Soil Spring Research Articles

The role of gas emissions (He, Rn, and CO2) from fault zones in understanding fault and seismic activity

Active fault zones are critical pathways for the migration of deep fluids to the Earth’s surface, carrying gases such as He, Rn, and CO2 that provide evidence for the physical and chemical dynamics of the Earth’s interior. This review examines the geochemical characteristics of fault zone gases and their implications for understanding fault activity and seismic events. Fault zones with high activity levels exhibit significant gas release, and variations in soil and hot spring gas concentrations can serve as indicators of seismic activity. Changes in gas concentrations and isotopic ratios, particularly before and after earthquakes, reflect the dynamic interplay between deep-sourced and shallow-sourced fluids. Seismic-induced stress alterations enhance gas release along fault zones, leading to observable anomalies that can aid in earthquake monitoring and prediction. The study underscores the importance of isotope tracing in deciphering fluid sources, migration pathways, and the evolution of fault zones, providing valuable information for assessing tectonic activity and mitigating seismic risks.

The Role of Antecedent Winter Soil Moisture Carryover on Spring Runoff Predictability in Snow-Influenced Western U.S. Catchments

Abstract Spring runoff is critical to agricultural, industrial, and municipal water supply as well as environmental uses in the western United States. Although spring runoff in this region has long been predicted based on late winter and early spring montane snow water storage, the role of soil moisture carryover from the previous winter is less understood and utilized in forecasts. We quantify the relationship between antecedent winter soil moisture and spring runoff for 85 unmanaged catchments in the western United States. Using a regression-based approach, we estimate the proportional reduction in error in seasonal runoff forecasts associated with soil moisture. We classify the catchments into two regimes: interior (cold and relatively dry) and maritime (warmer and wetter), based on seasonal variations in soil moisture. Soil moisture generally is relatively unchanged through the winter period in interior catchments, whereas it increases (mostly gradually, but occasionally rapidly) in maritime catchments. We find that winter temperature dominates soil moisture variability in both types of catchments. We find two patterns in the predictability of spring runoff. First, including antecedent winter soil moisture as a predictor enhances forecast accuracy and variance explanation in spring runoff for both interior and maritime catchments, particularly and with greater significance in interior catchments. Second, spring runoff prediction skill from antecedent winter soil moisture increases with elevation. Overall, we find strong evidence that the use of antecedent soil moisture can improve spring runoff forecast skill for catchments in the western United States. Significance Statement Spring runoff forecasts are crucial for water supply in the western United States, but typically exclude information about soil moisture despite its key role in the water balance. Our study explores how and why incorporating information about winter’s soil moisture levels affects spring runoff forecasts across 85 catchments in the western United States. We find that doing so can produce modest improvements in the prediction skill of spring runoff for both interior and maritime catchments but is particularly noticeable in interior catchments and at higher elevations where temperatures are lower. Overall, our research strongly supports the idea that using information about soil moisture from the previous winter can improve accuracy in spring runoff forecasts for the western United States.

Study on applicability of mathematical model of pipe-soil interaction

Abstract The applicability of the soil spring calculation model given in China’s standard SY/T 7403 “Code for strain-based design of oil & gas transmission pipelines” and GB/T 50470 “Seismic technical code for oil and gas transmission pipeline engineering” to large-diameter pipelines is not clear. In this paper, the soil spring calculation formulas recommended in the two standards are analyzed, and the corresponding finite element numerical simulation models are established. The applicability of the lateral and vertical soil spring models in the two standards is discussed. The results show that the calculation accuracy of the two standards needs to be improved, and the applicability is different for different pipe diameters and soil properties.

Collective Identification of Superstructures and Dynamic Soil Springs Considering the Effects of Higher Modes Based on the MIEC Method

Collective Identification of Superstructures and Dynamic Soil Springs Considering the Effects of Higher Modes Based on the MIEC Method

A modified Nonlinear Foundation Beam model for half-rigid monopiles with Timoshenko representation and compatible soil springs in sand

There is a large number of monopile foundations for offshore wind turbines falling in the type of half-rigid pile, and are recommended to be analyzed by the p-y method in design. However, the p-y method currently adopted in oil and gas industry for slender piles has proved to be inapplicable for monopile-soil interaction, with overestimated ultimate lateral resistance and underestimated initial stiffness predicted. Thus, factoring in the bending resistance provided by shaft friction and end bearing forces for large diameter monopiles, a modified Nonlinear Foundation Beam (NFB) method is proposed in this paper to predict the monopile response in sand, where a beam element considering sectional shear stress is adopted, and another three sets of soil springs are incorporated with the p-y soil spring. Unified relationships of the proposed soil springs are also proposed with varying sand and pile properties. The modified NFB method is validated by published test results with diameters ranging from 2 m to 6 m, and L/D ratios from 5.08 to 8.29, proving its applicability for analysis of half-rigid monopiles.

An enhanced polar-based GPGPU-parallelized contact detection algorithm for 3D FDEM and its application to cracking analysis of shield tunnel segmental linings

This study introduces the three-dimensional combined finite-discrete element method (3D FDEM) to perform cracking analysis of segmental linings under extreme conditions. Considering the complex contact interactions of segments, this study first proposes a polar-based GPGPU-parallelized contact detection algorithm to handle memory issues confronted by existing FDEM algorithms. Initially, a spatial decomposition approach based on the polar coordinate system is implemented during the broad search phase. Each tetrahedral element is positioned within suitable search cells according to the axis-aligned bounding box. Subsequently, element pairs within each search cell are iteratively traversed, and potential contact pairs are identified using the judge cell criteria. After the broad search, a narrow search phase is executed to determine all real contacts. Following the above implementation, a load-structure model encompassing soil spring and external pressure calculations is then proposed. Based on the shape functions and coordinate transformation, the formulations of soil springs and external loads are derived and parallelized in the 3D FDEM framework. Three numerical tests are presented to validate the effectiveness of the proposed approach. Simulation results confirm the suitability of the proposed method for cracking analysis of segmental linings. Compared to the existing methods, it reduces GPU memory usage by 56 ∼ 76 % without extending time, which enhances the computational scale of 3D FDEM simulations. Furthermore, the proposed method is applied to two engineering scenarios, i.e., straight and curved segmental linings, both considering the absence and presence of contact defects between segments. The results show that contact defects can significantly reduce the resistance of the structural system comprising bolts and concrete segments for straight and curved scenarios.

Influence of local scour on the dynamic response of bridges under barge collisions

The response assessment of bridges crossing navigable waterways under vessel collisions is commonly conducted assuming intact bridge models. However, local scour may occur at bridge foundations, which has been identified as one of the major hydraulic causes of bridge failures. Therefore, it is imperative to consider local scour in the design and analysis of bridges against vessel collisions. Many previous studies have focused on the bridge response under vessel collisions assuming deterministic scour depths with incremental values, without integrating a scour prediction modeling in the analysis. This work investigates the barge-bridge collisions in the presence of scour at pile foundations, by using empirical scour prediction models. The accuracy of each prediction model is evaluated using relevant laboratory test and field measurement records. Finite element (FE) models of a four-span continuous reinforced concrete (RC) bridge and a jumbo hopper barge are developed in LS-DYNA. The current study identifies the correlation between the upstream flow depth and the barge collision location in the analyses. Numerical results illustrate that both scour depth and collision location influence the displacement, shear force, and bending moment response of bridge piles. The struck bridge pier accommodates a considerably increased displacement with an increased scour depth, while the shear force and bending moment are primarily influenced by the collision location. The influence of scour on the barge-pier collision force is marginal. The maximum axial force in soil springs increases considerably with scour depth. The choice of scour prediction model shows a significant impact on the displacement, shear force, bending moment of piles, the displacement of struck pier, and the axial force of soil springs.

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.

Evaluation of stiffness and damping of a base-isolated building considering higher-order modes

Introduction: Structural health monitoring (SHM) is an effective method of understanding the seismic safety of seismic design models and the continued use of buildings after earthquakes. Various system identification methods applicable to SHM have been proposed; however, most target only superstructures. Their applicability for evaluating the soundness of foundations and soil structures should also be examined. In addition, evaluating high-order modes in addition to low-order modes is necessary to capture changes in the vibration characteristics of superstructures, foundations, and soil structures. However, the impact of considering higher-order modes on the identification results has not been sufficiently evaluated. This study aims to address these issues by clarifying the importance of considering higher-order modes and proposing a method that can contribute to improving the accuracy of future building health evaluation methods.Methods: This study proposes a method of evaluating the stiffness and damping of a superstructure and dynamic soil spring considering low-order to high-order modes using the efficient transfer function fitting system for a base-isolated (BI) building. First, numerical experiments were performed to examine the accuracy of the proposed method in evaluating the stiffness and damping of each part when using acceleration data from limited observation points. Furthermore, this method was applied to an existing BI building subjected to the 2011 off the Pacific Coast of Tohoku Earthquake (2011 Tohoku Earthquake) to identify each parameter while considering higher-order modes. In addition, secular changes and the amplitude dependence of each structure were analyzed.Results: The results showed that the stiffness and damping of the seismic isolation layer, superstructure, and dynamic soil spring were stable with little variation owing to aging; however, the influence of amplitude dependence was relatively large.Conclusion: The significance of considering higher-order modes in evaluations of the soundness of foundations and soil structures was demonstrated. Moreover, the response characteristics of earthquakes recorded from 2007, before the 2011 Tohoku Earthquake, up to 2023 were accurately reproduced through numerical simulation by considering the amplitude dependence of the identified physical parameters based on the proposed identification framework.

Sensitive and selective electrochemical characterization and analytical determination of linezolid in environmental samples using TiO2 nanoparticles and MWCNT-COOH modified glassy carbon electrode

In this study, a sensitive, selective, and applicable electrochemical method based on the oxidation of linezolid active material was developed using a bare glassy carbon electrode (GCE) and modified glassy carbon electrodes treated with titanium dioxide nanoparticles/carboxyl-function multi-walled carbon nanotubes (TiO2/MWCNT-COOH/GCE). The surface characterization of the developed TiO2/MWCNT-COOH/GCE was examined using scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). The electrochemical properties of the linezolid substance were investigated using cyclic voltammetry. Furthermore, drug determination was carried out by differential pulse voltammetry (DPV) and absorptive stripping differential pulse voltammetry (AdSDPV). The linearity range under optimized conditions was determined as 1–20 µM and 0.2–2.0 µM on the bare GCE and TiO2/MWCNT-COOH modified electrode, respectively. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.0365 µM and 0.1215 µM for bare GCE, and 0.00056 µM and 0.00188 µM for TiO2/MWCNT-COOH/GCE, respectively. Interference studies were also performed by the developed sensor with various inorganic and organic substances that could affect LNZ detection. Then, the proposed sensor was applied for the determination of LNZ in real samples such as soil, tap water, and natural spring water samples, and the accuracy of the proposed method was proven in recovery studies, with values of 99.90 %, 100.94 %, and 101.17 %, respectively. In conclusion, a new sensor with high recovery, low relative error, and high selectivity was successfully produced and applied to detect LNZ in actual samples.

Structural monitoring, FEM updating and performance assessment of a wind turbine

In this study, long-term monitoring of a 900-kW onshore wind turbine with a tubular steel tower of 54 meters high and foundation with 26 reinforced concrete piles was performed based on vibration data. Modal properties such as frequency, mode shape and damping ratios were obtained by Enhanced Frequency Domain Decomposition method. Then, change in modal parameters due to environmental and operational conditions was determined. Modal parameters after cleansing such effects were obtained by multiple linear regression analyses.Finite element model of the wind turbine was developed in ANSYS including piles. Soil-structure interaction was modelled by p-y, t-z and q-z soil springs. Finite element model of the wind turbine was updated based on identified modal parameters.Finally, nonlinear time histories were performed to obtain seismic fragility curves of the structure with limit states being the local buckling under different levels of wind speed. In the context of this study, it was observed that identified modal values had significant scattering and level of wind speed significantly changed the seismic fragility curve of the wind turbine.

A microbial ecosystem enhanced by regulating soil carbon and nitrogen balance using biochar and nitrogen fertiliser five years after application

The indiscriminate use of nitrogen fertiliser (NF) is a obstruction to improve soil quality and crop yields. However, the effect of biochar and NF on soil microbial ecosystem (SME) and crop yields is unknown. A five-year field experiment in China aimed to evaluate the effects of biochar and nitrogen fertiliser (NF) combination on soil structure, C-to-N ratio (CNR), microbial biomass, and spring maize yield. Biochar and NF were applied at different rates, and the combined application resulted in a soil solid–liquid–gas ratio closer to the ideal value. The use of biochar alone and in combination with NF significantly increased soil's C, N, and CNR. A moderate application of biochar and NF resulted in favourable biological and chemical properties of the soil. The application of biochar and NF at moderate levels led to an increase in SME, with the B8N150 producing the highest yield. The highest yield of B8N150 represents a 24.25% increase compared to the unfertilized control and a 9.04% increase compared to B0N150. Moderate use of biochar and NF could be beneficial in areas with similar climatic conditions.

Impact of Tunneling on Adjacent Piles Based on the Kerr Foundation Model Considering the Influence of Lateral Soil

The Kerr foundation model simulates the interaction between piles and soil. Considering the impact of lateral soil displacement on adjacent piles, the lateral displacement and bending moment of the adjacent piles caused by shield tunnel excavation are calculated in detail. Additionally, the reactions of groups of piles are obtained by focusing on the shielding effect of the piles on the soil displacement caused by shield tunnel excavation. The validity of the solutions is verified by comparing the calculated results with the boundary element program GEPAN. Additionally, adjacent pile lateral displacement and bending moment are compared, with and without considering lateral soil effects. Furthermore, this study investigates the influence of various factors, such as soil spring stiffness, pile–tunnel distance, ground loss ratio, and pile diameter on the pile group’s lateral displacement and bending moment. The research findings indicate that increasing the soil spring stiffness or the horizontal distance between the pile and tunnel can reduce the lateral displacement and the bending moment of the pile. On the other hand, as the ground loss ratio gradually increases, the pile lateral displacement and bending moment will also increase. However, when the diameter of the pile grows, the lateral displacement reduces, while the bending moment increases.

System identification and finite element model updating of a 6 MW offshore wind turbine using vibrational response measurements

Offshore wind energy is playing an increasingly vital role in the clean energy transition around the world, and improved reliability of wind turbine structures is necessary for the long-term success and efficiency of renewable energy. Increased reliability would reduce costs associated with maintenance due to breakages and in turn reduce the levelized cost of energy for offshore wind energy sources. Structural health monitoring methods can be used to predict breakages and extend lifetimes by continuously monitoring instrumented structures. This paper presents system identification and model updating of a 6 MW offshore wind turbine using vibration measurements under varying operational conditions. The turbine is monopile-supported and instrumented with strain gauges and accelerometers at several elevations along the tower and monopile. Effective stiffness of soil springs in the model are updated to match modal-predicted natural frequencies and mode shapes of the first two modes with those identified from measurements at different operating conditions. A deterministic and probabilistic (Bayesian) approach to model updating are compared. The sensitivity of identified modal parameters and the updated model parameters are investigated with respect to operational and environmental conditions such as wind speed. Results show that deterministic model updating can match modal parameters with high accuracy across datasets and environmental conditions. Bayesian model updating results successfully estimate the posterior distribution of updating model parameters with an increasing degree of certainty as more data is used.

Effect of Plastic Membrane and Geotextile Cloth Mulching on Soil Moisture and Spring Maize Growth in the Loess–Hilly Region of Yan’an, China

In order to study the effect of a plastic membrane and geotextile cloth mulching on soil moisture and crop growth in the loess–hilly region, a one-year continuous field monitoring experiment was carried out in Ansai District, City of Yan’an, Shaanxi Province, China. The experimentation included three treatments: plastic membrane and geotextile cloth mulching on the ridge (MB), geotextile cloth mulching on the ridge (DB), and bare soil ridge (CK). Soil moisture and water potential sensors were installed to monitor the changes in soil moisture content and water potential at 5, 15, and 30 cm below the furrow surface and meteorological data above the soil surface, and the growth traits, yield, and quality of maize were analyzed. The results showed the following: (1) The soil water-storage capacity of the three treatments dropped to a minimum in the filling stage and gradually recovered in the mature stage. The average water-storage capacity for the MB treatment was 35.5% higher than that for the DB treatment and 85.1% higher than that for the CK treatment, significant throughout the whole growth period. (2) For four types of rainfall events, namely, light, medium, heavy, and storm rainfall, significant responses were observed at 5 cm below the ground for three treatments, and the fastest response was in MB due to its best rain-collection effect. A significant response was also observed at 15 and 30 cm below the surface of the furrow during medium, heavy, and storm rainfall, while no significant difference in response time was found between the three treatments due to the restriction of the soil infiltration capacity. (3) The differences between the three treatments in the agronomic traits of maize, except for plant height and stem thickness, were insignificant (p < 0.05). The seed moisture content and yield for the MB treatment were the highest, with values of 40.33% and 8366 kg/hm2, respectively, followed closely by the DB treatment, with values of 38.61% and 7780 kg/hm2, respectively, and the smallest values were observed in the CK treatment, with values of 35.80% and 6897 kg/hm2, respectively. Compared with those for the CK treatment, the average starch content and the average lipid content for the mulching treatments (MB, DB) decreased by 13.40% and 17.11%, respectively, while the average protein content of maize increased by 7.86%. Overall, a plastic membrane and geotextile cloth mulching could significantly increase soil moisture and spring maize yield due to their better rain-collection effect.

On the buckling propagation and its arrest in buried offshore pipeline crossing strike-slip fault

This study focused on buckling propagation and its arrest in buried offshore pipelines crossing strike-slip faults. A buried offshore pipeline with integral arrestors was analyzed using nonlinear vector-form-intrinsic-finite-element-method-based shell elements and modified soil springs. The effects of different external pressures on structural response were investigated. Integral arrestors with different design parameters were tested to prevent flattening and flipping propagation. The results showed seven or five fluctuations in the flattening parameters with alternating orthogonal directions along the pipeline. These fluctuations led to multi-failure modes, including S-shaped and Z-shaped flexures, two local collapses followed by flattening propagations, and a single local collapse followed by flipping propagation. Integral arrestors should be designed specifically to provide sufficient local bending rigidity in the circumferential direction. The arrest mode of flattening propagation is stopping the earliest fluctuations whilst that of flipping propagation is stopping the earliest fluctuations and depressing the downstream reverse ovalities. For the same arrestor thickness, the smallest effective arrestor length to stop flattening propagation was significantly less than that for flipping propagation. The arrest is temporary because of gross deformation of cross-sections at integral arrestors or the downstream pipes, and secondary failure accidents are likely to occur with any external perturbation.

Numerical modelling approaches for predicting the seismic response of monopole-supported dissipative controlled rocking bridge piers

In this paper, rotational spring and multi-spring models are implemented in SAP2000® software, and numerical solutions are presented for monotonic and cyclic behaviour of a dissipative controlled rocking (DCR) bridge column supported on a monopile foundation that is embedded in sand. The pile-soil system is modelled with elastic frame elements connected to vertically-spaced bi-linear soil springs. Three soil conditions (i.e. loose, medium-dense and dense sand) are considered to account for soil-structure interaction effects. The results from an experimental programme, carried out by the authors at the University of Canterbury, are used to validate the numerical solutions. The numerical simulation results for the three sand conditions are in good agreement with the experimental ones. From a computational standpoint, the relatively simple mathematical formulation and easy implementation would make the rotational spring model more desirable than the complex multi-spring model. On the other hand, the multi-spring model is more versatile and capable of describing the cyclic response of the DCR pier, such as the post-tensioning force, axial stress in the steel dissipaters and gap-opening interface rocking characteristics.

Efficient numerical implementation for nonlinear analysis of pile-supported structures during soil liquefaction through adaptive pile element formulations

The structural behavior of pile-supported structures during soil liquefaction is sometimes insufficiently investigated properly due to the inefficiency in the existing line finite element method (LFEM), which is widely used in practice. The traditional LFEM to simulate pile response requires dense element mesh for accurate results, as it simplifies the continuous surrounding soil as discrete spring elements, resulting in high computational costs, especially for pile-supported structures with a significant number of piles. Additionally, analyzing pile-supported structures in different stages of soil liquefaction requires repetitive updating of p-y curves and tedious starting-over iteration processes. To address these issues, an innovative line element formulation named the pile element formulation is employed and improved to adaptively simulate the surrounding soil conditions at different stages during liquefaction within the element formulation, eliminating the need to model discrete soil springs and significantly improving computational efficiency. The adaptive pile element formulation is then implemented within a refined Newton-Raphson iteration procedure that is proposed for a more effective nonlinear analysis process to consider soil liquefaction without repetitive iteration processes from starting over. Through several examples, the computational efficiency of the proposed method is validated, which requires only 20% of the computational cost compared to traditional LFEM while still providing accurate results, highlighting the application potential of the present study.

Seismic performance of multi-span continuous reinforced concrete bridges considering flood-induced scour effects

Flood-induced scours near the pier foundation are an adverse phenomenon that may cause the collapse of bridges. However, in the seismic design of bridges, the scour impact is commonly ignored when evaluating the seismic response. This study aims to quantify the effect of flood-induced scours on nonlinear static and dynamic behaviors of typical reinforced concrete bridges. For this regard, three-dimensional finite element models of two- and three-span bridges with a multi-cell box girder, circular column bent, and extended pile-shaft foundation are first developed, where the column bent is modeled considering the material and geometry nonlinearity. The interaction between the soil and structure is also accounted for by using soil spring models. By considering different scour depths, the modal, static pushover, and dynamic time-history analyses of the bridges in both directions are investigated. It is observed from the modal analysis that the fundamental periods of the bridges increase with the increase of scour depth. In addition, the results in terms of the column drift ratio show that scour may increase the seismic damage to the bridges, which transfers damage from the column bent to the pile-shaft foundation. The findings of this study exhibit the significant effect of the scour on the seismic damage of reinforced concrete bridges; therefore, it is recommended that this phenomenon should be considered in the bridge seismic design.

Sensitivity Analysis of Modal Parameters of a Jacket Offshore Wind Turbine to Operational Conditions

Accurate estimation of offshore wind turbine (OWT) modal parameters has a prominent effect on the design loads, lifetime prediction, and dynamic response of the system. Modal parameters can vary during the operation of OWTs. This paper studies the variation and sensitivity analysis of an OWT’s modal parameters with respect to operational and environmental conditions. Three finite element models of a jacket-supported OWT at the Block Island Wind Farm are created within the OpenSees, SAP2000, and OpenFAST platforms and validated using experimental measurements. The OpenFAST model is used to simulate the modal parameters of the turbine under various wind speed, rotor speed, power, yaw angle, mean sea level, blade pitch angle, and soil spring values. The model-predicted modal parameters of the first fore–aft (FA) and side–side (SS) modes are compared to those identified from experimental measurements. Results from the simulations show that the first FA natural frequency and damping ratio mostly depend on the rotor speed and wind speed, respectively, while yaw angle and mean sea level do not have a visible effect. It is observed that there is about 8% stiffening in the first FA frequency and an aerodynamic damping of 7.5% during the operation of the OWT.