Numerical Solution of Nonlinear Large Strain Consolidation Based on Non-Darcian Flow

In this paper, based on non-Darcian flow, the governing equation of 1D nonlinear large strain consolidation is established, which comprehensively accounts for vertical strain, soil self-weight, geometrical nonlinearity, continuity of pore water flow, the relative velocity of the fluid and solid phases, and changing compressibility and hydraulic conductivity during consolidation. Then the numerical solution is obtained with the finite difference method (FDM). Verification of the FDM solution shows excellent accuracy. On this basis, we investigate the influence of the non-Darcian flow on consolidation behavior. The results show that the increase of the non-Darcian exponent will accelerate the consolidation rate in the beginning, while slowing down the consolidation rate in the end. However, it has no effect on the final settlement of the soil layer. In addition, boundary drainage conditions have a huge impact on the consolidation rate, whether it is Darcian or non-Darcian flow.

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Large-strain consolidation analysis of PVD-installed soft soil considering the discharge capacity variation according to depth and time

Engineering Computations ◽

10.1108/ec-05-2020-0253 ◽

2020 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Ba-Phu Nguyen ◽

Ananta Man Singh Pradhan ◽

Tan Hung Nguyen ◽

Nhat-Phi Doan ◽

Van-Quang Nguyen ◽

...

Keyword(s):

Numerical Solution ◽

Discharge Capacity ◽

Large Strain ◽

Soft Soil ◽

Monitoring Data ◽

Two Dimensional ◽

Content Type ◽

Prefabricated Vertical Drain ◽

Consolidation Rate ◽

Consolidation Behavior

Purpose The consolidation behavior of prefabricated vertical drain (PVD)-installed soft deposits mainly depends on the PVD performance. The purpose of this study is to propose a numerical solution for the consolidation of PVD-installed soft soil using the large-strain theory, in which the reduction of discharge capacity of PVD according to depth and time is simultaneously considered. Design/methodology/approach The proposed solution also takes into account the general constitute relationship of soft soil. Subsequently, the proposed solution is applied to analyze and compare with the monitoring data of two cases, one is the experimental test and another is the test embankment in Saga airport. Findings The results show that the reduction of PVD discharge capacity according to depth and time increased the duration required to achieve a certain degree of consolidation. The consolidation rate is more sensitive to the reduction of PVD discharge capacity according to time than that according to the depth. The effects of the reduction of PVD discharge capacity according to depth are more evident when PVD discharge capacity decreases. The predicted results using the proposed numerical solution were validated well with the monitoring data for both cases in verification. Research limitations/implications In this study, the variation of PVD discharge capacity is only considered in one-dimensional consolidation. However, it is challenging to implement a general expression for discharge capacity variation according to time in the two-dimensional numerical solution (two-dimensional plane strain model). This is the motivation for further study. Practical implications A geotechnical engineer could use the proposed numerical solution to predict the consolidation behavior of the drainage-improved soft deposit considering the PVD discharge capacity variation. Originality/value The large-strain consolidation of PVD-installed soft deposits could be predicted well by using the proposed numerical solution considering the PVD discharge capacity variations according to depth and time.

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

Advances in Civil Engineering ◽

10.1155/2018/5918492 ◽

2018 ◽

Vol 2018 ◽

pp. 1-15 ◽

Cited By ~ 1

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.

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Physically-based modelling of hydrological processes in a tropical headwater catchment (West Africa) – process representation and multi-criteria validation

Hydrology and Earth System Sciences ◽

10.5194/hess-10-829-2006 ◽

2006 ◽

Vol 10 (6) ◽

pp. 829-847 ◽

Cited By ~ 45

Author(s):

S. Giertz ◽

B. Diekkrüger ◽

G. Steup

Keyword(s):

Soil Moisture ◽

Rainy Season ◽

Overland Flow ◽

Soil Layer ◽

Hydrological Processes ◽

Runoff Generation ◽

Field Investigations ◽

Physically Based ◽

In The Beginning ◽

Headwater Catchment

Abstract. The aim of the study was to test the applicability of a physically-based model to simulate the hydrological processes in a headwater catchment in Benin. Field investigations in the catchment have shown that lateral processes such as surface runoff and interflow are most important. Therefore, the 1-D SVAT-model SIMULAT was modified to a semi-distributed hillslope version (SIMULAT-H). Based on a good database, the model was evaluated in a multi-criteria validation using discharge, discharge components and soil moisture data. For the validation of discharge, good results were achieved for dry and wet years. The main differences were observable in the beginning of the rainy season. A comparison of the discharge components determined by hydro-chemical measurements with the simulation revealed that the model simulated the ratio of groundwater fluxes and fast runoff components correctly. For the validation of the discharge components of single events, larger differences were observable, which was partly caused by uncertainties in the precipitation data. The representation of the soil moisture dynamics by the model was good for the top soil layer. For deeper soil horizons, which are characterized by higher gravel content, the differences between simulated and measured soil moisture were larger. A good agreement of simulation results and field investigations was achieved for the runoff generation processes. Interflow is the predominant process on the upper and the middle slopes, while at the bottom of the hillslope groundwater recharge and – during the rainy season – saturated overland flow are important processes.

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Physically-based modelling of hydrological processes in a tropical headwater catchment in Benin (West Africa) – process representation and multi-criteria validation

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-3-595-2006 ◽

2006 ◽

Vol 3 (2) ◽

pp. 595-651 ◽

Cited By ~ 6

Author(s):

S. Giertz ◽

B. Diekkrüger ◽

G. Steup

Keyword(s):

Soil Moisture ◽

Rainy Season ◽

Overland Flow ◽

Soil Layer ◽

Hydrological Processes ◽

Runoff Generation ◽

Field Investigations ◽

Physically Based ◽

In The Beginning ◽

Headwater Catchment

Abstract. The aim of the study was to test the applicability of a physically-based model to simulate the hydrological processes in a headwater catchment in Benin. Field investigations in the catchment have shown that lateral processes as surface runoff and interflow are most important. Therefore the 1-D SVAT-model SIMULAT was modified to a hillslope version (SIMULAT-H). Due to a good database the model was evaluated in a multi-criteria validation using discharge, discharge components and spatially distributed soil moisture data. For the validation of discharge good results were achieved for dry and wet years. Main differences were observable in the beginning of the rainy season. The comparison of the discharge components determined by hydrochemical measurements with the simulation revealed that the model simulated the ratio of groundwater fluxes and fast runoff components correctly. For the validation of the discharge components of single events larger differences were observable, which was partly caused by uncertainties in the precipitation data. The representation of the soil moisture dynamics by the model was good for the top soil layer. For deeper soil horizons, which are characterized by higher gravel content, the differences between simulated and measured soil moisture were larger. Concerning the runoff generation processes a good agreement of simulation results and field investigations was achieved. On the upper and the middle slope interflow is the predominant process, while at the bottom of the hillslope groundwater recharge and – during the rainy season – saturated overland flow are important processes.

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Assessment of subsidence and consolidation of dredger fill area based on SBAS-InSAR and laboratory tests

Proceedings of the International Association of Hydrological Sciences ◽

10.5194/piahs-382-381-2020 ◽

2020 ◽

Vol 382 ◽

pp. 381-386

Author(s):

Qing-bo Yu ◽

Qing Wang ◽

Xue-xin Yan ◽

Tian-liang Yang ◽

Jian-ping Chen ◽

...

Keyword(s):

Land Subsidence ◽

Laboratory Tests ◽

Soil Layer ◽

Soil Layers ◽

Building Load ◽

Dredger Fill ◽

Sbas Insar ◽

Consolidation Degree ◽

Final Settlement ◽

Underlying Soil

Abstract. With the development of economy, land reclamation by dredger fill has become an effective measure to alleviate the shortage of land resources. However, the accompanying subsidence has always been a challenge to the safe use of soil in dredger fill area. In this study, Chongming East Shoal, China, where dredger filling activities are going on in recent years was selected as the study area. SBAS-InSAR was applied to monitor the variation of land subsidence and deformation in the recent two years. Furthermore, a total of 25 undisturbed soil samples including dredger fill and underlying soil were collected from 5 boreholes (maximum depth 55 m), and the land at each borehole had different a formation time. The physical properties and compressibility were tested by laboratory tests. Results show that for the current state, fast to slow subsidence velocity was observed in the reclamation area close to the coastline, which is controlled by building load and geological features of soil layers. The building load is the main factor affecting the land subsidence and special attention should be paid. It is the poor drainage condition of the soil layer in the offshore area resulting in slow subsidence. Consolidation degree and final settlement of soil can be obtained from monitoring data of land subsidence. Based on the settlement-time curve obtained by SBAS-InSAR, the estimated final settlement of typical settlement area is −27.03 to −38.96 mm, and the corresponding consolidation degree is 58.95 % on average. It still takes a long time to achieve stability. In conclusion, land subsidence is essentially the macro-accumulation of drainage consolidation of all the soil layers, so it is controlled by soil structure and engineering geological properties of both dredger fill and underlying soil layer. The research combined with field investigation, laboratory testing can provide a mechanism explanation for monitoring results. Future research will focus on longer monitoring time and a higher sampling frequency to enrich and improve the research.

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Effect of Smear on Finite Strain Radial Consolidation for Vertical Prefabricated Drain in Compressible Soils

Seismic Engineering ◽

10.1115/pvp2003-2116 ◽

2003 ◽

Author(s):

Kuang-Hsiang Chen ◽

Tzung-Hsun Hsieh ◽

I.-Fan Lin

Keyword(s):

Finite Strain ◽

Soil Layer ◽

Strain Condition ◽

Peripheral Smear ◽

Drain Spacing ◽

Vertical Strain ◽

Time Result ◽

Time Required ◽

Compressible Soil ◽

First Time

Radial consolidation equations for vertical prefabricated drain which considers the effects of drain spacing, well resistance, extension of drain above the compressible soil layer, well peripheral smear effect, and differential vertical strain between smear zone and undisturbed zone at finite strain condition are derived. Particularly, the effects of smear as well as differential vertical strain between smear zone and undisturbed zone at finite strain condition are studied for the first time. Result indicating the time required for consolidation is increased by the effect of well peripheral smear. The effect of differential vertical strain can be ignored.

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Handling the water content discontinuity at the interface between layered soils within a numerical scheme

Soil Research ◽

10.1071/sr05069 ◽

2005 ◽

Vol 43 (8) ◽

pp. 945 ◽

Cited By ~ 8

Author(s):

C. J. Matthews ◽

F. J. Cook ◽

J. H. Knight ◽

R. D. Braddock

Keyword(s):

Numerical Solution ◽

Water Content ◽

Numerical Scheme ◽

Iterative Scheme ◽

Method Of Lines ◽

Soil Layer ◽

Iterative Solution ◽

Richards Equation ◽

Layered Soils ◽

Fine Soil

In general, the water content (θ) form of Richards’ equation is not used when modeling water flow through layered soil since θ is discontinuous across soil layers. Within the literature, there have been some examples of models developed for layered soils using the θ-form of Richards’ equation. However, these models usually rely on an approximation of the discontinuity at the soil layer interface. For the first time, we will develop an iterative scheme based on Newton’s method, to explicitly solve for θ at the interface between 2 soils within a numerical scheme. The numerical scheme used here is the Method of Lines (MoL); however, the principles of the iterative solution could be used in other numerical techniques. It will be shown that the iterative scheme is highly effective, converging within 1 to 2 iterations. To ensure the convergence behaviour holds, the numerical scheme will be tested on a fine-over-coarse and a coarse-over-fine soil with highly contrasting soil properties. For each case, the contrast between the soil types will be controlled artificially to extend and decrease the extent of the θ discontinuity. In addition, the numerical solution will be compared against a steady-state analytical solution and a numerical solution from the literature.

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Progressive failure of a constrained creeping landslide

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2011.0063 ◽

2011 ◽

Vol 467 (2133) ◽

pp. 2444-2461 ◽

Cited By ~ 11

Author(s):

Alexander M. Puzrin ◽

Andreas Schmid

Keyword(s):

Slip Surface ◽

Pore Water Pressure ◽

Progressive Failure ◽

Water Pressure ◽

Field Tests ◽

Warning System ◽

Earth Pressure ◽

Compression Zone ◽

Slowing Down ◽

In The Beginning

The ski resort town of St Moritz, Switzerland, is partially constructed on a large creeping landslide, which has been causing damage to buildings and infrastructure. At the town centre, the landslide is constrained by a rock outcrop, creating a compression zone in the sliding mass. After decades of gradual slowing down,s in the beginning of 1990s the landslide started to accelerate, in spite of the fact that the average yearly precipitation and the pore water pressure on the sliding surface remained fairly constant. The paper shows that a constrained creeping landslide experiences progressive failure caused by the propagation of a zone of intense shearing along the slip surface resulting in significant earth pressure increase and visco-plastic yielding of soil in the compression zone. This basic physical mechanism, relying on extensive laboratory and field tests and long-term displacement monitoring, explains the paradox of the St Moritz landslide acceleration. Although the model predicts that the landslide could eventually slow down, its displacements may become excessive for some buildings, requiring an early warning system and further stabilization of the historic Leaning Tower. In general, by predicting the onset of yielding, the model can provide an important timeframe for stabilization of constrained landslides.

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