Back in 1997, China Railway No.3 Engineering Group Co., Ltd. conducted the preliminary scientific research on ballastless track. After 20 years, its research & development work on ballastless track construction technology has continued uninterruptedly. It has also successively cooperated with such specialized research institutes as China Academy of Railway Science Corporation Limited as well as China Railway Siyuan Survey & Design Group Co., Ltd. to systematically study CRTS I, CRTS II & CRTS III slab ballastless tracks, CRTS I & CRTS II bi-block & long-sleeper-embedded ballastless track construction technologies. It mastered the core technologies & reached the international leading, advanced level for many key technologies including manufacturing equipment & processes, construction equipment & processes, ballastless track engineering measurement, special engineering material preparation & construction technology, making a big difference in the history of constructing ballastless track in China.

Form complete construction technology of CRTS I slab ballastless track. In 1998, China Railway No.3 Engineering Group Co., Ltd. cooperated with China Academy of Railway Science Corporation Limited to complete the key experimental study of ballastless tracks on high-speed railway viaduct, laying the foundation for the construction of the field test section of ballastless track in China. Their research conquered such key technologies as ordinary track slab, post-tensioned prestressing track slab, pre-tensioned prestressing track slab, cationic emulsified asphalt, CA mortar preparation, test detection as well as construction. They also independently developed high-precision steel model of track slab, tensioning platform of pre-tensioned track slab & CA mortar mixer with continuously variable single horizontal axis. The dynamic & static load tests of China Academy of Railway Science Corporation Limited (in Dongjiao Test Field) showed that various experimental indicators of the manufactured track slab met the design requirements. From 1999 to 2003, experimental application researches were initially carried out for slab ballastless tracks on bridges & those inside tunnels on Qinhuangdao-Shenyang High-speed Railway & Ganzhou-Longyan Railway, with the success development of bidirectional post-tensioned prestressing track slab, insulated track slab as well as anti-vibration track slab, which solved a series of technical difficulties, including the treatment of concrete base foundation, the preparation, laying & fine adjustment of high-performance CA mortar, as well as CA mortar pouring. A large number of trial application studies of China Railway No.3 Engineering Group Co., Ltd. laid a solid technical foundation for CRTS I slab ballastless track system in China. The scientific research achievements of the Comprehensive Construction Technology of Slab Ballastless Track on Hyperbolic Bridge of Qinhuangdao-Shenyang High-speed Railway & the Comprehensive Construction Technology of Slab Ballastless Track Inside Tunnel of Ganzhou-Longyan Railway have reached the international advanced level.

The design & construction technologies of on-bridge ballastless track for urban mass transit urged the railway track engineering construction technology of Chinese cities into a new stage. After the trial laying of ballastless track test section, China basically mastered the construction processes & methods of the I-type ballastless track, but its development of complete sets of construction equipment & high-performance CA mortar still lagged far behind, which was far from being able to meet the requirements for large-scale field laying. The construction quality & work efficiency of slab ballastless tracks could not be guaranteed.Therefore, the former Ministry of Railways of the People's Republic of China made this project (Research on Design & Construction Technology of Ballastless Track on Urban Mass Transit Bridge) as a key scientific research project in 2006,which was co-undertaken by China Railway No.3 Engineering Group Co., Ltd. & China Railway NO.4 Survey & Design Group Co., Ltd.(Contract No. 2006G009-D). They set up systematic design theory for the frame slab ballastless track on urban mass transit bridge, initially developed CRTS I ordinary reinforced concrete frame track slab, developed tyre moving mortar mixer, cross-line cantilever gantry crane, tyre bi-directional slab transporter as well as other complete sets of equipment, solving such great problems of ballastless track logistics as high piers in bridge areas, crossing over residential areas, fish ponds, trenches & rivers, discontinuous pioneer roads, poor construction & transportation conditions, as well as partial pioneer roads deviating from the line. Their scientific research achievements have reached the international advanced level, successively winning the Second Prize of China Railway Technology Progress Award & the Third Prize of Shanxi Scientific & Technological Progress Award. They also obtained 4 provincial & ministerial construction methods & 2 patents.

Break technical barriers & form special measurement tooling for CRTS II track slab prefabrication. Beijing-Shanghai High-speed Railway is mainly based on the laying of CRTS II slab integrated ballast beds, creating a historical record for the laying span, combined length & bridge length. CRTS II slab ballastless track was based on the German Bogl slab technology. At the early stage of constructing ballastless track for Beijing-Shanghai High-speed Railway, foreign parties imposed layers of restrictions on construction technology, especially CRTS II track slab prefabrication measures. If this key technology could not be broken thorough, the manufacturing precision of the track slab could not be guaranteed. Also, the manufacturing cost of the track slab would also increase significantly. In face of practical difficulties of tight schedules & high-quality requirements, special measurement tooling & technology were developed for CRTS II track slab prefabrication, which broke the foreign companies' technical barriers to China & made active contribution to the localization of CRTS II slab ballast technology. This measurement technology greatly improved the manufacturing precision of track slab, lowered the grinding energy consumption of blank slabs & cut down the amount of wastewater treatment as well as solid waste discharge, contributing to the protection of the environment. This scientific research achievement has reached the international advanced level, obtaining 1 provincial construction method & 6 patents.

Introduce innovation & take the lead in automating the manufacturing of railway bi-block sleeper. Year 2007 was a crucial year for the introduction, digestion, absorption & innovation of high-speed railways in China. In order to digest & assimilate foreign technologies as soon as possible, China Railway No.3 Engineering Group Co., Ltd. made a breakthrough in the prefabrication of bi-block sleepers. In the construction of Zhengzhou-Xi'an High-speed Railway, a systematic study was conducted on the prefabrication technology & production equipment of railway bi-block sleepers. China Railway No.3 Engineering Group Co., Ltd. independently developed the Production Line of Bi-block Sleeper, defining seven major systems (i.e. control, feeding mixing, cloth vibration, maintenance, rollover & mold release, mold return as well as finished product delivery) based on production processes & equipment functions. These systems are relatively independent from each other but also connected. Through such integrated technologies as sensing, precision control, modern information processing, network control technology, variable frequency drive, safety protection technology & PLC control, China Railway No.3 Engineering Group Co., Ltd. achieved automatic control production, saving RMB 3.15 million when compared to imported foreign equipment. The traditional production mode of domestic railway sleepers was changed, playing an exemplary & leading role in the transformation of this field into automation & informatization. The achievement has reached the domestic leading level, obtaining 1 provincial construction method & 1 patent. In the past 10 years, 3.54 million bi-block sleepers have been produced for the completed Zhengzhou-Xi'an High-speed Railway, Taiyuan-Zhongwei (Yinchuan) Railway, Shanghai-Kunming Railway, Lanzhou-Xinjiang Railway as well as other railways, with a total output value of RMB 1.239 billion & a profit of nearly RMB 400 million.

Digest, absorb & achieve construction technology upgrade of bi-block sleeper ballastless track. During the construction of Wuhan-Guangzhou High-speed Railway, by systematically studying the auxiliary equipment & manufacturing processes of CRTS I bi-block sleeper & by combining the project features & construction requirements, China Railway No.3 Engineering Group Co., Ltd. developed such complete sets of special equipment as sleeper-spreading equipment, dump truck, rough adjustment equipment, screw adjuster, horizontal formwork erecting machine, vertical formwork erecting machine, track measuring system, concreting machine & curing tent. The construction method of the formed Rheda2000 ballastless track slab was rated as a provincial construction method of Shanxi Province.

During the construction of Zhengzhou-Xi'an High-speed Railway, China Railway No.3 Engineering Group Co., Ltd. systematically studied the comprehensive construction technology of CRTS II bi-block ballastless track, mastered core construction technology concerning CRTS II bi-block ballastless track on soil subgrade, inside tunnels & on bridges, developed complete sets of equipment for line production, & realized true mechanized construction of CRTS II bi-block ballastless track.

　　
The manufacturing of CRTS III pre-tensioned prestressing concrete track slab firstly used the production technology of "matrix all-steel tensioning platform method". In 2013, Zhengzhou-Xuzhou High-speed Railway became the first project using CRTS III pre-tensioned slab ballastless track for the full line. Zhengzhou-Xi'an Railway Passenger Dedicated Co., Ltd., China Academy of Railway Sciences Corporation Limited, China Railway No.4 Survey & Design Group Co., Ltd. as well as other participating companies jointly undertook China Railway Corporation 's important projects of "Research on Key Technologies of CRTS III Type Ballastless Track Construction in Zhengzhou-Xuzhou High-speed Railway" (contract no.: 2013G003-B), "Further Research on Complete Construction Technology & Operation Monitoring Technology of CRTS III Slab Ballastless Track for High-speed Railway" (contract no.: 2014G001-B), as well as "Further Research on the Preparation Technology & Construction Method of Self-compacting Concrete for CRTS III Slab Ballast Track for High-speed Railway" (contract no.: 2014G001-C). A standard was prepared for CRTS III slab ballastless track, creating the first ballastless track system in China with completely independent intellectual property rights & leading the development orientation of China's ballastless track. As a main participating party, it developed 11 authorized patents (2 utility patents), 1 provincial construction method as well as 1 paper in core journal, becoming the enterprise that has completed the most projects & achieved the most technological innovation results.

Overcome difficulties & independently develop special equipment for long-sleeper-embedded ballastless track. In 2003, China Railway No.3 Engineering Group Co., Ltd., according to the construction features of the long-sleeper-embedded ballastless track project inside Yuzui No. 2 tunnel of Chongqing-Huaihua Railway, independently developed special laying & locating gantry crane, special track panel flat truck as well as track panel support frame, which ensured the construction schedule & construction quality, laying solid technical foundation for the adoption of long-sleeper-embedded ballastless track in long tunnels of high-speed railways & passenger dedicated lines as well as urban rail transit. This scientific research achievement has reached the domestic leading level, obtaining the Second Prize of China Railway Technology Progress Award & 1 provincial construction method.

Innumerable great achievements in construction technology of long ballastless track of heavy haul railway. In 2012, relying on the ballastless track project of Taiyue Mountain Tunnel in the central & southern railways, China Railway No.3 Engineering Group Co., Ltd. systematically studied the construction technologies of ballastless track inside the long tunnel of 30t-axle-load heavy haul railway. It also overcame difficulties in tunnel base reinforcement & quality defect rectification technology, CPII control network measuring technology for long tunnels as well as the construction technology of combined track panel of low vibration track bed inside the tunnel, achieving great results. Secondly, it initially proposed to, according to the geological conditions of surrounding rocks & in combination with groundwater as well as other factors, take grouting treatment measures to reinforce the tunnel inverts in soil formation with poor geological conditions, soil-rock boundary formation as well as water-rich soft rock, weak & uneven formation. Besides, it proposed to carry out appropriate grouting reinforcing for the overbreak backfilling part on the subgrade base, which prevented & resolved such problems as mud pumping & sinking of heavy haul railway. China Railway No.3 Engineering Group Co., Ltd. was the first to put forward & implement the new method of measuring CPII control network inside long tunnels, which laid CPII control points inside the tunnel, forcefully align the signs & set up them in a right & left symmetrical way, used total station & free station, simultaneously observed of 6 adjacent points on the front, rear, left & right by the directional observation method, converted the observation data to the edge relationship between adjacent points to form a closed loop, moved station in turn to form an attached control network to set up a CPII control network, hence reducing the error of centralization & improving the measurement precision of angle & distance. Meanwhile, the work load in the field was reduced by half compared to the conventional dual-traverse, with the efficiency raised by 50%. Its achievement has reached the domestic leading level, obtaining the Second Prize of China Railway Technology Progress Award, 1 provincial construction method & 1 patent.