Uplift Phenomenon Research Articles

Failure analysis and comparative study on tunnels under strike-slip fault and oblique-slip fault movements

To deeply study and compare the failure characteristics of tunnels under strike-slip and oblique-slip active faults, with the engineering background of a railway tunnel in western China crossing both strike-slip and oblique-slip active faults, two sets of large-scale indoor model tests with a geometric similarity ratio of 1:35 were conducted. The fissure development patterns and strain trends of the tunnel under the movement of both types of faults were monitored and analyzed. Meanwhile, a three-dimensional model of tunnel-rock-fault interaction was established using ABAQUS finite element analysis software to determine the variation patterns of bending moments and shear forces of the tunnel under the movement of both types of faults. The results showed that under the movement of strike-slip and oblique-slip active faults, circumferential bending fissures appear at the right waist of the hanging wall and the left waist of the footwall of the tunnel, and shear oblique fissures appear at the vault of the fault fracture zone. Among them, the number of cracks, the range of tunnel cracking and the degree of crack damage under the condition of the oblique-slip fault are obviously more serious than those under the condition of the strike-slip fault. Under the dislocation of the oblique-slip fault, a large area of broken zone appears in the vault of the fault fracture zone, the lining falls off, the steel bar is exposed, and there is an obvious uplift phenomenon. The right waist of the tunnel’s hanging wall mainly experiences tension while the left waist experiences compression, whereas on the hanging wall, the right waist experiences compression while the left waist experiences tension. Under the fault movement, the maximum bending moment value mainly occurs at a distance of 10 m from the fault fracture zone on both the hanging wall and the footwall, with the bending moment values at the fault fracture zone nearly approaching zero. The maximum shear force value occurs at the fault fracture zone. Under the movement of both types of faults, the failure mode of the tunnel is mainly characterized by bending failure of the hanging wall and the footwall and shear failure at the fault fracture zone. Compared to strike-slip active faults, the development of fissures in tunnels under oblique-slip active faults is more severe, with larger bending moment and shear force values, and a wider range of tunnel failure. These results can provide theoretical and technical experience for future similar projects.

Research on construction monitoring of curvilinear continuous beam bridge jacking and horizontal moving construction

This article investigates the issue of beam misalignment in continuous curved beam bridges. Taking the D0–D6 spans of the Gongbin Road elevated bridge as a basis, real-time monitoring of the stress and displacement of the beams is carried out during the jacking and shifting construction process. At the same time, the reaction forces of each support are monitored. The jacking force of the hydraulic jacks is controlled to ensure the stability and safety of the beam during the construction process. Finally, the jacking and shifting monitoring data is organized and compared with theoretical values. It is found that the stress values generated during the jacking phase of the bridge are below the stress control standard. No uplift phenomenon occurs at the supports, and the jacking height is controlled within a reasonable range. The construction process does not cause damage to the beams, and it is safe and reliable. During the shifting construction, the whole bridge was displaced using the jacking method, and the three working conditions were monitored throughout the process. The stress increment at the 2# and 4# sections was relatively small, and the measured stress increments for the entire bridge were all below the stress control standard. The displacement of the bridge abutment during the jacking process was minimal, with no contact with the abutment blocks, and no significant elastic deformation occurred. The jacking displacement was successfully achieved.

Ảnh hưởng của điều kiện biên tới phản ứng địa chấn của cẩu hàng container

Container crane structure plays a crucial role in loading and unloading goods from a container ship to harbors. In any case, a breakdown of the container crane would harm the economy of a country. The modern crane is bigger to satisfy the demand of the owner; therefore, it is less stable under seismic excitation. Engineers often encounter an issue for choosing the boundary condition of the simulated model of the container crane as the legs can be uplifted or derailed under strong earthquakes. In this case, the simple work of pinned boundary condition can be replaced by the elastic-no-tension element between the structure and the ground. In this way, the leg base is free to move in vertical direction, and its vertical reaction reduces to zero. The objective of this paper is to evaluate the seismic performance of a container crane by the time history acceleration analysis using two different base supports, i.e., pin and elasticno-tension supports. Firstly, horizontal response spectra of actual earthquakes are adjusted by scaling the amplitude of each ground motion to coincides with a specific target spectral acceleration at the fundamental period of the container crane and then determined the scale factor. Afterwards, the ground motions are generated based on the scale factor, and they are used as input data for dynamic analysis by time history method. Two cases of target spectral accelerations will be determined to evaluate the dynamic responses of structure for uplift and no uplift phenomenon. Some response characteristics, i.e., total base shear and portal drift, are investigated. From that, the results show that the elastic-no-tensions supports are suitable for simulating the real behavior of the container crane when it is analyzed under high seismic excitation.

Deformation Analysis of a New Subway Transfer Channel Closely Undercrossing an Existing Station

Disturbances that occur due to the construction of new subway transfer channels in cities pose a significant threat to the safe operation and structural stability of existing subway stations. Due to the construction of the new Jin-Fu Station of Chengdu Rail Transit Line 27, the transfer channel of the new Jin-Fu Station closely underpasses the station of the existing Metro Line 6. First, based on the random medium theory, the curved integral boundaries of the rectangular section are improved and simplified by the numerical simulation. Second, the mechanical response of the underpass construction to the existing subway station is analyzed by Pasternak foundation model theory. Finally, the accuracy of the theoretical calculation is verified by the three-dimensional numerical calculation and the measured data, and the sensitivity of its parameters is analyzed. The results show that maintaining a certain net distance d (that is, increasing the thickness of the interlayer soil) is conducive to forming the soil arch effect and reducing the deformation of the existing station above. The settlement of the existing station can be reduced by increasing the height-to-width ratio of the excavated section, but the maximum bending moment of the floor will increase slightly. With the increase in the foundation reaction coefficient k, the interaction between the soil mass and the existing station is enhanced, and the deformation, bending moment, and shear force on the floor of the existing station increase significantly. When the foundation reaction coefficient increases to 10k, there is an obvious uplift phenomenon outside the settlement trough of the existing station floor.

Behavioral Investigations of Three Parallel Large Reinforced Concrete Circular Pipes with the Construction of Pipe Jacking

The pipe jacking method is gradually attracting increasing levels of attention and is becoming an important method for constructing underground engineering. However, jacking large-size concrete pipes in urban core areas subjected to complicated geological conditions is still a big problem preventing the employment of the pipe jacking method, and further studies related to pipe jacking are required. This paper presents a case study on the construction of three parallel large-size reinforced concrete circular pipes in the upper-soft and lower-hard composite formations, in which the construction work was implemented using the slurry balance pipe jacking method with the sequence of jacking the 1# and 3# pipes prior to the 2# pipe being implemented in field construction. This case study was implemented by employing numerical simulations with the aforementioned pipe jacking sequence, which focused on the stress and deformation variations of the reinforced concrete circular pipes, as well as the vertical settlement of the ground surface during the jacking processes, and considering the influences from the excavation pressure and grouting pressure of the drag-reducing thixotropic slurry. The simulation results revealed that a higher excavation pressure from the pipe jacking machine can easily induce an excessive pushing and squeezing effect of the excavated soil with the uplift phenomenon, while the increasing grouting pressure can be used to reduce the overall vertical settlement of the ground surface, whereas an excessive grouting pressure may have no effectiveness on protecting the reinforced concrete circular pipes. This work provides the numerical foundations for investigating the behavior of jacked parallel large-size reinforced concrete circular pipes.

Analysis of Landslide Displacement and Stress under the Condition of Overturning Failure of Fully Buried Anti-slide Piles

In this paper, on the basis of proving the basic consistency between numerical experiments and on-site physical experiments, a three-dimensional model of push pile FLAC3D was established. Based on relevant engineering analogies, parameters were selected to simulate and analyze the overturning failure mechanism of fully buried anti-slide piles. The research results indicate that the displacement of sand filling in front of the pile is significantly smaller than that of sand filling behind the pile. When approaching the failure load, a large area of uplift phenomenon appears at the top of the sliding body behind the pile; Most of the sand filling above the sliding surface showed a positive displacement along the x-axis, and the maximum displacement occurred at the top of the bulldozer. As the load increases, the sliding and upwelling area behind the pile tends to expand, and the vertical displacement at each point increases to a certain extent. At this time, the pile body is subjected to a "pull-out" effect from the surrounding sand.

High-precision monitoring method for airport deformation based on time-series InSAR technology

In order to solve the problems of low efficiency and discrete data that are associated with current airport area deformation monitoring and to realize the long-term and large-scale deformation monitoring of ground objects at airports, this paper proposes a method to monitor deformation in airport using time-series interferometry synthetic aperture radar (InSAR) technology. Based on analysis of the technical principles and data processing methods of persistent scatterer (PS)-InSAR and small baseline subset (SBAS)-InSAR, 89 SAR datasets from two airports located in different areas that cover a three-year period were collected in this study. Using the collected data, data denoising and precision assurance methods, such as data cropping, connection graph generation, geocoding, etc., were researched. The deformation rate map and cumulative deformation variable map were analyzed to study the deformation development laws of the airport area for the different years. The three-year maximum settlement rate of the airport area investigated in this study is less than 70 mm/year, with the deformation rate concentrated between −13.34 mm/year and 14.54 mm/year. The sinking phenomenon is more significant than the uplift phenomenon in the Xianyang Airport area, indicating that the airport’s foundation is relatively stable and concentrated. The settlement area is the junction of the southern cement runway and the D6 taxiway, and the settlement rate exceeds 30 mm/year.

Spatio-Temporal Evolution Law of Surface Subsidence Basin with Insufficient Exploitation of Deep Coal Resources in Aeolian Sand Area of Western China

Coal is one of the fundamental fossil energy supporting the world’s economy. The synergistic development between efficient coal mining and ecological environment protection is the inevitable requirement for the preservation of global harmony. As the world’s largest coal producer, China has conducted a strategic shift from east to west in terms of the exploitation of its energy resources, posing a serious threat to the fragile ecological environment of the western region. In particular, the surface subsidence caused by coal mining is the root of the ecological deteriotation and the destruction of ground structures. However, it is difficult to reveal the law of large-scale surface subsidence in western mining areas merely by conventional measurement methods such as leveling, on account of the high intensity of coal seam mining, the weakness of the lithology of overlying rock and the large thickness of wind-blown sand strata. In view of this, small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technology was used in this study to obtain the time series of surface vertical displacement during the whole mining process of the 2401 working face in the Yingpanhao coal mine, Inner Mongolia. Based on the deformation data, the dynamic evolution characteristics of surface subsidence under high intensity mining in the western mining area were analyzed exhaustively. It was found that the surface subsidence is characterized by an extensive coverage range (48.52 km2) with minimal ground settlement (250 mm) in the study area. Meanwhile, the boundary shape of the subsidence basin followed a “circular-parallelogram-trapezoid” changeable process and the coverage area of the basin experienced three stages: a linear increasing period, a temporary stagnation period, and a re-expansion period. Furthermore, there existed an abnormal uplift phenomenon on the east side of the open-off cut in the 2401 working face. Combined with the structure of overlying strata, this paper carried out a preliminary analysis on the reasons of the abovementioned phenomenon. The research results are of vital realistic significance for ground buildings and ecological environmental protection in the aeolian sand mining area in Western China.

Inflating Source Imaging and Stress/Strain Field Analysis at Campi Flegrei Caldera: The 2009–2013 Unrest Episode

In this study, we analyze the 2009–2013 uplift phenomenon at Campi Flegrei (CF) caldera in terms of temporal and spatial variations in the stress/strain field due to the effect of an inflating source. We start by performing a 3D stationary finite element (FE) modeling of X-band COSMO-SkyMed DInSAR and GPS mean velocities to retrieve the geometry and location of the deformation source. The modeling results suggest that the best-fit source is a three-axis oblate spheroid ~3 km deep, which is mostly elongated in the NE–SW direction. Furthermore, we verify the reliability of model results by calculating the total horizontal derivative (THD) of the modeled vertical velocity component; the findings emphasize that the THD maxima overlap with the projection of source boundaries at the surface. Then, we generate a 3D time-dependent FE model, comparing the spatial and temporal distribution of the shear stress and volumetric strain with the seismic swarms beneath the caldera. We found that low values of shear stress are observed corresponding with the shallow hydrothermal system where low-magnitude earthquakes occur, whereas high values of shear stress are found at depths of about 3 km, where high-magnitude earthquakes nucleate. Finally, the volumetric strain analysis highlights that the seismicity occurs mainly at the border between compression and dilatation modeled regions, and some seismic events occur within compression regions.

Numerical simulation of the effect of uplift on seismic behavior of uncontrolled surface steel tanks with Abaqus software

Cylindrical liquid storage tanks are widely used in various industries such as water storage, fuel and chemicals. Failure of fuel tanks, especially in refineries, can lead to terrible and uncontrollable fires, as well as destructive environmental effects. Ground cylindrical steel fluid storage tanks are widely used in different industries. Regarding the significance of these structures, ensuring the proper performance of such structures in earthquakes needs evaluating their seismic performance. The present study examines the seismic behavior of an unanchored fluid storage system via ABAQUS after validation using an experimental model. Next, the uplift of the bottom sheet is studied using the accelerogram records of the 1940 El Centro and 1994 Northridge earthquakes. The overturning moment time history of the fluid storage system and the maximum overturning moments were obtained to identify their behavior. The results indicated that not bracing storage tanks leads to the uplift phenomenon. Finally, the maximum axial stress of the storage tank shell was compared with the values recommended in the construction codes to control the buckling.

Land Subsidence Monitoring in Cepu Block Area Using PS-Insar Technique

Land subsidence can be caused by many factors, from natural through anthropogenic processes. Land subsidence due to anthropogenic factors results from such as fluid withdrawal, like oil and gas extraction. Cepu block is one of the oil and gas extraction areas that become Indonesia’s largest oil producer. This paper employs the Permanent Scatterers Interferometry Synthetic Aperture Radar (PS-InSAR) with C-Band Sentinel-1A imagery data to monitor the land subsidence phenomena. The PS-InSAR method is chosen because it can measure small movements in an area over time with millimeters DEM accuracy. The processing result showed deformation in the form of land subsidence in almost all of the blocks, except for Block D, with the mean velocity ranging from -27,75 to -9,78 mm/yr. An uplift phenomenon is also achieved in the eastern part of Block E. These PS-InSAR results are in the form of Line Of Sight (LOS). This paper correlates the land subsidence with geological maps to better understand the phenomena’ causes.

Plastic Deformation of Copper under the Action of High-Power Nanosecond UV Laser Pulse

Modification of a polished surface of oxygen-free copper under the action of single pulse of focused high-power UV radiation of an Nd:YAG laser has been studied. It is established, that at a subthreshold energy density (E ∼ 0.6 J/cm2) the metal surface in the irradiated region exhibited irreversible uplift in the absence of significant traces of material ablation. With an increase in the laser energy density, the ablation process develops that leads to leveling of the surface uplift phenomenon.

Numerical Investigation of the Seismic Behavior of Unanchored Steel Tanks with an emphasis on the Uplift Phenomenon

Ground steel storage tanks are widely used in different industries. Regarding the significance of these structures, ensuring the proper performance of such structures in earthquakes needs evaluating their seismic performance. The present study examines the seismic behavior of an unanchored fluid storage system via ABAQUS after validation using an experimental model. Next, the uplift of the bottom sheet is studied using the accelerogram records of the 1940 El Centro and 1994 Northridge earthquakes. The overturning moment time history of the fluid storage system and the maximum overturning moments were obtained to identify their behavior. The results indicated that not bracing storage tanks leads to the uplift phenomenon. Finally, the maximum axial stress of the storage tank shell was compared with the values recommended in the design codes to control the buckling.

The effects of foundation uplift on seismic response of diagonally braced steel frames

The foundation of buildings commonly assumed to be fixed in practical seismic response analysis. However, in severe earthquake loadings, the uplift phenomenon would be occurred due to the lack of tensile strength in the subsoil. This research aims to investigate this nonlinear phenomenon to obtain the actual behavior of diagonally braced steel frames. For this purpose, four 4-, 8-, 12-, and 15-story X-braced frames are modeled in the software framework of OpenSees. Some key parameters such as the natural period of vibration, inter-story drift ratio, base-shear force, the axial force along with the plastic deformation of braces are examined in two cases consist of fully and partially restrained supports. In the latter case, gap link elements (no tension behavior) are employed to model the soil–structure interaction (SSI). Overall, the results showed that by occurring the uplift the first period and inter-story drifts of the structure are increased; while, the base-shear, axial force and plastic deformation of braces will be reduced.

Making post-glacial uplift visible: A model based high-resolution animation of shore displacement

Making post-glacial uplift visible: A model based high-resolution animation of shore displacement

Multiscale Analysis of DInSAR Measurements for Multi-Source Investigation at Uturuncu Volcano (Bolivia)

Uturuncu volcano (southwestern Bolivia) is localized within one of the largest updoming volcanic zones, the Altiplano Puna Volcanic Complex (APVC). In several geodetic studies the observed uplift phenomenon is analyzed and modeled by considering a deep source, related to the Altiplano Puna Magma Body (APMB). In this framework, we perform a multiscale analysis on the 2003–2010 ENVISAT satellite data to investigate the existence of a multi-source scenario for this region. The proposed analysis is based on Cross-correlation and Multiridge method, pointing out the spatial and temporal multiscale properties of the deformation field. In particular, we analyze the vertical component of ground deformation during two time interval: within the 2005–2008 time interval an inflating source at 18.7 km depth beneath the central zone of the APVC is retrieved; this result is in good agreement with those proposed by several authors for the APMB. Between August 2006 and February 2007, we identify a further inflating source at 4.5 km depth, beneath Uturuncu volcano; the existence of this latter, located just below the 2009–2010 seismic swarm, is supported by petrological, geochemical, and geophysical evidence, indicating as a possible interpretative scenario the action of shallow, temporarily trapped fluids.

대지진에 의한 지하구조물 부상과 지질학적 특성의 상관성 연구

2004년 일본의 니가타켄 츄에츠 지방의 나가오카, 오지야시에서 1,450개 이상의 지하구조물이 1.5m까지 부상하였다. 융기손상은 Lifeline 시스템의 일부인 하수 시스템의 흐름뿐만 아니라 교통흐름을 방해로 인해 심각한 문제를 야기 시킨다. 복구작업의 경우 손상된 하수 시스템의 오픈 컷 조사는 나가오카시 정부에 의해 수행되었다. 지진으로 인한 매설된 파이프 라인의 손상에 대한 중요한 데이터는 조사결과로부터 수집하였다. 본 연구는 지하 구조물의 부상량에 영향을 미치는 요인을 SPT 시추공 logs를 통해 손상된 지역의 위치와 파이프라인의 경사를 포함하는 데이터를 사용하여 조사하였다. 지하구조물의 부상과 영향을 받는 지역의 지질학적 특성 사이의 상관관계 분석을 통해 부상현상의 주요변수는 지하수의 깊이, 원지반에서의 점토층 두께, SPT N값인 것으로 밝혔다. During the 2004 Niigata-ken Chuetsu, Japan, earthquake, more than 1,450 underground structures, known as sewer manhole, were uplifted up to 1.5m in Nagaoka and Ojiya city. The uplift damage can be a serious matter because they not only hinder the flow of wastewater systems, as a part of lifeline systems, but also disturb traffic flows. For restoration works, an open-cut investigation of damaged wastewater system was conducted by the Nagaoka city government. The results from the investigation compiled valuable data sets for buried pipeline damage due to earthquakes. In the present study, the factors affecting the uplift amount of the underground structure is investigated by using the data sets which include locations of damaged sections and inclination of pipeline before and after the earthquake and the SPT borehole logs in the affected area. Correlation analysis between the underground structure uplift and the geological settings in the affected area revealed that ground water depth and original subsoil, including thickness of clay layer, SPT N-value and fill thickness are the key parameters for the uplift phenomenon.

A Method for Weakening Residual Errors in Multi - beam Swath Joins based on Terrain Spectrum Analysis

Some factors lead to spurious signals in the multi-beam sounding process, including complex changes of the sea, the vessel motion attitede, the unreasonable setting of equipment parameters and so on. Although these factors were filtered strictly and the system errors were compensated in the post processing, residual errors still exist in multi-beam swath joins. Such errors produce uplift and abnormal phenomena in the measured terrain between swaths. Therefore, a new method of terrain spectrum analysis was established to improve the efficiency of massive data processing and to accurately reflect the submarine topography. This method was based on the blend of extraction technology of short-wave signals and fitting model of long-wave signals, among which wavelet analysis was used to extract the terrain highfrequency signals (short-wave) and multi-surface function was applied to fit the long-wave signals. Then, the two types of signals were fused to reconstruct the actual seabed topography. Finally, the indexes of depth discrepancy were used to estimate the effect of residual errors. Experimental results show that the proposed method could effectively eliminate the uplift phenomenon of the seabed Digital Elevation Model (DEM), and correctly reflect the detailed topographical variation. This work could further improve the sounding accuracy and the efficiency of swath joins, and beneficial to the fusion of multi-beam digital signals and the image information of side scan sonar.

Investigating uplift in Lesina Marina (Southern Italy) with the aid of persistent scatterer SAR interferometry and in situ measurements

We apply persistent scatterer interferometry (PSI) techniques to synthetic aperture radar (SAR) data from ERS and ENVISAT satellites on the Lesina Marina area, a coastal tourist village in Apulia, Southern Italy, where the excavation of a canal exposed grey micro- and meso-crystalline gypsum which is now showing a high density of cavities and sinkholes due to gravitational collapse processes. We observe PS objects undergoing displacements, along the sensor line of sight, forming the same relatively smooth pattern in all the processed data stacks. Vertical displacement rates, derived through integration of ascending and descending geometries, reach about 4 mm/year on locations adjacent to the canal, gently decreasing towards the western end of the built-up area . High-precision leveling measurements, performed in 1999 and 2010, reveal a substantial agreement with the ENVISAT PSI data, taking into account a small bias due to the choice of the leveling reference point. The dataset, thus validated, suggests the presence of an uplift phenomenon going on steadily for the entire timespan covered by the SAR observations (1992–2009). These observations, supported by petrographic data and in situ investigations, seem only in part compatible with a residual diapirism, and hint instead to more complex processes, such as a combination of diapirism and the hydration of the residual anhydrite in the core of the gypsum mass. These results confirm the importance of the integration between in situ, geologic and geophysical, remotely sensed investigations, as the latter often represent an essential tool to infer whether a given phenomenon, which can be hypothesized by the former, is presently under development.

Land Uplift in CO<sub>2</sub> Geological Storage Projects

Technology of CO2 Geologic Storage (CGS) especially its possible developments is helpful for improvements in reducing greenhouse gases and alleviating the greenhouse effect, which are necessary at global scale due to rising demand for fossil energy. The theory of deformation due to liquid injection was learned. A test on laboratory scale which injects water into compacted sand covered by low permeability clay showed the land uplift phenomenon. Some further discussions of the land uplift with different injection quantity was studied.