**2. Process dynamic design technology for ballastless track construction in high-speed railway**

Ballastless track is greatly affected by changes in the substructure, such as subgrade, bridges and tunnels. Realizing the intelligent update of design results and complete intelligent operation with dynamic data driven construction equipment is

**Figure 2.** *The overall technical scheme of ballastless track intelligent construction.*

#### **Figure 3.**

the key to promoting the efficiency of ballastless track construction and controling quality. Based on the collected data of the whole construction process, taking into account the changes of the substructure such as subgrade, bridge and tunnel as the input conditions, the plane and elevation dynamic design of the concrete base and track slab is realized. Problems such as the fastener at beam end exceeding the standard requirement, the control of the concrete base plate hanging out, and the precise control of the geometric size of the ballastless track are solved. The dynamic updating of the design results in the construction process is realized, and dynamic design problems such as alignment changes at long-span Bridges, deformation joints and transition section position updating are all overcome.

Take the extremely long span bridge such as Ganjiang bridge of Chang-Gan Railway (main span 300 m), Yuxihe bridge of Shang-He-Hang Railway (main span 324 m) as an example, which were affected by bridge creep, temperature deformation, load on the bridge and wind speed and other factors, as a result of which the ballastless track line is difficult to control. The dynamic design technology was adopted to obtain the exact correspondence between bridge loads and cable force and design model (main beam line type) after the main bridge design was finally closed and preloaded. The main bridge line type was systematically adjusted and the digitized track results have been corrected in real time (**Figure 3**).

This mainly includes the layout algorithm of ballastless track, the coordinate cluster calculation method of ballastless track under the condition of complex line and the virtual preassembly technology of ballastless track.

#### **2.1 The layout algorithm of ballastless track**

During the construction period, due to the great difference between the actual working conditions of the substructure such as the subgrade, bridge and tunnel and the assumed design working conditions, the ballastless track needs to be dynamically adjusted according to the actual working conditions. The layout of the track is as follows:

1.By configuring different lengths of track slab and adjusting the gap of the track slab to meet the layout requirements, the layout of track slab is disconnected at the bridge joint, settlement joint, deformation joint of subgrade and bridge, subgrade and tunnel, bridge and tunnel boundary, etc.

*Perspective Chapter: Intelligent Construction Technology of Ballastless Track for High-Speed… DOI: http://dx.doi.org/10.5772/intechopen.109611*

2.The track slab lays on such as a 24, 32 m beam, and commonly used continuous beam and other areas of standardized layout, the track layout should consider the sleeper spacing uniformity and the maximum spacing of fastener at the beam end and other restrictions.

According to the above track slab layout principles, the track slab layout in the track slab design software is implemented as follows:

1.The left line and right line are arranged separately.

Due to the different lengths of the left line and right line, the different beam joints at the center line of the track in curved sections, and the different beam lengths at the center line of the track when the bridge is designed into a curved beam in a small radius curve section, the layout of the track slab should be arranged separately on the left line and right line. According to the way that the left line and right line is laid separately, the more accurate data file of the track slab can be obtained.

2.The track layout mode of "the whole is zero and set zero for the whole" will adopted.

The line is composed of straight line, front easing curve, round curve and back easing curve, etc. which is composed of subgrade, bridge and tunnel. The line of track layout design can be decomposed into different sections, each section is composed of many small sections with the same length, that is one line can be divided into several blocks. Each block is composed of a lot of simply supported beam and continuous beam bridge, for example: there are a lot of same span 32.6 m beam, the track layout on the 32.6 m beam takes the same parameters. Therefore, the detailed idea of the track layout design is: the parameters of the same length that compose the line are first laid out, for example, the 32.6 m simply supported beams are arranged first, and all the later simply supported beams of the same type are arranged in the same way.

Therefore, the layout design of track slab is designed to find the optimal layout scheme under the constraints of slab length, slab gap, sleeper spacing, etc., to achieve uniform layout of fastener spacing, the fastener spacing at beam end that meets the design requirements, and the optimal control of curve vector distance deviation on small radius curve (**Figure 4**).
