scholarly journals Analysis of elastic viscoplastic consolidation of sand drain foundations with exponential seepages

2021 ◽  
Vol 248 ◽  
pp. 01039
Author(s):  
Duanyang Yang ◽  
Fengyuan Li ◽  
Yangyang Xia ◽  
Mingsheng Shi ◽  
Yanjie Hao ◽  
...  
Keyword(s):  
Pore Pressure ◽  
External Load ◽  
Permeability Coefficient ◽  
Numerical Solutions ◽  
Darcy’S Law ◽  
Soft Clay ◽  
Darcy's Law ◽  
Consolidation Process ◽  
Soil Skeleton ◽  
The Impact

Studies have shown that the pore seepage in soft clay deviates from Darcy's law, with the compressibility and permeability of the soil demonstrating obvious nonlinear characteristics during the consolidation process. These factors will affect the sand drain foundation consolidation process. In order to explore the consolidation mechanism of sand drain foundation in saturated clay, this paper introduces the UH model considering the time effect to describe the nonlinear deformation relation of the soil skeleton under the Barron free strain assumption and introduces the exponential seepage equation as an alternative to Darcy's law. Additionally, the impact of the permeability coefficient and the smearing effect is considered which is used to re-derive the conventional sand drain consolidation equation, and then the finite difference method is adopted to give the implicit numerical solutions of the equation. By comparing with literature results, the validity of the method developed in this paper is verified. Then, the effects of the soil nonlinearity, construction disturbance, and external load on the sand drain foundation nonlinear consolidation process are studied as a function of time. The current results reveal that due to the viscous effect of soil, the pore pressure near the undrained boundary of the sand drain foundation during the pre-loading period increases. The above phenomenon is more evident when considering the non-Darcy seepage; meanwhile, the consolidation rate of the sand drain foundation also becomes increasingly slow. Moreover, the decrease of the permeability coefficient in the smear zone can significantly reduce the dissipation rate of the overall pore pressure of the sand drain foundation, while the increase of the external load accelerates foundation consolidation.

Effects of Large Rock Particles on Permeability of Soil and Rock Mixture

2011 ◽  
Vol 250-253 ◽  
pp. 1804-1807
Author(s):  
Xian Chao Xiang ◽  
Guo Sheng Jiang
Keyword(s):  
Pore Pressure ◽  
Darcy’S Law ◽  
Fluid Velocity ◽  
Darcy's Law ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Large Particles ◽  
The World ◽  
Lab Test

The soil and rock mixture is widely spread in the world， which is much different from homogeneous and continuous soil, it is hard to get the permeability of the soil and rock mixture by theories, and it is also hard to get that from the large lab test as the difficulty in sampling. The particle flow code (PFC) method is used to study the permeability character influenced by large rock particles. The result shows that the seepage of the soil and rock mixture obeys the linearity of Darcy’s law in low fluid velocity, but the large particles influence the local pore pressure evidently. The permeability increases while the ratio of rock to soil increase first, and decreases while the ratio enlarge to 0.5, then increases after the ratio enlarge to 0.7. The large rock particles jam the fluid path, but decrease the length of the pipe, the permeability is influenced by the two effects.

scholarly journals Comparative analysis of Piled Raft Foundation System (PRFS) settlements placed on soft soils via geotechnical centrifuge

2021 ◽  
Vol 44 (2) ◽  
pp. 1-12
Author(s):  
Edgar Rodríguez Rincon ◽  
Bernardo Caicedo Hormaza ◽  
Juan Felix Rodríguez Rebolledo
Keyword(s):  
Pore Pressure ◽  
Soft Clay ◽  
Clay Soils ◽  
Deep Soil ◽  
Consolidation Process ◽  
Soil Layers ◽  
Geotechnical Centrifuge ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Scale Models

The use of Piled Raft Foundations Systems (PRFS) has been extended to different types of soils, including soft clay soils. In this type of soil it is possible that, in addition to the consolidation process due to the presence of loads, a subsidence process is generated, associated with variations in pore pressure with depth. In many cases, these variations are associated with the loss of recharge of the aquifers or with the extraction of water from deep soil layers. In this work, the behaviour of some PRFS built on soft clay soils, which are subjected to the double consolidation process, are evaluated, both by loading and by the extraction of water from deep soil layers. The research is based on the implementation of reduced-scale models in a geotechnical centrifuge; the influence of the separation and number of piles on the deformation or settlement of the system is analysed. It is shown that, normally, groups of piles with greater separation control settlement more effectively. However, the settlements are greater when the soil is subjected to the weight of the structure in addition to a process of depletion of the pore pressure, because the settlement depends on the distribution of the piles, which is described using the Filling Factor (FF).

Numerical modelling of nonlinear effects in laminar flow through a porous medium

1988 ◽  
Vol 190 ◽  
pp. 393-407 ◽  
Author(s):  
O. Coulaud ◽  
P. Morel ◽  
J. P. Caltagirone
Keyword(s):  
Porous Medium ◽  
Pressure Drop ◽  
Nonlinear Term ◽  
Numerical Solutions ◽  
Darcy’S Law ◽  
Darcy's Law ◽  
Quadratic Term ◽  
Inertial Effects ◽  
Operator Splitting Methods ◽  
Flow Through

This paper deals with the introduction of a nonlinear term into Darcy's equation to describe inertial effects in a porous medium. The method chosen is the numerical resolution of flow equations at a pore scale. The medium is modelled by cylinders of either equal or unequal diameters arranged in a regular pattern with a square or triangular base. For a given flow through this medium the pressure drop is evaluated numerically.The Navier-Stokes equations are discretized by the mixed finite-element method. The numerical solution is based on operator-splitting methods whose purpose is to separate the difficulties due to the nonlinear operator in the equation of motion and the necessity of taking into account the continuity equation. The associated Stokes problems are solved by a mixed formulation proposed by Glowinski & Pironneau.For Reynolds numbers lower than 1, the relationship between the global pressure gradient and the filtration velocity is linear as predicted by Darcy's law. For higher values of the Reynolds number the pressure drop is influenced by inertial effects which can be interpreted by the addition of a quadratic term in Darcy's law.On the one hand this study confirms the presence of a nonlinear term in the motion equation as experimentally predicted by several authors, and on the other hand analyses the fluid behaviour in simple media. In addition to the detailed numerical solutions, an estimation of the hydrodynamical constants in the Forchheimer equation is given in terms of porosity and the geometrical characteristics of the models studied.

An Approximate Method for Computing Nonsteady-State Flow of Gases in Porous Media

1961 ◽  
Vol 1 (04) ◽  
pp. 264-276 ◽  
Author(s):  
L.G. Jones
Keyword(s):  
Approximate Method ◽  
Test Data ◽  
Gas Flow ◽  
Numerical Solutions ◽  
Darcy’S Law ◽  
Darcy's Law ◽  
Reservoir Rock ◽  
Well Test ◽  
Nonsteady State ◽  
Flow Law

Abstract An approximate method of calculation is developed in this paper which allows duplication of radial unsteady-state gas flow computer results where Darcy's law applies, such as those reported by Aronofsky and Jenkins and Bruce, Peaceman, Rachford, and Rice. Moreover, the new calculation method can be used to obtain results for radial unsteady-state gas flow obeying the quadratic flow law proposed by Duwez and Green. Means are discussed for predicting well behavior at single or superimposed flow rates in finite or infinite reservoirs, determining reservoir rock properties from well-test data, reproducing and interpreting back-pressure test data, and determining the radial extent and reserves of gas reservoirs from well-test data. Example calculations are presented for gas flow following both Darcy's law and the quadratic flow law. Introduction Since the publishing of U. S. Bureau of Mines Monograph 7, most gas-well testing methods have been based on the equation where q= production rate, pf and Pw are formation pressure and sandface pressure, respectively, and y and a are constants to be obtained from test data. These methods, used for predicting both deliverability and "open-flow" capacity of gas wells have been useful and accurate in many cases but unsatisfactory in others. Even at best, however, they do not supply information about the formation or lead to an understanding of nonsteady-state gas flow in porous media. Many theoretically based studies of gas flow obeying Darcy's law have been made. Since the partial differential equations which result from combining Darcy's flow law with the continuity equation are nonlinear, most of the published research consists of either numerical solutions or analytical solutions for linear approximating equations. Such solutions have been of limited value in field work due to their unhandy form and their failure to correlate most field data. There is evidence which indicates that Darcy's law is inadequate to describe gas flow at some flow rates of practical interest. A quadratic flow law, which reduces to Darcy's law at low rates, is more successful in accounting for experimentally observed behavior. This flow law has been applied successfully to a few hypothetical reservoir cases in work which has not yet been published. However, these numerical solutions of the equations involved have been successful only on a special analog computer. Routine applications to field cases would be awkward and have not been attempted. The present paper describes an approximate method for computing nonsteady-state gas flow solutions which has been completely successful in predicting the results for both Darcy flow and quadratic flow obtained by elaborate numerical methods. The new calculation method allows determination of the observable variables in gas-well testing at constant rates. It is similar to the scheme of using a succession of steady states suggested by Muskat in that it makes use of steady-state and material-balance equations. It also is similar to the work of Aronofsky and Jenkins in that the new method includes Aronofsky and Jenkins stabilized flow equation as a special case. It improves upon both of these calculation schemes in that it accurately describes all portions of reservoir history and suggests means of determining reservoir rock properties from well-test data. This paper deals only with production from a reservoir, in which case the rate is defined as being negative. The reservoir studied here is a homogeneous, disk-shaped porous body of uniform thickness, with all boundaries sealed except the inner radial boundary of the well. SPEJ P. 264^

Theoretical and Experimental Studies on Thermal Consolidations Characteristics of Ningbo Soft Clay

2014 ◽  
Vol 501-504 ◽  
pp. 141-149
Author(s):  
Tie Feng Yin
Keyword(s):  
Extreme Values ◽  
Soft Clay ◽  
Experimental Studies ◽  
Effect Of Temperature ◽  
Consolidation Process ◽  
Confining Pressures ◽  
Degree Of Consolidation ◽  
The Difference ◽  
Increasing Temperature ◽  
The Impact

When considering the effect of temperature, consolidation deformation of the soil is a complex multi-physics coupling problem. For soil of different regions, the influence of temperature on soil physical properties vary widely, even presents the opposite result. In order to realize the thermal consolidations characteristics of Ningbo soft clay, this paper selected Ningbo soft clay and done consolidation test with temperature controlled under different temperatures and confining pressures. Combined with the analysis of theory, this paper carried out the reasonable explanation to the experimenting phenomenon. The results show that: temperature increase the penetration rate of the soil by changing the coefficient of the water, thereby accelerating the consolidation process. The degree of consolidation increases with increasing temperature. In the same conditions and time, the higher the degree of consolidation of soil with increasing temperature, and the difference of the degree of consolidation increases with the increase of the difference in temperature. The difference of the degree of consolidation under different temperature increases with time showing a rapid increase in the extreme values first, and then gradually reduced to zero. Therefore, effect of temperature is mainly reflected in the drainage consolidation process less than half the period of time before, and the greater the temperature difference, the impact effect is more obvious.

Instability and Collapse in Discrete Wave Equations

2005 ◽  
Vol 5 (3) ◽  
pp. 223-241
Author(s):  
A. Carpio ◽  
G. Duro
Keyword(s):  
Continuum Limit ◽  
Wave Equations ◽  
Numerical Solutions ◽  
Blow Up ◽  
Theoretical Predictions ◽  
Initial States ◽  
The Impact ◽  
The Continuum

AbstractUnstable growth phenomena in spatially discrete wave equations are studied. We characterize sets of initial states leading to instability and collapse and obtain analytical predictions for the blow-up time. The theoretical predictions are con- trasted with the numerical solutions computed by a variety of schemes. The behavior of the systems in the continuum limit and the impact of discreteness and friction are discussed.

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