Numerical Laplace-Fourier transform inversion technique for layered soil consolidation problems; II, Gibson soil layer

Abstract A modified Green–Ampt model (MGAM) was proposed to simulate infiltrations into layered soil profiles with the entrapped air under unsteady rainfall conditions. To account for the effects of the air resistance, the saturation coefficient, actual water content, air bubbling pressure, and water bubbling pressure were introduced in the model. One-dimensional infiltration-runoff experiments were then conducted in multi-layered soil columns, under unsteady rainfall conditions, to evaluate the performance of the MGAM model. The cumulative infiltration, runoff rate, and water content of the soil, calculated by MGAM, were compared with the observed data and the results, calculated by the traditional Green–Ampt model (TGAM), the Bouwer Green–Ampt model (BGAM), and the Mein–Larson model (MLGAM), respectively. The results indicated that the cumulative infiltration, runoff rate, and soil water content, calculated by MGAM, were in better agreement with the observed results than previous models. A parameter sensitivity of MGAM was also analyzed. It was found that the sensitivity of the saturated coefficient was high in the first soil layer, and those of the air bubbling pressure and initial moisture deficit were high or medium in the first and second layers, while those of the other parameters were relatively low.

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Degradation of permafrost beneath a road embankment enhanced by heat advected in groundwater1This article is one of a series of papers published in this CJES Special Issue on the theme of Fundamental and applied research on permafrost in Canada.

Canadian Journal of Earth Sciences ◽

10.1139/e2012-018 ◽

2012 ◽

Vol 49 (8) ◽

pp. 953-962 ◽

Cited By ~ 43

Author(s):

Isabelle de Grandpré ◽

Daniel Fortier ◽

Eva Stephani

Keyword(s):

Groundwater Flow ◽

Soil Layer ◽

Permafrost Degradation ◽

Soil Consolidation ◽

Monitoring Wells ◽

The Road ◽

Road Pavement ◽

Advective Heat Transfer ◽

Road Data ◽

Northwestern North America

For the past few decades, northwestern North America has been affected by climate warming, leading to permafrost degradation and instability of the ground. This is problematic for all infrastructure built on permafrost, especially roads and runways. Thaw settlement and soil consolidation promote embankment subsidence and the development of cracks, potholes, and depressions in road pavement. In this study, we investigate highway stability in permafrost terrain at an experimentally built road embankment near Beaver Creek, Yukon. A network of 25 groundwater monitoring wells was installed along the sides of the road to estimate groundwater flow and its thermal impact on the permafrost beneath the road. Data on topography, water-table elevation, ground temperature, and stratigraphy of the soil were collected at the site. The geotechnical properties of each soil layer were determined by laboratory analysis and used to calibrate a two-dimensional groundwater flow model. Field observations showed that water was progressively losing heat as it flowed under the road embankment. Our results suggest that advective heat transfer related to groundwater flow accelerated permafrost degradation under the road embankment.

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Radial consolidation modelling incorporating the effect of a smear zone for a multilayer soil with downdrag caused by mandrel action

Canadian Geotechnical Journal ◽

10.1139/t09-149 ◽

2010 ◽

Vol 47 (9) ◽

pp. 1024-1035 ◽

Cited By ~ 5

Author(s):

Cholachat Rujikiatkamjorn ◽

Buddhima Indraratna

Keyword(s):

Lower Layer ◽

Soil Layer ◽

Soil Consolidation ◽

Soil Permeability ◽

Soil System ◽

Prefabricated Vertical Drains ◽

Vertical Drains ◽

Design Procedures ◽

Surcharge Preloading ◽

Time Required

A system of prefabricated vertical drains with surcharge preloading is an effective method for promoting radial drainage and accelerated soil consolidation. A piecewise technique is employed to analyse the radial consolidation in a multilayer soil system to include (i) the effect of soil downdrag and (ii) a smear zone having linearly varying soil permeability. The effect of soil dragged down from the upper soil layer into the lower layer has been analysed in terms of the time required for consolidation. It can be seen that the consolidation of the multilayer soil depends on smear zone characteristics, the permeability ratio between upper and lower soil layers, penetration depth, and drain spacing. Design procedures are described with the help of an example.

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Stiffness matrix method for analysis of torsionally loaded piles in multi-layered soil

Proceedings of the Institution of Civil Engineers - Geotechnical Engineering ◽

10.1680/jgeen.21.00140 ◽

2021 ◽

pp. 1-19

Author(s):

Carlos A. Vega-Posada

Keyword(s):

Stiffness Matrix ◽

Soil Layer ◽

Quadratic Function ◽

Practical Method ◽

Transformation Method ◽

Layered Soil ◽

Structural Element ◽

The Matrix ◽

Governing Differential Equation ◽

Air Interfaces

A new, simple, and practical method to investigate the response of torsionally loaded piles on homogeneous or non-homogeneous multi-layered elastic soil is developed. The soil non-homogeneity is accounted for by assuming for each layer a shear modulus distribution that fits a quadratic function. The analysis of piles in multi-layered soil is carried out by subdividing the pile, at the soil-soil layer and soil-air interfaces, into multiple elements, and then using conventional matrix methods -such as those commonly implemented in structural analysis- to connect them. The governing differential equation (GDE) of an individual structural element is solved using the Differential Transformation Method (DTM). Next, the stiffness matrix is derived by applying compatibility conditions at the ends of the element. Piles partially or fully embedded in multiple layers and subjected to torsion can be analyzed in a simple manner with the proposed formulation -a tedious endeavor with other available solutions. Finally, explicit expressions for the coefficients of the matrix are provided. Four examples are presented to show the simplicity, accuracy, and capabilities of the proposed formulation.

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Energy-Based Approach for the Analysis of a Vertically Loaded Pile in Multi-layered Non-linear Soil Strata

10.21203/rs.3.rs-337774/v1 ◽

2021 ◽

Author(s):

Prakash Ankitha Arvan ◽

Madasamy Arockiasamy

Keyword(s):

Soil Layer ◽

Layered Soil ◽

Lateral Loads ◽

Axial Loads ◽

Element Analysis ◽

Soil Stiffness ◽

Perfectly Plastic ◽

Combined Action ◽

Group Piles ◽

Nonlinear Elastic

Abstract Numerous studies have been reported in published literature on analytical solutions for a vertically loaded pile installed in a homogeneous single soil layer. However, piles are rarely installed in an ideal homogeneous single soil layer. This study presents an energy-based approach to obtain displacements in an axially loaded pile embedded in multi-layered soil considering soil non-linearity. A simple power law based on published literature is used where the soil is assumed to be nonlinear-elastic and perfectly plastic. A Tresca yield surface is assumed to develop the soil stiffness variation with different strain levels that defines the non-linearity of the soil strata. The pile displacement response is obtained using the software MATLAB R2019a and the results from the energy-based method are compared with those obtained from the field test data as well as the finite element analysis based on the software ANSYS 2019R3. It is observed that the results obtained from the energy-based method are in better agreement with the field measured values than those obtained from the FEA. The approach presented in this study can be extended to piles embedded in multi-layered soil strata subjected to different cases of lateral loads as well as the combined action of lateral and axial loads. Furthermore, the same approach can be extended to study the response of the soil to group piles.

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Full-Scale Well Instrumented Large Diameter Bored Pile Load Test in Multi Layered Soil: A Case Study of Damietta Port New Grain Silos Project

International Journal of Current Engineering and Technology ◽

10.14741/ijcet.v8i01.10895 ◽

2018 ◽

Vol 8 (01) ◽

Author(s):

M. Eid ◽

A. Hefny ◽

T. Sorour ◽

Y. Zagh

Keyword(s):

Load Distribution ◽

Large Diameter ◽

Soil Layer ◽

Full Scale ◽

Layered Soil ◽

Load Test ◽

Test Field ◽

Loading Test ◽

Bored Pile ◽

Pile Load Test

A Large diameter bored pile with diameter of 1.00 m and length of 34.00 m has been implemented in multi layered soil. The pile was tested under three axially loading and unloading cycles, in order to determine the load settlement curve and assess the ultimate pile capacity. Extensive investigation was carried out to obtain reliable soil properties at the examined pile location, through in situ and laboratory soil tests. Twelve strain gauges were fixed on pile steel reinforcement bars at top of each soil layer level. Moreover, four dial gauges were set up at pile head. Also, three telltales were extended to three different levels inside the pile. The pile load test field measurements are presented in the form of load settlement and load distribution curves for different loading steps. In addition, the pile ultimate capacity is calculated using different codes criterions and compared with the loading test results. Large diameter bored pile, Settlement, Pile load distribution, Pile installation, Instrumentation, Full scale pile load test, Pile behavior.

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On: “A waveform inversion technique for measuring elastic wave attenuation in cylindrical bars” by X. M. Tang (June 1992 GEOPHYSICS, p. 854–859)

Geophysics ◽

10.1190/1.1443475 ◽

1993 ◽

Vol 58 (6) ◽

pp. 904-904 ◽

Cited By ~ 1

Author(s):

Dane P. Blair

Keyword(s):

Fourier Transform ◽

Elastic Wave ◽

Fast Fourier Transform ◽

Wave Attenuation ◽

Waveform Inversion ◽

Inversion Technique ◽

Attenuation Characteristics

The author has recently presented a waveform inversion technique for measuring elastic wave attenuation in cylindrical bars. However, it is worthwhile pointing out some previous, relevant studies which may have been overlooked. The Pochhammer technique employed to derive the pulse attenuation characteristics is not new. In fact it was first used by Hsieh and Kolsky (1958); Blair (1985, 1990) also implemented the method using a Fast Fourier Transform.

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Pre- and Postcollapse Ground Deformation Revealed by SAR Interferometry: A Case Study of Foshan (China) Ground Collapse

Journal of Sensors ◽

10.1155/2020/8899054 ◽

2020 ◽

Vol 2020 ◽

pp. 1-17

Author(s):

Wu Zhu ◽

Yan Zhang ◽

Zhanke Liu ◽

Qian Zhu

Keyword(s):

Ground Deformation ◽

Southern China ◽

Soft Soil ◽

Soil Layer ◽

Sar Interferometry ◽

Ground Subsidence ◽

Soil Consolidation ◽

Tunnel Excavation ◽

Ground Collapse ◽

Before And After

On the evening of 7 February 2018, a deadly collapse of a metro tunnel under construction in the Southern China city of Foshan caused 11 deaths, 8 injuries, and 1 missing person. For disaster prevention and mitigation, the spatiotemporal ground deformations before and after the collapse event were derived from 55 Sentinel-1A synthetic aperture radar (SAR) images spanning from March 2017 to January 2019. The results showed that prominent ground subsidence in the shape of a funnel with a maximum rate of 42 mm/year was observed in the vicinity of the collapse area before the accident. After the accident, the area and magnitude of subsidence decreased compared with precollapse subsidence. This decrease is related to the progress of tunnel excavation and groundwater changes. In the temporal domain, continuous subsidence was observed over a year before and after the accident, and accelerated subsidence appeared one month before the collapse accident. Soft soil consolidation and tunnel-induced soil losses were the main reasons for the subsidence over the study area. The leakage of groundwater accounted for the collapse event. The leaked groundwater eroded the soil, resulting in the formation of an arched hole. The connection between the arched hole and the tunnel reduced the bearing capacity of the soil layer above the arched hole, triggering the collapse event. The findings provide scientific evidence for future collapse monitoring and early warning due to tunnel excavation.

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