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The pre-bored grouted planted (PGP) pile shaft consists of a core PHC pile and the surrounding cemented soil column. The shaft capacity of PGP pile is controlled by the PHC pile–cemented soil–soil interface. In this paper, the effect of curing time on the frictional capacity of smooth concrete pipe pile–cemented soil interface was investigated through pile–soil interface shear tests. The test results show that the peak skin friction of pipe pile–cemented soil interface increased with the curing time. Nevertheless, the normalized peak skin friction (peak skin friction/cemented soil strength) of interface decreased with the curing time. The thickness of the cemented soil layer had a large effect on the residual skin friction of pipe pile–cemented soil interface. The scale effect also existed in the smooth concrete pipe pile–cemented soil interface shear tests, as the stiffness and shear strength of interface would decrease with the pipe pile diameter, which would eventually induce the decrease of radial confining pressure of the interface. [ABSTRACT FROM AUTHOR]

The frictional capacity of pile–cemented soil interface is similar to the frictional capacity of pile–rock interface as the strength of cemented soil is close to the strength of soft rock. A series of pile–soil interface shear tests were carried out to study the frictional capacity of square pile–cemented soil interface. The shear test results show that the peak skin friction of square pile–cemented soil interface decreased with the increase in the side length of square pile; the failure mode of square pile–cemented soil interface was affected by the cemented soil thickness; the peak skin friction of square pile–cemented soil interface would increase with the roughness of square pile surface when the mean size of coated silica sand reached 0.94 mm, and the peak skin friction increased slightly with the density of coating sand. [ABSTRACT FROM AUTHOR]

This paper presents the results of field tests performed to investigate the compressive bearing capacity of pre-bored grouted planted (PGP) pile with enlarged grout base focusing on its base bearing capacity. The bi-directional O-cell load test was conducted to evaluate the behavior of full scale PGP piles. The test results show that the pile head displacements needed to fully mobilize the shaft resistance were 5.9% and 6.4% D (D is pile diameter), respectively, of two test piles, owing to the large elastic shortening of pile shaft. Furthermore, the results demonstrated that the PHC nodular pile base and grout body at the enlarged base could act as a unit in the loading process, and the enlarged grout base could effectively promote the base bearing capacity of PGP pile through increasing the base area. The normalized base resistances (unit base resistance/average cone base resistance) of two test piles were 0.17 and 0.19, respectively, when the base displacement reached 5% Db (Db is pile base diameter). The permeation of grout into the silty sand layer under pile base increased the elastic modulus of silty sand, which could help to decrease pile head displacement under working load. [ABSTRACT FROM AUTHOR]

The rigid pile composite foundation is widely used in highway projects in soft soil area as it can effectively increase the bearing capacity and stability of the foundation. While the research on the behavior and failure mode of rigid pile composite foundation under embankment is not enough, instability failure of rigid pile composite foundation often occurs in practical projects. This paper presents a centrifuge model test to investigate the load transfer mechanism, settlement characteristic and failure mode of rigid pile composite foundation under embankment. The test results show that: the soil displacement of different region in rigid pile composite foundation was different, obvious vertical displacement occurred in the soil under the center of embankment and the horizontal displacement was very small in this region; both vertical and horizontal displacement occurred in the soil under the shoulder of embankment; and obvious horizontal displacement occurred in the soil under the slope toe of embankment; moreover, ground heave also occurred near the slope toe of embankment. The soil displacement in rigid pile composite foundation had a large influence on the stress characteristic and failure mode of rigid piles, the compressive failure and bending failure would probably occur for the piles under the center and shoulder of the embankment, respectively, and the tension-bending failure would probably occur for the piles under the slope toe of embankment. The different failure modes of piles at different regions should be considered in the design of rigid pile composite foundation under embankment. The test results can be used to improve the design method for rigid pile composite foundation under embankment in practical projects. [ABSTRACT FROM AUTHOR]

This paper presents the results of field tests performed to investigate the behavior of pre-bored grouted planted nodular (PGPN) pile embedded in deep clayey soil. The test piles were all instrumented to measure the shaft and tip resistance and to determine the load transfer along the pile shaft. The test results show that the displacement necessary to fully mobilize the shaft resistance of PGPN pile is in the range of 1.83–3.32% D (D is pile diameter), and that the ultimate skin frictions of grout–soil interface of different soil layers are larger than the conventional proposed ultimate skin frictions for non-displacement piles. Furthermore, the pile tip resistance accounts for about 16% of the total applied pile head load corresponding to a pile head displacement of 0.1 D, and the pile tip resistance continues to increase after tip displacement reaches 5% of pile tip diameter. [ABSTRACT FROM AUTHOR]

The pre-bored grouted planted pile is a new type of composite pile foundation that consists of a precast concrete pile and the surrounding cemented soil. A series of shear tests were conducted in a specific shear test apparatus to investigate the shaft capacity of the different pile-soil interfaces. The test results show that the frictional capacity of the cemented soil-sand interface is controlled mainly by the sand properties, while the strength of the cemented soil slightly influences the interface properties by affecting the normalized roughness coefficient Rn. The frictional capacity of the concrete-sand interface is similar to the frictional capacity of the cemented soil-sand interface, and the existence of mud cake layer virtually hampers the frictional properties of the interface. The maximum skin friction of the concrete-cemented soil interface increases approximately linearly with the increasing cemented soil strength, and the value of the maximum skin friction is much larger than that of the cemented soil-sand interface of identical cemented soil strength, which demonstrates the integrity of the pre-bored grouted planted pile in the load transfer process. [ABSTRACT FROM AUTHOR]

A group of field tests and three-dimensional finite element simulation were used to investigate the behavior of the pre-bored grouting planted pile under compression and tension; moreover, a group of shear tests of the concrete-cemented soil interface was carried out to study the frictional capacity of the pile-cemented soil interface. The load-displacement response, shaft resistance and mobilized base load were discussed based on the measured and computed results. The measured and computed results show that the frictional capacity of the cemented soil-soil interface is better than the frictional capacity of the concrete-soil interface. The frictional capacity of the concrete-cemented soil interface is mainly controlled by the properties of the cemented soil, and the ultimate skin friction of the concrete-cemented soil interface is much larger than that of the cemented soil-soil interface. The frictional capacity of the soil layer close to the enlarged base is also promoted because of the compaction of the enlarged base. The enlarged cemented soil base can promote the behavior of the pile foundation under tension, and the enlarged cemented soil base undertakes approximately 26.3% of the total uplift load under the ultimate bearing capacity in this research. [ABSTRACT FROM AUTHOR]