Large Uplift Research Articles

Investigation on the installation and monotonic uplift performance of bucket foundation in clay

Bucket foundations are usually used as foundations to support offshore wind turbines or anchors to secure floating platforms. Though many researchers have concerned the performance of the bucket foundation in sand and clay, there still exists uncertainties associated with the installation and monotonic uplift of the bucket foundation in clay. First, the effect of chamfer on the bearing capacity of the skirt and the soil plug heave during installation is unclear. Second, the effect of overloading during installation on the mobilisation of the suction during monotonic uplift is lack of study. The present study conducts physical model tests and finite element analyses to simulate the installation and vertical uplift of the bucket foundation, aiming at quantitatively addressing the above uncertainties. Results from model tests and numerical simulations indicate the skirt with external chamfer increases the bearing capacity factor during installation, while significantly reduces the soil plug heave. The overloading during installation facilitates the fully mobilisation of the suction, ensuring the suction to maintain for a large uplift displacement.

Manifestations of Strong IMF‐By on the Equatorial Ionospheric Electrodynamics During 10 May 2024 Geomagnetic Storm

AbstractUnderstanding the effects of east‐west component of interplanetary magnetic field (IMF‐By) on the equatorial ionospheric electrodynamics is challenging due to the complex response caused by the simultaneous occurrence of multiple mechanisms during disturbed times. The extreme geomagnetic storm on 10 May 2024 caused by multiple‐ICME interactions accompanied with unprecedented IMF‐By magnitudes and its polarity, changed from west to east by 130 nT during northward IMF‐Bz turning. The ground ionosonde observations of h’F from near‐equatorial locations, along with the latitudinal profiles of plasma densities from Swarm satellites reveal the first observational evidence of the impact of strong IMF‐By near the dusk‐terminator (17–19.5 LT), causing strong dawn‐to‐dusk ionospheric electric fields during northward IMF‐Bz. This electric field produces large uplift of the ionospheric plasma near equator and subsequent super‐fountain effect near the dusk. The combined effect of increased IMF‐By amplitudes and viscous terms might have resulted into the enhanced coupling of solar wind with the magnetosphere.

Studying the Freezing Law of Reinforcement by Using the Artificial Ground Freezing Method in Shallow Buried Tunnels

In this paper, the freezing and strengthening project of the Sanya estuary tunnel is analyzed, which is facilitated by the use of the partial differential equation (PDE) module in COMSOL Multiphysics software. The solid–liquid ratio is utilized as the water–heat coupling term, and the solid mechanics module is introduced to achieve three-field coupling. Numerical simulations are conducted to study changes in the temperature field, moisture field, and vertical displacement due to freezing and expansion in the most unfavorable soil layer during the freezing process. The results indicate that a complete freezing curtain forms around the 30th day. The distribution of freezing pipes significantly influences the freezing effect. The strong freezing zone is characterized by a high cooling rate and rapid water content reduction with the opposite trends being observed in the weak freezing zone. Upon completion of the freezing process, a large uplift of the ground surface is observed with more pronounced vertical displacement changes in areas affected by temperature and phase changes. The maximum vertical displacement of the ground surface deviates from the center position. While the frozen soil curtain meets the design requirements for freezing, the effects of freezing and expansion should be taken into account. These findings could be instrumental in elaborating the most effective freezing and expansion control measures for areas with powdery clay-based layers in AGF-based projects.

Pemetaan Perubahan Permukaan Tanah di Kawasan Pulau Nias dengan Menggunakan Data Sentinel - 1A IW

The determination of changes in the land surface is an event caused by changes in the volume of the rock layer below. and geological processes such as tectonic and volcanic activity, removal of material from the subsurface such as mining and natural causes such as the occurrence of holes in limestone. The purpose of this study is to determine the magnitude of land surface changes that occur in the Nias Island area caused by earthquakes. The data used in the processing stage with the DinSAR method in 2022 recording, with specifications of dual polarization VV + VH, beam mode IW (interferometric wide) and flight direction ascending. Sentinel 1 data used in this study are 4 pairs of scans, where each pair of scans consists of one scans being the master and another scans being the slave. The master image is the SAR image before the earthquake, while the slave image is after the earthquake. The magnitude of land surface changes that occurred on Nias Island, based on the 2022 earthquake, the largest uplift was the earthquake on December 30, 2022, with a range of values (1.012042) mm with an area of 72,641,981 Hectares. The largest subsidence occurred in the earthquake on December 30, 2022, with a range of values ranging from (-1.373125) mm to (-1.235427) mm with an area of 61347,891 Hectares.

Experimental study on wind load characteristics of rooftop canopies of low and medium rise buildings

Rooftop canopy is popular in buildings, and it is prone to wind induced damage due to its light weight and slender configuration. However, investigation on the wind load on this kind of structure has not been conducted, leading to a wind resistant design without a firm basis. This study measures the wind pressure acting on the rooftop canopy considering 4 different underneath building heights, whose prototype vary from 6m to 24m. The mean, fluctuating, and extreme wind pressure coefficients are examined. The correlation coefficients between the pressures at different positions are also checked. Results show that the underneath building height has significant effect on the wind load coefficients of the canopy. The correlation between wind pressures on both the upper and lower surfaces decreases gradually with the increase of the building height. The most unfavorable height of building found in this study is 12m, with the largest uplift net pressure coefficient of the canopy close to −7.0. Comparison with the design values for claddings of free roof in ASCE 7–22 shows that the rooftop canopy can practically have much larger uplift (negative) net pressure in the edge region.

Influence of shaft diameter and soil rigidity on uplift capacity factor of circular plate anchor in uniform clay

ABSTRACT The helix plate of the helical anchor can provide large uplift resistance for offshore floating structures. Although numerous studies have been conducted to estimate the uplift capacity factor of circular plate anchors in uniform clay, few studies have considered the effects of soil rigidity and shaft diameter on the uplift capacity factor. This paper studied the effects of soil rigidity and shaft diameter on the uplift capacity factor of shafted circular plate anchors in uniform clay through large deformation finite element analysis. The numerical analysis results showed that the increase in soil rigidity increased the uplift capacity factors. The increase in the shaft diameter ratio decreased the projected bearing area on the top of the circular plate anchor and uplift capacity factors. For the convenience of design engineers, a design process based on a conservative solution was proposed to estimate the uplift capacity factor of circular plate anchors.

Petroleum System Analysis and Burial History of Middle Permian Source Rock in Turpan–Hami Basin, NW China

The pre-Jurassic in the north depression of the Tuha depression is the most favorable replacement strata to obtain new reserves in the Turpan–Hami Basin. (Pre-Jurassic, in this paper, refers to the Permian and Triassic.) The main source rocks are the Taodonggou Group, of which the burial history and hydrocarbon generation potential remain unconfirmed. The investigation of the burial and thermal history is vital for the basin analysis and hydrocarbon exploration. Therefore, in this paper, by using the acoustic time difference method, vitrinite reflectance method, stratigraphic trend method and PetroMod-1D software, the differential characteristics of denudation thickness, burial history and thermal evolution history of different tectonic units in different periods of Taibei Sag in the Turpan–Hami basin are studied, and their influence on the petroleum system is analyzed, and then the zones with exploration potential are optimized. The results show that the Taibei Sag has experienced multiple tectonic uplift events. The Late Indosinian movement has profound effects on the Taodonggou Group source rocks. The rather large uplift amplitude postpones the maturation of source rocks. In addition, the Turpan–Hami Basin is a typical cold basin. Therefore, the thermal maturity of the source rocks is relatively low, with respect to the relatively deep burial. The thermal histories of the different sub-sags in the study area are slightly differentiated from each other. The Taodonggou Group source rocks in the Taibei Sag generally became mature during the Mid–Late Jurassic epoch, except for those in the Central–Southern Shanbei sub-sag, represented by Well LT-1, which reached the mature stage during the Late Triassic epoch. The study area has well-developed reservoir rocks, and effective reservoir bodies are formed in the slope zone and near the Tainan Sag, due to the higher porosity and permeability of reservoir rocks. The statistics related to the faults and an analysis of the structural styles of oil reservoirs indicate that the structural slope and anticline of the Huobei, Lianbei and Shanbei sub-sags are favorable for increasing reserves and production of hydrocarbons.

Installation Disturbance of Helical Anchor in Dense Sand and the Effect on Uplift Capacity Based on Discrete Element Method

Helical anchors have been extensively employed as foundation systems for carrying tension loads due to their installation efficiency and large uplift capacity. However, the installation influences of helical anchors are still not well understood, especially for multi-helical anchors. The matrix discrete element method was used to model the process of helical anchor penetration and pull-out in dense sand to investigate the effects of the anchor geometry and advancement ratio (AR, the relative vertical movement per rotation) on soil disturbance, the particle flow mechanism, and the uplift capacity. For shallow helical anchors, the overall disturbance zone is the shape of an inverted cone after installation, while for deep helical anchors, it is funnel-shaped. The advancement ratio has significant effects on the soil particle movement and uplift capacity of helical anchors. The soil particle flow mechanism around helical plates has been identified for single-helix anchors at various advancement ratios, and for double-helix anchors, the influence of the top plate on particle movement during installation was investigated. The uplift capacities of both single- and double-helix anchors increase with the decrease in the AR (AR = 0.5~1), and the influence decreases with the anchor embedment ratio. The efficiency of double-helix anchors induced by installation is close to 1 at pitch-matched installation (AR = 1), indicating that the impact of the top plate during installation is minimal in this case.

Uplift and towers of states in warped throat

We investigate the connection between the distance conjecture and the uplift potential. For this purpose, we consider the concrete model, the warped deformed conifold embedded into Type IIB flux compactifications, with the uplift potential produced by overline{textrm{D}3} -branes at the tip of the throat. Whereas the various mass scales associated with towers of states can be found, it turns out that the lightest tower mass scale satisfies the scaling behavior with respect to the uplift potential, which is meaningful provided the number of overline{textrm{D}3} -branes is nonzero. This indicates that the effective theory becomes invalid in the vanishing limit of the uplift potential by the descent of an infinite tower of states from UV, as predicted in the distance conjecture. Since too large uplift potential is also problematic due to the runaway behavior of the moduli potential as well as the sizeable backreaction of overline{textrm{D}3} -branes, the uplift potential is bounded from both above and below. In the simple model like the KKLT or the large volume scenario in which non-perturbative effect is dominatd by the single term, this bound can be rewritten as the bound on the size of the superpotential.

“Whenever big changes come, big talks don't” – An examination of the police experience of recruitment and promotion positive action processes

Policing in England Wales is currently experiencing a large uplift in police recruitment. This has been due to the Government's target to uplift officers by 20,000. As a result, police forces are implementing large scale, sustained recruitment drives. These are accompanied by positive action schemes to address deficits in officer representation. Current statistics now indicate that representation in forces is rising slowly, as these initiatives are employed. There is little literature that examines the impact of positive action on existing police officers' perceptions, despite the initiative's relative proliferation. Procedural Justice theoretical literature is utilised to situate this in the research context.This study represents 17 theoretically informed, long form, phenomenological interviews conducted with serving officers in a uniform, response policing environment. The interviews were semi-structured, open ended and participant led, allowing the officers to present and explore their own thoughts and feelings about positive action, developed through their lived experience in an active police role. These interviews were conducted in an operational environment, from an insider-outsider perspective with total privacy. Officers openly discussed how they felt about the implementation of such policies and procedures.The findings indicate that a taboo exists with regards to the discussion of positive action processes in the police workplace. A juxtaposition also exists between the existence of positive action initiatives and the theme of meritocracy amongst the police officers. Officers strongly refuted the need for positive action to remedy issues with representation, but similarly criticised the current representation levels within forces. Theoretically this indicates an informational gap between police implementation of positive action interventions, and the perceived need for them to exist at all amongst rank and file. Implications for the study's findings are explored and possible remedies discussed.

DInSAR Data Reveal an Intriguing Contemporaneous Onset of Deep Deflation below Vesuvio and the Ongoing Campi Flegrei Uplift

Campi Flegrei and Vesuvio volcanoes are only about 25 km apart, located on opposite sides of the densely inhabited area of Naples (Italy). Since neighbouring volcanoes may influence each other’s activity, it is of great interest to identify signs of any mutual interaction between Campi Flegrei and Vesuvio, or at least note coincidences in their recent deformation dynamics. After a large uplift, Campi Flegrei was generally subsiding from 1985 to 2001, while it has been uplifting—probably driven by deep magma inflation—at an accelerating rate since then. Here, we analysed the ground displacement in the whole Vesuvian area and its surroundings around the early 2000s using 1993–2010 ERS/ENVISAT ascending- and descending-orbit line-of-sight displacements obtained through the Small BAseline Subset Differential Synthetic Aperture Radar Interferometry technique. Although ground deformation is slow—a few millimetres per year—Empirical Orthogonal Function analysis shows a sudden trend change around 2001. Pre-2001 velocity maps confirm previously published results: subsidence mainly occurred inside the caldera rim—probably because of the sliding and compaction of young incoherent materials—and in a few spots around 10 km from the summital crater; eastward displacement occurred in a lobe east of Vesuvio, and westward displacement occurred in a lobe west of Vesuvio, as in the case of the spreading of the volcanic edifice and/or extensional tectonics. We attribute the subsidence spots to the previous high local number of new buildings per year. Post-2002 velocity maps provide evidence of a very different scenario: general subsidence in the whole Vesuvian area, westward displacement in a lobe east of Vesuvio, and eastward displacement in a lobe west of Vesuvio. This last arrangement of the ground displacement field is made even clearer by subtracting the post-2002 velocity from the pre-2001 value. The results of our analyses are consistent with the deflation of a deep pressurised source. Additionally, Vesuvio’s deep seismicity decreased at the beginning of 2002. The coincidence between the transition from deflation to inflation at Campi Flegrei and the onset of deflation below Vesuvio may suggest the possible transfer of magma and/or magmatic fluids between the two plumbing systems.

Lithofacies and depositional regimes of the Kolosh Formation Successions in the Tigran region, North-eastern Iraq

The current study depends on lithofacies analysis of Kolosh Formation at Tigran region in north-eastern Iraq. Depending on the physical criteria as grain size, color, texture, and etc., the formation is divided to five lithofacies: pebbly sandstone, coarse sandstone, graded sandstone, mudstone and shale lithofacies. Several sedimentary cycles and depositional regimes were fixed in the studied section represent by high energy regime as pebbly sandstone and medium to low regime as mudstone and shale lithofacies. Based on the data of lithofacies which compared with hypothetical model of the common turbidity deposits, the formation was deposited in submarine fans environments. The secondary depositional environments of the study section are divided into channel and inner fan environments. The Kolosh Formation in northern Iraq was deposited in an active margin basin when the northeast Arabian Plate collided with the Eurasian plate at the final stages of Neo-Tethys closing, which has resulted in large uplifts and subsidence episodes due to eustatic rises and falls.

Numerical Analysis of Passive Piles under Surcharge Load in Extensively Deep Soft Soil

The three-dimensional finite difference method was used in this study to analyze the deformation and stresses of a passive pile under surcharge load in extensively deep soft soil. A three-dimensional numerical model was proposed and verified by a field test. The horizontal displacements of the pile agreed well with the field results. This study investigated the pile-foundation soil interaction, the load transfer mechanism, the excess pore water pressure (EPWP), and the horizontal resistance of the foundation soil. The results show that the soil in the corner of the loading area developed a large uplift deformation, while the center of the loading area developed a large settlement. The lateral displacement of the pile decreased sharply with the increase of the depth and increased with the surcharge load. The lateral displacement of the soil was negligible when the depth exceeded 30 m. The EPWP increased in a nonlinear way with the increase of the surcharge load and accumulated with the placement of the new lift. The distribution of the lateral earth pressure in the shallow soil layer was complex, and the negative value was observed under a high surcharge load due to the suction effect. The proportion coefficient of the horizontal resistance coefficient showed much smaller value in the situation of large lateral deformation and high surcharge load. The design code overestimated the horizontal resistance of the shallow foundation soil, which should be given attention for the design and analysis of the laterally loaded structures in extensively soft soil.

Experimental Investigation on Behavior of Single-Helix Anchor in Sand Subjected to Uplift Cyclic Loading

Helical anchors have been widely used in geotechnical engineering due to their large uplift resistance. However, the current knowledge of the cyclic performance of helical anchors is still insufficient. Consequently, a series of small-scale model tests are carried out in sand to investigate the influences of embedment ratio, sand compactness and the cyclic parameters on the monotonic, cyclic and post-cyclic performance of single-helix anchors. The tests results indicate that the single-helix anchors with optimal embedment ratio still exhibit a relatively high uplift capacity after suffering cyclic load. The cyclic frequency has the greatest influence on the accumulated displacement, and the influence of amplitude is relatively greater than that of the mean cyclic load. The anchors in dense sand exhibit better performance to resist pullout than those in medium–dense sand under the same cyclic parameter ratios. Moreover, the correlation of post-cyclic uplift capacity and displacement after cyclic loading as well as the possible influence of the upward displacement on the sand flow above the helix are discussed.

Numerical study on aeroelastic behavior of spoiler on low-rise building based on fluid-structure interaction method

Technical mitigation devices have been demonstrated to be efficient for decreasing the peak and mean wind pressures on the roof systems of low-rise buildings through disrupting vortex formation. Previous investigations have regarded mitigation devices as rigid bodies and neglected aeroelastic behavior. However, the relatively large uplift force induces small-stiffness mitigation devices vibration and introduces a considerable aeroelastic effect. These effects might result in an increase in negative wind pressure on the building roof and the aeroelastic instability problems of mitigation devices. Therefore, the current study conducted two-way fluid-structure interaction (FSI) numerical simulation for a low-rise flat-roof building with mitigation devices (metal and polymer spoilers) to investigate the influence of the aeroelastic effect of spoiler on the wind pressure on the building roof. The large eddy simulation (LES) method and the finite element analysis (FEA) model are used to solve the flow field and the structural responses of the spoiler, respectively. The computational model and method are verified by comparing the calculation results with previous experimental results and benchmark computational tests. The dynamic response of spoiler, the flow instabilities and the wind pressure on the building roof are analyzed. The influence mechanism of the spoiler vibration on the flow field over the building, the wind pressure on the building roof and the uplift force on the spoiler were revealed considering the influencing factors, including the vibrational amplitude of spoiler and the wind direction. The results show that the aeroelastic effect of spoiler increases the negative wind pressure on the roof, and the larger the vibrational amplitude of spoiler is, the more the negative wind pressure increases. The negative wind pressure on the eave also increases with increasing wind direction angle. The main reason for this phenomenon is that the spoiler vibration increases the degree of flow separation over the building roof.

Dynamic off-fault failure and tsunamigenesis at strike-slip restraining bends: Fully-coupled models of dynamic rupture, ocean acoustic waves, and tsunami in a shallow bay

Inelastic off-fault deformation can lead to large tsunamigenesis in different tectonic settings. Here a mechanism for tsunami generation by strike-slip earthquakes that involves dynamic off-fault failure at restraining bends is presented. Dynamic rupture on a vertical strike-slip fault is modeled with undrained inelastic off-fault response incorporated by the Drucker-Prager yield criterion. I show that in a local transpressive stress regime dynamic off-fault failure at restraining bends produces significantly larger and more localized surface uplift than is produced by purely elastic dislocation models, resulting in a positive flower and coseismic pop-up structure. The larger uplift is due to frictional sliding with a thrust component on conjugate microfractures, modeled by inelastic deformation. The short-wavelength inelastic uplift, largely controlled by bend size, is shown to generate localized tsunami efficiently in a shallow bay by fully coupling dynamic rupture, ocean acoustic waves, and tsunami. Fully-coupled models also indicate that supershear rupture on a vertical planar strike-slip fault does not generate large tsunami as the large kinetic energy of supershear rupture is carried away by ocean acoustic waves. Dynamic off-fault failure at fault complexities, such as restraining bends and compressional stepovers, may need be urgently incorporated in the current tsunami hazard assessments in strike-slip environments.

Hybrid cosmological attractors

We construct $\alpha$-attractor versions of hybrid inflation models. In these models, the potential of the inflaton field $\varphi$ is uplifted by the potential of the second field $\chi$. This uplifting ends due to a tachyonic instability with respect to the field $\chi$, which appears when $\varphi$ becomes smaller than some critical value $\varphi_{c}$. In the large $N$ limit, these models have the standard universal $\alpha$-attractor predictions. In particular, $n_{s }= 1- {2 \over N}$ for the exponential attractors. However, in some special cases the large $N$ limit is reached only beyond the horizon, for $N \gtrsim 60$. This may change predictions for the cosmological observations. For any fixed $N$, in the limit of large uplift $V_{\rm up}$, or in the limit of large $\varphi_{c}$, we find another attractor prediction, $ n_s = 1$. By changing the parameters $V_{\rm up}$ and $\varphi_{c}$ one can continuously interpolate between the two attractor predictions $n_{s }= 1- {2 \over N}$ and $n_{s} = 1$. This provides significant flexibility, which can be very welcome in view of the rapidly growing amount and precision of the cosmological data. Our main result is not specific to the hybrid inflation models. Rather, it is generic to any inflationary models where the inflaton potential, for some reasons, is uplifted, and inflation ends prematurely.

Evidence of Seasonal Uplift in the Argentière Glacier (Mont Blanc Area, France)

AbstractThe hydromechanical processes by which basal water controls sliding at the glacier bed are poorly known, despite glacier basal motion being responsible for a large part of ice flux in temperate alpine glaciers. Previous studies suggest that sliding strongly relates to the quantity of water being stored at the ice‐bedrock interface. However, this water storage is difficult to quantify accurately on the basis of surface‐motion observations, given that uplift can also be affected by changes in vertical‐strain rates and sliding velocity change. Here, we use a comprehensive data set of in situ measurements performed over 2 years on the Argentière Glacier in the French Alps to investigate the relationships between horizontal and vertical velocities, basal sliding, subglacial runoff and bed separation. We observe strikingly large uplifts varying spatially between 0.20 and 0.90 m over the winter/spring seasons between January and June and with a consistent spatial pattern from 1 year to another. We show, based on observations and three dimensional ice‐flow modeling, that these large uplifts cannot be explained solely by changes in strain rates or in sliding up an inclined bed. Our results reveal that more than 80% of the observed uplift is related to enhanced bed separation through cavitation, allowing us to estimate the volume occupied by water‐filled subglacial cavities. Our interpretation of uplift being mainly caused by increased cavitation is also consistent with an associated increase in the observed surface horizontal velocity. These findings provide important observational constraints for testing subglacial hydrological models.

Measurement of pile uplift forces due to soil heave in expansive clays

Piled foundations are widely used to limit the movement of foundations in expansive clays. These piles are subjected to large uplift forces as the clay swells (and downdrag forces when it shrinks). The appropriate method to estimate these forces is not well understood, and estimates from various methods presented in literature result in large variations. The uplift force generated in piles by soil heave was derived from strain measurements in full-scale field tests where a pile was installed in a highly expansive soil profile and flooded for several months. The results were compared to available theoretical estimates to comment on the most appropriate procedure to estimate the generated tension in the pile. The results showed that the use of an elastic solution related to the expected soil heave combined with a limiting shaft friction estimated from total stress capacity methods provided the most appropriate match to the measured results both in terms of the magnitude of the developed tension in the pile and shape of the tension profile along the depth of the pile.

Origin of coseismic anelastic deformation during the 2016 Mw 6.4 Meinong Earthquake, Taiwan

An unexpectedly large uplift of 91 mm was detected by geodetic observations during the rupture of 2016 Mw 6.4 Meinong earthquake, Taiwan, which has been attributed as either a triggered anelastic and hydrologic related deformation from a proposed duplex/mud diapir or a triggered aseismic slip on a proposed backthrust. Here, using both high-rate GNSS and free-field strong motion data, we first estimated the coseismic source model. The locations of high PGV were inferred to explain the unexpected distribution of damaged buildings approximately 25–30 km west of the epicenter. Then, the aseismic surface displacements during the earthquake was differentiated using the coseismic source model. The aseismic extension of 3.8 μstrain is inferred at the unexpectedly large uplift region. Combining with local geology, residual gravity anomaly, seismic tomography, interseismic leveling vertical velocities, coseismic leveling uplifts and proposed Coulomb stress changes, the accelerated mud diapirism during the earthquake triggered by slip on the deep seismogenic fault was identified as the cause of unexpectedly large coseismic uplift.