Abstract:

 In order to study the variation of soil pressure in the process of jacked pile penetration. A model test of jacked pile driving in saturated clay was carried out. The double-wall model pipe pile was used to separate the internal and external friction resistance, and a micro-soil pressure sensor was installed on the pile to monitor the soil pressure at the pile-soil interface. The variation law of pile pressure and pile tip resistance in pile driving process was analyzed. The distribution characteristics of soil pressure at the pile-soil interface in the process of pile sinking under static pressure were discussed. It was clear that the soil pressure at the pile-soil interface had obvious degradation effect in the process of pile driving. The change mechanism of soil pressure at the pile-soil interface during the process of pile sinking in saturated clay was revealed. The test results showed that the pile compression force increased linearly with the penetration depth, and the pile compression force of the closed pile was obviously larger than that of the open pile in the later period of penetration. The pile tip resistance increased linearly, accounting for 62.3% of the pile pressure in the process of piling. The soil pressure at the pile-soil interface increased at a low rate at the initial stage of the static pile penetration, but increased linearly and at a high rate with the gradual penetration of the static pile. At the same depth, with the gradual penetration of the static pile into the pile-soil interface, there was an obvious phenomenon of earth pressure degradation. The research results could provide reference for the study of soil pressure at the interface between piles and soil under static pressure. At the depth of 20, 30, 40, 50, 60 and 70 cm, the earth pressure degraded by 14.6%, 13.8%, 13.2%, 9.2%, 7.2% and 6.1% on average.

Key words:  jacked pile, laboratory test, the pile soil interface, earth pressure, degradation effect