Uneven Settlement Research Articles

Automatic detection of deteriorated inverted-T patching using 3D laser imaging system based on a true story indiana

Abstract Deteriorated Inverted-T patching can lead to uneven settlement, dip, or reflective transverse cracking on the asphalt overlay. This paper demonstrates a hybrid method to automatically detect deteriorated Inverted-T patching for an efficient maintenance schedule. First, hundreds of 2D/3D pavement images with deteriorated Inverted-T patching were manually identified and labelled from more than 400 miles of field data in Indiana. All data were collected through a high-speed 3D laser imaging system. Afterward, three deep learning architectures, including the Single Shot Detector network (SSD300), an advanced Region-based Convolutional Neural Network (Mask R-CNN), and a fast and precise convolutional network (U-Net), were applied to develop artificial intelligence models to identify deteriorated Inverted-T patching from 3D images. The results indicate that the Mask R-CNN model can achieve good detection accuracy only on the prepared testing images. Further, a hybrid deep learning model was developed to combine International Roughness Index (IRI) values and the corresponding 3D images to detect deteriorated Inverted-T patching. The hybrid method was promising and significantly improved the efficiency of locating deteriorated Inverted-T patching from network screening.

Case analysis of sudden cracking in buildings near a landfill pit in China

The causes of cracks in a six-storey building are studied. Based on analyses of crack morphology, settlement observation and geological survey, it is determined that the landfill pit and uneven settlement are the main cause of cracks. The 20 July Zhengzhou rainstorm in China caused a sharp rise in groundwater level, so that the uneven settlement of the office building near the landfill pit intensified, and then, wall cracking followed. The interaction between buildings and landfill pits under different water levels is studied by three-dimensional numerical simulation. As the water level rises, the horizontal displacement of soil in the landfill pit increases, and the lateral constraint of landfill soil to foundation soil decreases. The result is that the settlement of the column foundation near the landfill pits increases and the differential settlement intensifies. Based on the analysis results, the further development of differential settlement and cracks are evaluated and treatment suggestions are given.

Dynamic Response Mechanism of Silt Ground under Vibration Load

The frequent vibration loads during the operation of trains can cause vibration deformation of the tunnel structure and surrounding weak strata, thereby endangering the safe operation of trains. The purpose of this paper is to study the dynamic response of surrounding soil layers caused by train vibrations through the finite difference method with FLAC3D. Based on existing research, we studied the artificially deterministic exciting force function. Then, we simulated the tunnel working conditions of a train with a 3D model, and applied the artificially deterministic exciting force function to the tunnel model. To study the vibration caused by trains in silty soil, we divided the trains into two cases, one-way and two-way. We compared the displacement–time curves of one-way and two-way trains. When the horizontal distance between the monitoring point and the vibration source increases, the peak value of the displacement–time curve decreases. As the speed of the train increases, the peak value of the displacement–time curve increases. The vertical displacement of the ground under the dynamic load of the two-way train is greater than that of the one-way train. In the acceleration–time curve, there is a lag in the ground acceleration response. The faster the speed of the subway train, the greater the peak value of the acceleration–time curve. This study can provide a guide for the evaluation and prevention of ground vibration subsidence and uneven subsidence of strata in the silt area of the Yellow River Region.

Decision-making fusion of InSAR technology and offset tracking to study the deformation of large gradients in mining areas-Xuemiaotan mine as an example

The multi-level disturbance of underground and surface caused by coal mining activities intensifies the deterioration of the ecological environment in the mining area. Among them, the uneven settlement caused by coal mining is the most intuitive manifestation of surface environmental damage. The uneven settlement in the mining area has the characteristics of large settlement magnitude and severe deformation. Therefore, based on 15 Sentinel-1A image data, this paper uses three methods: SBAS InSAR, continuous D-InSAR and offset tracking technology to monitor the surface deformation of the mining area. The results show that the continuous D-InSAR technology SBAS-InSAR technology is applied to the small deformation in the edge area of the subsidence basin. The mining area with low gradient subsidence of SBAS-InSAR can obtain better performance than continuous D-InSAR technology. The offset tracking technique is used to monitor the large gradient deformation in the center of the subsidence basin. Therefore, this paper proposes to expand the quantitative analysis through the spatial coherence threshold and the accuracy and successful image elements of the interference fringe displacement. Combine the advantages of the three methods and overcome the shortcomings of each method, fuse the deformation information of the three methods, and obtain the deformation law of the whole surface subsidence. The results show that the mean absolute error (MAE1-1) of continuity D-InSAR is 0.92 m, the mean absolute error (MAE2-1) of SBAS-InSAR is 0.94 m, and the mean absolute error (MAE3-1) of Offset-tracking is 0.25 m. The results of this fusion method are in good agreement with the measured data, and the mean absolute error (MAE4-1) of vertical displacement is 7 cm. Therefore, the fusion method has advantages over individual methods and provides a new idea in monitoring the large gradient deformation of coal mining subsidence in mining areas.

Analysis of the Working Response Mechanism of Wrapped Face Reinforced Soil Retaining Wall under Strong Vibration

A series of shaking table tests were carried out to explore the dynamic characteristics and working mechanisms of wrapped-face reinforced soil-retaining walls under strong vibration. Under the 0.1–1.0 g horizontal peak ground acceleration (HPGA), the damping ratio of sand shows a downward trend as a whole, so the acceleration amplification coefficient decreases with the increase of HPGA. However, when HPGA reaches 1.0 g, the acceleration amplification coefficient increases; the range of acceleration amplification coefficient at the top of the wall is 1.69–1.36. When HPGA is 1.0 g, the maximum cumulative residual displacement of the panel is 2.96% H, and the maximum uneven settlement of the sand is 3.57% H, both of which have exceeded the limit of the specification. With the increase of HPGA, the ratio of the dynamic earth force increment to the total dynamic earth force gradually approaches 50%. Since the reinforcement effect of geogrid is not considered, the predicted value of traditional earth pressure theory is different from the measured value. According to the Washington State Department of Transportation displacement index, the deformation range of wrapped-face reinforced soil-retaining walls is divided into three stages: the quasi-elastic stage, the plastic stage, and the failure stage.

Bell-and-spigot joints mechanical properties study of PCCP under the uneven settlement of foundation: Simulation and full-scale test

Prestressed concrete cylinder pipe (PCCP) makes full use of the compressive and corrosion resistance of concrete and mortar, as well as the tensile and sealing properties of steel, and has good mechanical properties. But the bell-spigot joints are the weak points of the PCCP pipeline and are easy to be damaged. In this study, a fined 3-D FEM model of PCCP is established. Based on the calculation model of fluid–solid coupling, the stress responses of joints are analyzed when uneven settlement occurs in the foundation. The cases of the different interfaces between the two foundation soils are considered. Then, a full-scale test is carried out, and the FEM model is evaluated. The results show that visible crack will occur in the concrete when the vertical relative displacement is 83 mm, 76 mm, and 83 mm under case 1, case 2, and case 3, respectively. And the concrete damage of J3 occurs first at the root of the crown. Along the hoop direction, the damage extends from the crown to both sides, and along the axial direction, the damage extends from the root of the spigot to both sides. And there is a minimum difference of 0.11 % and a maximum difference of 26.59 % between the test and FEM results.

Research on the Application of MEMS Intelligent Sensor in Abnormal Monitoring of Metro Tunnel by Simplified Model Tests.

The current monitoring methods for tunnel structure deformation mainly focus on laser distance measurement, fiber Bragg grating, photogrammetry, electronic total station, hydrostatic leveling and so on. Compared with traditional monitoring methods, MEMS sensors have the advantages of small size, low cost, low energy consumption and high accuracy. In this paper, MEMS sensors are used for the continuous real-time intelligent monitoring of model tunnels, and the multi-point deployment of MEMS sensors is set up for the tunnel structure monitoring with the indicators of acceleration and inclination. The results demonstrated that β-sample interpolation of the angles of the MEMS measurement points, and then integration of the overall displacements can better reflect the form of uneven settlement of the tunnel. For tunnel models with uneven settlement as the main deformation, the angle interpolation method allows the MEMS sensor to measure the vertical displacement more accurately and to determine the load mode to a certain extent. However, for tunnel models with global settlement as the main deformation, the results vary considerably from reality, as only the uneven part of the settlement can be measured using the angular interpolation method.

Regulating the albedo and radiation absorption of engineering surfaces for cooling the embankments in high-altitude permafrost regions

Under the influences of global warming and strong solar radiation, the construction of the wide high-grade roads in high-altitude permafrost regions becomes more challenging. To reach the challenges and further improve the thermal-mechanical stabilities of the permafrost embankment, this study proposes a novel cooling embankment structure based on the heat-reflective coatings. The principle is to reduce and regulate the solar radiation absorption by the permafrost embankment surface, thus improving the temperature field of the embankment and preventing uneven settlement and other freeze-thaw damages of the embankment. First, a theoretical-empirical model is proposed to describe the transfer processes of incident radiations on the pavement and slope surfaces. Based on the model, we carry out a systematic study of the main factors influencing the solar radiation absorption of the embankment surfaces and their variation patterns. By analyzing the calculation results, we propose the regulating schemes of the heat-reflective coatings for the radiation absorption balance of the embankment surfaces. Meanwhile, the solar albedo properties of the heat-reflective coatings under different solar spectral are also studied. The results indicate that the heat-reflective coatings can significantly reduce the solar radiation absorbed by the embankment surfaces. It proves that the cooling embankment structure and albedo regulation schemes proposed in this paper are expected to be applied in practical engineering. Finally, we discuss the shortcomings of the current research and the next research plans.

Behavior of large shaft sinking headframe subjected to uneven foundation settlement

Deep mining is an inevitable trend in China and the world, for which the construction of deep and large vertical shafts is the primary task. A shaft sinking headframe is a basic structure for supporting various hoisting and sinking equipment during vertical shaft construction. The design of the shaft sinking headframe is challenging due to the significant differences in the geometry and working load compared to conventional steel structures. Recently, the effect of uneven foundation settlement on the shaft sinking headframe has been of great concern when sinking shafts by the freezing sinking method or in permafrost soil areas. In this study, finite element calculations were performed to investigate the mechanical behavior of the SA-3 shaft sinking headframe under uneven foundation settlement (0.001–0.006 L) and normal working-load conditions. The results indicate that the most unfavorable condition for the stress of members is the diagonal double foundation settlement, and in the view of the geometric offset, the most unfavorable condition is the same-side double foundation settlement. The corner members near the settled foundation were changed from a state of compression to tension. Uneven foundation settlement of less than 0.001 L is acceptable for the safety and service performance of the shaft sinking headframe. These criteria can be used for reference in engineering practice.

Performance Deterioration of Underground Culverts Considering the Effect of Dissolution and Its Impact on the Surrounding Soil

To address the problem of dissolution damage during the long-term service of concrete hydraulic buildings, the concrete dissolution damage degree D and contact dissolution loss model with time were proposed by combining the results of indoor concrete dissolution tests. A mathematical model of the evolution of concrete parameters with time was developed. In the context of an underground concrete culvert project, a numerical analysis model of concrete dissolution deterioration was established, according to which the effects of different damage locations on the stress and displacement of concrete culverts were analyzed. The results show that the settlement value of the surface and the soil pore pressure value increase more when the bottom of the culvert is damaged by dissolution, and the settlement of the surface from the bottom damage is about 1.07~1.16 times of that from the top damage. When the damage position deviates from the center line of the culvert, the maximum point of vertical displacement in the transverse settlement trough of the ground surface deviates from the centerline of the culvert by about 3~5 m in the horizontal direction. At the bottom of the culvert, the concrete permeability coefficient reaches 6.957 × 10−8 m/s~8.354 × 10−8 m/s in about 13~16 years after the occurrence of dissolution damage, and local leakage occurs, causing a significant increase in the pore pressure of the soil near the leakage location. The overall settlement and uneven settlement resulting from the dual action of dissolution deterioration of concrete and infiltration pressure can have a serious impact on the upper channel buildings.

Foundation Settlement Response of Existing High-Speed Railway Bridge Induced by Construction of Undercrossing Roads

The construction of undercrossing roads often has an adverse effect on the upper existing railway line, and can cause an uneven subsidence of the crossed section. In response to the influence of new road construction on the existing high-speed railway bridge, a highway passing under an existing high-speed railway bridge was taken as the research object. Based on the FLAC3D finite difference software, a computational model of new roads undercrossing a high-speed railway bridge was established to analyze the structural deformation response of a high-speed railway bridge. The results show that the excavation of foundation pits during new road construction causes an overall upward heaving of the soil layers between the pits, with a greater amount of heaving near the high-speed railway piers than that at other locations. Meanwhile, a degree of upward displacement of the high-speed railway bridge piers occurred. The filling of a road base structure generates an additional stress greater than the original consolidation pressure, inducing an overall subsidence of the soil layers between the pits. The final deformation during construction of new roads undercrossing the high-speed railway bridge shows that the displacement of adjacent piles is manifested as an overall settlement and as a horizontal displacement to the side of soil excavation.

Experimental Analysis on Mechanical Characteristics of Foundation Soil in Rift Valley Area of Kenya Nairobi-Malaba Railway

The Rift Valley section of Kenya Nairobi-Malaba Railway locates in the Great Rift Valley of East Africa, with complex engineering geological conditions and well-developed geological structures. During the rainy season from March to May 2018, four large-scale ground fissures were formed in the first-stage project of the Nairobi-Malaba Railway of the valley floor section, accompanied by uneven surface settlement and trenches, seriously endangering the safety of the railway and its nearby projects. Through field investigation, it is preliminarily considered that the main reason induced ground fissures and surface settlement is the underlying soil layer being eroded by groundwater. The gully is further formed by surface water erosion on a base of uneven surface subsidence. The geological exploration trench at DK77 ground fissure revealed that the overlying soil layer is respectively grayish-yellow silty clay, cyan-gray volcanic ash, and brownish-yellow silty clay from top to bottom, and the underlying bedrock is volcanic tuff with wide cracks. The fluid flows out or into the bedrock through the cracks developing channels for groundwater up-down flowage. Under the erosion of groundwater to the underlying soil, this study proved the possibility of the occurrence of uneven settlement. When exposed to the groundwater, the underlying soil will exhibit special physical and mechanical properties which are conducive to the occurrence of ground cracks and subsidence. The conventional geotechnical tests are conducted for the three types of overlying soil, and the results reveal the causes of ground fissures and surface settlement from the physical and mechanical properties of the overlying soil and provide a basis for the further qualitative analysis of the mechanism of ground fissures and surface settlement.

РОБОТА БУРОНАБИВНИХ ПАЛЬ З РОЗШИРЕНОЮ ПЯТОЮ В НАБУХАЮЧИХ ГРУНТАХ ЗА ЧИСЛОВИМ МЕТОДОМ ГРАНИЧНИХ ЕЛЕМЕНТІВ

The topic is devoted to the topical problem of foundation construction and soil mechanics - elastic-plastic modeling of joint work of the system "soil base - brown pile" in order to determine the bearing capacity of the foundation to ensure stability and low subsidence of the structure, thus avoiding its possible uneven subsidence or destruction. To do this, it is necessary to provide forecasting and numerical implementation of calculations of the pile foundation structure.
 From the standpoint of the mechanics of a dispersed elastic-plastic medium, the idea of the peculiarities of the behavior under the load of a brown pile with an extended heel in clay swellable soils is presented.
 The calculations take into account the main content of the theory of elastic-plastic processes - the dependence of the stress- deformed state on the load history.
 The main computational equation of the soil model is the integral equation received K. Brebbia [1].
 Depending on the properties of the soil and the applied stresses, the sediment of the building is carried out as a result of compaction or extrusion of the soil from under the foundation.
 In both cases, the phenomenon of subsidence is due to soil flow, so it is natural that to the forefront of solving static problems of foundation construction is a condition or equation that determines the boundary between solid and fluid state of the soil depending on stresses.
 The application of numerical MGE to the solution of the nonlinear problem of geomechanics is substantiated by theoretical calculations, supported and illustrated by data of numerical calculation

INFLUENCE OF UNEQUAL DEPOSITIONS OF SEVERAL ARCH FOUNDATIONS ON THE STRESSED AND DEFORMED CONDITION OF THE WHOLE BUILDING

The need to use large-span structures arises in the design of public and industrial buildings. Glued arches are most often used as load-bearing structures for such buildings. With relatively high strength and low bulk density, plywood construction is economically feasible to use in longspan structures. In addition, glued wood has specialproperties in the operation of structures that are built in seismic areas. Also, it should be noted that the service life of such buildings is much higher than that of traditional metal and reinforced concretestructures. One of the problems of large-span, especially frame, buildings is the uneven subsidence of the supports, which is associated with the heterogeneity of the geological composition of the base (soils) orthe presence of layers of weak soils. This is especially true of such a constructive form as the arch, the change in the stress-strain state of which leads to a radical redistribution of stresses.Given the fact that the soil environment is more heterogeneous, survey data insufficiently describe the actual geological composition of the base of the building site. The biggest problem in the design ofstructures is the presence of lenses of weak soils in the areas of the foundations for load-bearing structures, which were not detected during engineering and geological surveys. The presence of even insignificant layers of weak soils can cause uneven subsidence of supports and changes in the stress-strain state of all structures.As a result of this work, the behavior of a building that partially fell on a layer of weak soils was studied. This is realized by numerical study of the influence of uneven subsidence of several buildingfoundations on the stress-strain state of the wholeframe, which allows to analyze the actual stressstrain state of the building and increase the reliability of the structure as a whole.

Stability Control of Slopes in Open-Pit Mines and Resilience Methods for Disaster Prevention in Urban Areas: A Case Study of Fushun West Open Pit Mine

During the century-long mining process of the Fushun west open pit, slope slippage and deformation caused varying degrees of horizontal deformation, uneven settlement, and ground cracks on the surface of the urban areas, which caused a certain degree of damage to buildings and infrastructure and affected the livings of residents in the surrounding communities. In this study, a set of building reinforcement and community resilience enhancement methods that can resist slope deformation was proposed to improve the ability of urban areas to cope with slope geological hazards and emergency response. The main research contents included: Firstly, this paper systematically analyzed the deformation mechanism of the dip sloping and the inverse dip sloping section of the open pit mine, which was based on the field measured data and simulation calculation results. In other words, the horizontal deformation of the stratum in the dip sloping section was dominant, while the stratum in the inverse dip sloping section was prone to ground cracks and uneven settlement. In view of this, three surface deformation characteristic subdivisions of the surrounding urban area were proposed. In addition, a study on the damage characteristics of buildings with different types of foundations and structures under the influence of side slope deformation were carried out, and the anti-deformation reinforcement measures for load-bearing members mainly based on steel fiber concrete, carbon fiber materials and profile steel were proposed. Finally, a three-level disaster emergency setting system for urban areas around open pit mine was established, and the disaster prevention and resilience enhancement strategy for build and unbuilt the communities around the side slopes was constructed. The study aims to provide technical support to the overall resilience and response of the urban communities adjacent to open-pit mine slopes against consequent geological hazards and emergencies, thereby promoting sustainable urban development.

Shear Strength and Mesoscopic Characteristics of Basalt Fiber–Reinforced Loess after Dry–Wet Cycles

Frequent dry–wet cycles induced uneven settlement and slope failure of transportation infrastructures in the Loess Plateau of China. Fiber reinforcement provides a method for solving these problems. In this study, a digital image–based triaxial shear test system was adopted through which to study the dry–wet action on mechanical behavior and failure mode of basalt fiber–reinforced loess. The apparent cracks and mesostructure of fiber-reinforced loess after dry–wet cycles were observed by digital camera and X-ray computed tomography technique (CT). Results show that the shear strength of fiber-reinforced loess decreases after dry–wet cycles, whereas it shows inverted U-shaped variations with fiber content, with the optimal resistance to dry–wet action at 0.6%. Compared with unreinforced loess, the samples with fiber reinforcement show fewer cracks, implying the effectiveness of fibers in inhibiting initiation and propagation of apparent cracks. The failure mode changes from brittle shear failure to overall bulging after fiber addition. The CT scan results showed that the fibers inhibited the generation and propagation of microcracks, and the damage mainly occurred in the early stage of the dry–wet cycles.

INFLUENCE OF POSITION ERRORS ON THE STABILITY OF A LOADBEARING VERTICAL ROD OF GREAT FLEXIBILITY

Many building structures are considered as rod systems. Bearing elements of rod systems are under load and experience large stresses and deformations. When external loads increase, these stresses and strains also increase. There may come a point where some elements lack strength, stiffness or stability. Such cases may arise due to uneven settlement and roll of the structure in conjunction with errors in the manufacture and installation of structures, insufficient development of projects, etc. One of the main measures for the timely prevention of emergency situations is the properly organized monitoring of the stress-strain state of the elements. In this paper, we consider a model of stressed structure, which combines elements in the form of flexible deformable rods and elements acting on them, represented by force vectors. As an example, we consider a structure of two vertical rectilinear rods pointing along one plumb line and connected in a node. The lower rod is pinched in the base and is a load bearing element. The upper rod is an external load for the lower one and is represented by the equivalent force vector. In theory, the lines of action of forces lie on one vertical line, so there are no other forces and moments besides axial longitudinal forces; the forces are applied at one point with given coordinates. When constructing the rod system, each rod must be set to a given design position. There will be position errors of the elements during the installation phase of the structure. Position errors are generally represented by errors in the specified angles of inclination of the rods and errors in the position of the ends of the rods in the assembly. In a stressed structure, these errors are equivalent to the errors of the force vectors. A modified system of force vectors arises. In such a system, due to position errors, a horizontal force arises which has the main influence on the stability of the supporting flexible rod when the external load increases.

Stability analysis of varying height waste dump in open-pit mine under particle size gradation and reconstruction effect of waste materials

ABSTRACT This study determines the safety-stability factors of the waste dump benches at different heights and analyses the deformation law, stress variation, and crack propagation characteristics of typical slope models. The meso-mechanical parameters obtained by discrete element numerical simulation are modified through slope radar monitoring data. The results show that the critical height of the dumping benches of the studied open-pit mine is 60 ~ 70 m, and the amount of bench settlement is positively correlated with the height of the benches. After the critical height is exceeded, the bench forms a three-wedge failure due to uneven settlement.

Analysis of Settlement Induced by Shield Construction of the Metro Passing under Existing Buildings Based on the Finite Difference Method

A frequent problem when constructing metro tunnels is the uneven settlement of adjacent buildings, which results in huge economic losses. Due to shields causing the settlement of adjacent buildings, this study took the Nantong Metro Line 1 as the research object. The metro runs from the East Huancheng Road Station to the Nantong Intermediate People’s Court Station and passes under the old residential area of the Community Sendadi-Huayuan building. Based on the settlement monitoring data, this study analyzed the impact of tunnel shield construction on the foundation settlement of adjacent buildings. The computational analysis of the shield tunnel was performed by numerical simulation, taking into account the upper building load and the construction disturbance to the surrounding rock. Afterward, the study summarized the law behind the settlement. The results show that when the boring machine was tunneling through sandy soil and silt rich in water, its head was prone to twisting due to soil disturbance and the dissipation of pore water, causing instability in the excavation process and eventual ground settlement. In the sandy strata, the relationship between foundation settlement caused by shield construction and time can be approximated as an exponential function in a certain area. The vibrations from shield excavation caused the foundations to vibrate for a short period of time. Therefore, the average settlement of buildings directly above the underpass reached 7 mm/d. Likewise, the tunneling shield caused a 1.5 mm settlement before passing under the building. It caused a peak settlement of 4.0 and 5.1 mm during and after passing under the buildings, respectively. The width of the settlement troughs of approximately 7D formed after the tunnel was excavated. Shield excavation placed the soil at the top of the excavation face in a state of tensile stress, causing tensile and shear damage to the soil and forming a local plastic zone.

Numerical Analysis of Ground Settlement Patterns Resulting from Tunnel Excavation in Composite Strata

Cross-river twin tunnels are prone to deformation and uneven settlement of the surrounding soil due to the complexity of the strata crossed, which has a negative impact on the tunnel structure. A numerical calculation model was established using the COMSOL Multiphysics to study the effects of twin tunnel excavation in composite strata on the ground settlement and the ground settlement pattern. The results indicated that after the construction of the twin tunnels is completed, the ground settlement above the first tunnel is slightly larger than the ground settlement above the second tunnel. The further the spacing between the two tunnels before and after excavation, the smaller the amount of ground settlement and the impact on the surrounding soil. The ground settlement value increases with the increase in burial depth, and the ground settlement curve gradually changes from a W-shaped curve to a V-shaped curve. As the distance between the two tunnels increases, the maximum settlement value of the settlement curve gradually decreases, and the ground lateral settlement curve changes from V-shaped to W-shaped. The higher the water level on the riverbed side, the greater the settlement value of the ground.