Ground Surface Displacement Research Articles

Ground surface displacements and stress localization driven by dual magma chamber dynamics: analytical and numerical model estimates

Ground surface displacements and stress localization driven by dual magma chamber dynamics: analytical and numerical model estimates

Mathematical modelling for strata deformation caused by rectangular pipe jacking construction in composite layered ground

In this study, analytical solutions of vertical deformation of ground surface and horizontal displacement of strata are derived combining the Mindlin solution and the mirror method due to rectangular pipe jacking tunneling in composite strata, which considers the combined effect of five factors of additional excavation pressure, friction of rectangular pipe jacking and soils, segment-soil friction, grouting filling and strata loss, respectively. The theoretical calculation results were verified against the measured data in two project cases. Moreover, effect factors of rectangular jacking pipe cross-sectional dimensions, embedment of tunnel axial depth, elasticity modulus on the interlayer and the Poisson's ratio of the interlayer on strata deformation is investigated. The results imply that the theoretical calculation values obtained using this method are more closely correlated with the observed values compared to those computed using the single stratum model. The primary cause of terrene upheaval in front of the working surface is the increased excavation pressure on the working face and the horizontal displacement of the deep soils and the surface subsidence behind the excavation face is resulting from the soil loss as the main influencing factor. The varying cross-section size of pipe jacking is able to impact on the vertical deformation of the soil, but it has a limited impact on the lateral displacement of the strata. The affection of the buried depth of the tunnel axis on strata deformation is more notable in the rectangular pipe jacking construction. As the axial tunnel depth growth, the ground surface maximum subsidence value gradually decreases, while the crest value of horizontal distortion mildly increases. When the rise of the interlayered modulus of elasticity, the maximum earth surface subsidence enlarged gradually while the subsidence trough slight diminution. Moreover, the greatest horizontal displacement exhibits a relatively minor fluctuation, but there is a trend of upward movement in the position. The influence of Poisson's ratio of the interlayer on the strata deformation is comparatively weak.

EGMS-toolkit: a set of Python scripts for improved access to datasets from the European Ground Motion Service

Continental-scale, open-access datasets of ground surface displacement in all countries of the European Union, plus Norway, United Kingdom, and Iceland, are now available from the European Ground Motion Service (EGMS). Under the European Union’s Copernicus program, the EGMS has been available since the end of 2022 and will continue for the foreseeable future. The EGMS data are presently derived from Interferometric Synthetic Aperture Radar (InSAR) processing of the Sentinel-1 SAR satellite imagery, which has been collected from 2015 to date. While EGMS data can be visualised and obtained through an online platform (EGMS Explorer), the data access arrangements are inefficient for large-scale analysis of ground surface displacements due to the volume of data, the tile-formatting of datasets and some server limitations. Here we present a Python-based toolkit, named EGMS-toolkit, to provide a unified and more efficient workflow for accessing EGMS datasets. The toolkit can automatically detect and download EGMS datasets based on a Region of Interest provided by users, then it can merge, clip, and crop the results to that region regardless of its scale. The toolkit then produces files of EGMS ground surface motions in GIS-ready formats for further analysis.

An object-based region-growing phase unwrapping method for mapping vertical displacement in permafrost landscapes

Terrain displacement due to the seasonal thaw of the active layer above permafrost can be sensitive to climate change; however, its accurate characterization remains a challenge. This study aimed to improve the measurement of the subsidence or vertical ground surface displacement using differential synthetic aperture radar interferometry (InSAR). Existing methods for reliable phase unwrapping are hindered by the decorrelation between time-series of SAR acquisitions that can result due to the heterogeneity and structural sensitivity of permafrost landscapes to external conditions. In this study, an advanced phase unwrapping method was proposed, in which three types of regions, namely non-residue, sparse residue, and dense residue objects, were obtained from wrapped interferogram and residue map using a segmentation method. Two variants of Polynomial-Based Region Growing Phase Unwrapping (PBRGPU) were developed, which are sparse-residue Object-based PBRGPU(SOP) and dense-residue Object-based PBRGPU(DOP). The results demonstrated that the proposed method outperformed the existing phase unwrapping methods by partially suppressing the decorrelation phase and enhancing robustness for complex terrain deformation in the absence of measured field data. Both the PBRGPU variants and segmentation strategies compose the object-based unwrapping method for permafrost, and also provide a new framework by combining the segmentations and scenarios for phase unwrapping for permafrost regions.

Model test on cooling performance of a new method for mitigating permafrost thaw around buried oil pipeline

Buried pipelines have been widely used to transport petroleum-based products over long distances in permafrost regions. Field observations reveal that they are endangered by rapid permafrost thawing and resulting massive soil movements, despite adopting some measures to protect pipeline foundation permafrost. A new mitigation technique is proposed to slow down the permafrost thawing ulteriorly. With this technique, a seasonal air-cooled embankment (SACE), mainly composed of a crushed rock layer, supports the pipeline and transfers the heat from the pipeline to ambient air in the cold seasons. A scale model test with the controlled air and oil temperatures was carried out to evaluate the proposed measure. The temperature and volumetric unfrozen water content of the permafrost subgrade beneath both the SACE and the direct-buried pipeline, as well as ground surface displacements, were measured during the whole testing process. A comparison of the hydrothermal process of the subgrade permafrost under the SACE and the direct-buried warm pipeline indicates that the proposed measure can substantially mitigate the rapid thawing of permafrost by controlling the geothermal regimes of the pipeline.

Effect of assembled H-shaped steel struts with servo system on the safe excavation of a subway station

An innovative design of assembled H-shaped steel struts (AHSS) with servo system is introduced for the deep excavation of a T-shaped subway interchange station in soft soil. Analysis of the field monitored axial force of the strut, horizontal displacement of retaining wall, ground surface settlement and displacement of the nearby existing tunnel showed that the servo system could provide a convincing stable axial force for each level of AHSS. When a new level of AHSS with servo system was put into operation, the axial force of the closest level of concrete strut above tended to be more greatly affected than the other levels of strut. The first level of concrete strut contributed much less to resisting horizontal displacement of the diaphragm wall than the other levels of strut, and was under tension during the later stage of excavation. The maximum horizontal displacement of diaphragm wall, displacement of the existing tunnel and ground surface settlement were all controlled well with the operation of AHSS with servo system. Meanwhile, stricter control of the horizontal displacement of the diaphragm wall in the early stage is considered to be beneficial to the control of further deformation of the excavation at a later stage.

Mechanism of vertical displacement beneath shallow compression zone in coastal area

Previous studies showed that there is a discrepancy between total subsidence (measured on the ground surface) and shallow compression (measured within several hundred meters beneath the ground surface) in Taiwan. This difference is referred to as deep displacement in this study. The variations of deep displacement are opposite to those of ground surface displacement and groundwater level within the depth of several hundred meters. The mechanism is unknown and requires further investigation. This study adopts two kinds of geodetic observation data and separates land subsidence into shallow compression and deep displacement to investigate the mechanism of deep displacement. A tectonically active coastal area in Taiwan is selected as the study area. The assessment results show that the associated variations are likely due to cyclic hydraulic loading and unloading. The variations of deep displacement are opposite to those of ground surface displacement. This study proposes that these variations are due to hydraulic expansion and contraction. The mechanism is demonstrated using a hydromechanical model. The results of a cross-correlation analysis show that hydraulic expansion and contraction occur at certain depths. The study results provide important information on the mechanism of deep displacement that can be used in tectonophysical and land subsidence investigations.Graphical

Centrifuge study on the uplift behavior of spread foundation for transmission tower in sand

Realistic simulation of in-situ stresses is an essential consideration in evaluating the bearing capacities of spread foundations. Therefore, this study aimed to investigate the uplift behavior of large spread foundations by performing a series of centrifuge tests. A total of 12 centrifuge test models were constructed considering the variation in the foundation width (3.5–6.5 m), embedment depth ratio (0.67–1.39), and relative density of dry silica sandy soil (40%, 80%). The measured load–displacement curves indicated that the uplift bearing capacity and the corresponding uplift displacement increased with the foundation width at a certain embedment depth ratio. Two sets of empirical equations were proposed by adopting genetic programming to estimate the uplift resistance factor and uplift displacement with consideration of field stress conditions. The proposed equations reasonably matched these parameters under various conditions reported in the literature. Furthermore, a simplified empirical influence zone was proposed on the basis of the measurement of the ground surface displacement. The empirical influence zone, which was a straight line with an inclination angle of ~0.9 times the soil friction angle measured from vertical, could be considered a significant reference for predicting the failure surface of the shallow foundation under uplift loading.

Insights into Deformation and Mechanism of a Reactivated Landslide Occurrence from Multi-Source Data: A Case Study in Li County, China

The investigation of reactivated landslides in the alpine-canyon areas suffers the difficult accessibility of precipitous terrain. In particular, when reactivated landslides occur along the major roads, efforts are focused on measuring ground surface displacements during road construction. Nevertheless, the ancient landslide deposits may reactivate after several years of road operation, while they show a stable state during the road construction. The characterization of this type of reactivated landslides is challenging, due to their complex mechanism and the limited monitoring data. Appropriate multi-source data can provide insights into deformation fields and enhance the understanding of landslide mechanisms, ensuring the outperformance of remedial works. This paper reports a recent Tangjiawan reactivated landslide along the Wenchuan-Maerkang Highway in Li County, China. The outcomes, including satellite InSAR, in situ real-time monitoring, and detailed ground and UAV investigation, conducted at this landslide are presented. Early deformation of the reactivated landslide began from 2019, with an InSAR-derived velocity of −11.7 mm/year, furthermore, a significant subsidence of about 21.2 mm, which occurred within a span of only 12 days from 3 June 2020 to 15 June 2020, was observed. The deformation characteristics derived from in situ monitoring during the remedial works were likely firstly associated with the initial unreinforced slope condition and the heavy rainfall. Subsequently, the displacement evolution transformed into deformation induced by time-dependent reduction in slope strength under rainfall conditions. The existing of unconsolidated deposits derived from ancient landslides, along with a fragile geo-structure consisting of rock blocks and gravels interlayered with breccias, exacerbated by large relief created a predisposition for landslide reactivation. Furthermore, 13 days of antecedent cumulative rainfall totaling 224.5 mm directly triggered the occurrence of a landslide event. The significance and implications of integrating multiple monitoring techniques are emphasized.

Ground subsidence and polygon development due to thermokarst in the Lena-Aldan interfluve, eastern Siberia, revealed by satellite remote sensing data

Thermokarst development is a topographic change in the landscape that is commonly associated with permafrost degradation in ice-rich permafrost regions. The Lena-Aldan interfluvial area in Central Yakutia in eastern Siberia has undergone extensive thermokarst development in the last three decades, particularly in the vicinity of settlements. Despite the negative effects of thermokarst development on the inhabitants of these settlements, no quantitative observation methods have been developed to investigate the surface displacement due to thermokarst development over entire towns. This study utilized interferometric synthetic aperture radar to reveal ground-surface displacement associated with thermokarst near the settlements of selected towns. The findings showed that significant subsidence was detected in disturbed areas (farming and abundant arable land) near the towns. The magnitude of subsidence in the Tyungyulyu and Mayya areas was less than that in Churapcha and Amga. Polygon density in a defined area in each town was examined using high-resolution optical images. The polygon density in Churapcha was considerably lower than that in Mayya, whereas polygonal texture in some areas in Tyungyulyu and Amga was unclear. Spatial frequency analysis using satellite optical images showed clear differences in averaged spectrum models between well-developed and less-developed polygons, which may reflect trough depths and density of vegetation between polygons. Satellite-based subsidence maps and statistics describing polygon development may be useful for evaluating both initial and subsequent stages of thermokarst development.

Prognosis of Ground Surface Deformation of the Victoria Mine –Slănic Prahova Saline

The Victoria mine, from Slănic Prahova Saline operated in the period 1970-1992 and was mined with small rooms and square pillars, on 11 overstory levels, of 16 m high. It resulted in a volume of mining voids of 7.4 million m3, which led to the pronounced degradation of the resistance structures (rooms and pillars) and to the deformation of the ground surface of the saline. Systematic, annual monitoring of ground surface deformation has been carried out since 2004, through geometric levelling, on certain representative alignments. The prediction of the time evolution of ground surface subsidence was carried out with some power approximation functions of prognosis and the future ground subsidence curves were established on the analyzed alignments. Also, 3D numerical modeling was used to estimate ground surface subsidence and displacements.

Simulation study on surface deformation of shallow buried coal seam mining in a gully area

Coal mining subsidence leads to frequent surface ecological and environmental problems. Due to the unique topographic conditions within gully areas, the deformation and damage characteristics, along with the evolution laws of the surface, have been difficult to analyze. To explore the surface movement and deformation law of shallow-buried coal seam mining in a gully area, this study designed a three-dimensional similar-material simulation test simulating the complete movement and deformation of the ground surface under real terrain conditions and proposed a complete data acquisition and processing scheme. Combined with the numerical simulation analysis, we utilized this scheme to analyze the dynamic influence law of coal seam mining in a gully area on the distribution of ground surface stress and displacement as well as on the dynamic characteristics of the ground surface damage. The results show that the existence of gully topography affects the stress distribution of the ground surface and the raw rock of the coal seams underneath and that there exists a stress concentration in the gully area of the ground surface. Furthermore, the mining activities of the coal seams lead to an increase in the degree of stress concentration in the gully area of the ground surface, and the slopes enter into the process of energy accumulation and sudden release, which makes the region prone to the occurrence of geological disasters such as landslides and collapses. In addition, the surface movement and deformation in the gully area are more intense, exceeding the plain area, and the surface movement is affected by the spatial location relationship between the mining area and the slope body, causing the center of the mining area to show obvious eccentricity characteristics. The results of this study provide a reference basis for the safe mining of coal mines in gully topography.

Reasonable mechanical model on shallow tunnel excavation to eliminate displacement singularity caused by unbalanced resultant

When considering initial stress field in geomaterial, nonzero resultant of shallow tunnel excavation exists, which produces logarithmic items in complex potentials, and would further lead to a unique displacement singularity at infinity to violate geo-engineering fact in real world. The mechanical and mathematical reasons of such a unique displacement singularity in the existing mechanical models are elaborated, and a new mechanical model is subsequently proposed to eliminate this singularity by constraining far-field ground surface displacement, and the original unbalanced resultant problem is converted into an equilibrium one with mixed boundary conditions. To solve stress and displacement in the new model, the analytic continuation is applied to transform the mixed boundary conditions into a homogenerous Riemann-Hilbert problem with extra constraints, which is then solved using an approximate and iterative method with good numerical stability. The Lanczos filtering is applied to the stress and displacement solution to reduce the Gibbs phenomena caused by abrupt change of the boundary conditions along ground surface. Several numerical cases are conducted to verify the proposed mechanical model and the results strongly validate that the proposed mechanical model successfully eliminates the displacement singularity caused by unbalanced resultant with good convergence and accuracy to obtain stress and displacement for shallow tunnel excavation. A parametric investigation is subsequently conducted to study the influence of tunnel depth, lateral coefficient, and free surface range on stress and displacement distribution in geomaterial.

InSAR Monitoring Using Persistent Scatterer Interferometry (PSI) and Small Baseline Subset (SBAS) Techniques for Ground Deformation Measurement in Metropolitan Area of Concepción, Chile

InSAR capabilities allow us to understand ground deformations in large metropolitan areas, this is key to assessing site conditions in areas in an inherently expanding context. The multi-temporal interferometry of SAR data records ground surface displacement velocities over large metropolitan areas, identifying anomalous and potential geological hazards. The metropolitan city of Concepción, Chile, is an alluvial basin in one of the world’s most seismically active subduction zones, where many subduction earthquakes have occurred throughout history. In this study, we monitored the deformations of the ground surface in the metropolitan area of Concepción using two interferometric techniques, the first being Persistent Scatterer Interferometry (PSI) and the second, the Small Baseline Subset (SBAS) technique. To do this, we have used the same Sentinel-1 dataset, obtaining ground movement rates between 2019 and 2021. The velocities were aligned with the GNSS station available in the area. Ground deformation patterns show local deformations depending on factors such as soil type and heterogeneity, and regional deformations due to geographical location in the subduction area. Our results highlight the similarity of the deformation rates obtained with different processing techniques and have also allowed us to identify areas of deformation and compare them to site conditions. These results are essential to evaluate ground conditions and contribute to urban planning and risk management in highly seismic areas.

Investigation of the Feasibility of Increasing the Tail-grouting Zone during Mechanized Tunneling in Sandy Soils

Nowadays, excavation in urban environments can have many risks; one of these hazards is improper tail-grouting of Earth Pressure Balance Machine (EPBM) and the consequent ground surface settlement. Failure to fill the tail space with suitable grout significantly affects the surface displacements. Injecting more grout to penetrate deeper around the tunnel will play a more effective role in reducing displacements and permeability of the soil. Therefore, experimentally investigation of the feasibility of increasing the tail-grouting zone during excavation around the tunnel space and the effect of this penetration on the amount of ground surface displacements is the main purpose of this paper. Thus, experimental tests were performed with different grout injection pressure and the effect of each of the pressure on the penetration depth of grout into the soil new laboratory model were examined. Then to study the effect of the grout penetration depth on surface settlement to determination of the adequate amount of grout injection pressure a numerical modeling of Tabriz metro line 2 by FLAC3D software were completed. For this purpose, the results of the laboratory tests (the penetration depth of grout) were used in numerical modeling. The results indicated that the amount of penetration in the implemented granulation has increased due to the increase in pressure, so doubling the pressure causes a 30% increase in grout penetration in the surrounding soil. The results of numerical studies showed that increasing the range of injection in the modeling causes a significant reduction (80 percent) in the ground surface settlement.

Bedrock Fractures Control Groundwater‐Driven Mountain Slope Deformations

AbstractSeasonal deformation of mountain rock slopes can be driven by groundwater infiltration and depletion. Such processes could explain our field observation in the Aletsch Valley, Switzerland, where GNSS‐derived 3D annual displacement amplitudes reach 3.4 cm. However, the physical mechanisms behind such groundwater‐driven surface displacements are not well understood. Here, we develop a fully coupled hydromechanical model to simulate the relevant processes in a valley slope embedded with numerous fractures of variable sizes. The magnitude and orientation of transient annual slope surface displacement obtained from our model are in overall agreement with the field observations. The key geological factors controlling the type and magnitude of reversible mountain slope deformations are fracture network geometry, fracture aperture, and regional stress field. We show that the heterogeneity and anisotropy of bedrock hydromechanical responses, originating from depth‐dependent variations of fracture properties, play a critical role in groundwater recharge and valley slope deformation. During recharge events, pore pressure perturbations migrate downward from the groundwater table and toward the receiving stream and the deep subsurface. This process driven by pressure diffusion and poroelastic stressing develops in the subsurface with a great reach of up to a few kilometers, called critical hydromechanical response zone, and controls surface deformation patterns. During groundwater recession, this hydromechanical response zone expands downward and ground surface displacement vectors rotate upwards. Our results suggest that slope surface deformation can inform about subsurface permeability structures and pore pressure fluctuations, which have important implications for understanding groundwater flow in fractured bedrock slopes.

Surface motion of P/SV wave scattering by a semicircular canyon in saturated half-space by complex function and conformal mapping

Based on the complex function theory of elastic dynamics, a complex function solution of P/SV-wave scattering by a semicircular canyon in an elastic porous saturated half-space is obtained. Firstly, through Biot theory and Helmholtz decomposition, the wave potential functions with unknown coefficients in the model are obtained based on the wave function expansion method. Secondly, the complex function expressions of stress and displacement in the model are obtained by using the complex function method and conformal mapping. According to the boundary conditions of the horizontal ground surface and semicircular canyon surface, this boundary value problem can be converted into a series of algebraic equations and solved numerically by truncation. Then, the correctness of the complex function solution in this paper is verified by comparing it with the published results through degenerating the scattering problem in the saturated porous elastic half-space in this paper into that in the elastic half-space. Finally, the influence of the boundary drainage conditions, the medium porosity, and the incident angle and frequency of the incident wave on the ground surface displacement is investigated. Although the P/SV-wave scattering problem is a traditional problem, there is currently no accepted analytical solution that strictly satisfies the zero-stress condition on the horizontal ground surface. This paper is an attempt at this problem, which may provide insight into the search for the strictly analytical solution for P/SV-wave scattering.

PSO-based Machine Learning Methods for Predicting Ground Surface Displacement Induced by Shallow Underground Excavation Method

Four hybrid intelligent methods are developed to predict the maximum ground surface settlement (Smax) induced by shallow underground excavation method (SUEM). Particle swarm optimization (PSO) algorithm with k-fold cross validation is used to determine the optimal hyperparameters or random parameters in the four machine learning (ML) methods, namely that, back-propagation neural network (BPNN), extreme learning machine (ELM), support vector regression (SVR) and random forest (RF). 100 field engineering samples are collected from published papers. In each data sample, the effect of stratum mechanical conditions, tunnel geometric parameters and construction parameters on Smax is considered. Correlation laws among parameters are investigated through Pearson correlation coefficient, data distribution histogram and correlation confidence ellipse. The performance of four PSO-based ML methods is comprehensively compared by fitness function, time cost and prediction accuracy in the training and test processes. PSO-RF outperforms PSO-SVR, PSO-ELM and PSO-BPNN in the prediction accuracy for Smax owing to larger R2, smaller MAE and RMSE. Calculation time that the optimal hyperparameters are determined is the fastest for PSO-RF, and PSO-ELM has the smallest fitness function. The prediction performance of PSO-RF method for construction parameters is also discussed. This work can provide theoretical guidance for design and construction of SUEM.

Analyses of the Ground Surface Displacement under Reinforcement Construction in the Shield Tunnel End Using the Artificial Ground Freezing Method

There are stringent requirements on the vertical movement of a ground surface when using artificial ground freezing method to reinforce a shield tunnel in a city. This paper focused on the tunnel of Nanjing Metro Line Two between Yixianqiao and Daxinggong. Based on the discrete element thermo-mechanical coupling theory, the horizontal freezing reinforcement project was numerically simulated. The numerical results of the soil temperature field and displacement field are approximately compatible with the field measurements. When the tunnel was frozen for 40 days, an effectively frozen soil wall was created and satisfied the construction requirements. During the freezing construction, both frost heave and thaw settlement obviously occurred. Above the tunnel, the vertical deformation of the ground surface was symmetrical about the center of the tunnel and decayed towards the ends. The maximum vertical displacement of ground surface frost heave was 8 mm, and the maximum vertical displacement of ground surface thaw settlement was 18 mm. Increasing the depth of the tunnel embedment can result in a decline in ground surface displacement. The study serves as a viable means of predicting ground surface displacements.

Influence of a low viscosity zone on the evolution of post-eruption deformation: A case study of the crustal deformation of Aira Caldera after the 1914 eruption of Sakurajima Volcano

Spatial viscosity variations in the crust can be inferred from geophysical imaging and may be essential for interpreting volcano deformations that show more complex behaviours than what simple uni-viscous models predict. In southern Kyushu, Japan, recent seismic imaging implies the presence of a low viscosity zone (LVZ) beneath Aira Caldera, and geodetic data in and around the caldera require uni-viscous model to have lower and higher viscosities earliest and later, respectively, in the period following the 1914 eruption of Sakurajima Volcano. Here, we use a 3D finite element model comprising an elastic layer underlain by a linear Maxwell viscoelastic layer to examine the influence of a LVZ on ground surface displacement in response to two different deformation source modes, i.e., instantaneous source deflation during a major eruption and subsequent continuous source inflation due to magma recharge. A LVZ is introduced into the viscoelastic layer by gradually reducing its viscosity towards the centre. The behaviour of the LVZ model quantified by comparison with the behaviour of a uniform viscosity (UNV) model reveals that, for a given LVZ structure, an apparent UNV model that best represents the LVZ model displacement in response to the instantaneous deflation has lower viscosity than that in response to gradual inflation, i.e., the rate-controlling viscosities of the LVZ model are those in the inner and outer parts of the LVZ for the instantaneous source deflation and subsequent continuous inflation, respectively. Such LVZ model behaviour, for a LVZ spatial extent comparable with the imaged low velocity anomaly, explains well the geodetic data in and around Aira Caldera at any stage after the 1914 eruption, as the predominant viscoelastic response changes with time from that to the instantaneous deflation to that to the subsequent continuous inflation. This study highlights the need for interdisciplinary investigations that integrate geodetic and geophysical datasets to better understand volcanic unrest.