Non-uniform Soil Research Articles

An improved discretization‐based kinematic approach for stability analyses of nonuniform c‐φ soil slopes

AbstractThis paper proposes an improved discretization‐based kinematic approach (DKA) with an efficient and robust algorithm to investigate slope stability in nonuniform soils. In an effort to ensure rigorous upper‐bound solutions which may be not satisfied by the initial DKA based on a forward difference method (DKA‐FD), a central and backward difference “point‐to‐point” method (DKA‐CD and DKA‐BD) is proposed to generate discretized points to form a velocity discontinuity surface. Varying (including constant) soil frictional angles along depth are discussed, which can be readily considered in the improved DKA‐CD. Work rate calculations are performed to derive upper‐bound formulations of slope stability number, and critical failure surface is correspondingly obtained at limit state. The comparison with forward and backward difference methods clearly reveals that the improved DKA‐CD could significantly reduce the mesh‐dependency issue and enhance efficacy of slope stability analyses in nonuniform soils.

Investigation of Lateral and Longitudinal Deformation of Submarine Nuclear Power Plant Water-Intake Tunnel on Non-Uniform Soft Soil during Earthquake

The safety-grade water-intake immersed tunnel plays a vital role in the nuclear power cooling system, and its seismic safety is crucial. This paper employs the response displacement method and dynamic time-history analysis using the finite element software ANSYS to construct a beam–spring model and a 3D finite element model of a shield tunnel and foundation. It also develops equivalent linear dynamic constitutive and viscoelastic boundary element subprograms. This study focuses on the weak joint sections of immersed tunnels, conducting a seismic performance analysis under extreme safety earthquake conditions (SL-2). The results indicate that the joint stiffness of immersed tunnels and the increase in seismic peak values do not affect the trend of joint opening variation with longitudinal position. The change in joint opening is primarily located where the thickness of the cover layer changes abruptly or where the soil hardness is unevenly distributed. The joint opening is mainly influenced by seismic forces when considering static and dynamic superposition. When the stiffness of the joint GINA water stop exceeds a certain value, the correlation between stiffness change and joint compression–tension variation gradually weakens. This research can provide a reference for the seismic design of similar projects.

Experimental Investigation of Leakage Flow Rate and Fluidisation beneath Polyethylene Pipes in Non-Uniform Soils

Soil fluidisation around buried pipes is one of the water leakage effects that has a direct influence on the ultimate failure of pipelines. In this research, using a laboratory model, the fluidisation caused by water leakage from three cracks with three lengths (14, 17, and 20 mm) and a 3 mm diameter hole for five pressures (1.5–5.5 bar) in non-uniform soils has been evaluated. The experiments were carried out both for pipes buried in soil, as well as exposed pipes. In the buried pipe tests, leakage flow rate, fluidisation, and mobile bed zone dimensions were investigated. The results showed that the increase in leakage flow rate due to an increase in pressure and crack length in exposed pipes is higher than in buried pipes. The exponent of the leakage–pressure relationship was obtained between 0.40 and 0.47 for the hole and between 0.8 and 1.9 in the crack. Observing different development patterns for fluidisation and mobile bed zones in cracks and holes, new relationships are presented for the height, width, and cross-sectional area of the leakage zones.

A simplified three-parameter model for analyzing torsional vibration of rectangular foundations on layered soil

Dynamic soil-structure interaction (SSI) significantly impacts structural vibration. Over the past few decades, numerous simplified models were developed to analyze dynamic SSI on homogeneous soil. In this study, however, a lumped-parameter model is adopted to investigate the dynamic behavior of rectangular foundations overlying nonuniform soil. The simplified three-parameter model is utilized to analyze the torsional vibration of rectangular foundations on layered soil with linearly varying shear-wave velocities. Non-dimensional parameters (shear-wave velocity ratios, layer depth ratios, and mass ratios) are also investigated herein. The frequency-magnification curves of the foundation using three-parameter model are found to agree well with theoretical solutions. Consistent agreements are also observed at the resonant response and its corresponding frequency ratio. Additionally, the resultant resonant magnification factors against mass ratios clearly show the impacts of the whipping effect resulting from soil-foundation interactions. The proposed model excels in simulating layered soil and includes fewer parameters than existing lumped-parameter models. The proposed model also demonstrates the adaptivity and reliability to simulate the dynamic responses calculated from the published in-situ experimental data. The time-domain application based on the proposed model effectively estimates the structural displacement of the soil-foundation-superstructure system. This research could contribute to the SSI analysis regarding the torsional vibration of a foundation on nonuniform soil.

Numerical study on soil springs stiffnesses of laterally loaded monopiles

Unlike traditional pile foundations, monopiles supporting offshore wind turbines usually have the characteristics of large diameter (D) and relatively low length-to-diameter ratio (L m /D). Accurate evaluation of the soil springs stiffnesses around the monopile is crucial for the design requirements and assessment of the dynamic response of offshore wind turbines. Over the past decade, a large number of initial stiffness models of lateral p-y spring have been proposed. However, limited research has been devoted to additional soil reaction springs, namely the rotational m-θ spring and pile base shear Q b-y b spring. Moreover, the contribution of these additional components is closely related to the pile-soil relative stiffness (K R), and it is a challenge to consider their relationship in the design. In this paper, a three-dimensional finite element analysis of elastic soil is performed to systematically investigate the effects of pile D, L m /D and soil elastic modulus (E s) on soil spring stiffness, and the effect of non-uniform soil is also discussed. The relationship between the initial load contribution ratio of each spring and the K R is clarified, and a new proposal for the soil springs stiffnesses considering the K R is put forward and verified for reasonableness.

Dynamic Response Analysis of Non-Uniform Unsaturated Soil Layer Roadbed under Uniform Moving Load

Dynamic Response Analysis of Non-Uniform Unsaturated Soil Layer Roadbed under Uniform Moving Load

Water uptake by plants under nonuniform soil moisture conditions: A comprehensive numerical and experimental analysis

The spatiotemporal pattern of root water uptake (RWU) depends on multiple factors, such as plant root biomass, soil water availability, and prevailing weather conditions at the site. The water uptake reduction due to the nonuniformity in soil water contents is often mitigated through compensated root water uptake (CRWU) and hydraulic redistribution (HR). Although previous studies have often considered these two processes independently due to the simplicity and feasibility of analyzing them separately, CRWU and HR can coexist in field conditions. Therefore, this work demonstrates the importance of considering CRWU and HR simultaneously in estimating daily transpiration and RWU distribution for nonuniform soil moisture conditions. For that, we have implemented the mechanistic RWU models developed by de Jong van Lier et al. (denoted below as the DJ model), Couvreur (CR), and Nimah and Hanks (NH) (see the references in the main text) into the widely-used HYDRUS-1D model, in addition to the previously available Jarvis (JF) and Feddes (FD) models. The performance of these models was then compared for varying soil water contents and boundary conditions using experimental data and hypothetical modeling scenarios. Our analysis has shown that these models are beneficial in estimating RWU with varying degrees of accuracy. The DJ and CR models are effective in simultaneously simulating CRWU and HR. NH and JF models can simulate CRWU but cannot simulate HR satisfactorily. Implementing these models into the HYDRUS platform for simultaneously considering CRWU and HR will significantly improve the accuracy of RWU predictions.

Differential Gene Expression Patterns in Peach Roots under Non-Uniform Soil Conditions in Response to Organic Matter.

Organic matter (OM) amendments are often encouraged in sustainable agriculture programs but can create heterogeneous soil environments when applied to perennial crops such as peaches (Prunus persica (L.) Batsch). To better understand the responses of peach roots to non-uniform soil conditions, transcriptomic analysis was performed in a split-root study using uniform soil (the same soil type for all roots) or non-uniform soil (different soil types for each half of the root system) from either (1) autoclaved sand (S), (2) autoclaved sand with autoclaved compost (A), or (3) autoclaved sand with compost which included inherent biological soil life (B). Each uniform soil type (S, A, and B) was grouped and compared by uniform and non-uniform soil comparisons for a total of nine treatments. Comparisons revealed peach roots had differentially expressed genes (DEGs) and gene ontology terms between soil groups, with the S and B groups having a range of 106-411 DEGs and the A group having a range of 19-94 DEGs. Additionally, six modules were identified and correlated (p > 0.69) for six of the nine treatment combinations. This study broadly highlights the complexity of how OM and biological life in the rhizosphere interact with immediate and distant roots and sheds light on how non-homogenous soil conditions can influence peach root gene expression.

Effects of geometry of soil specimens on the formation of desiccation cracks

Desiccation cracks in soils are important in engineering structures that need hydraulic integrity such as earth dams, and containment facilities. At the element test level, such cracks are a hindrance when the volume change of the soil specimen needs to be measured during the test. One such test is the volumetric shrinkage test where the volume of the soil specimen needs to be continuously determined together with its mass change as the soil specimen dries. The soil specimen may deform non-uniformly. Previously hazardous and cumbersome methods using mercury or wax are needed to determine the volume of soil specimens that deform non-uniformly, but the advent of 3D scanning and photogrammetry enables the volume of non-uniform soil specimens to be measured quite accurately. However, such techniques cannot accurately determine the volume of the deformed soil specimen once cracks start appearing in the soil specimen. Volumetric shrinkage tests are commonly conducted for cylindrical soil specimens. This paper investigates the geometry (shapes and dimensions) of soil specimens other than cylindrical on the formation of desiccation cracks. Bentonite is used as the test soil as it experiences large volume change on drying. The test results provide guidance for the geometry of a soil specimen to be used in the volumetric shrinkage test.

Influence of cutterhead opening ratio on soil arching effect and face stability during tunnelling through non-uniform soils

Tunnelling has increasingly become an essential tool in the exploration of underground space. A typical construction problem is the face instability during tunnelling, posing a great threat to associated infrastructures. Tunnel face instability often occurs with the soil arching collapse. This study investigates the combined effect of cutterhead opening ratio and soil non-uniformity on soil arching effect and face stability, via conducting random finite-element analysis coupled with Monte–Carlo simulations. The results underscore that the face stability is strongly associated with the evolution of stress arch. The obtained stability factors in the uniform soils can serve as a reference for the design of support pressure in practical tunnelling engineering. In addition, non-uniform soils exhibit a lower stability factor than uniform soils, which implies that the latter likely yields an underestimated probability of face failure. The tunnel face is found to have a probability of failure more than 50% if the spatial non-uniformity of soil is ignored. In the end, a practical framework is established to determine factor of safety (FOS) corresponding to different levels of probability of face failure considering various opening ratios in non-uniform soils. The required FOS is 1.70 to limit the probability of face instability no more than 0.1%. Our findings can facilitate the prediction of probability of instability in the conventionally deterministic design of face pressure.

On vibration response of heavy hammer self-falling pile driver in uneven unsaturated soil – Experimental and analytical study

The goal of this study is to determine the scope of the impact of pile driving construction vibration on surrounding residential houses and buildings during engineering construction. Firstly, introducing the gradient factor of unsaturated soil, proposed a model for non-uniform variation of pores with depth. Secondly, Consider the coupling between the model and soil skeleton density, relative fluid density, relative gas density, pore fluid, pore gas, and shear modulus. Finally, coupling the pile with the driving depth and propose a pile driving vibration model for non-uniform unsaturated soil. Proposed a new method for solving coupled equations using Hankel transform. Moreover, the analytical solution of this study was validated through on-site experiments. Results show that, deeper the pile is inserted into the soil, the greater the peak vertical velocity at different measuring points. The vibration of the pile is strongest at the last 1 m into the soil. When close to the vibration source, the amplitude values in the three directions are: maximum in vertical direction, followed by horizontal and radial direction, and minimum in horizontal and tangential direction. When pile driving construction is carried out outside the range of vibration influence, the seismic damage generated is equivalent to the seismic intensity below V (excluding V). The rate amplitude calculated by the model established in this study is closer to the measured value. Therefore, using the model established in this work can more accurately evaluate the impact of pile driving vibration during the construction process of highways and high-speed railways.

The Shear Strength of Clay Stabilized with Palm Bunch Ash and Cement

Roads with soft subgrade have low bearing capacity. The result is non-uniform soil settlement. One way to overcome this is with soil stabilization. Stabilization of clay soil is done chemically with palm bunch ash and cement. The purpose of this study was to determine the bearing capacity of soil for the shear strength value of clay soil with variations in mixing 5%, 10%, 15%, 20% oil palm bunch ash, and 10% cement with a 7-day curing period, and then the samples were tested using a direct shear test tool SNI 3420: 2016. The results showed that in the addition of a mixture of oil palm bunch ash and cement with levels of 5%, 10%, 15%, 20%, and 10% cement, the cohesion value increased at a percentage of 20% oil palm bunch ash and 10% cement, namely 0.5448 kg/cm2 compared to the cohesion value in the original soil of 0.0081 kg/cm2, an increase of 98.51%, and a shear angle value of 53.12° while the value of the original soil shear angle was 16.93°. This research concludes that the shear strength value of clay soil stabilized with oil palm bunch ash and cement increases.

Engineering Significance of Annular Raft Foundations over Solid Raft FoundationsJ

Abstract: Raft foundations play a pivotal role in distributing structural loads to the underlying soil, thereby ensuring the stability and integrity of various civil engineering structures. The choice between different types of raft foundations, such as solid and annular rafts, significantly impacts the overall performance and durability of a structure. This paper explores the engineering significance of annular raft foundations in comparison to solid raft foundations. The traditional solid raft foundation offers uniform load distribution and settlement control; however, it often encounters challenges when dealing with non-uniform soil profiles, differential settlements, and expansive soils. Annular raft foundations, a relatively innovative approach, address these challenges by featuring a central void within the raft. This void introduces a controlled differential settlement mechanism, enabling the foundation to accommodate non-uniform soil conditions effectively. Moreover, annular rafts offer improved structural performance in regions prone to ground movements, as the central void allows the foundation to adjust to soil displacements more flexibly than a solid raft. The engineering significance of annular rafts extends to their enhanced loadbearing capacity and reduction in material usage compared to solid rafts. The design of annular rafts takes advantage of the arching effect within the void, which enables the foundation to support heavier loads while minimizing the amount of concrete and reinforcement required. This not only contributes to cost savings but also aligns with sustainable construction practices by reducing the environmental impact associated with excessive material consumption.

Research on the Lamb Problem in Semi-Infinite Space of Non-Uniform Unsaturated Soil

Research on the Lamb Problem in Semi-Infinite Space of Non-Uniform Unsaturated Soil

Simplified Equations to Find the Relationship Between Soil and Structure Displacements for Rectangular Single Column and Footing on Dry Voidless Cohesionless Soil Due to Vertical Loads

Usually, structural designers are assuming the soil as rigid object when they design small to intermediate structures, or assuming the settlement of soil to be always within the acceptable range. However, the engineering practice shows that high percentage of cracks and failures in structures are related to soil settlement reasons, non-uniform soil settlement for example. Geotechnical engineers developed many methods to calculate the settlement of soil, but the majority of these methods are geotechnical engineering oriented, and standard structural engineer may struggle using them. Therefore, because of the importance of finding the approximate soil settlement in many cas-es during the design process or during the implementation of the structure, this study gives simple equations that can predict the soil settlement with acceptable accuracy, by creating a relationship between the soil settlement and the displacement of the structure. The targeted equation will allow us to find the soil settlement from knowing the approximate displacement of the structure. Such an equation gives a conceptual value to be used in 3D analysis of structures using computer programs like SAP2000 and ETABS. The targeted structure in this study is a simple one rectangular column and footing structure

Building foundation settlement in groundwater lowering on sliding territory of Lagerny Garden in Tomsk

Groundwater lowering is a method of stabilizing landslide slopes. To date, the effect of water reduction on the technical condition of buildings has not been sufficiently studied. This may negatively affect the technical condition of buildings due to the development of additional deformation of foundations and foundation soils.Purpose: The aim of this work is to assess the impact of cased hole with filters on the technical condition of buildings in the area of groundwater lowering.Methodology/approach: Long-term field observations of the groundwater level at the water supply site; monitoring of the technical condition of buildings; analysis and generalization of the data obtained.Research findings: Based on annual monitoring of the building height, monitoring of changes in the building state and the engineering and geological analysis are performed in the period from 1987 to 2020. It is found that groundwater lowering leads to building deformation and a decrease in its technical condition due to nonuniform soil compaction in this area.Research implication: Groundwater lowering near buildings can significantly affect their technical condition due to the soil compaction even at a considerable distance from the waterlowering devices. In developing groundwater lowering projects, special attention should be paid to heterogeneity of the ground layer on the building site and its impact on the formation of relative deformation of buildings.

Hydrodynamic response of a loam soil after wetting with different methods

Different points in a field can be wetted with different natural or artificial rainfall amounts and intensities. Therefore, a non-uniform soil wetting could occur during short-term monitoring of soil hydrodynamic parameters and its global effect on soil characterization is not easily predictable. For an initially dry loam soil, a sequence of three beerkan infiltration runs was performed at fixed sampling points in a period of two weeks. Immediately after the first beerkan run, the soil was perturbed by adding an additional water volume differing with the sampling point by the amount of water (0, 100 or 227 mm) and the application methodology (rainfall simulation, another beerkan run). As compared with the initial conditions, the soil infiltration parameters (mean, initial and final infiltration rates; constant of the Horton’s infiltration model) decreased by 2.9–4.3 times after wetting. A decrease of these parameters by 1.6–2.3 times remained detectable at the end of the sampling period, even if the soil likely returned to wetness conditions close to the initial ones. Relative variability decreased too (coefficients of variation = 52–135%, depending on the parameter, for the initial runs and 36–95% for the final ones). Nevertheless, a link was recognized between the infiltration parameters determined in the subsequent runs of the sequence. The correlation was stronger when the initial runs were compared with the last runs (coefficients of determination, R2 = 0.104–0.749, depending on the parameter; R >0 at P = 0.05 in all cases) than with those performed immediately after the intermediate wetting (R2 varying from a non-significant value of 0.059 to significant 0.196–0.211 values). The hydrodynamic response of a disturbed soil appears overall related to that of the initially undisturbed soil even if the disturbing agent is not exactly the same over the sampled area. Performing other investigations by characterizing the antecedent soil conditions in more detail could help to improve interpretation and modelling of hydrological processes by a more realistic description of temporal variability of soil infiltration parameters.

Large-deformation modelling of earthquake-triggered landslides considering non-uniform soils with a stratigraphic dip

Natural soil slopes often exhibit both spatial variability and stratigraphic dips due to complex depositional processes of soil, exerting a remarkable influence on landslide behaviors. Existing research mostly focused on the influence of soil spatial variability on slope stability or landslide runout behaviors, and the investigation of the effect of stratigraphic dip on large-deformation landslide consequences are relatively limited and have not been fully understood. This study therefore proposed a random large-deformation finite-element (LDFE) computation framework, combining the coupled Eulerian-Lagrangian technique and a three-dimensional (3D) rotational random field to insight the earthquake-triggered landslide consequences considering non-uniform soils with a stratigraphic dip. The whole runout process of earthquake-triggered landslides from activation to termination is realistically reproduced. By implementing both two-dimension (2D) and 3D random LDFE analyses coupled with Monte-Carlo simulations, both effects of spatial non-uniformity and stratigraphic dip of soil on the evolution process and consequences of landslides are analyzed in detail. The results reveal that the stratigraphic dip greatly influences landslide behaviors. In addition, the 2D analyses probably underestimate the landslide consequences when contrasting with 3D analyses. These findings highlight the importance of considering stratigraphic dip of soil slope and the advantage of 3D random LDFE analysis on landslide behaviors.

Simulation of Influencing Factors of Buried Pipeline Interfered by Subway Stray Current

The degree of interference of stray currents generated by urban rail transit to nearby buried pipeline was governed by a variety of factors. The buried pipeline model containing the subway return current system was built by COMSOL software, and the fluctuation characteristics of pipeline potential under single and bilateral power supply modes were analyzed to determine the influence of subway return current system parameters and soil resistivity and pipeline corrosion layer resistivity on pipeline potential, while the distribution of pipeline potential under non-uniform soil model was calculated. The results show that when the locomotive traction current and rail longitudinal resistance are doubled, the fluctuation degree of pipeline potential is approximately the same multiple. When the soil resistivity is 1000Ω·m or the pipeline anti-corrosion coating resistivity is 106Ω·m, the pipeline is free from stray current interference. The rail ground transition resistance is not a significant factor of pipeline potential fluctuation. The operation of the train causes the corrosion sate of the pipeline to change constantly. When the longitudinal soil resistivity is unevenly distributed, the increase of soil resistivity at the traction substation side leads to the overall positive shift of pipeline potential and further intensification of pipeline corrosion. The simulation results provide a reference for the railway department and pipeline department in the reasonable planning and layout of rail transit and pipeline.

Investigation into the heat transfer models for the hot crude oil transportation in a long‐buried pipeline

AbstractBased on reasonable simplifications of a two‐dimensional (2D) energy equation, a basic heat transfer equation in 1D form is obtained for the hot crude oil transportation in a long‐buried pipeline. To enclose the heat transfer equation, the overall heat transfer coefficient and the numerical simulation of temperature fields of pipe wall and soil are introduced, and they together with the basic heat transfer equation constitute 1D and cross‐dimensional heat transfer models of crude oil transportation, respectively. Some numerical procedures, including grid generation, partial differential equation discretization, and algebraic equation solution, are combined to solve the two heat transfer models. Based on the designed cases with different pipeline parameters, the relative deviation between the numerical results from the two heat transfer models does not exceed 1%, and the two heat transfer models agree well. Furthermore, the nonuniform natural soil temperature field is designed, and its influence on the oil temperature and the deviation of the 1D heat transfer model is investigated. Under the condition of the nonuniform natural soil temperature field, the atmospheric temperature as the ambient temperature in the 1D heat transfer model causes an apparent deviation, whereas the soil temperature at the buried depth of the pipeline in the natural soil temperature field as the ambient temperature does not. This study can provide a reference for the reasonable selection and use of the heat transfer models of the buried hot oil pipeline.