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Characteristics of soils
Published in Yanrong Li, Handbook of Geotechnical Testing, 2019
Soil consolidation refers to the process in which excess water is discharged from the soil, the excess pore water pressure is dissipated, and the soil is compressed and deformed. The compressibility parameters and consolidation coefficients of the soil can be determined by a consolidation test. Full details on the operations of the consolidation test are given in GB 50123-1999, BS 1377-5, BS 1377-6 and ASTM D2435/D2435M-11.
Analytical solution for one-dimensional nonlinear consolidation of double-layered soil with improved continuous drainage boundary
Published in European Journal of Environmental and Civil Engineering, 2023
Mengfan Zong, Wenbing Wu, M. Hesham El Naggar, Guoxiong Mei, Pengpeng Ni, Meijuan Xu
Figure 9 reflects the influence of the η value on Us. It can be found that the consolidation degree of soil decreases with the increase of η value. The larger the η value is, the greater the initial pore water pressure at the boundary will be, which indicates that the pore water will be hindered more and the consolidation rate of soil will be slower. In addition, η value has great influence on soil consolidation at the early stage, but little influence on soil consolidation at the later stage. In engineering, when the sand cushion is designed according to the complete drainage effect, the pore water dissipates rapidly at the early stage of consolidation. At this stage, the traditional drainage boundary plays a very good drainage role. However, in the middle and late stage of soil consolidation, pore water pressure decreases gradually and the dissipation rate of pore water slows down gradually. In this stage, the drainage capacity provided by traditional drainage boundary is greatly wasted. Therefore, the sand cushion can be designed according to the continuous drainage boundary, and the required consolidation drainage rate can be achieved by adjusting the interface parameter value.
Effect of the pressurized duration on improving dredged slurry with air booster vacuum preloading
Published in Marine Georesources & Geotechnology, 2020
Shanwei Ke, Peng Wang, Xiuqing Hu, Xueyue Geng, Jun Hai, Jinqiang Jin, Ziwu Jiang, Qiang Ye, Zhijian Chen
In China, there are many land reclamation projects currently being rapidly developed. Dredged slurry from the seabed is widely used as the fill material in these projects. However, dredged slurry possesses a high water content, high compressibility, low permeability, and low bearing capacity (Wang et al. 2016a; Fu et al. 2017a; Yan, Wang, and Zhang 2010; Wu et al., 2019). In order to achieve the required bearing capacity for a construction project, the dredged slurry must be treated with vacuum pressure reinforcement. Vacuum preloading technology was first proposed by the Swedish geologist Kjellman (1952), where negative pressure is generated in the soil by using a sealed film to cover the ground and pumping air from the soil with prefabricated vertical drains (PVDs) (Cai et al. 2017). Because of the negative pressure, the pore water in the soil moves to the surface through the vertical drainage. This reduces the pore water pressure and increases the effective stress, which promotes soil consolidation (Chai, Carter, and Hayashi 2005, 2006; Chai and Carter 2011; Chai, Hong, and Shen 2010; Wang et al. 2017).
Application and design method of dredging sludge ground treated via prefabricated radiant drain vacuum preloading
Published in Marine Georesources & Geotechnology, 2023
Shuangxi Feng, Huayang Lei, Anyi Liu, Shitao Dai, Tianlu Ma, Zheng Lei
The pore water pressure contours derived for different PHD lengths at a PHD spacing of 10 cm are shown in Figure 16. The figure demonstrates that the PHD length can affect both the pore water pressure distribution and settlement distribution. For example, when the PHD length is 25 cm, the pore water pressure distribution exhibits an elliptical shape. In contrast, when the PHD length is shorter than 10 cm, the pore water pressure distribution presents a quasi-circular shape. In addition, relatively long PHD lengths can enlarge the influencing scope of the pore water pressure, thus accelerating soil consolidation. These findings illustrate that a better PRD vacuum preloading-induced reinforcement effect can be obtained by increasing the PHD length.