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Zhang W.-L.,Wuhan University | Zhang W.-L.,South China University of Technology | Cai J.,South China University of Technology | Lin Y.-X.,Zhuhai Municipal Construction Engineering Quality Supervision and Test Station | Huang L.-J.,Zhuhai Municipal Construction Engineering Quality Supervision and Test Station
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

The influence of cushion thickness on the settlement of cement-soil mixing pile composite foundation was studied by the static load tests and numerical simulation. The static load tests of natural foundation and four cement-soil mixing pile composite foundations in which the cushion thickness was different were carried out for the silt soil in Zhuhai area. The settlement-tubes and magnetic rings were pre-buried in the foundation. And the probe with scale was used to detect the positions of the magnetic rings and obtain the data of the layered settlements. According to these experimental data of composite foundation for four cement-soil mixing piles, the settlement law was analyzed; and layered settlements of piles and soil in different composite foundation were calculated by numerical calculation. The comparison between the different composite foundation shows that the settlement of pile could be reduced by the cushion, but the thickness of cushion has a significant influence on the supporting capacity of composite foundation-a much thicker cushion could weaken the supporting capacity and increase the settlement of composite foundation. For choosing the optimal thickness of cushion, the geological condition was suggested to be considered except for the supporting capacity and settlement of composite foundation. The cushion thickness could be from 20 cm to 40 cm-the higher value is selected when the silt layer is below the middle sector of pile, conversely the lower value is selected. Source


Zhang W.,South China University of Technology | Zhang W.,Wuhan University | Cai J.,South China University of Technology | Lin Y.,Zhuhai Municipal Construction Engineering Quality Supervision and Test Station | Huang L.,Zhuhai Municipal Construction Engineering Quality Supervision and Test Station
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2010

The load transfer mechanism of cement-soil pile composite foundations with different cushion heights were studied according to the results of static loading tests. Four types of static load tests of 4-pile composite foundation were carried out with different cushion heights. Using the data collected from the pressure cells, the stresses of the pile and the soil were calculated. Comparison and analysis of the data show that, with the increase of the cushion height, the negative friction of the pile increases, the location of the maximum stress of the pile shifts downwards, and the decreasing rate of the stresses of the pile is smaller. The location of the maximum stress of the pile is in the range of 2-4 times pile diameters distance from the top of the pile. During the period of stability, the change of the pile-soil stress ratio indicates the redistribution of load between soil and piles. With the increase of load, the pile-soil stress ratio first increases and then decreases, and it is inversely proportional to the cushion height. Suggestions are given for the design of composite foundation to increase its supporting capacity. Source


Mo H.,South China University of Technology | Wang J.,South China University of Technology | Lin Y.,Zhuhai Municipal Construction Engineering Quality Supervision and Test Station
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

The macro and micro analyses of soft soil before foundation treatment are important to predict the effectiveness of vacuum preloading treatment. Through the laboratory macro and micro tests, the properties of soft soil from Zhuhai Jinwan area are investigated, including mineral composition, specific surface area, microstructure, pore properties before and after consolidation, etc.. The key factors are concluded which indicate vacuum preloading treatment effect, such as amount of bound water, strength index. Research result shows that clay content of soft soil from Zhuhai Jinwan area is not high, with the clay content about 50%; and specific surface area is small. The soft soil grains are curved flocculation polymer. After consolidation, microscopic structure has noticeably aggregated with compactness and no particle breaking. The micro-pore distribution is mainly between 400 and 2 500 nm. The cumulative intrusions sharply decrease after consolidation, and pores turn smaller. Therefore, the amount of bound water is not high with more free water. The change of internal friction angle is not big, and cohesion has larger growth. It shows good availability of the vacuum preloading method in soft soil from Zhuhai Jinwan area. Source

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