Total concrete placement in the TGP construction amounts to 28¡Á10 6 m3 , its quality requirement is strict, and the construction is difficult. Advanced equipment and fast concrete placement technology were applied to ensure the quality and the timetable. Concrete placement on the TGP dam started in 1998, and for the three successive years from 1999 to 2001, annual concrete placement amounted to more than 4 ¡Á10 6 m3 ; the total of the three years added up to 14.09¡Á10 6 m3 ; in 2000 new world records were created as follows: annual concrete placement of 5.48¡Á10 6 m3 , monthly concrete placement of 553500 m3 , and daily concrete placement of 22000 m3 . The reason why the concrete placement for TGP dam was conducted at such a high speed and intensity lies in the following five aspects of technology breakthroughs.
Joint Construction Technology Based on Hi-tower Flatliners
In order to ensure high quality and high intensity placement, TGP constructors abandoned traditional concepts, and optimized the allocation of resources, and selected the construction scheme of application of Hi-tower Flatliners as the main equipment and subordinate application of gantry cranes, belt cranes, and cable cranes as auxiliaries. The traditional bucket placement was changed into continuous concrete production technology. The belt conveyor sent concrete from the batching plant to hi-tower Flatliner and then directly to the placement area, combining both horizontal and vertical transportation. At the same time, five concrete batching systems were equipped to produce 2500 m3 concrete on hourly basis.
A Whole System of Technology and Management for Fast Pouring
By fully implementing concrete placement technology design, a computerized supervision and control system for concrete production, conveying and pouring was developed to realize real-time monitoring, dynamic adjustment, and optimal dispatch for the whole process of concrete construction. Meantime, computer simulation system for concrete construction was developed to address the complicated situation of concrete placement.
Raw Materials and Gradation Optimization of Concrete
By applying high-quality efficient water-reducing agent which was mixed with Grade I fly ash, water consumption for Gradation IV concrete, which was made with artificial granite aggregate, was cut from 110 kg/m 3 to about 90 kg/m3 . The approach of lower water-cement ratio and more fly ash content helped to more effectively upgrade the durability of concrete. Mid-heat dam cement 525#, which features compensation for contraction, was applied to reduce contraction and deformation of concrete and to eliminate the risk of cracks developing in the concrete.
Secondary Air Cooling Technology
With repeated tests to address the TGP characteristics and the pre-cooling requirement of concrete, secondary air cooling of aggregates were applied for the first time. The new point is to replace conventional water cooling of the ground aggregates with air cooling. Cold air closed circulating system, including the efficient cooling fan and the corresponding air feeding and distributing equipment, helps to cool down aggregate continuously.
Overall Temperature Control of the Concrete
On the basis of extensively analyzing present temperature control measures taken in the projects home and abroad, overall temperature control technology for whole process was implemented for the first time in an all-around way and at high standard and large capacity. The temperature control measures includes selecting good-quality raw materials, optimizing concrete gradation, controlling concrete exit temperature and pouring temperature, cooling with running water, surface temperature keeping, and curing with running water, and etc. Especially in summer, high-tower flatliner helps to place concrete in constraint areas of the concrete dam at high speed and intensity, which is the first practice of this kind in the world.
6252 monitoring devices of various kinds embedded in every corner of the dam indicate that deformation of the dam foundation is less than 1mm, foundation seepage is only 1/10 of the design value, and horizontal shift and stress are within the design scope, completely meeting the design requirement. The quality of the dam is excellent.
River Close-off and Cofferdam in Deep Water 
