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Zhao C.-F.,Tongji University | Zou Y.-W.,Tongji University | Zhao C.,Tongji University | Xie X.-D.,Shanghai Chengdi Construction and Development Co. | Zhou Y.-S.,Shanghai Chengdi Construction and Development Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2014

Based on a review of disadvantages of the construction techniques for cement-soil mixed piles in China, a new construction method called five-axis mixed pile method is developed. This new method has low cost, environmental pollution, short construction period and high efficiency. In order to investigate the improvement effect of five-axis mixed piles for soft ground in excavation engineering, comparison tests between five-axis mixed piles and biaxial, triaxial mixed piles are conducted in the same geological field. Through the unconfined compression tests on coring samples taken from cement-soil mixed piles, the test results show that the strength of the triaxial mixed piles is low and much more discrete, the strength of the biaxial mixed piles is better in every layer, but the discreteness of strength values greatly changes at different ages. However, the five-axis mixed piles with higher strength and low discrete behavior may have a good population and application value in the future. Source


Zhao C.-F.,Tongji University | Du X.-H.,Tongji University | Zhao C.,Tongji University | Xie X.-D.,Shanghai Chengdi Construction and Development Co. | Zhou Y.-S.,Shanghai Chengdi Construction and Development Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

Prestressed concrete pile is a kind of soil displacement pile, and its application is limited because of the squeezing effect. A new construction method called the inner-digging method which can be employed to dig soil while the pile is sinking is developed to solve this problem. It is environmentally friendly and highly efficienct. To test and verify the squeezing effect of inner-digging piles, the deep horizontal displacement and pore water pressure during construction process of soil after different kinds of pile sinking are measured through contrast tests. The squeezing effect rules of a single displacement pile along the horizontal direction and depth direction in soft clay area are studied, and the squeezing effect of the inner-digging piles is compared with that of hammer piles and bored piles. The test results show that the sinking of the hammer piles leads to strong squeezing effect and exhibits notable rules along the horizontal direction and depth, and different degrees of squeezing effect are shown in different horizons of soil. After the sinking of the new developed inner-digging piles, deep horizontal displacement of soil is very low and pore water pressure has little change. A conclusion is drawn that the inner-digging piles lead to little squeezing effect and have little impact on the surrounding environment in construction. Moreover, they will have a good popularization and application value in the future. Source


Zhao C.,Tongji University | Du X.-H.,Tongji University | Du X.-H.,Shanghai Municipal Engineering Design General Institute Group Co. | Zhao C.-F.,Tongji University | And 2 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

To solve the disadvantages of the traditional construction methods for prestressed pipe piles like squeezing effect and noise and to expend their application, a new construction method, inner-digging method is studied. The static load test and other series field tests on hammer piles and inner-digging piles and are discussed, the vertical compressive properties and rules of load transfer of different kinds of piles are investigated. The test results show that the rules of load transfer of inner-digging pipe piles is the same as those of other kinds of piles. The inner-digging method will reduce the pile side resistance and make it lower than that of hammer-piles, but the post-grouting technology can effectively develop the ultimate bearing capacity. The ultimate bearing capacity of inner-digging piles is close to that of hammer piles, which can meet the requirements of construction and will have a good population and application value in the future. Source

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