Abstract
This paper examines the performance of a novel technology, vertical steel floral tube micropiles with double grouting. It is the combination of micropile technology and double grouting technology. A large-scale model tank was applied to impart horizontal bearing capacity, and the slope soil pressure and flexural performance of the micropile were investigated under four experimental conditions. The peak grouting pressure during the double grouting process was defined as the fracturing pressure of the double grouting, and it was positively correlated to the interval time between first grouting and secondary grouting. Compared with traditional grouting, double grouting increased the horizontal bearing capacity of the single micropile with the vertical steel floral tube by 24.42%. The horizontal bearing capacity was also 20.25% higher for the structure with three micropiles, compared with a 3-fold value of horizontal sliding resistance. In the test, the maximum bending moment acting on the pile above the sliding surface was located 2.0–2.5 m away from the pile top, and the largest negative bending moment acting on the pile below the slip surface was located 4.0 m away from the pile top. The ultimate bending moment of the single pile increased by 12.8 kN·m with double grouting, and the bending resistance increased by 96.2%. The experimental results showed that the double grouting technology significantly improved the horizontal bearing capacity of the micropile with the steel floral tube, and the soil reinforcement performance between piles was more pronounced. Also, the shear capacity and the flexural capacity were significantly improved compared with the original technology.
Highlights
E damage analyses of the steel floral tube with no pile, single pile, and three piles were conducted by means of the large-scale model test, and the effect of the double grouting on soil strength improvement and the stress performance of the pile were analysed. e displacement and stress transfer mechanisms of the vertical steel floral tube with double grouting were obtained under the action of the horizontal loading
A micropile of a steel floral tube with double grouting was developed based on the traditional steel tube technology. e performance of this technology to improve the horizontal bearing capacity of the pile and improve the reinforcement of soil between piles, as well as the shear and bending performances of the pile, was investigated using a large-scale test of the model tank. e following conclusions from this study can be drawn: (1) e initial grouting is fractured by the double grouting owing to high pressure inside the tube
A large diffusion area is formed surrounding the steel floral tube, which strengthens the soil between piles and improves the mechanical performance of the soil. e peak value of the grouting pressure during the double grouting process is defined as the fracturing pressure
Summary
Micropiles have characteristics of high mechanization, rapid and safe construction, and light equipment loads. Porous steel floral tube micropiles were selected, and double grouting was applied in the large diffusion area; this improved the bearing capacity of the single pile, the soil reinforcement between piles, the stress performance of the pipe group, and the overall flexural capacity. To obtain a deeper understanding of the combined micropile technology and double grouting technology, and to provide a reference for subsequent theoretical research as well as the engineering application, several performance characteristics were evaluated based on four groups of experiments. Us, the bearing capacity of the single steel floral tube, the soil reinforcement between piles, the antisliding, and the shearing resistance of the double grouting are improved.
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