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| Research on the Causes and Preventive Measures of Shallow Defects of Cast-in-place Pile |
| CHANG Juyou1, WANG Chen2, WANG Zhengrong3, HAO Lingxu3, LIAO Zhong1, YANG Hu1 |
1. China Railway Eryuan Engineering Group Co. Ltd, Chengdu, Sichuan 610031, China;
2. Hydro-engineering Team of Sichuan Metallurgical Geology & Exploration Bureau, Chengdu, Sichuan 610032, China;
3. China Railway 12th Bureau Engineering Group Co. Ltd, Taiyuan, Shanxi 030000, China |
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Abstract Research purposes:According to 7.3.3 of Q/CR 9212-2015 in Technical Specification for Bored Pile Works of Railway Bridge Construction, the height of over-pouring concrete at the design elevation of pile top should be 0.5～1.0 m, in order to increase the pressure to ensure the integrity of the pile at the design elevation at the top of the pile. The defects in the shallow part of the pile at the design elevation at the top of the pile can be detected on the spot, and the compressive strength of the core sample with a drilling depth of 0.5 m is not satisfied with the design requirements. The cause and how to prevent the defects should be studied.
Research conclusions:(1) The height of over-pouring concrete at the design elevation of pile top shall be 2 ~ 3 m. (2) The slump of concrete shall be controlled within 180 ~ 220 mm. (3) During pile cutting, a circle of the outer edge at the design elevation of the pile top shall be cut in a ring, the exposed part of the design elevation of the pile top shall be provided with coarse aggregate with the maximum particle size, and the strength of the core sample with a drilling depth of 0.5 m shall meet the design requirements. (4) The buried depth of concrete conduit shall not be less than 3 m, and the conduit shall be centered when pouring concrete. After the short cage is used for hole dredging, the hole shall be cleaned again, and the sediment thickness at the bottom of the end bearing pile shall not be greater than 50 mm. (5) The research results can provide reference for improving the construction quality of bridge bored pile in railway, highway and other fields.
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Received: 11 July 2022
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2022, Vol. 39 
