly.

Computation

Accuracy of workmanship and the verifi cation of the special foundation works executed are vital to us. The as-built survey of each structural ele-ment is documented to be transferred into a structural as-built drawing as per project requirements. By entering all the measurement data into an illustrative quality system the ex-act properties

and alignments of the diaphragm wall and the achievement of the minimum panel overlap can be con-fi rmed – refer to fi gure below.

Documentation

An actual example of such a task is the Sylvenstein Dam project (page 6) – where a trench was cut next to a re-cently completed panel. The required initial concrete strength in the panel was analyzed using the 3D-FEM tool PLAXIS. Both Fellenius‘ Method and the computed settlements method were used to assess the safety level of the system – refer to fi gures.

3D model of open trench, contour plot of total displacement

Model in plan view, contour plot of settlements

As-built drawing of a completed cut-off wall

Primary panelSecondary panel

Design

17Competences

Concrete

Bauer Concrete Competency has been established and has been constantly progressing due to:

• In-house scientifi c research sup-

ported through academic coope-ration with partner universities, in-vestigating and assessing materials’ infl uence on the installation process and their infl uence on the fi nal, in-tegral quality of the wall or pile.

• Cooperating in Standardization

BAUER Spezialtiefbau GmbH co-operates worldwide with various or-ganisations to specify standards and regulations. Amongst others we par-ticipate in the following groups: We

are a member of the concrete task group, which was established by TC 288 (= the Technical Committee of CEN in charge of European Stan-dards for Execution of special geo-technical works, Diaphragm Walls). We are also a member of the tremie concrete task group of the Concrete Institute of Australia (which com-piled the “Guideline on Tremie Con-crete for Deep Foundations” pub-lished in 2012). Furthermore, we act as chairman of the Concrete Task Group of the EFFC, the European Foundation Contractors, established in January 2014. Its aim is to adjust the composition, placement and quality control of concrete to latest developments and to introduce the results to the European and interna-tional market.

• Consulting in operational works, hence giving project-specifi c advice in concrete design, raw materials and concrete testing as well as quality assessment, in all construction phases from planning, calculating or fi nally executing the dam rehabilitation project.

Bauer aims to support own projects in all matters and steps of materials’ use for deep foundation works. Regarding concrete for dam rehabilitation princi-pal demands have to be specifi ed in order to proof both suffi cient fresh and hardened concrete properties:

• Permeability and erodibility, both must, within defi ned ranges,

ensure the demanded serviceabili-ty of the wall.

• According to Bauer’s experiences gathered in own research, stan-dards and consulting works the concrete, prior to its application in a project, must be properly de-signed, specifi cally tested and opti-mized. For placing concrete in deep excavations, the fresh concrete

behavior must be understood and required properties must conse-quently be controlled throughout

the concreting process.

• It is Bauer’s experience that the

cut-off wall construction safety, in terms of its function as a water barrier, should not be based on

the ultimate limit state thus on the strength of the plastic concrete used but on its deformation capa-

city, as it is a common practice for the service limit state.

18 Responsibility

Quality Management

Construction Quality Control (CQC)

System Commitment

Bauer is committed to deliver high quality products for all our projects.For each project we implement a project specifi c Construction Quality Control (CQC) System which aims to ensure a consistent, high quality standard of workmanship throughout all phases of the works. Our CQC Sys-tem intended to control and verify the works executed, is based on, amongst others, the following core fundamental quality principles:

• Ensuring the highest quality of works by establishing, monitoring, maintaining and updating quality control procedures. This is achieved by providing written instructions to govern quality control procedures and practices to clearly establish defi ned responsibilities and autho-rities early in the project to ensure quality compliance;

System

Our quality management system is based on ISO 9001 and the relevant legal and industrial norms. All relevant processes of our company are methodically analyzed and docu-mented. The processes are aimed at increasing the product quality for the continuous improvement process and thus help to improve the customers’ and employees’ satisfaction levels. We use key fi gures to regularly check if the planned quality objectives have been achieved. Deviations are ana-lyzed and rectifi ed in due time.

“Verifi ed Quality is our most successful product.

It is the key to success, today and tomorrow.”

Quality Strategy for Cut-off Walls

• Proper continuity of the entire wall

• Integrity of the cut-off wall concrete material placed

• Proper embedment of the wall into the defi ned strata

Quality Control Areas for Cut-off

Walls

• Trench stability

• Slurry mixing and recycling

• Monitoring of supporting slurry

• Monitoring abnormalities, soil conditions and wear & tear

• Panel verticality and overcut verifi cation

• As-built visualization

• Proper concrete mix design with quality products

• Concrete batching and testing

• Production analysis

• In-time documentation

• Compile accurate records of test results, certifi cations and other required documentation which con-form to the project specifi c contrac-tual requirements and standards;

• Notifying the client‘s representative of defi ciencies in quality and pro-posed corrective action, and ensuring that agreed corrective action is pro-perly implemented;

• Providing qualifi ed individuals who will be responsible for the manage-ment and implementation of an agreed CQC program; and

• Providing high quality workman-ship and project administration by implementing agreed transparent documentation procedures.

Quality is the basis for the BAUER Group’s worldwide success and there-fore it is part of the key-focuses of the company. The confi dence in the quality of our products, services and equipment gained throughout many years will be preserved and expanded to its optimum.

19Responsibility

HSE Management System

The required Health, Safety andEnvironmental performance is achieved through the:

• BAUER AG Health, Safety and Environmental Management state-ment and guidelines

• Bauer Spezialtiefbau HSE System

• National and international stan-dards and guidelines

Compliance with the HSE policy, system and standards are mandatory and subject to periodic audit. In part-nership projects, Bauer Spezialtiefbau subsidiaries are required to encourage the partner to work to Bauer HSE standards and to implement an appro-priate HSE management system that will achieve the following goals:

• Reduced work-related accidents and illness

The Bauer Spezialtiefbau HSE Ma-nagement System allows for a com-mon approach to be adopted across all businesses. The key elements are outlined below and are supported by the fundamental requirement:

• Leadership • Commitment• Involvement

• Reduced costs associated with accidents and illness

• Improved performance through policies and procedures

• Compliance to the latest legislation

• Reduced risk of citations/penalties

• Improved company image by de-monstrating a commitment to man-age and minimize risks to employees, stakeholders and customers

BAUER Spezialtiefbau GmbHBAUER - Strasse 186529 Schrobenhausen, GermanyTel.: + 49 8252 97- 0Fax: + 49 8252 97-1496BST@bauer.dewww.bauer.de

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http://www.bauerdamrehabilitation.com

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