Research on Logistic Model of Hydraulic Gradient in One-Dimensional Consolidation of Saturated Clay

2018 ◽  
Vol 08 (02) ◽  
pp. 22-34
Author(s):  
金柱 李
Keyword(s):  
Logistic Model ◽  
Hydraulic Gradient ◽  
One Dimensional ◽  
Saturated Clay

scholarly journals Measurement and Investigation on 1-D Consolidation Permeability of Saturated Clay considering Consolidation Stress Ratio and Stress History

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Le Zhang ◽  
Faning Dang ◽  
Jun Gao ◽  
Jiulong Ding
Keyword(s):  
Model Prediction ◽  
Permeability Coefficient ◽  
Stress Ratio ◽  
Void Ratio ◽  
Stress Difference ◽  
Stress History ◽  
One Dimensional ◽  
Consolidation Pressure ◽  
Saturated Clay ◽  
Stress Ratios

To study the influence of consolidation stress ratio and stress history on 1-D consolidation permeability of saturated clay, one-dimensional consolidation permeability tests were carried out with GDS triaxial device. The results indicated that the permeability coefficient and void ratio of normally and overconsolidated saturated clay decreased with the increase of consolidation stress ratio under different consolidation stress ratios but the same stress history. And the amount of final sample’s compression increased with the increase of the consolidation stress ratio. Under the condition of the same consolidation stress ratio but different stress history, the amount of final compression of the overconsolidated saturated clay was smaller than that of the normally consolidated saturated clay. Besides, the stress difference σdv between consolidation pressure σ and gravity stress σ c z was fitted to the amount of the final sample’s compression, and a good linear relationship between the stress difference σ d v and the amount of the final sample’s compression under each consolidation pressure was obtained. The results showed that it is necessary to consider the influence of consolidation stress ratio and stress history simultaneously on 1-D consolidation permeability of saturated clay. Meanwhile, it can accurately predict the amount of the final sample’s compression after knowing the gravity stress. Moreover, a model prediction analysis was conducted on the saturated clay and recommended to use the modified Kozeny-Carman’s equation to predict the permeability coefficient of Luochuan saturated clay during one-dimensional consolidation.

scholarly journals One-Dimensional Large-Strain Nonlinear Consolidation of Overconsolidated Clays with a Threshold Hydraulic Gradient

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Chuanxun Li ◽  
Jinyang Xiao ◽  
Yang Yang ◽  
Wenbing Wu
Keyword(s):  
Large Strain ◽  
Small Strain ◽  
Differential Method ◽  
Hydraulic Gradient ◽  
One Dimensional ◽  
Preconsolidation Pressure ◽  
Overconsolidated Clays ◽  
Consolidation Rate ◽  
The Difference ◽  
Final Settlement

The existence of the threshold hydraulic gradient in clays under a low hydraulic gradient has been recognized by many studies. Meanwhile, most nature clays to some extent exist in an overconsolidated state more or less. However, the consolidation theory of overconsolidated clays with the threshold hydraulic gradient has been rarely reported in the literature. In this paper, a one-dimensional large-strain consolidation model of overconsolidated clays with consideration of the threshold hydraulic gradient is developed, and the finite differential method is adopted to obtain solutions for this model. The influence of the threshold hydraulic gradient and the preconsolidation pressure of overconsolidated clay on consolidation behavior is investigated. The consolidation rate under large-strain supposition is faster than that under small-strain supposition, and the difference in the consolidation rate between different geometric suppositions increases with an increase in the threshold hydraulic gradient and a decrease in the preconsolidation pressure. If Darcy’s law is valid, the final settlement of overconsolidated clays under large-strain supposition is the same as that under small-strain supposition. For the existence of the threshold hydraulic gradient, the final settlement of the clay layer with large-strain supposition is greater than that with small-strain supposition.

scholarly journals Numerical Simulation and Experiment Study on the Characteristics of Non-Darcian Flow and Rheological Consolidation of Saturated Clay

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1385
Author(s):  
Zhongyu Liu ◽  
Yangyang Xia ◽  
Mingsheng Shi ◽  
Jiachao Zhang ◽  
Xinmu Zhu
Keyword(s):  
Constitutive Model ◽  
Flow Equation ◽  
Test Results ◽  
Permeability Test ◽  
One Dimensional ◽  
Saturated Clay ◽  
Simulation And Experiment ◽  
Flow Through ◽  
Constant Head ◽  
Oedometer Tests

To investigate the characteristics of the non-Darcian water flow through saturated clay and one-dimensional rheological consolidation behaviors of the soil in the Henan Province, we conducted constant-head permeability and one-dimensional rheological consolidation tests with one-way drainage using improved permeameter and oedometer tests, respectively. We then used Hansbo’s flow equation to classify the permeability test results and one-dimensional rheological consolidation equation combined with unified hardening (UH) constitutive model considering time effect was introduced to simulate the oedometer test results. The obtained results showed that the improved constant-head permeability test device was suitable for saturated clays, and that the UH constitutive model and Hansbo’s flow equation had good applications for the saturated clays investigated in this experiment.

Selection and application of a one-dimensional non-Darcy flow equation for two-dimensional flow through rockfill embankments

1995 ◽  
Vol 32 (2) ◽  
pp. 223-232 ◽  
Author(s):  
David Hansen ◽  
Vinod K. Garga ◽  
D. Ronald Townsend
Keyword(s):  
Packed Column ◽  
Flow Equation ◽  
Hydraulic Gradient ◽  
Darcy Flow ◽  
Two Dimensional ◽  
Rating Curve ◽  
One Dimensional ◽  
Flow Equations ◽  
Flow Through ◽  
Hydraulics Laboratory

Porous embankments comprised of relatively homogeneous coarse rockfill can be used to reduce the amount of spillage at downstream hydro dams or to control the outflow from stormwater detention basins. The stage-discharge rating curve is important in the design of such applications. In general, the coarseness of the material causes the flow to be non-Darcy; that is, characterized by a nonlinear relationship between bulk velocity and hydraulic gradient. Six one-dimensional (1D) non-Darcy flow equations, appearing in the literature, are presented. A limited comparison between computed and experimental results is then made on the basis of 1D packed-column tests performed in the hydraulics laboratory of the University of Ottawa. The question as to how such 1D closed-conduit equations might be used to estimate the quantity of flow through a porous embankment is then addressed, considering that the latter has a free surface and is a two-dimensional (2D) flow. The problem is successfully dealt with using the concept of "effective hydraulic gradient," a concept reminiscent of the method of sections used to analyze confined 2D seepage problems. A general equation is presented in which the effective hydraulic gradient is shown to be a function of two factors: (1) the shape of the embankment and (2) the upstream depth, relative to the height of the dam. The development and verification of the equation for the effective hydraulic gradient is described, together with its use in obtaining a rating curve for a hypothetical flowthrough dam composed of rock material 0.25 m in diameter. Key words : non-Darcy flow, flowthrough rockfill, effective hydraulic gradient, stage-discharge rating curve.

Viscous Property of Clay

2012 ◽  
Vol 455-456 ◽  
pp. 1532-1537 ◽  
Author(s):  
Jian Zhong Li
Keyword(s):  
Strain Rate ◽  
Water Content ◽  
Axial Strain ◽  
Constant Strain Rate ◽  
Test Results ◽  
Compression Tests ◽  
Viscous Property ◽  
One Dimensional ◽  
Saturated Clay ◽  
Rate Test

Viscous property of saturated, wet, air-dried and oven-dried clay was evaluated by performing a series of one dimensional compression tests including primary loading, creep, global unloading and reloading tests. In the tests, axial strain rate was changed stepwise many times during monotonic primary loading at a constant strain rate. Test results show that viscous property of clay with different water content under different test condition is similar. In order to evaluate the viscous property of clay, parameter β was introduced basing on the present test results of clay and author’s previous study. β value of clay with different water content under different test condition varied from 0.034 to 0.064. Test results show that β value of saturated clay is generally larger than that of dried clay.

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