Abstract
Well resistance depends on discharge capacity of prefabricated vertical drains (PVDs), which affects the consolidation rate of soil at high water content importantly. Due to the lack of an axisymmetric large-strain consolidation model considering well resistance under vacuum pressure, the effect of well resistance on the degree of consolidation of ultra-soft soil is not clear. An axisymmetric large-strain consolidation model under vacuum pressure accounts for well resistance, self-weight stress, and vacuum attenuation along depth; both vertical and radial flow are proposed. Existing models established by Cao et al. and Nguyen et al. are special cases of the proposed model. The model and calculation method in this study are verified by the reported laboratory tests. The change laws of degree of consolidation defined by stress affected by key parameters of well resistance factor are discussed. It is found that the development of degree of consolidation will be delayed by the decreases of discharge capacity of PVDs and initial water content, as well as the increases of spacing ratio and time parameter of well resistance. The minimum demands of discharge capacity of PVDs with negligible well resistance increase exponentially with the increase of length of PVDs. The attenuation of vacuum pressure along the depth has greater influence on the degree of consolidation of soil than the attenuation of discharge capacity along the depth.
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Abbreviations
- A w :
-
the time parameter of well resistance
- A x :
-
the spatial parameter of well resistance
- \( {C}_c^{\ast } \) :
-
the intrinsic compression index
- C h :
-
radial consolidation coefficient of soil
- d e :
-
the diameter of influence area
- d s :
-
the diameter of smeared area
- d w :
-
the diameter of PVDs
- e :
-
the void ratio of soil
- e L :
-
the void ratio at liquid limit
- e 0 :
-
the void ratio at initial state
- \( {e}_{100}^{\ast } \) :
-
the void ratio of the remolded soil at σ'=100 kPa
- \( {e}_{1000}^{\ast } \) :
-
the void ratio of the remolded soil at σ'=1000 kPa
- f :
-
the well resistance factor
- \( \overline{f} \) :
-
the average value of well resistance factor
- H :
-
the height of the solid phase in the spatial vertical coordinate
- k 1 :
-
the attenuation residual coefficient of vacuum pressure
- k h :
-
the permeability coefficient of undisturbed soil
- k s :
-
the permeability coefficient of smeared soil
- k v :
-
the vertical permeability coefficient of soil
- k w :
-
the permeability coefficient of PVDs
- L :
-
the initial total height of the soil layer
- m :
-
the ratio of permeability coefficient between undisturbed zone and smeared zone
- n :
-
the spacing ratio
- -p 0 :
-
the vacuum pressure
- q w :
-
the discharge capacity of PVDs
- q w0 :
-
the initial value of qw
- r e :
-
the radius of influence area
- r s :
-
the radius of smeared area
- r w :
-
the radius of PVDs
- s :
-
the smear ratio
- \( \overline{u} \) :
-
the average excess-pore-water-pressure at any depth throughout the soil cylinder
- u h :
-
the excess pore water pressure in undisturbed zone
- u w :
-
the excess pore water pressure in the PVDs
- u s :
-
the excess pore water pressure in smeared zone
- w 0 :
-
the initial water content of soil
- w L :
-
the liquid limit of soil
- z :
-
the spatial vertical coordinate
- ξ :
-
the convective vertical coordinate
- γ w :
-
the unit weight of water
- ε v :
-
the unit volumetric strain of soil
- σ':
-
the effective vertical stress
- σ s':
-
the yield stress at remolded state
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Funding
This research was supported by National Natural Science Foundation of China (Grant No. 52178347, 51608312), Excellent Doctor Young Teacher Support Program of Weifang University, Scientific Research Foundation of Weifang University (Grant No. 2021BS32), Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University (Grant No. B210204004).
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Responsible Editor: Zeynal Abiddin Erguler
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Cao, Y., Zhang, R., Xu, G. et al. Axisymmetric large strain consolidation by vertical drains considering well resistance under vacuum pressure. Arab J Geosci 14, 2016 (2021). https://doi.org/10.1007/s12517-021-08354-y
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DOI: https://doi.org/10.1007/s12517-021-08354-y