Experimental study about the influence of cyclic load on the hydraulic conductivity of clay
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RESEARCH PAPER
Experimental study about the influence of cyclic load on the hydraulic conductivity of clay Jian Zhou1,2
•
Ling-Hui Luo1,3 • Liang-Gui Yu1,2 • Horris Nangulama1,2
Received: 16 January 2020 / Accepted: 28 August 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The hydraulic conductivity k, one of the most important engineering properties of soft clay, plays a great role during the whole life cycle of underwater tunnel. Therefore, it is necessary to systematically study the responses of k to the dynamic load under the background of the great development of geotechnical engineering in the world. In this study, a series of seepage tests after cyclic loading were conducted on reconstituted kaolin clay using a modified hollow cylinder apparatus. The influence of cyclic load on the permeability characteristics of soft clay was illustrated in two aspects. The cumulative axial deformation of clay induced by cyclic loading resulted in the smaller hydraulic conductivity of the specimens, and also, the dynamic load reconstructed the microstructure of clay and made the number of large pores getting decreased and the small pores increased. There was a positive correlation between the deformation of soil and the change of hydraulic conductivity, but the reconstruction effect was irregular with the frequency of dynamic load. The measured k values got affected at the beginning, this phenomenon appropriately explains the positive correlation between the number of cycles of dynamic load and the change of hydraulic conductivity. Keywords Frequency HCA seepage instrument Hydraulic conductivity Number of cycles Reconstituted kaolin
1 Introduction Hydraulic conductivity k is one of the most important parameters of soft clay, and it plays a great role during the whole life of underwater or underground construction. During construction stage, the excess pore pressure caused by excavation will dissipate by means of leaking through the annular joints and bolts, which leads to un-negligible settlement [23], and the dissipation rate is highly dependent upon the soil permeability. Zhang et al. [31] indicated that even the anisotropic permeability of soil will lead to the
& Jian Zhou [email protected] 1
Research Center of Coastal and Urban Geotechnical Engineering, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, Zhejiang Province, China
2
Research Center of Zhejiang Urban Underground Space Development Engineering, Zhejiang University, Hangzhou 310058, China
3
Shanghai Municipal Engineering Design Institute (Group) Co., Ltd, Shanghai 200082, China
nonuniform drainage boundary around the tunnel, which tends to induce larger ground and tunnel settlement. While the permeability characteristics of soil are closely related to the pore distribution, some microscopic evidence had shown that not only the internal structure of clay has been reconstructed by dynamic load, but also the distribution of micro-pores differs from that before, f
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