"The second pile foundation of the main bridge was successfully poured."! This is the first pile foundation completed after solving the problem of hole cleaning. Recently, at the construction site of the Qujiang Bridge on the Chengdu-Dawan Railway of the Third Company of the 15th Bureau of China Railway, the builders celebrated excitedly when the problem of "fast settlement, more sediment and oily" pile foundation hole cleaning was successfully solved.
This is the first construction problem of Qujiang Bridge and the first "ice-breaking" battle of Chengdu-Dawan Railway in 2023.
▲ Construction Site
of Qujiang River Bridge of Chengdu-Dazhou-Wanzhou Railway Located in Quxian County, Dazhou City, Sichuan Province, Qujiang River Bridge of Chengdu-Dazhou-Wanzhou Railway crosses the Qujiang River, with a total length of 1983.81 meters and a total of 47 spans. The main bridge is a low-pylon cable-stayed bridge of (139 + 278 + 139) meters crossing the navigable river. The micro-landform of the bridge site is the floodplain and terrace of the canal and river, with 495 cast-in-place piles. The diameter of the main
pier pile foundation is 2.5 meters, and the design hole depth is 41.5 meters, all of which are located in the Qujiang River. The underwater rock stratum is mainly sandy mudstone, which is hard and has a slow opening. The sand content is very high, the sediment settlement speed is fast, and the sediment is oily. It is difficult to clean hole and the hole is formed slowly. On December 23, 2022, the opening of the first pile foundation encountered a thorny problem.
▲ Pile foundation pouring
is being carried out. "At the very beginning, we used flat-bottom drilling to clear the hole. After two days, the large sediment was basically cleared, but the small sediment could hardly be cleared, and there was still a thick layer in the hole." Faced with technical difficulties, the construction team actively responded, held technical seminars and formulated construction plans. The first attempt ended in failure, but they were not discouraged. After reporting to the owner and the company and listening to the suggestions, they readjusted the construction plan according to the actual situation of the site sediment.
Considering that the sediment was oily, they tried to use the gas lift method to drain the liquid in the hole out of the casing. According to the second edition of the construction plan, they quickly transferred two high-power air compressors to the site to clean up the sediment. As the liquid in the hole is slowly discharged, only a part of the fine sediment is brought out, with little effect.
▲ Fighting day and night to solve difficult problems
In the face of the first technical problems in China, the three companies attached great importance to it. While sending the company's technical team to the scene to help and supervise, they timely reported to the relevant leaders of the group company in detail and sought help.
"Slurry with caustic soda, bentonite, cellulose, etc., and use mud pumps to remove and transport cuttings to the surface in positive circulation drilling." After the technical specialist team of the three companies rushed to the site for inspection, the third edition of the construction plan was worked out. After digging the mud pit on the spot, they transferred two mud pumps to cooperate with the rotary excavator to drill holes, bring the debris to the surface and clean up the fine oily sediment, but the cleaning speed is relatively slow and the effect is not good.
In order to improve the construction speed, they optimized the third edition of the construction plan, and put forward a series of measures to optimize the construction, such as using large reverse circulation drilling equipment and reducing the number of reaming.
▲ The technical specialist team of the group company is investigating
on the spot. On January 5, the expert technical team of the group company went to the construction site of Qujiang Bridge for joint demonstration and affirmed the current construction scheme. At the same time, they guide the project laboratory to analyze the composition of sediment and optimize the specific gravity of mud. After two days of continuous experimental comparison of mud optimization construction, the pile foundation construction is getting better and the speed is obviously improved.
Through the adjustment of three to four construction schemes, the renewal of technology by four professional construction teams and the comparison of the effectiveness of three sets of equipment, we finally found a solution and successfully solved the problem of "fast settlement, more sediment and oil", which accelerated the construction of pile foundation and made a good start for the new year.
Smoke rises from the river bank, the wind ripples, and the mechanical sound along the canal rises and falls with the river. At present, at the construction site of the Qujiang Bridge on the Chengdu-Dawan Railway, eight domestic advanced high-power rotary excavators have started drilling, tankers are in an endless stream, and front-line personnel are fighting fervently to welcome the coming Spring Festival.
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