SUPERENGINEERING

Qixiang FAN

Technology improvements and management innovations inconstruction of Xiluodu hydropower station on Jinsha River

© The Author (s) 2017. Published by Higher Education Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0)

Keywords super-high arch dam, intelligent construction,mass concrete temperature control, structure behaviorcontrol, anti-erosion concrete, low-heat portland cement,large-discharge and high-velocity spillway tunnels, largescale underground powerhouse, green hydropower station,sustainable development, Xiluodu hydropower station

Developer and owner: China Three Gorges Corporation(CTG)Engineering management: China Three Gorges ProjectsDevelopment Corporation (CTGPC)Designer: Chengdu Engineering Corporation Co., Ltd.,Power ChinaConstruction contractors: Sinohydro Bureau 8 Co., Ltd.,

China Gezhouba Group Co., Ltd., Sinohydro Bureau 14Co., Ltd., Sinohydro Bureau 7 Co., Ltd., CAPF Hydro-power Force No. 6 Detachment etc.Supervisor: Yangtze Three Gorges Technology &

Economy Development Co., Ltd., Sichuan Ertan Interna-tional Engineering Consulting Co., Ltd., China WaterConservancy and Hydropower Engineering ConsultingMid-south Co. Ltd etc.The Jinsha River is located in the upper stretches of the

Yangtze River, and it contains a segment with abundanthydropower resources. The hydropower reserve in thisstretch is as high as 1.12�108 kW, which is the highestamong the thirteen planned hydropower bases in China.From Panzhihua to Yibin on the downstream of the JinshaRiver, four giant hydropower stations have been planned.This includes, from upstream to downstream, Wudongde,Baihetan, Xiluodu and Xiangjiaba stations. The totalinstalled capacity is 46,460 MW, equivalent to two ThreeGorges projects. China Three Gorges Corporation isdeveloping and constructing these projects. The Xiluoduhydropower station is the backbone of the West-East

Electricity Transmission Project in China, which focuseson power generation with complimentary benefits such asflood control and navigation improvement. The Xiluodustation has a total installed capacity of 13,860 MW. Thisstation ranks third in the world, following Three Gorgeshydropower station and the Itaipu hydropower stationamong all constructed hydropower stations. The reservoirof Xiluodu station has a flood control capacity of 46.5�108

m3 and is an important part of the Yangtze River basinflood control system. Preparation for the constructionstarted in August 2003, construction initiated in December2005, and river closure in November 2007. Waterimpoundment began in May, 2013 and the first batch ofpower generating units were commissioned in July 2013 asscheduled. Strictly following the reservoir dispatchingregulations, Xiluodu station has been operating safely andstably ever since. Xiluodu project has received multipleawards both in China and across the world, such as the“FIDIC 2016 Outstanding Project”.The Xiluodu project consists of three main elements,

which include the dam, water discharging structure, andpower generation system. The dam is a concrete doublecurvature arch dam, with an elegantly curved transversesection and longitudinal section and a maximum damheight of 285.5 m. The water discharging section consistsof seven crest outlets and eight bottom outlets in the dam,with a plunge pool and a secondary concrete gravity dambehind the arch dam, and two spillway tunnels in themountain on each bank. The maximum flood dischargeflow is 48,926 m3/s; 32,278 m3/s from the dam and 16,648m3/s from spillway tunnels respectively. These threeindices rank first among all arch dams around the world.The power generation system is built in the mountainssurrounding the river. Each generator is connected withone headrace tunnel. The underground cavern group comeswith a compact layout, consisting of the main power houseand main transformer chamber, the tailgate shaft, the tailsurge shaft. Every two generators are connected with onetailrace tunnel. In an area of less than 1 km2, there arealmost one hundred interconnected chambers and tunnels;

Qixiang FAN (✉)China Three Gorges Corporation, Beijing 100038, ChinaE-mail: fan_qixiang@ctg.com.cn

Front. Eng. Manag. 2017, 4(2): 231–237DOI 10.15302/J-FEM-2017103

that forms an underground labyrinth. The main powerhouses on both banks are 31.9 m wide, 75.6 m high, and439.7 m long and each power house is installed with9 turbine generator units with an installed capacity of 770MW each, making it the largest underground chambergroup in the world. Xiluodu station sits at one valley in themountainous southwest area of China and is a part ofHengduanshan Mountain with developed tectonic struc-ture, intense erosion and complicated geological andseismic conditions. Therefore, Xiluodu project features ahigh arch dam, high side slopes, high flow velocity, highearthquake intensity as well as large flood dischargingflow, large single unit capacity and a large undergroundchamber group. Multiple groundbreaking technologieshave been developed during the project construction.Xiluodu is also the most challenging hydropower projectafter Three Gorges Project in China in terms of the scaleand technological difficulties.The Xiluodu dam is a 300 m super-high arch dam. The

central arc length at the top of the dam is 681.51 m; thethicknesses of the top and foundation of the dam are 14 mand 60 m, respectively; the thickness-height ratio is 0.21;the total concrete volume is approximately 670�104 m3.Compared with a gravity dam, the arch dam has a smallerdimension and thinner dam body, is safer and moreeconomically viable, and has a more complex stresscondition and structure. The Xiluodu arch dam has anoverall hydraulic thrust of 1,400�104 t. To divert waterafter the closure of the diversion tunnels and for permanentdischarging, 25 orifices are placed in four layers in thedam. These orifices further complicate the structure.Considering the interlayer staggered zone at the basalticriverbed dam foundation, the dam foundation structure is

expanded. The dam’s concrete coarse aggregate isexcavated basalt, which requires strict temperature controlto prevent cracking. It is a challenge to coordinate suchmulti-work, multi-procedure and multi-objective construc-tion and even more difficult to ensure the quality. To ensurethe lifecycle safety of dam, key intelligent constructiontechnologies are developed and applied to tackle technicalchallenges such as dam foundation consolidation treat-ment, concrete temperature control and dam structurebehavior safety control during construction. Such technol-ogy development are under the guidance of close-loopcontrol theory featuring all-around sensing, fact-basedanalysis and real-time controlling.The project team overcame multiple key technical

challenges, including precise blasting, digital grouting,intelligent concrete placing and intelligent water coolingthrough the development of corresponding control systemsand equipment. In addition, the project team performedmulti-factor coupling simulation analysis of constructionprogress and actual operation behavior. More particularly,a structure behavior safety control strategy is proposed toprovide a precise forecast, instant feedback and real-timecontrolling during the construction cycle of the dam. Aninclusive Dam Information Model (DIM) for the lifecyclewas set up. A collaboration digital management platform(iDam) of multiple works to bring together all parties wasalso developed. Study and application of these keyintelligent construction technologies transforms the archdam construction from a conventional management modelto an intelligent one, which guaranteed the integrity,balance, continuity and uniformity of the dam construc-tion, and opens an intelligent era in China’s hydropowerstation construction practice.

232 Front. Eng. Manag. 2017, 4(2): 231–237

The Xiluodu hydropower station is located in a dry andhot valley. The dam concrete has inferior anti-crackperformance because of the basalt coarse aggregate. Thisissue, along with the unique structure and shape of thedam, as well as the construction environments, creates asignificant challenge to dam concrete temperature andcracking control. The Xiluodu hydropower station is thefirst project to develop and apply an intelligent watercooling system, a whole set of control equipment andsimulation software. The project team implementedtemperature sensing and real-time data transmission viawireless digital thermometers and optical fiber. Through anintegrated water cooling flow and temperature controllingequipment, the concrete peak temperature, temperaturedrop rates and abnormal temperature can be pre-warnedand controlled, to ensure that the concrete temperaturestress is under control, especially at specific blocks of damand during environment temperature abrupt drop or thechange of seasons. With intelligent temperature control,real-time online customized temperature control is rea-lized. Early cooling, slow cooling and smaller temperaturedifference between cooling water and concrete becamerealistic. In this way, the continuity, evenness and accuracyare ensured, both for the concrete temperature control in

three phases with nine sub-sessions, and for the five layersvertical temperature gradient control of the block jointgrouting. This system reduces the cooling water by 25%and the cost of temperature control by a large percentage.This innovation in the construction industry addresses thedifficulties of precise, effective and reliable control of thetemperature process for mass concrete.To address the challenge of temperature control to

prevent cracking in mass concrete and lining concrete, andto solve the anti-erosion difficulty with high velocity waterflow, a comprehensive study on the characteristics of lowheat Portland cement concrete for hydraulic structure isconducted to reveal its performance and evolution features.To meet the requirements of durability, anti-crack, andanti-erosion of hydraulic concrete, based on China’s codefor cement, namely, the mineral composition, chemicalcomposition, specific surface area, heat of hydration andstrength of the low heat Portland cement is refined witheven stricter terms. Based on the composite cementitiousmaterial consisting of low-heat cement, low addition ofganister sand and high addition of fly ash, a construction-friendly concrete with high strength, greater anti-erosion,anti-cracking ability, is developed. This new concretematerial was then successfully applied in the Xiluodu

Qixiang FAN. Xiluodu hydropower station on Jinsha River 233

spillway tunnel in order to solve the problem caused byconcrete that is fragile to cracking and erosion. To fullyleverage the advantages of low heat Portland cement suchas low heat of hydration, gradual temperature rise, high-strength at a later stage and superior durability, thismaterial was first applied to some sections of the Xiluoduarch dam. Moreover a construction technology matchingearly stage strength characteristics of this concrete wasdeveloped. All these methods and materials forms a newapproach proven to be effective for dam temperaturecontrol and crack prevention.The spillway tunnels of Xiluodu hydropower station

have the largest discharge capacity in the world. It has apeak discharge capacity of approximately 16,700 m3/s anda peak flow velocity of 50 m/s. To ensure successfulconstruction and safe operation of the spillway tunnel, keyconstruction technologies regarding spillway tunnel lay-out, aeration facility, construction material, equipmentmanufacturing and process, are studied and applied. Newtechnologies for the high water head and ultra-capacityspillway tunnel are adopted, including the design of a tail-drop tunnel, the technology of all-dimensional crosssection aeration, technology of concrete protection inhigh velocity section and the dissipation technology of ski-jump plus underwater collision. These technologies havesuccessfully solved challenges including spillway tunneldeployment along a straight river course, 50 m/s highspeed water flow cavitation and energy dissipation anderosion control downstream of the dam. A new preparationformula for composite cementitious material has been

developed, featuring low-heat Portland cement, lowaddition of ganister sand and high addition of fly ash. Inthis way, anti-erosion concrete with optimal performancehas been created. A comprehensive technology is devel-oped to build large scale lining concrete that is precise indimension, wear and crack resistant with smooth surface.A complete construction equipment set of conventionalconcrete lining in a large cross section with varyinggradient and multi-curve, is developed. Technology andconstruction procedures are developed to build smooth-surface concrete lining for high-speed water flow, whicheffectively improves the dimension precision and smooth-ness and prevents cavitation failure.In the construction of Xiluodu underground power

house, the project team is facing technical and managerialchallenges because of its large scale, great number ofchambers, large span, high side wall, compact layout andharsh working conditions and high safety risks. To addressthese issues, construction technology and managementexperiences summarized from other large scale under-ground plants in China are fully leveraged. Suchtechnology and experience synthesis generated a range oftechnological breakthroughs including the technology ofoptimized mechanical and natural ventilation combinationin complex chamber group, a series of technologies of aone-step finishing of excavation and supporting of large-scale powerhouse group, and the construction technologyof deep vertical shaft with large cross section in thickoverburden layer without pre-consolidation. The construc-tion of such underground chamber group in complex

234 Front. Eng. Manag. 2017, 4(2): 231–237

tectonic conditions has stringent requirements for safety,quality, environmental protection, energy saving and avery aggressive schedule. The powerhouse is constructedsafely with high quality as scheduled under the guidelineof “understanding, analyzing, utilizing, monitoring andfeedback on surrounding rocks”, and strictly followed theworking procedures of “excavating one layer, reviewingone layer, accepting one layer and forecasting the nextlayers”— the physical and mechanical parameters of thesurrounding rocks are collected, monitored and analyzedthroughout excavation process and are indicators forfollowing excavation and supporting work on a layer bylayer basis. These challenges and engineering processesessentially drive the development of key constructiontechnologies for complex projects. The maximum singleunit capacity of the turbine generator in Xiluodu is 770MW. All are designed and manufactured by Chinesecompanies. Major cast and forged pieces as well as criticalmaterial are also provided by Chinese manufacturers. Theinstallation and testing of units are carried out withintegrated mechanical and electrical working team com-mitted to the first-rate standards, and to guarantee seamlesshandover with joint participation of construction andoperation. In this way, a world record has been created:four turbine generators were put into operation in onemonth, twelve in six months and eighteen in twelvemonths. All generators were commissioned successfully,passed the pilot run and achieved stable operation duringthe first one hundred days without malfunction. This is a

milestone indicating that design, manufacturing, installa-tion capability, testing and operation quality of large scalehydro turbine generator in China has topped the world.To construct a green hydropower station, construction of

the entire Xiluodu project follows a sustainable develop-ment principle, which is people-oriented, eco-friendly andcenters on intensive utilization of resources, environmentalprotection and social harmony. The project team developedvarious ecological protection technologies including dryand hot river valley slope restoration, waste waterrecycling, fish reproduction, release and habitat protection,cascade power station ecological dispatching, mitigation ofaccumulated effect of low temperature water via a layeredstop log water intake. Reproduction and release stations forrare and endemic fish upstream of the Yangtze River areconstructed. The aquatic ecosystem is monitored andevaluated continuously. The project design is optimizedconstantly to reduce the impact of the project on theenvironment. Environmental and water soil conservationmeasures are taken to achieve a harmonious relationshipbetween human and nature.During the project development on Jinsha River, to

promote the overall development of the local communityand the welfare of the resettled migrants while preservingenvironment where we are operation is the philosophyChina Three Gorges Corporation has always been follow-ing. The management goal of zero quality defect and zerosafety incident is followed strictly. By following themanagement requirements of standardized, orderly,

Qixiang FAN. Xiluodu hydropower station on Jinsha River 235

236 Front. Eng. Manag. 2017, 4(2): 231–237

coordinated and healthy project construction, six manage-ment goals including safety, quality, environmentalprotection, schedule, cost and construction area stabilityare achieved through technology development and man-agement innovations to ensure the Xiluodu station abenchmark project in west China with remarkableconstruction achievements, excellent environmental pro-tection, outstanding resettlement and good public security.By the end of 2016, the Xiluodu hydropower station

had been in sound operation for five years whilecomprehensive benefits being delivered in a sustainableway. The project has a cumulative investment of838.63�108 CNY, which includes 12�108 CNY inenvironmental protection. The accumulated powergeneration has exceeded 1800�108 kWh, providing alarge amount of clean energy to Zhejiang and Guangdongand other areas in east China. Its reservoir flood controlcapacity significantly mitigates the flooding threats to

cities including Yibin, Luzhou and Chongqing. This dam,in joint operation with the Three Gorges project,significantly releases the flood control pressure in themiddle and downstream of Yangtze River. Economydevelopment in the reservoir region has been boostedwhile having more than 370 km roads been built in thereservoir region to provide more convenient and safetransportation to the local residents. Thirteen newtowns were built and 60,000 resettled residents’ livingstandards have been improved significantly. Artificialgreen areas in the project region cover 120�104 m2 with42% vegetation coverage, and the project well fits intothe natural landscape where it sits. Rare and endemicfish reproduction and release stations are in operationand more than 120�104 fish fries have been bred andreleased. In brief, eco-friendly operation of this dam isimplemented to ensure that the project is in harmony withenvironment.

Qixiang FAN. Xiluodu hydropower station on Jinsha River 237