Assessment of Reclamation-induced Consolidation Settlement Considering Stratigraphic Uncertainty and Spatial Variability of Soil Properties

Canadian Geotechnical Journal ◽

10.1139/cgj-2021-0349 ◽

2021 ◽

Author(s):

Chao Shi ◽

Yu Wang

Keyword(s):

Spatial Distribution ◽

Spatial Variability ◽

Random Field ◽

Soil Properties ◽

Site Investigation ◽

Angular Distortion ◽

Field Samples ◽

Consolidation Settlement ◽

Random Field Simulation ◽

Stratigraphic Uncertainty

Consolidation analysis is a key task for reclamation design. Although consolidation is a long-term process, acceleration of consolidation is often preferred for speeding up the reclamations. Before proposing measures to accelerate consolidation and reclamation process, it is imperative to have an accurate prediction of consolidation settlement for fine-grained materials, which is greatly affected by spatial distribution of subsurface zones with different soil types (i.e., stratigraphic heterogeneities and uncertainty) and spatial variability of soil properties. In current practice, calculation of consolidation settlement often uses simplified stratigraphic boundaries and deterministic consolidation parameters without considering stratigraphic uncertainty or soil property spatial variability. The oversimplified practice might result in unconservative estimations of consolidation settlement and pose threats to safety and serviceability of constructed facilities on reclaimed lands. In this study, a stochastic framework is proposed for consolidation settlement assessment with explicit modeling of stratigraphic uncertainty and spatial variability of soil properties by machine learning and random field simulation from limited site investigation data. The proposed method effectively generates multiple realizations of geological cross-section and random field samples of geotechnical properties from limited measurements and offers valuable insights into spatial distribution of the estimated total primary consolidation settlement curves and angular distortion.

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Spatial variability of saturated hydraulic conductivity and its links with other soil properties at the regional scale

Scientific Reports ◽

10.1038/s41598-021-86862-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Boguslaw Usowicz ◽

Jerzy Lipiec

Keyword(s):

Spatial Distribution ◽

Hydraulic Conductivity ◽

Organic Carbon ◽

Spatial Variability ◽

Soil Properties ◽

Regional Scale ◽

Total Porosity ◽

The Other ◽

Study Region ◽

The Mean

AbstractSaturated hydraulic conductivity (K) is a key property for evaluating soil water movement and quality. Most studies on spatial variability of K have been performed soil at a field or smaller scale. Therefore, the aim of this work was to assess (quantify) the spatial distribution of K at the larger regional scale in south-eastern Poland and its relationship with other soil properties, including intrinsic sand, silt, and clay contents, relatively stable organic carbon, cation exchange capacity (CEC) and temporally variable water content (WC), total porosity (FI), and dry bulk density (BD) in the surface layer (0–20 cm). The spatial relationships were assessed using a semivariogram and a cross-semivariogram. The studied region (140 km2) with predominantly permeable sandy soils with low fertility and productivity is located in the south-eastern part of Poland (Podlasie region). The mean sand and organic carbon contents are 74 and 0.86 and their ranges (in %) are 45–95 and 0.002–3.75, respectively. The number of individual samples varied from 216 to 228 (for K, WC, BD, FI) to 691 for the other soil properties. The best fitting models were adjusted to the empirical semivariogram (exponential) and the cross-semivariogram (exponential, Gaussian, or linear) used to draw maps with kriging. The results showed that, among the soil properties studied, K was most variable (coefficient of variation 77.3%) and significantly (p < 0.05) positively correlated with total porosity (r = 0.300) and negatively correlated with soil bulk density (r = – 0.283). The normal or close to the normal distribution was obtained by natural logarithmic and root square transformations. The mean K was 2.597 m day−1 and ranged from 0.01 up to 11.54 m day−1. The spatial autocorrelation (range) of K in the single (direct) semivariograms was 0.081° (8.1 km), while it favourably increased up to 0.149°–0.81° (14.9–81 km) in the cross-semivariograms using the OC contents, textural fractions, and CEC as auxiliary variables. The generated spatial maps allowed outlining two sub-areas with predominantly high K above 3.0 m day−1 in the northern sandier (sand content > 74%) and less silty (silt content < 22%) part and, with lower K in the southern part of the study region. Generally, the spatial distribution of the K values in the study region depended on the share of individual intrinsic textural fractions. On the other hand, the ranges of the spatial relationship between K and the intrinsic and relatively stable soil properties were much larger (from ~ 15 to 81 km) than between K and the temporally variable soil properties (0.3–0.9 km). This knowledge is supportive for making decisions related to land management aimed at alteration of hydraulic conductivity to improve soil water resources and crop productivity and reduce chemical leaching.

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Selection of Standard Penetration Test Number for Geotechnical Investigation of a Vertical Cross-section Considering Spatial Variability and Correlation in Soil Properties

Canadian Geotechnical Journal ◽

10.1139/cgj-2020-0440 ◽

2021 ◽

Author(s):

Zheng Guan ◽

Yu Wang

Keyword(s):

Spatial Variability ◽

Soil Properties ◽

Cross Section ◽

Site Investigation ◽

Standard Penetration Test ◽

Vertical Cross Section ◽

Penetration Test ◽

Geotechnical Design ◽

Selection Of

Standard Penetration test (SPT) is a widely used in-situ test for characterizing variation of subsurface soil properties, and results of site investigation are usually simplified as a 2D vertical cross-section for subsequent geotechnical design and construction. Current geotechnical design codes and guidelines only provide general recommendations for selection of an appropriate number of in-situ tests (e.g., SPT) (e.g., the greater variability of subsurface conditions, the larger number of SPTs required to obtain sufficient underground information). No quantitative or rational method is available for selecting the appropriate number of SPTs considering spatial variability and correlation in subsurface conditions. A comprehensive parametric study is carried out in this study to investigate the influence of spatial variability in subsurface conditions on the minimum SPT number needed for satisfying an accuracy requirement of site investigation. Random field is adopted to model spatial variation and correlation in soil properties in typical site conditions, and 2D Bayesian compressive sampling is used to interpolate sparse SPT data. Based on the parametric study results, a statistical chart is developed for geotechnical engineers to conveniently select appropriate number of SPTs in a vertical cross-section. Real SPT data from New Zealand are used to illustrate and validate the proposed method.

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Probabilistic Framework for Strength Limit and Service Limit Checks of Drilled Shafts considering Soil Spatial Variability

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/2363-04 ◽

2013 ◽

Vol 2363 (1) ◽

pp. 30-35 ◽

Cited By ~ 2

Author(s):

Haijian Fan ◽

Robert Liang

Keyword(s):

Spatial Variability ◽

Soil Properties ◽

Correlation Length ◽

Failure Modes ◽

Performance Criteria ◽

Angular Distortion ◽

Drilled Shaft ◽

Probabilistic Framework ◽

Strength Limit ◽

Site Variability

This paper presents a performance-based, probabilistic framework for design of a drilled shaft under axial and lateral loading that can consider spatial variability of soil properties at a project site. The performance criteria of a drilled shaft are stated in relation to the limiting tolerable deformations for strength limit and service limit, respectively. The computational algorithm for calculating the deformation of a drilled shaft is based on the commonly adopted load transfer method and the p-y method. “Geotechnical failure” is defined as an event in which the specified performance criteria are not met. Three failure modes are considered: axial movement, lateral deflection, and angular distortion. The spatial variability of soil properties is considered by using random field modeling techniques in which correlation length is introduced to account for site variability in addition to mean and variance. The method of fitting a sample autocorrelation function to a prescribed correlation function by using the method of ordinary least squares is introduced for determining site-specific correlation length for soil parameters. Geostatistical principles known as kriging are employed to estimate unknown parameters at unsampled locations from neighboring sampled locations. A numerical example is given to illustrate the application of the proposed methodologies. The example demonstrates that correlation length is an important statistical descriptor for characterizing site variability. Performance-based design provides unified consideration for both strength limit and service limit. Finally, the overall probability of failure for a drilled shaft when all three failure modes are considered is greater than the failure probability for any individual failure mode.

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Spatial Variability of Saturated Hydraulic Conductivity and its Links with other Soil Properties at the Commune Scale

10.21203/rs.3.rs-138269/v1 ◽

2021 ◽

Author(s):

Boguslaw Usowicz ◽

Jerzy Lipiec

Keyword(s):

Spatial Distribution ◽

Hydraulic Conductivity ◽

Organic Carbon ◽

Spatial Variability ◽

Soil Properties ◽

Bulk Density ◽

Soil Water ◽

Total Porosity ◽

The Other ◽

The Mean

Abstract Saturated hydraulic conductivity (SHC) is a key property for evaluating soil water movement and quality. Most studies on spatial variability of SHC have been performed soil at a field or smaller scale. Therefore, the aim of this work was to assess (quantify) the spatial distribution of SHC at the commune scale and its relationship with other soil properties, including intrinsic sand, silt, and clay contents, relatively stable organic carbon, cation exchange capacity (CEC), dynamic water content (WC), total porosity (FI), and dry bulk density (BD) in the surface layer (0–20 cm). The spatial relationships were assessed using a semivariogram and a cross-semivariogram. The studied commune (140 km2) with predominantly permeable sandy soils with low fertility and productivity is located in the south-eastern part of Poland (Podlasie region). The mean sand and organic carbon contents are 74 andobablyctknąć, czy o to chodzid mniej znacznie mniejszed? ? 0.86 and their ranges (in %) are 45-95 and 0.002-3.75, respectively. The number of individual samples varied from 216–228 (for SHC, WC, BD, FI) to 691 for the other soil properties. The best fitting models were adjusted to the empirical semivariogram (exponential) and the cross-semivariogram (exponential, Gaussian, or linear) used to draw maps with kriging. The results showed that, among the soil properties studied, SHC was most variable (coefficient of variation 77.3%) and significantly (p <0.05) positively correlated with total porosity (r = 0.300) and negatively correlated with soil bulk density (r = –0.283). The mean SHC was 2.597 m day–1 and ranged from 0.01 up to 11.54 m day–1. The spatial autocorrelation (range) of SHC in the single (direct) semivariograms was 0.081° (8.1 km), while it favourably increased up to 0.149–0.81° (14.9–81 km) in the cross-semivariograms using the OC contents, textural fractions, and CEC as auxiliary variables. The generated spatial maps allowed outlining two sub-areas with predominantly high SHC above 3.0 m day–1 in the northern sandier (sand content >74%) and less silty (silt content <22%) part and, with lower SHC in the southern part of the commune. Generally, the spatial distribution of the SHC values in the commune area depended on the share of individual intrinsic textural fractions. On the other hand, the ranges of the spatial relationship between SHC and the intrinsic and relatively stable soil properties were much larger (from ~15 to 81 km) than between SHC and the dynamic soil properties (0.3-0.9 km). This knowledge is supportive for making decisions related to land management aimed at reduction of hydraulic conductivity and chemical leaching and improvement of soil water resources and crop productivity.

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Spatial variability of imazethapyr sorption in soil

Weed Science ◽

10.1017/s0043174500091670 ◽

1999 ◽

Vol 47 (2) ◽

pp. 243-248 ◽

Cited By ~ 27

Author(s):

Rubem S. Oliveira ◽

William C. Koskinen ◽

Francisco A. Ferreira ◽

Bhairav R. Khakural ◽

David J. Mulla ◽

...

Keyword(s):

Spatial Distribution ◽

Organic Carbon ◽

Spatial Variability ◽

Soil Properties ◽

Large Field ◽

Site Specific ◽

Average Value ◽

Measured Property ◽

Ph Range ◽

Representative Samples

A significant limitation in using sorption coefficients (Kd) to predict solute transport through natural soils is the spatial variability of soil properties over large field areas. Spatial variability inKdfor imazethapyr was determined on representative samples from a 31.4-ha field, covering a pH range from 4.9 to 7.6 and an organic carbon (OC) range from 1.45 to 5.80 g kg−-1.Kdvaried from 0.18 to 3.78 across the field, with an average value of 1.56. The analysis ofKdvariability showed two distinct patterns in spatial distribution: areas in which pH > 6.25 andKd< 1.5, whereKdvariation is based primarily on pH, and areas in which pH < 6.25 andKd> 1.5, where other soil properties, i.e., OC content, have a significant influence onKdvariation. Based on soil pH distribution, an easily measured property, the field was divided into two potential management areas. This separation allowed identification of portions of the field where herbicide sorption would be minimal, with a relatively higher potential for leaching (i.e., areas withKd< 1.5), and provided a rationale for site-specific imazethapyr application.

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