Supervision Outline of a Special Railway Project in Sichuan Province
(2) Main engineering characteristics 1. Subgrade (1) The terrain where the whole line crosses is mainly hilly, with excavation volume greater than filling volume, large amount of spoil, which has a great impact on the ecological environment and water and soil conservation along the line, and sufficient engineering measures must be taken; (2) The terrain and geological structure along the line are complex, and there are many forms of retaining structures. The filling and preloading period (or natural settlement period) of the soft soil subgrade section is long, which has a great impact on the construction period of beam erection, track and four electricity projects; (3) As the transportation channel for bridge erection and track bed construction, the subgrade must develop measures to ensure the subgrade quality; (4) The characteristics of high smoothness and uniformity of special line track put forward higher requirements for subgrade design and construction. A lot of new engineering measures have been adopted for the subgrade works. Post construction settlement and differential settlement must be strictly controlled, and the geological conditions must be checked during construction; (5) Special settlement observation device is required for subgrade construction to observe and analyze the subgrade settlement, so as to determine and guide the construction of the next process and determine the natural settlement period of the subgrade, and determine the start time of ballastless track bed according to the observation and analysis results; (6) The construction coordination between subgrade works and relevant professional interfaces such as bridges, tunnels, tracks and four electricity is complex and the construction interference is large; (7) The transition section has many types and complex construction procedures, which is the key part to control differential settlement. 2. Due to the long kilometers of the special railway line, all of the bridges are located in hilly areas and cross many rivers. The bridges along the whole line are characterized by huge quantities, long bridge length, high content of new technology and complex construction. Due to the wide distribution of soft soil, the foundation type is mainly pile foundation. In order to ensure the requirements of beauty, noise reduction and structural lateral stiffness, the superstructure of the bridge is mainly of 24m and 32m T-beam type, and the number of prefabricated simply supported T-beams along the whole line is large. Due to the large section and heavy weight of the bridge, the requirements for beam erection and transportation machinery are very high, so the manufacture, transportation and installation of the superstructure of the bridge become the key issues of construction organization, Therefore, the construction method of setting up the corresponding beam prefabrication yard, transporting the beam with the beam carrier, and erecting with the large tonnage bridge erecting machine or the transport and erection machine is adopted. The construction of the long track along the whole line puts forward strict requirements for the linear control of the bridge superstructure. During the construction, strict technical measures must be taken to ensure that the structural linear change caused by shrinkage and creep is controlled. The pier and abutment settlement and the differential settlement of adjacent piers and abutments are required to be high, and the pier and abutment settlement must be observed in strict accordance with the design requirements. 3. Ballasted track is adopted as the track is long. The laying technology and process are also different from those of the previous national railways and urban tracks. A new set of processes different from those of the previous ordinary railways must be adopted from the construction processes of ballasted track construction, rail joint connection, rail laying, stress release and track temperature locking, track stability, etc. The construction must be completed in strict accordance with the construction procedures, and the process standards are high. 4. The communication line of communication engineering is the information platform for safe driving and transportation management of the line. Its main task is to ensure the real-time, accurate and reliable processing and transmission of the required information. It should be able to provide multimedia communication means such as voice, data, images, etc. It has the characteristics of diversified service objects, high security, high reliability and specificity. The communication private network designed in this design is mainly composed of communication bearer network, communication service network, communication support network, and related communication service systems. 5. The signal system of the special rail transit line of the signal project is generally composed of train operation command system, train operation control system, station interlocking equipment and centralized monitoring system for signaling.