Abstract
Prestressed high-strength concrete (PHC) pipe pile with the static press-in method has been widely used in recent years. The generation and dissipation of excess pore water pressure at the pile–soil interface during pile jacking have an important influence on the pile’s mechanical characteristics and bearing capacity. In addition, this can cause uncontrolled concrete damage. Monitoring the change in excess pore water pressure at the pile–soil interface during pile jacking is a plan that many researchers hope to implement. In this paper, field tests of two full-footjacked piles were carried out in a viscous soil foundation, the laws of generation and dissipation of excess pore water pressure at the pile–soil interface during pile jacking were monitored in real time, and the laws of variation in excess pore water pressure at the pile–soil interface with the burial depth and time were analyzed. As can be seen from the test results, the excess pore water pressure at the pile–soil interface increased to the peak and then began to decline, but the excess pore water pressure after the decline was still relatively large. Test pile S1 decreased from 201.4 to 86.3 kPa, while test pile S2 decreased from 374.1 to 114.3 kPa after pile jacking. The excess pore water pressure at the pile–soil interface rose first at the initial stage of consolidation and dissipated only after the hydraulic gradient between the pile–soil interface and the soil surrounding the pile disappeared. The dissipation degree of excess pore water pressure reached about 75–85%. The excess pore water pressure at the pile–soil interface increased with the increase in buried depth and finally tended to stabilize.
Highlights
The pile foundation has the advantages of high bearing capacity, strong resistance to non-uniform deformation, and high degree of mechanized construction, so it is widely used in industrial and civil buildings with a self-heavy superstructure, low strength of foundation soil, and high compressibility [1,2,3,4].With the development of marine economy and high-speed traffic engineering in the 21st century, offshore engineering and high-speed railways and expressways, which can bear complicated loads such as wind, wave, and traffic for a long time, have put forward higher requirements for pile foundations [5,6,7,8]
(3) After the completion of pile jacking, there is a hydraulic gradient between the pile–soil interface and the soil around the pile, and the pore water pressure in the soil around the pile will transfer to the pile–soil interface under the action of seepage
As the test site is a viscous soil layer above 20 m, the study is conducted on the basis of the dissipation law of excess pore water pressure at the pile–soil interface in the viscous soil, and the pore water pressure sensor h/B = 1 (h is the distance between the pore water pressure sensor and the pile end; B is the pile diameter of the test pile) from the pile end is still taken as an example
Summary
The pile foundation has the advantages of high bearing capacity, strong resistance to non-uniform deformation, and high degree of mechanized construction, so it is widely used in industrial and civil buildings with a self-heavy superstructure, low strength of foundation soil, and high compressibility [1,2,3,4]. In view of the lack of research on the influence of excess pore water pressure on the pile–soil interface resistance at present, this paper conducted field tests by installing a micro-silicon piezoresistive pore water pressure sensor on the surface of a PHC pipe pile, and measured the change process of excess pore water pressure at the pile–soil interface during pile jacking. It lays the foundation for further study on the influence of excess pore water pressure on the mechanical properties of the pile–soil interface, and proves that the change law of excess pore water pressure has important engineering significance for pile foundation design
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