Settlement rate of foundations on unsaturated soils

1999 ◽  
Vol 36 (5) ◽  
pp. 940-946 ◽  
Author(s):  
Ernesto Ausilio ◽  
Enrico Conte
Keyword(s):  
Volume Change ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Shallow Foundations ◽  
Settlement Rate ◽  
One Dimensional ◽  
Consolidation Rate ◽  
Degree Of Consolidation ◽  
The One ◽  
External Loads

This paper deals with the one-dimensional consolidation of unsaturated soils due to the application of external loads. A simple equation is derived that enables one to predict the rate of settlement of shallow foundations with time. This equation uses the constitutive relationships proposed by Fredlund and Morgenstern to define the volume change of unsaturated soils, and relates the settlement rate to the average degree of consolidation for both the water and air phases. A series of examples is shown to demonstrate the feasibility and usefulness of the derived equation. Key words: one-dimensional consolidation, unsaturated soil, degree of consolidation, rate of settlement.

scholarly journals One-Dimensional Vacuum Steady Seepage Model of Unsaturated Soil and Finite Difference Solution

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Feng Huang ◽  
Jianguo Lyu ◽  
Guihe Wang ◽  
Hongyan Liu
Keyword(s):  
Finite Difference ◽  
Unsaturated Soil ◽  
Vacuum Pressure ◽  
Vacuum Field ◽  
One Dimensional ◽  
Steady Seepage ◽  
Basic Equations ◽  
The One ◽  
Seepage Law ◽  
Relationship Of

Vacuum tube dewatering method and light well point method have been widely used in engineering dewatering and foundation treatment. However, there is little research on the calculation method of unsaturated seepage under the effect of vacuum pressure which is generated by the vacuum well. In view of this, the one-dimensional (1D) steady seepage law of unsaturated soil in vacuum field has been analyzed based on Darcy’s law, basic equations, and finite difference method. First, the gravity drainage ability is analyzed. The analysis presents that much unsaturated water can not be drained off only by gravity effect because of surface tension. Second, the unsaturated vacuum seepage equations are built up in conditions of flux boundary and waterhead boundary. Finally, two examples are analyzed based on the relationship of matric suction and permeability coefficient after boundary conditions are determined. The results show that vacuum pressure will significantly enhance the drainage ability of unsaturated water by improving the hydraulic gradient of unsaturated water.

Semi-analytical solution for the one-dimensional consolidation of multi-layered unsaturated soils with semi-permeable boundary

2021 ◽  
Vol 130 (1) ◽  
Author(s):  
Linzhong Li ◽  
Aifang Qin ◽  
Lianghua Jiang
Keyword(s):  
Analytical Solution ◽  
Unsaturated Soils ◽  
One Dimensional ◽  
The One

Phenomenological Approach to Flow and Volume Change in Soils and Other Media

1995 ◽  
Vol 48 (10) ◽  
pp. 650-658 ◽  
Author(s):  
J. R. Philip
Keyword(s):  
Volume Change ◽  
Colloidal Particles ◽  
Three Dimensional ◽  
Phenomenological Approach ◽  
Solid Particles ◽  
Soil Physics ◽  
One Dimensional ◽  
Component Systems ◽  
Poisson Boltzmann Equation ◽  
The One

We review the phenomenological approach, on the macroscopic or Darcy scale, to flow and volume change in clays and other swelling media. The formulation represents the generalization to media subject to volume change of the well-established phenomenological approach to flow in non-swelling media primarily established in the context of soil physics. The one-dimensional generalization to swelling media is straightforward, and may be usefully applied to practical one-dimensional systems, including three-component systems with solid particles, water, and air. On the other hand, the further generalizations to two- and three-dimensional systems have not yet been developed fully convincingly. Difficult questions include the mode of stress transmission and the tensorial stress-strain relations in multidimensional and multi-component systems. One means of gaining insight into these questions for media of high colloid content (such as clays) is through relevant solutions of the Poisson-Boltzmann equation governing electrical double-layer interactions in dense arrays of colloidal particles. These solutions give pertinent information on both the macroscopic and the microscopic scales. We present a progress report on work along these lines.

Analysis of One-Dimensional Consolidation of Non-Homogeneous Layer with Exponential Flow Law

2014 ◽  
Vol 638-640 ◽  
pp. 374-379 ◽  
Author(s):  
Feng Xi Zhou ◽  
Yi Ming He ◽  
Ying Xin
Keyword(s):  
Numerical Solution ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Decisive Role ◽  
Homogeneous Layer ◽  
One Dimensional ◽  
Governing Differential Equation ◽  
Degree Of Consolidation ◽  
Flow Law ◽  
The One

Based on exponential flow law, the analytical solution to the one-dimension consolidation governing differential equation was deduced when the laws of permeability and compressibility coefficients with depth can be expressed as exponential function. By finite difference method, the numerical solution of excess pore water pressure and degree of consolidation was obtained, then the reliability of numerical solution is verified by comparing numerical results with analytical results, and consolidation behavior of non-homogeneous layer with exponential flow law under various parameters is analyzed. The results showed that under the condition of the two-sided drainage, the heterogeneity of foundation consolidation of index of seepage speed depends on the index of the size and the size of the non-uniform parameters. That is when the index m is bigger, increase the permeability coefficient, reduce the compression coefficient, the consolidation is faster, but the inhomogeneous parameters are still play a decisive role.

scholarly journals One-Dimensional Consolidation of Multi-Layered Unsaturated Soil with Impeded Drainage Boundaries

2020 ◽  
Vol 11 (1) ◽  
pp. 133
Author(s):  
Suhua Zhou ◽  
Jiatao Kang ◽  
Chang Lv ◽  
Minghua Huang
Keyword(s):  
Boundary Condition ◽  
Unsaturated Soil ◽  
Numerical Solutions ◽  
Laplace Domain ◽  
One Dimensional ◽  
Soil Settlement ◽  
The One ◽  
The Time Domain ◽  
Consolidation Behavior ◽  
Excess Pore

In geotechnical engineering, the consolidation of unsaturated soil is a common issue of great interest. Considering the multi-layered property and impeded drainage boundary condition of the soil stratum in real engineering, this study aimed to develop a general semi-analytical solution for assessing the one-dimensional (1D) consolidation behavior of multi-layered unsaturated soil that is subjected to a general impeded drainage boundary condition and a time-dependent loading. To achieve the final solution, the proposed consolidation system is firstly decoupled and solved in the Laplace domain. Then, the semi-analytical solutions for the excess pore-air pressure and excess pore-water pressures as well as the soil settlement are formulated. The Crump method is employed to provide their final results in the time domain. The correctness of the derived solutions was verified against the available analytical and numerical solutions, and excellent agreements were found for the two comparisons. Moreover, two studied examples are presented to illustrate the 1D consolidation behavior of multi-layered unsaturated soil and the influences stemming from the impeded drainage parameters are discussed.

scholarly journals One-Dimensional Consolidation of Viscoelastic Soils Incorporating Caputo-Fabrizio Fractional Derivative

2021 ◽  
Vol 11 (3) ◽  
pp. 927
Author(s):  
Minghua Huang ◽  
Chang Lv ◽  
Suhua Zhou ◽  
Shuaikang Zhou ◽  
Jiatao Kang
Keyword(s):  
Fractional Derivative ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Distribution Patterns ◽  
One Dimensional ◽  
Special Cases ◽  
Rectangular Pattern ◽  
Degree Of Consolidation ◽  
The One ◽  
Consolidation Behavior

In this paper, the Caputo-Fabrizio fractional derivative is introduced to investigate the one-dimensional consolidation behavior of viscoelastic soils. Using the Caputo-Fabrizio operator, a novel four-element fractional-derivative model is proposed to capture the viscoelastic properties of the soils, and further the one-dimensional consolidation equation is derived to simulate the consolidation behavior of the soils. Using the techniques of eigenfunction expansion and Laplace transform, a series of analytical solutions are derived to calculate the excess pore-water pressure and the average degree of consolidation of the soils. The total vertical stress in the soil is assumed to change linearly with depth, and its distribution patterns are classified to rectangular pattern, trapezoidal pattern and inverse trapezoidal pattern. Four loading types including instantaneous loading, ramp loading, sinusoidal loading and general cyclic loading are considered. Then, a comparison for several special cases is presented to verify the correctness of the proposed solutions through comparing with existing theories. Moreover, two examples considering ramp and sinusoidal loadings are given to study the consolidation behavior of the viscoelastic soils incorporating the Caputo-Fabrizio fractional derivative.

scholarly journals Controlling Conditions of the One-Dimensional Consolidation Test on Peat Soil

2021 ◽  
Vol 11 (23) ◽  
pp. 11125
Author(s):  
Bo Peng ◽  
Ruiling Feng ◽  
Lijian Wu ◽  
Yupeng Shen
Keyword(s):  
Ambient Temperature ◽  
Peat Soil ◽  
Small Range ◽  
Loss On Ignition ◽  
One Dimensional ◽  
Consolidation Test ◽  
Decomposition Of Organic Matter ◽  
Sample Height ◽  
Consolidation Rate ◽  
The One

This paper studies the changes in the loss on ignition (LOI), total nitrogen content (TN), and strain in a one-dimensional consolidation test on peat soil. The effects of small-range fluctuations in the ambient temperature and changes in the sample height on the consolidation process of peat soil are proposed and verify the inhibitory effect of thymol on the decomposition of organic matter. The results show that when the ambient temperature fluctuates in a small range, the consolidation rate is significantly affected. Under a low load, the ambient temperature increases by 1–2 °C, and the consolidation rate can be increased by up to 10 times. This study presents the changes in loss on ignition (LOI) and total nitrogen content (TN) during consolidation, which proves that soaking the samples with a thymol solution can effectively control the decomposition of organic matter in peat soil. The strain of peat soil at a height of 30 mm is greater than or equal to that of other height samples, while that of mucky soil is 20 mm. Therefore, 30mm is the recommended sample height for peat soil for the one-dimensional consolidation test.

scholarly journals A Study on the Creep Characteristics of Airport Viscous Subsoil Based on Unsaturated Stress Level

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jun Feng ◽  
Yue Ma ◽  
Zaobao Liu
Keyword(s):  
Stress Level ◽  
Unsaturated Soil ◽  
Three Dimensional ◽  
Matric Suction ◽  
Creep Model ◽  
Creep Stage ◽  
One Dimensional ◽  
Creep Characteristics ◽  
Stress Levels ◽  
The One

The present study takes the ratio of the matric suction to the net vertical stress and the ratio of the matric suction to the net mean stress as new unsaturated stress levels f and F , respectively. Based on the laboratory tests and theoretical derivation, the modified one-dimensional Mesri creep model and three-dimensional creep model were established, which takes the unsaturated stress level into account. Then, the one-dimensional and three-dimensional creep characteristics of the unsaturated viscous subsoil of an airport under different unsaturated stress levels were analyzed. The following conclusions could be drawn: (1) under different stress levels, the one-dimensional creep deformation of unsaturated soil has a power function relationship with time, and the change rate exponentially decreases with the stress level, which can be well-expressed by the proposed modified one-dimensional Mesri creep model; (2) under different stress levels, the three-dimensional creep strain of the unsaturated soil shows a hyperbolic curve with time and a near-linear relationship at the semilogarithmic coordinate, which can be well-expressed by the proposed modified three-dimensional creep model; (3) under different stress levels, both the one-dimensional creep and three-dimensional creep of the unsaturated soil can be divided into two stages, which are the accelerated creep stage and stable creep stage.

Measurement of the coefficient of permeability for a deformable unsaturated soil using a triaxial permeameter

1998 ◽  
Vol 35 (3) ◽  
pp. 426-432 ◽  
Author(s):  
Shangyan Huang ◽  
D G Fredlund ◽  
S L Barbour
Keyword(s):  
Volume Change ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Matric Suction ◽  
Soil Specimen ◽  
Normal Stresses ◽  
Permeability Measurement ◽  
Coefficient Of Permeability

The development of a specially designed triaxial permeameter for the measurement of the coefficient of permeability of deformable unsaturated soils is presented in this paper. The triaxial permeameter makes it possible to directly measure the coefficient of permeability at various combinations of net normal stresses and matric suction values. The volume change of the soil specimen during the permeability measurement can also be monitored. The performance of the permeameter is demonstrated for a group of tests conducted on slurried specimens of a silty sand.Key words: unsaturated soil, coefficient of permeability, triaxial permeameter, volume change.

scholarly journals Analysis of One-Dimensional Consolidation for Unsaturated Soils under Piecewise Cyclic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Yuanchun Huang ◽  
Sidong Shen ◽  
Lei Wang ◽  
Tianyi Li ◽  
Xianlei Fu
Keyword(s):  
Cyclic Loading ◽  
Unsaturated Soils ◽  
Laplace Domain ◽  
One Dimensional ◽  
Ground Treatment ◽  
Parametric Studies ◽  
The One ◽  
Semianalytical Method ◽  
Excess Pore Pressures

This paper studies the one-dimensional (1D) consolidation behavior for unsaturated stratum subjected to piecewise cyclic loading. Combined with the widely accepted consolidation theory of unsaturated soils, a semianalytical method was employed to investigate the consolidation of unsaturated foundation considering piecewise cyclic loading in the Laplace domain. Furthermore, the reduced solutions were produced to perform the verification work accompanied by the results in the existing literature. Finally, a case study was conducted to explore the consolidation characteristics under piecewise cyclic loading (i.e., triangular and trapezoidal cyclic loadings). Parametric studies were carried out by variations of excess pore pressures and settlement against the ratio of air-water permeability coefficients, depth, and loading parameters. The research proposed in this paper can provide theoretical basis for the ground treatment of unsaturated soils, especially for rationally accelerating consolidation or avoiding sudden settlement.

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