A new simplified method and its verification for calculation of consolidation settlement of a clayey soil with creep

Summary This paper presents a new simplified method, based on Hypothesis B, for calculating the consolidation settlements of double soil layers exhibiting creep. In the new simplified Hypothesis B method, different stress–strain states including over‐consolidation and normal consolidation states can be considered with the help of the ‘equivalent time’ concept. Zhu and Yin method and US Navy method are adopted to calculate the average degree of consolidation for a double soil layer profile. This new simplified Hypothesis B method is then used to calculate the consolidation settlements of double soil layers, which have two different total thicknesses of soil layer (4 m and 8 m) and three different OCR values (Over‐Consolidation Ratio, OCR = 1, 1.5 and 2). The accuracy and verification of this new simplified method are examined by comparing the calculated results with simulation results from a fully coupled finite element (FE) program using a soft soil creep model. Four cases of double layer soil profiles are analyzed. Hypothesis A method with US Navy method for the average degree of consolidation has also been used to for calculating consolidation settlements of the same cases. For Case I(4m) and Case III(8m), it is found that curves of the new simplified Hypothesis B method using both Zhu and Yin method and US Navy method are very close to the results from FE simulations with the relative errors within 8.5%. For Case II(4m) and Case IV(8m), it is found that curves of the new simplified Hypothesis B method using Zhu and Yin method agree better with results from FE simulations with the relative errors within 11.7% than curves of the new simplified Hypothesis B method adopting US Navy method with the relative error up to 36.1%. Curves of Hypothesis A method adopting US Navy method have the relative error up to 55.0% among all four cases. In overall, the new simplified Hypothesis B method is suitable for calculation of consolidation settlements of double soil layers exhibiting creep, in which, Zhu and Yin method is recommended to obtain the average degree of consolidation. Copyright © 2016 John Wiley & Sons, Ltd.

Section: A New Simplified Hypothesis B Methods For Calculating Consolimentioning

confidence: 94%

\begin{matrix} left \\ S_{italictotalB} = S_{" primary "} + S_{italiccreep} \\ = U_{v} S_{f} + [α S_{creep, f} + (1 - α) S_{" secondary "}] f o r t \geq 1 day (t \geq t_{E O P, field} f o r S_{" secondary "}) \end{matrix}

Section: Brief Review Of the New Simplified Methods Based On Hypothesimentioning

confidence: 99%

\begin{matrix} left \\ ε_{f} = ε_{z 2} = \frac{C_{e}}{1 + e_{o}} \log (\frac{σ_{z 2}^{'}}{σ_{z 1}^{'}}) + ε_{z 1} \\ ε_{creep, f} = \frac{C_{α e}}{1 + e_{0}} \log (\frac{t + t_{e 2}}{t_{0} + t_{e 2}}) \\ t_{e 2} = t_{0} \times 10^{(ε_{z 2} - ε_{z p}) \frac{((), 1 + e_{0})}{C α e}} {((), \frac{σ_{z 2}^{'}}{σ_{z p}^{'}})}^{- \frac{C_{c}}{C α e}} - t_{0} f o r t \geq 1 day . \end{matrix}

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Section: Brief Review Of the New Simplified Methods Based On Hypothesimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A new simplified Hypothesis B method for calculating consolidation settlements of double soil layers exhibiting creep

Feng

Yin

2016

“…Borja and Choo considered the macro‐ and micro‐scales and simulated the “secondary compression” during 1‐D consolidation. Yin and Feng and Feng and Yin proposed a simplified Hypothesis B method to calculate the consolidation settlement for both single and double soil layers exhibiting creep. Wang, Sun, Li, and Ye provided a semi‐analytical solution to Terzaghi's 1‐D consolidation of a viscoelastic soil fractional derivative Kelvin‐Voigt model.…”

Section: Introductionmentioning

confidence: 99%

Study of the 1‐D consolidation behavior of two‐layered soft soils: Parametric studies using a rheological model with viscoplastic body

Zou

Xie

et al. 2018

Summary The governing equations for the coupled processes of consolidation and creep of two‐layered soft soils are established. The Nishihara rheological model is adopted to simulate the elasto‐viscoplastic characteristics of soft soils, disregarding the effects of the soil self‐gravity. A semi‐analytical theory combined with numerical and analytical methods is introduced to solve the governing equations of the one‐dimensional rheological model. The computational procedure and the approximate solutions for two‐layered soft soils subjected to surface loading are obtained for two drainage conditions. The solutions and the computational procedure are used to study the effects of the two layers and constitutive parameters on rheological consolidation behavior of soft soils. It can be concluded that two layers affect the rate of excess pore water pressure dissipation and settlement development. The parametric studies show that when the parameters of the upper layer remain constant, increases in the permeability and elastic modulus in the lower layer accelerate the dissipation of the excess pore water pressure, and meanwhile increases in the viscosity coefficient and viscoplastic limit slows down the dissipation of the excess water pressure.

A new simplified Hypothesis B method for calculating the consolidation settlement of ground improved by vertical drains

Feng

Yin

2017

Self Cite

Vertical drains are widely used in soft ground improvements to accelerate the consolidation process. This paper develops a new simplified Hypothesis B method for calculating the consolidation settlement of a soil layer improved by vertical drains under the instant and ramp loadings. As a comparison, the traditional Hypothesis A method is also used to calculate the settlement.Then, a fully coupled finite element consolidation analysis is utilized to examine and verify this simplified method and Hypothesis A method. For the instant loading, Carrillo-Barron method and Zhu-Yin method are used to obtain the average degree of consolidation for vertical drain system. Typical parameters, such as over-consolidation ratio (OCR), smear zone, and space ratio of vertical drains, are considered. It is found that the calculation results from the new simplified method in this study agree well with finite element simulations, and relative errors are in the range of 0.1% to 12.3%. Comparatively, there are obvious differences between the calculated results from Hypothesis A method and finite element results. Carrillo-Olson method and Zhu-Yin method are utilized to obtain the average degree of consolidation for the vertical drain system to consider the ramp loading. Equivalent time is determined from half of the construction period to calculate the creep compression under the ramp loading. The accuracy of this simplified Hypothesis B method using both Carrillo-Olson method and Zhu-Yin method is acceptable with the relative errors less than 9.4%.