Observation board for displacement of pre embedded settlement plate for soft roadbed detection in Shizuishan

Description :

　　Observation board for displacement of pre embedded settlement plate for soft roadbed detection in Shizuishan

　　Observation of settlement and deformation in bridge and culvert engineering

　　1 General provisions

　　1. Before laying ballastless tracks, a systematic approach should be taken to confirm that the settlement and deformation of bridge and culvert foundations, as well as the deformation of beams, meet the technical standards.

　　1. By observing the settlement of piers and abutments during each construction stage, the design theory and calculation methods are verified and verified. Based on the analysis of settlement data, the total settlement and post construction settlement are predicted to determine whether the post construction settlement of the bridge meets the requirements for laying ballastless tracks.

　　1. Based on the analysis of settlement data, research countermeasures for piers and abutments that may exceed the settlement limit, and propose improvement measures to ensure the safety of bridge engineering; At the same time, accumulate settlement observation data of physical bridge engineering to provide technical reserves for improving pile foundation settlement analysis methods.

　　1. During the observation period, if the measured settlement of the foundation exceeds the design value by 20% or more, the cause should be identified in a timely manner. If necessary, geological review should be conducted, and calculation parameters should be adjusted based on the measured results. The predicted settlement of the design should be corrected or settlement control measures should be taken.

　　2 Bridge and Culvert Deformation Control Standards

　　2. 1. Beam section

　　The deformation of the beam is mainly caused by the creep deformation of prestressed concrete beams. After the track is laid, the creep arch value of the ballastless bridge deck beam should not exceed 10mm.

　　2. 2 Bridge piers and abutments

　　For the settlement control of high-speed railway bridge foundations, the settlement of pier and abutment foundations should be calculated based on dead load, and the post construction settlement should not exceed the following allowable values:

　　Uniform settlement of pier and abutment:

　　For ballastless bridge decks ≤ 20mm;

　　The difference in settlement between adjacent piers and abutments of a static structure:

　　For ballastless bridge decks ≤ 5mm.

　　For high-speed railways, controlling bridge and culvert settlement mainly involves post construction settlement, and calculating the value of post construction settlement often has significant deviations due to various factors. Therefore, it is necessary to conduct actual measurement verification and accumulate observation data.

　　2. 3 frames, passenger tunnels and culverts

　　When the foundation of frame structures, passenger tunnels, and culverts is a compressible soil layer, their settlement should be calculated. When laying ballastless tracks, the post construction settlement should not exceed the control standard of 15mm for the corresponding section of the roadbed.

　　3 Deformation observation plan

　　3. Observation point layout

　　In order to meet the needs of deformation observation, observation markers need to be set up on beams, bridge piers, and abutments. Six observation markers are set for a single hole beam of a simply supported beam; Set 18-28 observation markers for a continuous beam according to the size of the joint length; Observation markers shall be set up for special structural bridges according to the construction drawings; The observation mark of the pier cap is a temporary observation mark. When the observation mark of the pier body is used normally, the observation mark of the pier cap will no longer be used along with the backfilling of the foundation pit. The specific principles for burying observation markers are as follows:

　　a、 For prestressed concrete precast beams with minimal changes in raw materials, stable prefabrication processes, and mass production, one observation mark should be set every 30 holes. Observation markers shall be set up for each hole of the remaining cast-in-place beams. Pay special attention to the holes of the beams constructed with mobile formwork to verify the accuracy of the preset arch of the support. Six observation markers are set up for each beam, respectively at the fulcrum and mid span; Observation markers on continuous beams are set up with 18-28 markers in three holes per pair and 32 markers in four holes per pair according to different spans, respectively at the support point, mid span, and 1/4 mid span.

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