Ground Deformation Research Articles

Axial pullout behaviour of fusible PVC pipes and fusion weld joints assessed using distributed fibre optic sensors

Pipes are subjected to axial pulling forces that lead to shear stresses at the soil–pipe interface and axial strain distributions from various circumstances, including pulled-in-place pipe installation and permanent ground deformations. This study investigates the axial pullout response of fusible polyvinyl chloride pipes in dense sand. Three tests were conducted using a large-scale soil chamber to assess the development of axial resistance and the impact of non-continuous pulling and fusion weld joints. The measured maximum load response was significantly underpredicted by guidelines typically used in practice. Additionally, non-continuous pulling and changes to the pull rate had negligible impacts on the load–displacement response. Pipes were instrumented with distributed fibre optic sensors (DFOS) to capture the nonlinear development of strains along these flexible pipes and the mobilization of soil friction along the soil–pipe interface. Measurements have provided insight into the propagation of axial strains along the pipe, the additional longitudinal restraint provided by fusion weld joints, and their impact on the axial force distribution along pipes. The “locked-in” strains due to residual soil–pipe friction remaining after the axial pulling force is removed have also been measured using DFOS.

Ground deformation induced by shield tunneling posture in soft soil

Constructing tunnels in soft soil using shield machines would induce soil deformation. Several factors, such as support pressure, ground loss, grouting pressure may affect the soil deformation. In engineering practice, the ground deformation could also vary with the posture of the shield machine. This study proposed an approach for estimating the soil deformation considering shield posture. Firstly, the shield-soil interaction displacement was obtained by considering shield geometry and its kinematic behavior, such as shield diameter and length, articulation, and shield deviation. Secondly, based on the elastic half-space theory, a calculation method for mapping the shield-soil interaction displacement to soil deformation was established. Finally, the proposed model was verified by the field measurement in the tunnel of Suzhou Metro line S1, and the results confirm that the postures of the shield machine in the soil influence the magnitude, distribution, and evolution of the soil deformation.

Behavior and design of earthquake resistant concrete structure

Earthquake and seismic-resistant concrete structures are essential components and requirements of structural design. The performance and response of concrete structures during/after the earthquake event are significant to determine the condition of the structures as well as to identify the possibility of structural failure. The main objective is to investigate the appropriate method to evaluate the impact on the structure due to earthquakes based on closed-form solutions, and to determine its differences with the results of numerical modelling. The seismic behavior of structures is required to be designed in accordance with the minimum design requirements specified in the Standard. Seismic design, where ground behavior is considered, is presented as a significant part of design analyses, and ground movement and shaking, are associated with the ground deformation which is the primary seismic load consideration for the design of plain or reinforced concrete structures. The outcome of the longitudinal analysis provided the maximum axial and bending strain which is adopted to calculate the combined strain. These results of strain are considered with the design of concrete structures against Ultimate Limit State and Service Limit State design phases. Therefore, the results evaluate the effect of seismic design on the performance of the concrete structure.

Prediction and Application of Surface Settlement of Shallow Buried Tunnels Taking into Account Strata Slip Cracks

The empirical formula is one of the traditional methods used for predicting ground deformation settlement caused by tunnel excavation. Due to its rationality and simplicity, the Peck formula is widely used for predicting surface subsidence. However, due to its limitations, it is necessary to modify it when predicting surface settlement caused by tunnel excavation in different strata. In this paper, a correction formula for the width coefficient of a tunnel surface settlement slot is derived from the Peck formula by taking into account the theory of strata slip cracks. Values are calculated using the correction formula and compared with measured data to verify the effectiveness of the correction formula. The main conclusions are: (1) The position corresponding to the width of the settlement in the Peck curve is the point where the formation is most prone to slip cracking. (2) In the general shallow buried case, the settlement groove width coefficient K and the internal friction angle φ of the ground satisfy the formula K = 1/tan(45° + φ/2 + a) + b, and the values of parameters a and b reflect the average values of the geometric properties of the tunnel based on the measured data. (3) The prediction of the correction formula is consistent with the measured data, and thus the correction formula can be applied to problems related to the stability of shallow buried tunnels.

InterpolatiON of InSAR Time series for the dEtection of ground deforMatiOn eVEnts (ONtheMOVE): application to slow-moving landslides

The aim of this work is to develop an innovative methodology to analyse the time series (TS) of interferometric satellite data. TS are important tools for the ground displacement monitoring, mostly in areas in which in situ instruments are scarce. The proposed methodology allows to classify the trend of TS in three classes (uncorrelated, linear, non-linear) and to obtain the parameters of non-linear time series to characterise the magnitude and timing of changes of ground instabilities. These parameters are the beginning and end of the non-linear deformation break(s), the length of the event(s) in days, and the quantification of the cumulative displacement in mm. The methodology was tested on two Sentinel-1 datasets (2014–2020) covering the Alpine and Apennine sectors of the Piemonte region, an area prone to slow-moving slope instabilities. The results were validated at the basin scale (Pellice-Chisone and Piota basin) and at a local scale (Brenvetto, Champlas du Col and Casaleggio Boiro landslides) comparing with in situ monitoring system measurements, possible triggering factors (rainfall, snow) and already-collected events of the territory. The good correlation of the results has proven that the methodology can be a useful tool to local and regional authorities for risk planning and management of the area, also in terms of near real-time monitoring of the territory both at local and regional scale.

Quantifying seasonal ground deformation in Taiyuan basin, China, by Sentinel-1 InSAR time series analysis

The presence of seasonal surface deformation in areas that are subsiding/uplifting due to groundwater pumping/recovery can indicate aquifer recharge. Understanding seasonal surface deformation and the existing relationship between triggering factors and the deformation supports effective groundwater management and subsidence mitigation. Here, we investigated seasonal ground displacement in response to the aquifer compaction and expansion due to groundwater extraction and recharge within the Taiyuan basin, Northern China. We obtained Sentinel-1 InSAR displacement time series data from 2017 to 2020 and quantitatively analyzed relationships between triggering factors (e.g., groundwater level and precipitation) and the associated displacements using wavelet-based methods. The results show that the seasonal deformation is concentrated in the irrigated areas within the central basin, with a 1-year periodicity. The annual peak-to-peak amplitude was up to 2 cm, peaking in March with troughs in August. This seasonality present in the displacement time series is found to be ‘in-phase’ with respect to groundwater levels and ‘anti-phase’ in relation to natural precipitation. These results are consistent with the irrigation pumping practices in the basin, with increased groundwater withdrawals to meet irrigation water demand prior to the monsoon precipitation season, resulting in water level decline and land subsidence from mid-March to mid-August. During the non-irrigated season, groundwater extraction decreases, and the aquifer systems are replenished by precipitation, causing water levels to recover and the ground to uplift from late August to mid-March. A geological analysis indicates that the seasonal deformation is controlled by the thickness of Quaternary strata and fault systems, which play a critical role in forming the earth fissures in the basin. The elastic and inelastic deformation was separated; the estimated elastic/inelastic ratio was about 0.6–0.7, indicating that the inelastic component dominates the main aquifer compaction in the central basin. Our analysis is of hydrologic importance which could be used to guide groundwater management and subsidence mitigation, given the inter-basin water diversion projects in this arid basin.

Data-driven estimations of ground deformations induced by tunneling: a Bayesian perspective

Data-driven estimations of ground deformations induced by tunneling: a Bayesian perspective

Experimental Research on the Settlement Feature of Two Ground Deformation Modes Induced by Tunnelling

Two ground deformation modes, i.e., the arching mode and collapsing mode, may be caused by tunnel excavation. However, the development of the ground deformation corresponding to the two modes is unclear. A piece of a model test facility is designed to study the ground settlement induced by tunnel excavation. Tunnel excavation is realized by decreasing the area of the model tunnel. Two model tests with different soil cohesion are conducted, and the two ground deformation modes form in the two tests, respectively. The former mode is observed at higher soil cohesion while the latter is found to develop at lower soil cohesion. Whether the failure surface develops to the ground surface or not is the most significant difference between the two ground deformation modes. In the two modes, the failure surface occurs at the position where the ground settlement contours distribute densely, and the shape of the failure surface can be described by the semi-oval for both modes. Meanwhile, for both the arching mode and the collapsing mode, Gaussian curves can reasonably describe the ground settlement troughs before the ground surface settlement becomes stable or increases sharply, and distribution of the trough width parameter is similar.

An empirical formula for the accumulative deformation of saturated clay under different cyclic loading frequencies

Road and subway tunnels in soft clay soils subjected to traffic loading often cause lager settlement. It can pose danger to the surrounding buildings and structures. Hence, it is necessary for engineers to correctly predict the long-term deformation of saturated clay foundations under cyclic loading. In this paper, a series of dynamic triaxial tests were carried out on Nanning clay to investigate the effect of loading frequency and cyclic stress on axial strain accumulation of clay under undrained condition. Results show that loading frequency has a great effect on the axial strain accumulation of clay. Based on the experimental results, an empirical formula for calculating the accumulated deformation of saturated clay under cyclic loading was presented.

Damage Assessment Through the Use of SBAS-DInsar Data: An Application to the “Vittorino da Feltre” Masonry School Building in Rome

ABSTRACT The detection and monitoring of deformation patterns induced by causes of various nature is fundamental to prevent and mitigate the associated risk. To this aim, one of the most innovative, non-invasive monitoring approaches is based on the use of satellite radar images through the advanced multi-temporal Differential Interferometry Synthetic Aperture Radar (DInSAR) technique, which is able to detect deformations induced by slowly evolving phenomena. In this work, the multi-temporal DInSAR technique referred to as full resolution SBAS approach is exploited for the monitoring of the ground deformations and their effects on the “Vittorino da Feltre” school building located in the city of Rome (Italy), which is undergoing a retrofitting project. The displacement measurements were obtained by using the COSMO-SkyMed satellite dataset related to the city of Rome during the 2011–2019 time interval, processed with full resolution Small. The damage progression during the last years has been evaluated by comparing a recent survey of the structural damage with the previously available ones. An integration of SAR-derived data and outcomes of the on-site damage surveys is presented, aimed to perform a damage assessment of the structure using literature scales of damage.

Multi-sensor InSAR time series fusion for long-term land subsidence monitoring

ABSTRACT Satellite Interferometric Synthetic Aperture Radar (InSAR) is widely used for topographic, geological and natural resource investigations. However, most of the existing InSAR studies of ground deformation are based on relatively short periods and single sensors. This paper introduces a new multi-sensor InSAR time series data fusion method for time-overlapping and time-interval datasets, to address cases when partial overlaps and/or temporal gaps exist. A new Power Exponential Knothe Model (PEKM) fits and fuses overlaps in the deformation curves, while a Long Short-Term Memory (LSTM) neural network predicts and fuses any temporal gaps in the series. Taking the city of Wuhan (China) as experiment area, COSMO-SkyMed (2011–2015), TerraSAR-X (2015–2019) and Sentinel-1 (2019–2021) SAR datasets were fused to map long-term surface deformation over the last decade. An independent 2011–2020 InSAR time series analysis based on 230 COSMO-SkyMed scenes was also used as reference for comparison. The correlation coefficient between the results of the fusion algorithm and the reference data is 0.87 in the time overlapping region and 0.97 in the time-interval dataset. The correlation coefficient of the overall results is 0.78, which fully demonstrates that the algorithm proposed in our paper achieves a similar trend as the reference deformation curve. The experimental results are consistent with existing studies of surface deformation at Wuhan, demonstrating the accuracy of the proposed new fusion method to provide robust time series for the analysis of long-term land subsidence mechanisms.

Sulfur dioxide flux measurement at Mount Tokachi, Japan, with TROPOspheric Monitoring Instrument

Introduction: Monitoring the volcanic activity of a potentially hazardous volcano is essential for eruption warning and hazard mitigation. The SO2 flux from the volcano is one of the most important measures to understand its activity. Mount Tokachi, in Japan, is an active volcano that experienced three magmatic explosive eruptions in the 20th century (in 1926, 1962, and 1988–1989). Since 2006, geodetic observations have captured ground deformation, suggesting an inflation beneath the main crater. Moreover, since 2020 daily visual observations have detected the increase in plume heights and the occurrence of volcanic glow at the main crater. The high-time-resolution estimation of SO2 flux will help monitor the activity of Mount Tokachi and clarify the associating mechanisms. Furthermore, satellite remote sensing can estimate the vertical column density (VCD) of sulfur dioxide (SO2), enabling the daily determination of SO2 flux without the need to visit the site. Due to the improved spatial resolution, the TROPOspheric Monitoring Instrument (TROPOMI) has advanced satellite-based volcanic gas flux measurements.Methods: We have analyzed the available TROPOMI data and conducted ground-based observations to estimate the SO2 flux from Mount Tokachi at 100–2,000 tons/day.Result and Discussion: The average annual SO2 flux has been increasing since 2021, on par with the increase in plume height and volcanic glow. TROPOMI data enabled quantification of the annual SO2 flux, with a sufficient temporal resolution to monitor the volcanic activity at Mount Tokachi. However, a high flux, such as in excess of 2,000 tons/day, was observed in the winter season. The flux from the satellite data was similar to that from ground-based observations during the summer. However, a seasonal change in flux from the satellite data was observed in winter, with the flux being larger than that in summer, possibly because the flux increases during winter. Another possible reason is the influence of snow cover on satellite observations due to its high surface reflectance. We reanalyzed some TROPOMI data during the winter, in which the ground snow cover was misidentified as clouds at low altitudes. This procedure suppresses the error caused by the high surface reflectance due to winter snow coverage and improves the quality of the annual SO2 flux from satellite observations. This methodology is applicable to other high-latitude or high-altitude volcanoes during specific seasons characterized by frequent fluctuations in snow cover conditions.

Observation of spatial and temporal patterns of seasonal ground deformation in central Yakutia using time series InSAR data in the freezing season

The seasonal freeze/thaw variations of the active layer cause seasonal ground deformation, such as thaw subsidence in summer and frost heave in winter due to the cyclic phase changes of soil water. The Synthetic Aperture Radar (SAR) remote sensing, especially interferometric SAR (InSAR) techniques, has been proven to be a very useful tool for observing surface displacements of permafrost environments. Most previous studies on seasonal InSAR displacement have been concentrated in several study sites in the Arctic tundra regions. The objective of this study is to extend the InSAR analysis of seasonal ground deformations to boreal forest regions, where monitoring ground deformation is particularly important in terms of better understanding active layer dynamics under various ecological and geological conditions. In this study, we presented a strategy to analyze the time series SAR data in the freezing season to estimate the differential phase for seasonal ground deformation while overcoming the problem of coherence losses due to the rapid growth of vegetation during the short growing season. We applied the SBAS-based InSAR processing method to Sentinel-1 SAR in the central Yakutian lowlands, where boreal forests and thermokarst landforms are widely distributed, and retrieved frost-related displacement signals successfully. In addition to the magnitude of ground deformation in the freezing season, we further examined the temporal deformation pattern related to the progression of the freezing front in the soil during active freezing. Based on the Stefan solution, we proposed a piecewise linear model for the time series deformation. The proposed model divides the time series displacement according to the progression of freezing into three linear segments, and the slope parameter of each linear model can be interpreted as indicating the hydrological characteristics of the upper, middle, and lower parts of the soil. The results for the Yakutian lowlands illustrated the potential of SAR remote sensing to observe and quantify spatial details of the thermal and hydrological properties inside the active layer soil even in highly vegetated subarctic boreal forest areas.

Prevention And Control of Mass Concrete Cracks in Building Construction Engineering

As a kind of building material, mass concrete plays an important role in building construction. It is widely used in engineering projects and needs to be controlled in many aspects, otherwise cracks may appear and affect the safety and performance of the project. In this paper, the crack problems of mass concrete structures are studied and analyzed, such as cracks caused by mix ratio, temperature change, foundation deformation. Firstly, by understanding the internal and external causes of cracks in mass concrete, the key issues were suggested. Then, the method to prevent and control the crack of mass concrete is put forward from the selection of reasonable raw materials and mix ratio, pouring method, temperature control and other aspects. The research results can be used as reference to reduce the negative impact of cracks in building construction engineering. While improving the safety and service life of housing construction projects, it also improves the economic value and reduces the time cost of rework.

Test Study on the Influence of Foundation Pit Excavation on the Surface Settlement of Sandy Soil Natural Foundation of Adjacent Buildings

The excavation of a foundation pit will break the original stress balance and affect the surface settlement of the natural foundation of adjacent buildings, so deformation control is very important. In this paper, numerical simulation results of the additional stress of a natural foundation caused by a foundation pit excavation were compared with experimental results to verify the accuracy of the numerical model of a foundation pit excavation and obtain a reliable ratio of building width to the average particle size of the sand that was not affected by the particle size effect. Then, the distribution and variation law of the surface settlement of a natural foundation caused by excavation was studied by a model test, and the relationship between the deformation of a natural foundation and the depth of a foundation pit excavation and the additional load of building was obtained.

Impact assessment caused by bradyseism phenomena in the Campi Flegrei area

Campi Flegrei (Italy) is among the areas with the greatest volcanic explosive risk in the world due to the dangerousness of the expected hazards, the high exposed value (about 500,000 people will be evacuated during the “alarm phase”), and the vulnerability of the urban settlements under the effect of the volcanic phenomena. The last two dramatic bradyseism phases occurred in 1969–1972 and 1982–1984 when Pozzuoli town was affected by rapid ground inflation, which brought an overall higher level of about 3.5 m and caused numerous earthquakes (M ≤ 4.2), with severe damage to buildings. During 1984, the seismicity was intense, with 33 events with 0.5 < M ≤ 3 and six with 3 < M ≤ 3.8. Subsequently, the Campi Flegrei caldera was characterized by general subsidence for about 20 years until 2005, when a new inflation period started and is still ongoing (∼1 m). The areal distribution of the recent uplift is characterized by the maximum vertical displacement in the town of Pozzuoli, with a radial decrease from the caldera center outwards. The need to better understand Campi Flegrei volcanic activity is fundamental to protecting the population from hazards linked to explosive volcanic eruptions and understanding the role of seismicity as a possible precursor of a potential eruption. In this perspective, as part of the activities of the PLINIVS Study Centre (Centre of Competence of Italian Civil Protection Department for Volcanic Risk), the authors developed a procedure, implemented in a web application, that relates the monitoring of the ground deformation with the behavior of buildings to evaluate the level of progressive damage to the ordinary Phlegraean buildings due to bradyseism in near real time. This study describes the models adopted for the three impact/risk factors (hazard, exposure, and vulnerability) used to estimate building damage.

EGMStream, a Desktop App for EGMS Data Downstream

The recent release of European Ground Motion Service (EGMS) products implemented under the responsibility of the Copernicus Land Monitoring Service (CLMS) guarantees free and accessible Europe-wide ground motion data for ground deformation analysis at the local and regional scales. The need for value-adding services and tools for optimal dissemination of radar data from the Copernicus Sentinel-1 satellite mission urges the scientific community to find efficient solutions. A desktop R-based application with a user-friendly interface capable of automatically downloading and transforming EGMS products delivered as large .csv tiles, equivalent to a radar burst into geospatial databases, is presented here. EGMStream is a self-contained desktop app that enables users to systematically store, customize, and convert ground movement data into geospatial databases, burst per burst or for an area of interest directly selectable on the app interface.

Study on the influence of expansive soil slope on bridge foundation under excavation and rainfall conditions

AbstractExpansive soil is a kind of special soil that mainly composes of hydrophilic minerals and has significant deformation characteristics of water absorption expansion and water loss shrinkage. The characteristics often bring great harms to engineering construction. Relying on the bridge foundation on the expansive soil slope of the Yangtze‐to‐Huaihe Water Diversion Project, this study simulates the humidity field with temperature field for expansive soil using the numerical simulation method when short‐term or long‐term rainfall occurs during slope excavation. The horizontal deformation of bridge foundation on expansive soil slope considering four factors such as self‐weight of slope soil, excavation unloading rebound, hygroscopic expansion of expansive soil, and decrease of soil strength caused by change of water content was studied herein. The research results show that during the excavation process, the bridge foundation produces a horizontal displacement towards the top of the slope, and the rainfall after excavation introduces a decrease to the horizontal displacement of the bridge foundation and gradually develops in the opposite direction. During the excavation process, the rebound of slope excavation is the main factor affecting the horizontal displacement of the bridge foundation. Under short‐term rainfall conditions, the hygroscopic expansion of the slope soil becomes the main influencing factor. Under long‐term rainfall conditions, the main influencing factors of horizontal deformation of bridge foundation are the self‐weight of slope soil and the decrease of soil's strength.

Experimental and Analytical Evaluations of Ground Behaviors on Changing in Groundwater Level in Bangkok, Thailand

Groundwater level changes have numerous effects on buildings, such as differential ground deformation and cracking on the wall. In Bangkok, Thailand, change in groundwater levels changing was caused by groundwater pumping that took place from 1978 to 1997. This is the main effect of ground deformation in a wide area of the Bangkok plain. According to the regulation of groundwater pumping in Bangkok and urban areas, the trend of groundwater level tended to recover around the year 1997. However, the ground settlement still occurs for a while after groundwater recovery. The objective of this study is to evaluate and compare the capability of each approach for the ground deformation and the pile capacity in the situation of groundwater level change. Data in this study were obtained from the previous centrifuge test which had been modeled for the Bangkok area. The ground behavior and pile load capacity behavior were verified using numerical modeling. Both experimental modeling and numerical modeling represent very similar trends of ground deformation. The pile capacity results from both models’ increase while the groundwater level decreases and the pile capacity decreases when groundwater is recovered. The numerical modeling results reveal an overestimate of the ground behavior. However, both results present the loss of pile capacity in the range of 8 to 25% of maximum load when the groundwater level reach to the minimum level.

Impact of MHT9002HV Tracked Harvester on Forest Soil after Logging in Steeply Sloping Terrain

The article presents the results of measurements regarding the impact of the MHT9002HV tracked harvester on surface deformations and changing the physical parameters of the soil of three operational trails. The measurements were made in the terrain with a longitudinal slope of up to 14.9° (33.2%) and a transverse slope of up to 8.8° (17.9%). Spruce deadwood trees in mountain forest habitats were harvested. Static Eijkelkamp Penetrologger 0615SA and dynamic own design penetrometer were used to measure penetration resistance, soil samples were taken to determine bulk density, moisture content, and ground deformations on the trails were measured with a laser profilometer. A statistically significant increase in soil penetration resistance measured with penetrometers occurred for trails in the left rut at a depth of 16–20 cm. The change in the bulk density and moisture content proved statistically insignificant. The maximum ground deformation on the trails reached an average of 5.9 cm. The selection of a machine with low unit pressures (33 kPa), under the given favorable atmospheric conditions (there was a high temperature reaching 35 °C), with low soil moisture, protective organic layer of high thickness, and post-limbing residues, was optimal. The comparison of the results of the compactness measurements made with different penetrometers shows that the values obtained for the static penetrometer 0615SA are lower than those of the dynamic penetrometer of our own design. This is due to the lack of registration of high compactness in the memory of the 0615SA device. In the case of the impact penetrometer measurement, this problem does not occur, however, the presented solution does not allow performing a large number of measurements, and data processing in the case of such a simple solution is tedious. There is a need to develop a new penetrometer useful for determining soil compaction under similar difficult measurement conditions.