Deep Filling Pile Self-balanced Load Test Method And Negative Skin Friction

Pile foundation is one of the most common foundations in engineering, and is widely applied in the construction. Vertical bearing capacity of the single pile is an important problem which is paid the concentration by researchers at home and abroad. As the wide application of pile foundation under complicated geological conditions, negative friction problem with respect to pile foundation is increasingly significant and become one of the hot research areas. In this paper, on the basis of the project of pile foundation in newly-built Nanning-Guangzhou Railway, the self-balancing test method was applied to study the bearing capacity of pile foundation in deep filling soil. Meanwhile, considering that self-balanced test can't reflect the effect of negative friction problem on piles in long term, thus, the numerical analysis research was conducted to analyze the effect of negative friction on piles in deep filling soil. Accordingly, the results were obtained and the conclusions were drawn as follows:1. Through pile foundation field tests, the ultimate bearing capacity of the test pile was calculated and analyzed. Based on experimental data, the axial force, lateral friction and the tip resistance of the pile were analyzed and the general law of the performance of bearing capacity was presented. This study provided a reference to the pile design and construction under the similar geological conditions in engineering.2. According to the test results, the influence of construction on bearing capacity of the pile foundation was analyzed. To ensure that the bearing capacity of pile foundation performs well, some reasonable proposals were presented on construction technology of cast-pouring pile.3. The origin, mechanism,impact factors on negative friction, and the method to determine the neutral point were studied. Through numerical analysis, the effect of the thickness of filling soil, consolidation time, load on top of the pile and stiffness of the soil at the bottom of the pile on negative friction of piles were analyzed. The analysis results can provide a theoretical basis and reference to design and construction of pile foundation under the similar geological conditions. 4. The construction technology of asphalt coating method was introduced in detail in this paper. Based on the measured data, the effectiveness of asphalt coating method to eliminate negative friction on piles was evaluated and common measures and methods to eliminate negative friction were summarized.