Cumulative Deformation Research Articles

Hysteretic energy dissipation capacity of dual-steel welded-plate preloaded bolted T-stubs

With the high- and ultrahigh-strength steels applied in the construction industry, the seismic safety of their structural components is very concerned due to the inferior material ductility of those steels. The current studies on bolted high-strength steel T-stubs mainly focus on their monotonic loading behavior. There is limited research work conducted to study their cyclic loading behavior. In this study, cyclic tests of bolted dual-steel T-stubs were conducted. Their T-elements were produced by Q690 high-strength steel flanges and Q355 normal-strength steel webs, and class 10.9 high-strength bolts with pretension were used to connect the groove-welded T-elements. Failure modes, force-deformation hysteretic and backbone curves, cumulative plastic deformation and energy dissipation capacities were tested and analyzed. The test results indicated that an optimal β ratio between the plastic resistances of Mode 1 (neglecting the influence of bolt action on a finite contact area) and Mode 3 in Eurocode 3 Part 1–8, could be 0.3 for those bolted T-stubs to maximize hysteretic energy dissipation. Accordingly, predictive formulas with good precision were proposed for the low-cycle fatigue failure criterion and hysteretic energy dissipation capacity of those bolted T-stubs, respectively.

Effect of Repeated Processing Passes during Ultrasonic Rolling on Fatigue Performance and Corrosion Resistance of Ti6Al4V Alloy

Ultrasonic surface rolling processing (USRP) is a new method to improve the fatigue performance of titanium alloy, and repeated processing pass is an important factor that affects its strengthening effect. The effect of USRP passes on the surface microstructure, residual stress, fatigue performance and corrosion resistance of titanium alloy is researched via SEM, X-ray diffractometer, rotating–bending fatigue test and electrochemical impedance spectroscopy. The results show that Ti6Al4V alloy undergoes cumulative plastic deformation during USRP process, the surface grains are refined and a residual compressive stress field with a thickness of 500 μm is introduced, which together improve the fatigue performance of the Ti6Al4V alloy. Increasing the repeated processing passes will deepen the grain refinement layer and increase the surface hardening effect, but the fatigue life of the Ti6Al4V alloy does not increase with an increase in processing passes. A five-passes processing under a static force of 550 N can result in a greater gain for the fatigue resistance of the Ti6Al4V alloy; the fatigue life of a five-passes-processed sample under 600 MPa is 8 times higher than that of an untreated sample, and its fatigue crack source initiates at the subsurface away from the surface of 180 μm. Furthermore, Ti6Al4V alloys treated by USRP show a better corrosion resistance in both neutral and acidic solutions, especially for the five-passes-processed sample.

Experimental Study on Dynamic Characteristics of Saturated Soft Clay with Sand Interlayer under Unidirectional and Bidirectional Vibration

The marine and alluvial plains along the southeastern coast of China are widely distributed in sandy formations, including smaller sand lenses and interlayers. The interlayers of sand have a significant impact on the mechanical properties of soft clay. In this paper, a large number of undrained unidirectional and bidirectional cyclic loading tests for soft clay with sand interlayers were carried out by a dynamic triaxial test system. Test results show that, under unidirectional and bidirectional cyclic vibration, the area of the hysteresis loop decreases and the slope of the connecting line at both ends of the hysteresis loop increases with the increasing of frequency. For the same vibration frequency, the area of the bidirectional vibration hysteresis loop and the slope of the connecting line at both ends are smaller than that of the unidirectional cyclic vibration. Under the same dynamic stress ratio, cumulative axial deformation caused by unidirectional and bidirectional vibration increases with the increasing frequency. Under unidirectional vibration, dynamic elastic modulus decreases at first, and then increases with the increasing frequency. For the same frequency, dynamic elastic modulus of the sample increases with the increase in cycles. Due to the effect of radial cyclic stress, the curves of dynamic elastic modulus and damping ratio with frequency under bidirectional vibration are opposite to those under unidirectional vibration.

Cumulative buckling deformation of stiffened panel under cyclic loading

In this study, the cumulative buckling deformation process is evaluated for a stiffened panel subjected to two different uniaxial cyclic loading conditions, namely compressive loading only and alternating tensile-compressive loading. The impact of the cyclic load on the ultimate strength of the panel is then estimated. It should be noted that the occurrence of permanent deformations could be simulated by finite element analysis using a suitable model capable of correctly capturing the deformation components. The results show that the structure accumulates a deformation that appears to grow almost linearly therefore, consequently, it is realistic to expect that if a large number of load cycles of this magnitude are imposed, the accumulated plastic deformation can be quite severe. Furthermore, it is found that these residual deformations, caused by an entity of the cyclic load lower than the design limit, affect the tensile strength of the stiffened panel. Finally, the effects on the numerical evaluation of the ultimate strength of the structure are shown.

Field Tests on Thermal Performance of Bridge Pile Groups under Embankment Load and Cap Constraint Condition

Based on the project of National Highway No. 310 located in Sanmenxia City, China, field tests on the thermal responses of the 2 × 2 pile groups under embankment load in winter condition are carried out. The temperatures and stresses of piles along pile depth under the combined action of embankment load and temperature are measured. The thermal characteristics of the pile body, such as thermal-induced stress, cumulative deformation of the pile top, and heat exchange efficiency per unit area, are analyzed. The feasibility of a new piping method compatible with the segmented reinforcement cage is discussed. A calculation method for heat exchange in a large-diameter energy pile is proposed. The layout of the heat exchange pipe used in this study is feasible, and there is no large stress mutation in the dense and nondense areas. The maximum tensile stress in the middle of the pile body is about 0.4 MPa, which is nearly 22% of the concrete tensile strength value. The settlement of the pile top is about 0.33 mm after seven days of cooling condition, which is about 0.27‰ of the pile diameter.

Optimization of Reservoir Level Scheduling Based on InSAR-LSTM Deformation Prediction Model for Rockfill Dams

The Xiaolangdi reservoir has a storage capacity of more than 10 billion cubic meters, and the dam has significant seasonal deformation. Predicting the deformation of the dam during different periods is important for the safe operation of the dam. In this study, a long short-term memory (LSTM) model based on interferometric synthetic aperture radar (InSAR) deformation data is introduced to predict dam deformation. First, a time series deformation model of the Xiaolangdi Dam for 2017–2023 was established using Sentinel-1A data with small baseline subset InSAR (SBAS-InSAR), and a cumulative deformation accuracy of 95% was compared with the on-site measurement data at the typical point P. The correlation between reservoir level and dam deformation was found to be 0.81. Then, a model of reservoir level and dam deformation predicted by neural LSTM was established. The overall deformation error of the dam was predicted to be within 10 percent. Finally, we used the optimized reservoir level to simulate the deformation at the measured point P of the dam, which was reduced by about 36% compared to the real deformation. The results showed that the combination of InSAR and LSTM could predict dam failure and prevent potential failure risks by adjusting the reservoir levels.

Cumulative deformation and non-coaxial characteristics of fiber and cement-modified iron tailings under the rotation of principal stress

In order to study the deformation characteristics of fiber and cement-modified iron tailings (FCIT) under traffic loads, the cumulative deformation, stress–strain paths, cyclic stiffness, and non-coaxial characteristics of FCIT under the coupling of different cyclic stress ratios (CSR) and torsional shear stress ratios (η) were analyzed by using a heart-shaped stress path. The results indicate that: 1) The cumulative strain and torsional shear strain of FCIT under the rotation of the principal stress vary with CSR and η. The established empirical formula for the cumulative strain can be used to calculate the cumulative deformation of FCIT under different principal stress rotations based on the results of cyclic triaxial tests. 2) The difference between shear stiffness and positive deviation stiffness is the inherent mechanism that induces the non-coaxial characteristics of FCIT, that is, shear stiffness is subjected to torsional shear stress more than positive deviation stiffness is subjected to axial stress. 3) The non-coaxial characteristics of FCIT gradually weaken with the increase of axial force and torsional shear force, while the non-coaxial angle between the direction of strain increment and the direction of stress decreases.

Dam Surface Deformation Monitoring and Analysis Based on PS-InSAR Technology: A Case Study of Xiaolangdi Reservoir Dam in China

The Xiaolangdi Dam is a key project for the control and development of the Yellow River. It bears the functions of flood control, controlling water and sediment in the lower reaches, ice prevention, industrial and agricultural water supply, power generation, and so on. Its safety is related to people’s life and property safety and local economic and social development. It is of great significance to carry out comprehensive and regular deformation monitoring for dams since the deformation is an important evaluation index for dam safety. Interferometric Synthetic Aperture Radar (InSAR) technology has been a rapidly evolving technology in the field of space geodesy in recent years. It offers advantages such as high monitoring precision, extensive coverage, and high monitoring point density, making it a powerful tool for monitoring deformations in hydraulic engineering projects. Based on Sentinel-1 data covering the Xiaolangdi Dam from September 2020 to November 2022, the PS-InSAR technique was used to obtain the surface deformation of the Xiaolangdi Dam, and reservoir water level data on image acquisition dates were obtained for joint analysis. The results show that there is a large deformation in the center of the dam crest of the Xiaolangdi Dam, while both sides of the slope and downstream dam foot are relatively stable. The time series deformation of the dam body is closely related to the reservoir water level change. When the water level increases, the dam body tends to deform downstream; when the water level decreases, the dam body tends to deform upstream. The deformation and water level of the Xiaolangdi Dam exhibit a clear negative correlation. There is no significant cumulative deformation on the dam slopes or at the base of the dam. However, cumulative deformation occurs over time in the central area of the dam’s crest. The deformation process at the central area of the dam’s crest follows a continuous and non-disruptive pattern, which is consistent with the typical deformation behavior of the Xiaolangdi earth–rock dam structure. Therefore, it is judged that the current deformation of the Xiaolangdi Dam does not impact the safe operation of the dam. InSAR technology enables the rapid acquisition of high-precision, high-density deformation information on the surfaces of reservoir dams. With an increasing number of radar satellites in various frequency bands, such as Sentinel-1 and TerraSAR-X, there is now an ample supply of available data sources for InSAR applications. Consequently, InSAR technology can be extended to routine monitoring applications for reservoir dam deformations, especially for small and medium-sized reservoirs that may not be equipped with ground measurement tools like GNSS. This holds significant importance and potential for enhancing the safety monitoring of such reservoirs.

Current situation and development trend of design methods for subgrade structure of high speed railways

PurposeThis method will become a new development trend in subgrade structure design for high speed railways.Design/methodology/approachThis paper summarizes the structural types and design methods of subgrade bed for high speed railways in China, Japan, France, Germany, the United States and other countries based on the study and analysis of existing literature and combined with the research results and practices of high speed railway subgrade engineering at home and abroad.FindingsIt is found that in foreign countries, the layered reinforced structure is generally adopted for the subgrade bed of high speed railways, and the unified double-layer or multi-layer structure is adopted for the surface layer of subgrade bed, while the simple structure is adopted in China; in foreign countries, different inspection parameters are adopted to evaluate the compaction state of fillers according to their respective understanding and practice, while in China, compaction coefficient, subsoil coefficient and dynamic deformation modulus are adopted for such evaluation; in foreign countries, the subgrade top deformation control method, the subgrade bottom deformation control method, the subsurface fill strength control method are mainly adopted in subgrade bed structure design of high speed railways, while in China, dynamic deformation control of subgrade surface and dynamic strain control of subgrade bed bottom layer is adopted in the design. However, the cumulative deformation of subgrade caused by train cyclic vibration load is not considered in the existing design methods.Originality/valueThis paper introduces a new subgrade structure design method based on whole-process dynamics analysis that meets subgrade functional requirements and is established on the basis of the existing research at home and abroad on prediction methods for cumulative deformation of subgrade soil.

Effect of cumulative deformation and interlayer mechanical properties on bonding strength of corrugated interface steel/aluminum composite plate

Interface oxidation during hot rolling limits high quality fabrication of steel/aluminum composite plates. Q235/5083 composite plates were prepared by a process combining cold corrugated rolling (CCR) and hot flat rolling (HFR) in this study. The CCR & HFR process effectively prevents the oxidation of the base Q235 when bonding with clad 5083 aluminum alloy during hot rolling, by pre-rolling a thin interlayer 1060 aluminum on Q235, to improve the bonding strength. Bonding performance of steel/aluminum composite plate is studied in relation to the cumulative deformation when 1060 is the interlayer. The rolling experiments and performance analysis show that the shear strength initially increases and then stabilizes as the cumulative reduction rate increases since the shear fracture position occurs in the interlayer 1060. High-strength aluminum alloys including 6061, 5052, and 7075 are used as interlayers to increase the shear strength. The results show the shear strength rises first and then declines as the interlayer strength increases when the cumulative reduction rate is 40 %. The main reason for this phenomenon is the rupture of the hard brittle layers of components decreases when the interlayer strength exceeds a specific value in the CCR. This situation hinders the outflow and bonding of fresh metal, and reduces the bonding quality of steel/aluminum interface, which inhibits the high-strength interlayer from enhancing the shear strength.

Impact of ground motion duration on seismic performance of buckling restrained braced frames

Buckling restrained braced frames (BRBFs) are commonly employed as seismic lateral force resisting system due to their high stiffness and energy dissipation capacity. However, under long-duration strong earthquakes, buckling-constrained braces are susceptible to fracture due to low-cycle fatigue. Previous studies evaluating their seismic performance have not considered the impact of earthquake duration on the results. This study evaluates the impact of ground motion duration on the seismic performance of BRBFs. By employing 44 pairs of spectrally equivalent ground motions with varying durations, the impact of ground motion duration is studied independently from other effects arising from ground motion amplitude and acceleration spectral shape. Nonlinear numerical models considering low-cycle fracture of buckling restrained braces are developed for 4-, 8-, and 12-story archetypes. The effects of ground motion duration on the seismic performance of BRBFs are examined using standard performance and collapse-assessment procedures. The results indicate that under seismic excitations not exceeding the maximum considered earthquake level, ground motion duration does not significantly affect the structural maximum interstory drift, but longer duration generally results in larger cumulative plastic deformation for the buckling restrained brace. Meanwhile, ground motion duration has a significant impact on the results of collapse risk evaluation. In addition, using combined duration- and spectrum-related intensity measure can better evaluate the damage potential of ground motion.

Experimental study on seismic performance of low-yield point steel plate shear walls

This paper studies the seismic performance of the low-yield point steel plate shear wall (LSPSW) by conducting cyclic loading tests on three single-story single-span steel plate shear wall (SPSW) specimens, including a non-stiffened LSPSW (LYP) and a non-stiffened normal strength SPSW (NW). A new LSPSW with steel tube stiffeners (HSS) is then proposed to restrain the out-of-plane deformation of the infill panel. The failure modes, strain development, bearing capacity, stiffness, ductility, energy dissipation capacity, degradation characteristics, and deformation performance of the above three SPSWs are compared and analyzed. Afterwards, the corresponding numerical modeling approaches are developed and verified by the test results. Furthermore, supplementary analyses of the plate-frame interaction in terms of the shear distribution, energy dissipation behavior, and plastic damage performance are performed, and relevant suggestions are provided for the design of SPSW. The experimental and numerical results show that compared with the NW specimen, the use of low-yield point steel in the LYP specimen significantly improves the ductility and energy dissipation capacity of the SPSW, delays the tearing of the infill panels, reduces the residual deformation of the infill panels with higher ability of recovery, and achieves a more uniform distribution of cumulative plastic deformation. The application of steel tube stiffeners in the HSS specimen further enhances the energy dissipation capacity of LSPSW, effectively restrains the out-of-plane deformation of the infill panels, and reduces the impact of the tension strips on the edge columns. The analyses of the plate-frame interaction show that the boundary frame has more contribution to the shear resistance and energy dissipation after using the low-yield point steels for the infill panel. The proportion of shear force borne by the boundary frame is up to 65%–70%, which should be considered in the design procedure to optimize the geometrical dimensions of the infill panel and the boundary frame, allowing to optimize the structural performance and material utilization.

Full-scale cyclic testing of an innovative energy dissipating device for seismic resiliency

Metallic dissipaters, which dissipate seismic energy by plastic deformation of the metal, have been most widely used in building construction to achieve seismic resilience. In this research, an innovative metallic dissipater called multiple U-shaped flexural plates (UFP) dissipater (MUD), was discussed. MUD can be used as a bracing member in eccentrically or concentrically braced frames. It has three main components: internal core member (usually steel universal column), external casing member (usually steel hollow section) and UFPs. UFPs are bolted between the internal and the external members in pairs. The internal (movable) and external (fixed) members can move relative to each other by rolling motion of the UFPs under axial compression and tension. This paper presents the experimental findings of four quasi-static cyclic tests of the MUD with varied displacement amplitudes and loading rates. Deformation behavior, hysteretic response, equivalent viscous damping ratio, energy dissipation capacity and other structural performance are investigated. The experimental results show that the MUD is able to achieve stable and repeatable hysteresis performance. All specimens can meet the cumulative inelastic deformation criteria in ANSI/AISC 341-16. The last specimen was tested until the capacity decreased by 30% to study the failure behaviour. The results show that the MUD has a promising ability to maintain strength after initiation of fracture and to prevent sudden failure of the structure.

Seismic Mitigation Effect of Overlying Weakening Strata in Underground Coal Mines

Artificial construction of a weakening zone over the roadway is an essential method for preventing coal bursts and rock bursts caused by strong mining tremors. However, concerning the seismic absorption and load reduction capabilities of an artificial structural weakening zone, the degree of rock mass damage to the roadway under weakening zone protection remains unclear. This study employed principles of elasticity and UDEC (Universal Distinct Element Code) to explore the seismic attenuation and load reduction capabilities of the weakening zone. The results indicate that the absorbing ability of the weakening zone increases exponentially with its weakening coefficient. Under the same dynamic load disturbance, when the weakening coefficient rises from 0.00 to 0.99, the sidewall displacement from the elastic wave source side changes from 0.400 m to 0.228 m. The total number of cracks in the roadway-surrounding rock, and the ranges of overstressed zones decreased linearly. The critical threshold of the roadway resisting the mining tremor disturbance increased. In particular, when the mining tremor is located directly above the roadway, the initial deformation of the roof is the largest, and the cumulative deformation of the rib is greater than the roof. By creating a weakening zone with a coefficient exceeding 0.95, the roadway remains unaffected by the 20 MPa dynamic loading. The study provides a theoretical basis for controlling coal burst that is triggered by mining tremors.

Post-Event Surface Deformation of the 2018 Baige Landslide Revealed by Ground-Based and Spaceborne Radar Observations

On 11 October and 3 November 2018, two large landslides occurred in Baige Village, Tibet, China, forcing the Jinsha River to be cut off and form a dammed lake, resulting in massive economic damages and deaths. This paper uses ground-based radar (GBR) and spaceborne interferometric synthetic aperture radar (InSAR) technologies to perform dynamic monitoring of the Baige landslide. Firstly, the GBR results suggest that the cumulative deformation from 4 to 10 December 2018 was 1.4 m, and the landslide still exhibits a risk of instability. Secondly, with the Sentinel-1A ascending and descending orbit images from December 2018 to February 2022, the InSAR-stacking technology assisted by the generic atmospheric correction online service (GACOS) and the multidimensional small baseline subset (MSBAS) method are utilized to obtain the annual deformation velocity and cumulative deformation in the satellite radar line of sight (LOS) direction of the landslide. Finally, according to the spatial–temporal deformation characteristics of feature points, combined with optical images, field investigation, and geological conditions, the development trend and inducing factors of the Baige landslide are comprehensively analyzed. It is shown that the Baige landslide is in constant motion at present, and the deformation is spreading from the slope to its right side. This research establishes a framework of combining emergency monitoring (i.e., GBR) with long-term monitoring (i.e., spaceborne InSAR). The framework is more conducive to obtaining the deformation and evolution of landslides, providing a greater possibility for studying the development trend and risk assessment of landslides, and assisting in reducing or even avoiding the losses caused by landslides.

Monitoring and analysis of surface deformation in alpine valley areas based on multidimensional InSAR technology

Joshimath has received much attention for its massive ground subsidence at the beginning of the year. Rapid urbanization and its unique geographical location may have been one of the factors contributing to the occurrence of this geological disaster. In high mountain valley areas, the complex occurrence mechanism and diverse disaster patterns of geological hazards highlight the inadequacy of manual monitoring. To address this problem, the inversion of deformation of the Joshimath surface in multiple directions can be achieved by multidimensional InSAR techniques. Therefore, in this paper, the multidimensional SBAS-InSAR technique was used to process the lift-track Sentinel-1 data from 2020 to 2023 to obtain the two-dimensional vertical and horizontal deformation rates and time series characteristics of the Joshimath ground surface. To discover the causes of deformation and its correlation with anthropogenic activities and natural disasters by analyzing the spatial and temporal evolution of surface deformation. The results show that the area with the largest cumulative deformation is located in the northeastern part of the town, with a maximum cumulative subsidence of 271.2 mm and a cumulative horizontal movement of 336.5 mm. The spatial distribution of surface deformation is based on the lower part of the hill and develops towards the upper part of the hill, showing a trend of expansion from the bottom to the top. The temporal evolution is divided into two phases: gentle to rapid, and it is tentatively concluded that the decisive factor that caused the significant change in the rate of surface deformation and the early onset of the geological subsidence hazard was triggered by the 4.7 magnitude earthquake that struck near the town on 11 September 2021.

Research on Deformation and Loose Zone Characteristics of Large Cross Section Tunnel in High Geo-Stress Soft Rock

In constructing high-geo-stress soft rock tunnels, the major deformation disaster of the surrounding rock has always been the main problem faced during construction. The research on the deformation and loose zone characteristics of large deformation tunnels has positive significance for the safe and rapid construction of tunnels. Therefore, based on the Yuntunpu large deformation tunnel, this article first analyzes the geological and deformation characteristics of the tunnel site area in response to the problem of high-geo-stress soft rock large deformation. Subsequently, on-site testing and analysis were conducted on the loose zone characteristics of four tunnel sections. Finally, based on the comprehensive analysis of tunnel deformation and loose zone characteristics, the causes of large deformation in the tunnel are analyzed. The results indicate that the large deformation characteristics of the Yuntunpu Tunnel are mainly manifested as a large initial deformation rate of the surrounding rock, a short self-stabilization time of the surrounding rock, a large cumulative deformation amount, and a long deformation duration. The Yuntunpu Tunnel is influenced by the grade and structure of the surrounding rock, with a loosening zone ranging from 12 to 14 m, and the wave velocity variation characteristics exhibited by different grades of surrounding rock vary greatly. Adopting collaborative active control of long and short anchor rods is recommended to limit the continued development of loose zones and the deformation of surrounding rocks. The large deformation of tunnels is mainly affected by high geo-stress, formation lithology, geological structure, engineering disturbance, and groundwater. Among them, high geo-stress and formation lithology are the decisive and important factors for the occurrence of major deformation disasters in the tunnel.

Monitoring and prediction of landslide-related deformation based on the GCN-LSTM algorithm and SAR imagery

A key component of disaster management and infrastructure organization is predicting cumulative deformations caused by landslides. One of the critical points in predicting deformation is to consider the spatio-temporal relationships and interdependencies between the features, such as geological, geomorphological, and geospatial factors (predisposing factors). Using algorithms that create temporal and spatial connections is suggested in this study to address this important point. This study proposes a modified graph convolutional network (GCN) that incorporates a long and short-term memory (LSTM) network (GCN-LSTM) and applies it to the Moio della Civitella landslides (southern Italy) for predicting cumulative deformation. In our proposed deep learning algorithms (DLAs), two types of data are considered, the first is geological, geomorphological, and geospatial information, and the second is cumulative deformations obtained by permanent scatterer interferometry (PSI), with the first investigated as features and the second as labels and goals. This approach is divided into two processing strategies where: (a) Firstly, extracting the spatial interdependency between paired data points using the GCN regression model applied to velocity obtained by PSI and data depicting controlling predisposing factors; (b) secondly, the application of the GCN-LSTM model to predict cumulative landslide deformation (labels of DLAs) based on the correlation distance obtained through the first strategy and determination of spatio-temporal dependency. A comparative assessment of model performance illustrates that GCN-LSTM is superior and outperforms four different DLAs, including recurrent neural networks (RNNs), gated recurrent units (GRU), LSTM, and GCN-GRU. The absolute error between the real and predicted deformation is applied for validation, and in 92% of the data points, this error is lower than 4 mm.

Cumulative deformation prediction and microstructure change of coarse-grained soil under cyclic loading

This research aims to reveal the macroscopic cumulative deformation development pattern and internal structural change characteristics of coarse-grained soils under moving vehicle loads. Dynamic triaxial tests are used to investigate the development of cumulative deformation of coarse-grained soils under various deviatoric stresses, moisture contents, and loading frequencies. Based on the results of indoor tests, a comprehensive prediction model for the cumulative deformation of coarse-grained soils was established. The cumulative deformation increases with the increasing deviatoric stress, moisture content, and loading frequency. As the deviatoric stress grows, the cumulative deformation rate increases correspondingly. The cumulative deformation prediction model for coarse-grained soils proposed in this study has high accuracy. Cyclic loading reduces the number of large pores, increases the number of smaller pores, and increases the proportion of micropores with increasing deviatoric stress and moisture content. The effect of loading frequency on the deformation of coarse-grained soils is relatively small but still not negligible. Cyclic dynamic loading can transform the long pores in coarse-grained soil subgrade filler into elliptical and circular pores. The increase in moisture content can increase the proportion of long pores in coarse-grained soil filler. This research can deliver a valuable reference for analyzing the cumulative deformation of coarse-grained soils subjected to cyclic loading.

Coupling the Relationship between Land Subsidence and Groundwater Level, Ground Fissures in Xi’an City Using Multi-Orbit and Multi-Temporal InSAR

The Xi’an region of China has been suffering from groundwater depletion, ground fissure hazards, and surface subsidence for a long time. Due to the complex tectonics and frequent human and natural activities, land deformation in the region is aggravated, posing a threat to infrastructure and human life. This study adopted the multi-orbit and multi-temporal InSAR technology to measure multi-dimensional displacements and time-series displacements in Xi’an City. Through the multi-dimensional deformation verification, it was found that the control of groundwater flow direction by ground fissures is the cause of horizontal deformation. On the contrary, the flow direction of groundwater from west to east was inferred using multi-dimensional deformation. Further analysis was performed by calculating the deformation gradient of the cumulative deformation to obtain differential land subsidence and angular distortions, and it was quantitatively determined that the threshold for the generation of ground fissures caused by differential subsidence is 1/500. Then, through the mutual verification of the time series data and the groundwater level, a positive correlation was obtained. However, due to the inconsistent geological conditions and soil layers at the monitoring positions of Well 2 and Well 3, the lag time was 64 days and 4 days, respectively. Finally, the relationship between the surface deformation and the groundwater in the sustained uplift areas was explored. The Well 1 groundwater-level data with a monitoring period of 22 years and the corresponding monitoring points’ time series data were modeled; it was concluded that, in the future, the groundwater level will continue to rise and surface deformation will mainly increase, without a slowing trend. Therefore, research on the impact of surface uplift on infrastructure should be strengthened. By quantifying the relationship between land subsidence, ground fissures, and the groundwater level in Xi’an, the results of this study provide a reference for groundwater monitoring and management.