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Wang J.-C.,Ningbo University of Technology | Yu J.,Zhejiang University | Shiguo M.,Ningbo Urban Construction Investment Holding Company Ltd | Gong X.,Zhejiang University
Marine Georesources and Geotechnology | Year: 2015

Methods of energy and momentum conservation, vibration theories, and model tests are employed to research the impact force of a hammer on a pile and the pile's penetration. An analytical formula of impact force of the hammer on pile is obtained. A comparison of results from the three methods finds that the analytical formula proposed by this article conforms well to practical situations. Research results show that if the hammer's impact energy remains unchanged, penetration increases with the increase of hammer weight and cushion stiffness. In addition, the impact force received by the pile head degrades with the increase of hammer weight, but increases with the increase of cushion stiffness. Impact time decreases with the increase of cushion stiffness, but increases with the increase of hammer weight. The model test shows that, when compared with a cotton cloth cushion, an elastic cushion's advantages lie in that the relatively small pile head impact force can achieve significant pile penetration. The cotton cloth is gradually compacted with the increase of blow counts; hence, the impact force the pile head receives tends to increase gradually. 2015 Copyright © Taylor & Francis Group, LLC

Wang J.-C.,Zhejiang University | Wang J.-C.,Taizhou Vocational and Technical College | Yu J.-L.,Zhejiang University | Ma S.-G.,Ningbo Urban Construction Investment Holding Company Ltd | Gong X.-N.,Zhejiang University
European Journal of Environmental and Civil Engineering | Year: 2015

Pressure indicated by earth pressure cell (EPC) often deviates from field earth pressure. EPC in normally consolidated soil was analysed with Taylors indentation method. It is found that assumes a linear relationship with soils compression modulus and. When preconsolidation pressure imposed on overconsolidated soil is unloaded, soils rebound strain is greater than EPCs, and a gap between EPCs sensing plate and soil appears. Upon reloading, contact between sensing plate and soil resembles spherical contact. This contact was analysed with Hertzs solution and it is found that is in direct ratio with, and is less than for a relatively low earth pressure and is greater than for a relatively high earth pressure. Earth pressure measurement experiments were conducted with river sand. Experimental results conform to the theoretical analysis herein for a relatively low earth pressure made in this paper. © 2014 Taylor & Francis.

Wang J.-C.,Zhejiang University | Yu J.-L.,Zhejiang University | Gong X.-N.,Zhejiang University | Ma S.-G.,Ningbo Urban Construction Investment Holding Company Ltd
Yantu Lixue/Rock and Soil Mechanics | Year: 2014

For a large area of shallow slope covered with weathered soils, when the groundwater table or the impermeable bedrock is shallow, intense rainfall will result in the air in soils being closed. With the wetting front moving downward, air pressure increases constantly. Closed air pressure not only reduces rainwater infiltration rate of the soil in slope, but also has a significant effect on slope stability. This paper analyzed the formation of air pressure and its related theories, and suggested that a pressure head Hc = 1.105hd was used to study slope stability(Hc is a value of water head related to the pore size distribution; hd is an air-closing water head). Combining the Mohr-Coulomb failure criterion of unsaturated soil and the limit-equilibrium method, the closed air pressure head is applied to slope stability analysis; and the stability analysis model is established considering air pressure. The comparison was also carried out with the classical stability analysis method; and a concept of effect rate of air pressure is also defined. It is found that closed air pressure significantly reduce the safety factor of slope stability; the classical stability analysis method of infinite slope is more dangerous; research results in this study of infinite slope safety prediction have a great guide significance. ©, 2014, Academia Sinica. All right reserved.

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