Amount Of Subsidence Research Articles

Numerical study of the convergence of methods for determining bed coefficients under different geological conditions of the base

Despite the significant development of numerical modeling of the joint work of above-ground structures with the ground base, today the most popular in the community of design engineers is the calculation model of the slab on an elastic basis.This is primarily due to the simplicity of the implementation of such a model and the possibility of a comprehensive calculation of the base-foundation system. The key step in calculating the model of the slab on an elastic basis is to determine the coefficients of flexibility of the base. In this paper, with the help of software and computer system LIRA CAD 2016 conducted a study of methods for determining the stiffness coefficients of the bed under different variants of soil conditions. The study was implemented by numerical analysis of the characteristics of the stress-strain state (the amount of subsidence, reactive pressure and force) in a square in terms of evenly loaded foundation slab under different engineering and geological conditions of the construction site.Considered: 1) homogeneous in plan base, composed of a finite number of linearly deformed layers of constant thickness; 2) homogeneous in plan base, composed of layers of constant thickness, one of which is a loess subsidence; 3) inhomogeneous base, composed of alternating layers of cohesive and incoherent soils, one of which is not constant in thickness. The convergence of the absolute values of the controlled parameters obtained for the model with two stiffness coefficients (Pasternak model), which for multilayer soils are determined by the values of the modulus of deformation and Poisson's ratio averaged within the depth of compressible thick-ness and for the model with one variable in terms stiffness coefficient (Gorbunov-Posadov model). The results of the study show that the scope of the two-parameter Pasternak model (which is more correct than the one-parameter Gorbunov-Posadov model) is limited to a homogeneous single- or multilayer soil base, provided that the soil layers are of constant thickness. Instead, the Gorbunov-Posadov model allows to calculate inhomogeneous bases and soils with special properties (sieving). However, this model does not allow to take into account the spatial work of the soil and the mutual influence of load areas.

Percutaneous Fixation of Unstable Proximal Phalanx Fractures: A Biomechanical Study.

Unstable extra-articular proximal phalanx fractures are common injuries to the hand that are often treated by closed reduction and percutaneous pinning. Fracture-induced shortening of the proximal phalanx leads to an extensor lag at the proximal interphalangeal joint. We describe a biomechanical study in cadaver hands to compare the ability of each of three different pin configurations to resist shortening in unstable fractures. Seventeen fresh frozen hands were disarticulated at the proximal ends of the metacarpals. The second, third, and fourth proximal phalanges were tested. A 5-mm section of bone was resected from the mid-shaft of proximal phalanx to simulate an unstable fracture. Three techniques were employed and randomized for each finger: transmetacarpophalangeal joint pinning using 1 or 2 Kirschner wires (K-wires) and periarticular cross pinning using 2 K-wires. Compressive axial loads and energy at 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm of subsidence were examined. The forces and energy required to shorten the finger for each amount of subsidence were similar for all 3 pinning techniques and for all 3 finger types. Greater amounts of shortening were found to require larger forces. Closed reduction and percutaneous pinning using any of the presented techniques is an adequate method of treatment for unstable proximal phalanx fractures. All of the techniques were equivalent in their ability to resist axial loading, regardless of the complexity of technique, the number of pins used, or finger that was pinned.

Significance of Cervical Spine Computed Tomography Hounsfield Units to Predict Bone Mineral Density and the Subsidence After Anterior Cervical Discectomy and Fusion.

This study was a retrospective review. The purpose of this study was to investigate the correlation analysis between Hounsfield units (HU) and dual x-ray absorptiometry (DXA) based on the clinical results of patients who underwent anterior cervical discectomy and fusion (ACDF) surgery. There is no technique to directly measure bone mineral density (BMD) in the cervical spine. As computed tomography is a very popular preoperative planning modality, using the HU value from that analysis to predict osteoporosis is important for patient outcomes and applications in the clinical field. We reviewed the records for 235 patients who underwent 1-level (n=120) or 2-level (n=115) ACDF surgery. In the 1-level ACDF group, the HU was measured from C3 to C6 vertebra, while that for the 2-level ACDF group was measured from 3 surgical index vertebrae. The correlation patterns were analyzed with the corresponding DXA (T-score) for each patient. Subsidence of fusion segment was defined as change in distance between plate-tip and upper (lower) margin of the vertebra (index level) after 4 months of follow-up. In addition, to determine the relevant factors that influence fusion segment subsidence, other preoperative (C2 slope, C7 slope, C2-C7 angle, and C2-C7 sagittal vertical axis) and postoperative parameters (coronal angle and segmental angle change) were measured. The correlation coefficient between HU and DXA ranged from 0.57 to 0.71 in the 1-level ACDF group and from 0.59 to 0.66 in the 2-level ACDF group. The correlation between HU and DXA was statistically significant regardless of the degree of anterior osteophyte (r=-0.65 to 0.78). Total subsidence height was 3.8 mm after ACDF, and both HU and DXA were statistically correlated with total subsidence (r=0.26-0.28). In multivariate analysis, HU (middle vertebra) value was statistically associated with the degree of total subsidence. The high-subsidence group (≥4.5 mm) showed smaller HU values (284.1 vs. 316.0) and T-scores (-0.5 vs. 0.1) compared to the low-subsidence group (<4.5 mm). The discrepancy group, defined as cases with excess plate shift on 1 side, also showed smaller HU values (260.4 vs. 312.4) and higher degrees of total subsidence than the matched group. The correlation between HU in cervical computed tomography and lumbar DXA (T-score) was statistically significant in both 1-level and 2-level ACDF. The level of BMD (HU or DXA) is a very important factor for clinically determining the amount and regularity of subsidence after ACDF. Therefore, HU can be a good alternative assessment to accurately reflect as much of the BMD degree as DXA in the cervical spine.

What Are the Patient-reported Outcomes of Trapeziectomy and Tendon Suspension at Long-term Follow-up?

There are multiple options for the treatment of thumb carpometacarpal joint osteoarthritis (CMC1 OA), with evidence for pain relief and improved function. Although simple trapeziectomy has the lowest complication risk, tendon suspension of the first metacarpal and interposition is still the most commonly used surgical procedure in patients with CMC1 OA. Although there are several reports of good short-term results after trapeziectomy and tendon suspension-interposition arthroplasty, few studies have evaluated long-term outcomes. This study is one of the largest and longest follow-up evaluations of a cohort of patients with CMC1 OA who were treated with trapeziectomy and suspension-interposition arthroplasty, capturing 96% of the original cohort for evaluation. (1) After trapeziectomy and tendon suspension surgery, what are the long-term, patient-reported outcomes and clinical measurements (strength and ROM); and in unilateral procedures, how do these parameters compare with those of the contralateral hand that was not operated on? (2) What is the mean subsidence (unloaded trapezial space), and does pinch strength correlate with the amount of subsidence? From 1998 to 2005, 130 patients underwent trapeziectomy and abductor pollicis longus (APL) suspension-interposition arthroplasty for CMC1 OA at one orthopaedic department. During this period, 15 patients were treated with CMC1 arthrodesis and four were treated with implant arthroplasty, for a total of 149 patients. The surgeons used APL suspensionplasty for most patients, based on age and expected postoperative function; they also employed this procedure to avoid hardware or implant failure issues. The 100 living patients were asked to participate in this retrospective study, 96% (96) of whom were enrolled. The mean age at surgery was 58 ± 7 years. The patients completed a two-item thumb pain scale (modified from the SF-36 body pain scale), a hand pain VAS (average level of pain experienced over the week preceding measurement), and the 11-item QuickDASH. Patient-reported outcomes data were obtained from all 96 patients, and 83% (80) of patients underwent bilateral hand radiography and a physical examination at a mean follow-up of 17 ± 2.4 years. We calculated outcome data for each patient, and in 39 patients with unilateral surgery and intact contralateral CMC1 joint, we compared the operated side with the contralateral side. We compared our outcome data with that from the Swedish National Quality Registry for Hand Surgery (HAKIR), noting comparable outcomes for pain and QuickDASH scores. At long-term follow-up after trapeziectomy and APL suspension surgery, the mean thumb pain score was 19 ± 26, hand pain VAS score 23 ± 25, and QuickDASH score 26 ± 21. In the patients with unilateral surgery and intact contralateral CMC1 joint, the thumb pain score for the operated side was lower than the contralateral side, specifically 19 ± 25 compared with 29 ± 30 (mean difference -9.8 [95% CI -19.5 to -0.2]; p = 0.045); hand pain VAS score was 24 ± 23 versus 30 ± 25 (mean difference -6.1 [95% CI -15.2 to 3.1]; p = 0.19), and the QuickDASH score was 27 ± 19. Grip strength showed no differences between the operated and contralateral sides (mean 16.7 ± 7.3 kg versus 16.6 ± 6.9 kg, mean difference 0.1 [95% CI -1.6 to 1.8]; p = 0.90), while pinch was different (4.4 ± 1.4 versus 5.0 ± 1.5 kg, mean difference -0.6 [95% CI -0.9 to -0.3]; p = 0.001). The mean trapezial space was 4.4 ± 2.2 mm, and there was no association between the trapezial space and pinch strength (0.07 kg [95% CI -0.04 to 0.18] per mm of space; p = 0.17). The finding of comparable pain and function between operated and unoperated sides at long-term follow-up suggests that trapeziectomy and tendon suspension-interposition arthroplasty provides predictable outcomes, and surgeons can use these data to counsel patients that surgery can potentially return them to comparable use. However, as patients often have asymptomatic radiographic OA on the contralateral side, future studies are needed to examine the impact of asymptomatic disease on function. Level IV, therapeutic study.

Initial femoral stem position in cementless bipolar hemiarthroplasty for femoral neck fracture in elderly patients is associated with early implant subsidence: A radiographic analysis

BackgroundBipolar hemiarthroplasty is a well-established treatment for displaced femoral neck fracture in elderly patients. Implant subsidence is a potential complication with cementless femoral stems, and smaller canal fill ratio has been reported as a radiographic risk factor. We aimed to determine the risk factors for subsidence, particularly the initial implant position relative to the resected medial calcar of proximal femur. MethodsWe retrospectively reviewed all cementless bipolar hemiarthroplasties performed using a single proximally hydroxyapatite-coated femoral stem in patients with a minimum radiographic follow-up of 12 weeks between January 2017 and December 2018. The amount of subsidence (significant subsidence defined as ≥ 5 mm), canal fill ratio, and implant position relative to the point of resected medial calcar (position A: medial and superior to calcar; position B: lateral and superior to calcar; position C: lateral and inferior to calcar) were measured and analyzed. ResultsOne-hundred eighty patients were identified (mean age: 80.9 years). Significant subsidence was observed in 52 patients (28.9%). On multivariate analysis, older age, lower canal fill ratio, implant position B, C, and less medial overhang of stem were independent risk factors for early implant subsidence. The risk ratio of position B and C to position A was 5.13 (95% confidence interval, 2.23-11.80). ConclusionIn our analysis, older age and lower canal fill ratio were associated with increased risk of subsidence, whereas implant with position A and more medial overhang were less prone to subsidence with the tapered proximally hydroxyapatite-coated implant.

The Use of InSAR for Monitoring Deformation of Offshore Platforms

Fluid extraction or injection from reservoirs, which corresponds to subsidence or uplift, can cause offshore platform surface deformation. Extremely large deformation of offshore platforms often lead to production losses, threat to the structure integrity and loss of life. Therefore, preventing severe deformation incidents is important by monitoring surface deformation caused by oil and gas production activities. In this study, the A1 and B1 offshore platforms have been selected as research study areas to detect surface deformation caused by production activities. A total of 12 radar images from TerraSAR-X satellite were obtained from 24th August 2018 to 22nd August 2019 to derive surface deformation through the Stanford Method for Persistent Scatterers (StaMPS) method. The maximum amounts of subsidence observed on A1 and B1 platforms were -4 mm/yr and -6.3 mm/yr, respectively. This study provides an important insight the use of InSAR technology for the monitoring deformation of offshore platforms.

Shoreline Changes along Northern Ibaraki Coast after the Great East Japan Earthquake of 2011

In this study, we analyze the influence of the Great East Japan Earthquake, which occurred on 11 March 2011, on the shoreline of the northern Ibaraki Coast. After the earthquake, the area experienced subsidence of approximately 0.4 m. Shoreline changes at eight sandy beaches along the coast are estimated using various satellite images, including the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer), ALOS AVNIR-2 (Advanced Land Observing Satellite, Advanced Visible and Near-infrared Radiometer type 2), and Sentinel-2 (a multispectral sensor). Before the earthquake (for the period March 2001–January 2011), even though fluctuations in the shoreline position were observed, shorelines were quite stable, with the averaged change rates in the range of ±1.5 m/year. The shoreline suddenly retreated due to the earthquake by 20–40 m. Generally, the amount of retreat shows a strong correlation with the amount of land subsidence caused by the earthquake, and a moderate correlation with tsunami run-up height. The ground started to uplift gradually after the sudden subsidence, and shoreline positions advanced accordingly. The recovery speed of the beaches varied from +2.6 m/year to +6.6 m/year, depending on the beach conditions.

Investigation of Fahlian aquifer subsidence and its effect on groundwater loss

Land subsidence is one of the natural and geological hazards that can occur naturally or as a result of human activities such as long-term groundwater abstraction and traditional agriculture. In the last two decades, following climate change and successive droughts, as well as improper management of water resources, the uncontrolled abstraction of groundwater and the increase in population growth have caused land subsidence in Fars province, especially the Fahlian Basin in the northwest of the province. In general, the present study aimed to monitor and measure land subsidence using radar interferometry and also to analyze the relationship between groundwater level changes and land subsidence in the Fahlian Basin. DINSAR method was used to estimate the displacement of the ground surface and produce a map of the average displacement speed. The results of interferometric data show the continuous occurrence of subsidence in the agricultural lands of the region. The average rate of this deformation is about 4 cm per year, and in most parts, the amount of subsidence during the three consecutive years 2016, 2017, and 2018 is equal to 0.09, 0.11, and 0.12 cm, respectively. Also, the results of the study of groundwater level drop changes in 12 piezometric wells for the period 2009–2017 are −0.36 to −10. The overall correlation between groundwater level changes and subsidence levels was estimated at 75%, indicating the dependence of subsidence and groundwater decline in the region.

Fusion and subsidence rates of vertebral body sliding osteotomy: Comparison of 3 reconstructive techniques for multilevel cervical myelopathy

Vertebral body sliding osteotomy (VBSO) was previously reported as a technique to decompress spinal canal by translating the vertebral body anteriorly and is indicated for cervical myelopathy caused by spondylosis or ossification of the posterior longitudinal ligament. However, little is known about its fusion and subsidence rates. To compare the fusion and subsidence rates of VBSO, anterior cervical discectomy and fusion (ACDF), and anterior cervical corpectomy and fusion (ACCF). Retrospective cohort study PATIENT SAMPLE: One hundred sixty-eight patients who underwent VBSO, ACDF, or ACCF for the treatment of cervical myelopathy and were followed-up for more than 2 years were retrospectively reviewed. Fusion and subsidence rates, visual analog scale (VAS) scores for neck pain, neck disability index (NDI), and Japanese Orthopaedic Association (JOA) scores were assessed. Results of the VBSO, ACDF, and ACCF groups were compared using Student's t-test and chi-square test. The fusion rate at 1-year postoperatively and the final follow-up for VBSO was 92.9% (37/42). VBSO demonstrated a higher 1-year fusion rate than ACDF (77.9% [74/95], p=0.04) and ACCF (74.2% [23/31], p=0.04). However, the fusion rate at the final follow-up did not demonstrate significant difference. The mean amount of subsidence (ACDF group, 1.5±1.2 mm; VBSO group, 1.5±1.5 mm; p=1.00) and rate of significant subsidence of > 3 mm (ACDF group, 13.7% [13/95]; VBSO group, 14.3% [6/42]; p=1.00) were similar for ACDF and VBSO. Furthermore, the mean amount of subsidence in VBSO was significantly less than that in ACCF (1.5±1.5 mm vs 2.4±2.0 mm; p=0.04). Neck pain VAS, NDI, and JOA scores were not significantly different among the groups. VBSO demonstrated faster solid union than ACDF and ACCF, although the fusion rates at the final follow-up were similar. VBSO resulted in less subsidence than ACCF at the 1-year follow-up. VBSO could be applied safely when the shape and/or location of the pathologic foci and sagittal alignment favor its application without much concern for pseudarthrosis or subsidence.

Passivity Analysis of Track Walking Device on Soft Road Condition

With wheel-track vehicle as the research object, the passivity of track walking device on soft road conditions have been studied, establishing the track walking device dynamic model and finishing the dynamic simulation. By the theoretical calculation and dynamic silulation analysis: the method of average ground pressure to represent the vehicle’s passivity on soft road condition has limitations, the average maximum pressure P_mm(MMP) evaluation method is more effective and more accurate; with the same track grounding length, the more wheels of the track walking device, the smaller the vehicle’s subsidence on soft road conditions and the better its passing performance. When a track walking device was increased from one single load wheel to three load wheels, the amount of subsidence on soft road conditions decreased by about 35%.

Mid-term subsidence and periprosthetic radiolucency of the AMIStem: a 5-year EBRA-FCA analysis

BackgroundThere has been an evolution in cementless total hip arthroplasty (THA) with newer short stem designs aimed to preserve metaphyseal bone stock and facilitate implantation through minimally invasive approaches. While early subsidence has been correlated to aseptic loosening in conventional stems, there is a paucity of data regarding short stems. The current study aims to report on stem subsidence and mid-term clinical outcomes of a cementless, metaphyseal-anchored short femoral stem, specifically designed for the direct anterior approach (DAA).MethodsNinety-four consecutive patients (100 hips) with a minimum follow-up of 5 years following cementless THA were included in this single-center retrospective study. Subsidence was evaluated using the “Ein-Bild-Roentgen-Analyse” (EBRA). Periprosthetic radiolucency allocated to the zones of Charnley and Gruen was assessed. Additionally, demographic and implant-related factors potentially associated with increased subsidence and clinical outcomes were evaluated.ResultsAt the last follow-up, the average stem subsidence was 1.98 ± 1.20 mm, with 48% of the implants demonstrating subsidence of > 2 mm. Periprosthetic radiolucency of > 2 mm was found in 26% of the implants in zone 1 and in 9% in zone 7, respectively. Neither the amount of subsidence nor proximal periprosthetic radiolucency was associated with aseptic loosening or worse clinical outcomes.ConclusionsComparable to other proximally fixed short stem designs, the highest subsidence was observed within the first 3 months following implantation. No demographic or implant-related factors were found to have a statistically significant influence on stem subsidence. Periprosthetic radiolucency and subsidence of the AMISstem is not correlated with worse clinical outcomes at 5-year follow-up.

Multi-Modal Data Fusion for Land-Subsidence Image Improvement in PSInSAR Analysis

There are three popular methods to understand the land subsidence: leveling, Global Navigation Satellite System, and Interferometric Synthetic Aperture Radar (InSAR) analysis using SAR images. While both leveling and the Global Navigation Satellite System can measure the amount of land subsidence only at specific points, InSAR analysis can observe a wide area in short time intervals. In terms of accuracy, however, InSAR analysis is inferior to leveling; centimeter/millimeter order (InSAR/PSInSAR analysis) vs. millimeter order (leveling). Among all observation errors in InSAR analysis, a tropospheric delay error has a large adverse effect on the measurement. It is difficult to suppress this tropospheric delay error by conventional methods because they try to remove error at each pixel independently in an InSAR image. However, geometrically-neighboring regions/pixels should be naturally correlated. Our proposed method employs such a neighboring relationship in a convolutional neural network (CNN). Our CNN is designed to improve InSAR analysis by mutually incorporating the InSAR image and the tropospheric delay error, which are estimated by any conventional methods. Experimental results demonstrate that our proposed method can reduce the mean error compared with a conventional method: from 10.3mm to 6.80mm.

厦门市地面沉降影响分析与风险评价

PDF HTML阅读 XML下载 导出引用 引用提醒 厦门市地面沉降影响分析与风险评价 DOI: 10.5846/stxb202007031727 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（41571148）；中国科学院战略性先导科技专项（XDA23030103） Impact analysis and risk assessment of urban land subsidence in Xiamen City Author: Affiliation: Fund Project: the National Natural Science Foundation of China(41571148); the Strategic Priority Research Program (A) of the Chinese Academy of Sciences(XDA23030103) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:城市的地面沉降一直以来都是沿海城市密切关注的问题。在沿海城市对高层建筑群诱发的地面沉降进行深入研究具有重要意义。获取地面沉降监测点的高程信息，分析了厦门市地面沉降情况与空间差异性。重点探讨建设用地、建筑容积率与土地利用转化信息这3种因素对厦门市地面沉降的影响，并对厦门岛地面沉降风险进行评估，可为厦门岛的高层建筑三维空间布局与优化研究提供先验知识。结果表明：（1）在2001-2015年厦门市整体的高程存在下降的趋势且较为缓慢，同时厦门市的城市建设规模不断变大且建设面积增速不断增大，与厦门市的城市地面的沉降发展趋势相同。（2）厦门市的高层建筑密度需达到一定程度才对地面沉降有影响，厦门岛的建筑容积率与地面沉降没有存在显著的相关性。（3）在不同土地利用转化建设用地对地面沉降的影响中：原水域用地沉降最为明显，建成时间越长，总沉降量越大；原耕地用地转化成高层建筑之后沉降有明显发生，也随着建成时间的延长有逐渐增加沉降量的态势；原园地、林地用地沉降只在少部分地区发生且与建成时间无明显差别。（4）厦门岛可用于城市建设区域中的53.34%是地面沉降中风险等级以上的。此外，本研究给出防御防治城市地面沉降风险的有效建议与措施。本研究结果可为厦门市城市化进程中的地面沉降监测、规划设计与决策等提供重要的数据支撑，为城市可持续发展提供科学的依据；也可为国内外其他城市的地面沉降监测分析和可持续发展研究提供理论依据和借鉴意义。 Abstract:Urban land subsidence has always been a problem that coastal cities pay close attention to. It is of great significance to conduct in-depth research on land subsidence which was induced by high-rise buildings in the coastal cities. In this study, the elevation information of land subsidence monitoring sites were firstly obtained to analyze the spatial difference of land subsidence in Xiamen City. Secondly, the influence of construction land, floor area ratio and land use conversion information on land subsidence in Xiamen City was discussed emphatically. The land subsidence risks of Xiamen Island were evaluated, which can provide a priori knowledge for the research on three-dimensional layout and optimization of high-rise buildings in Xiamen Island. The results show that: (1) from 2001 to 2015, the overall elevation of Xiamen City presented a downward trend and was slow. Meanwhile, the urban construction scale continued to increase and the construction area increased in Xiamen City, which were the same as the development trend of urban land subsidence in Xiamen City. (2) The density of high-rise buildings needs to reach a certain degree to have an impact on the land subsidence in Xiamen City. There is no significant correlation between floor plot ratio and land subsidence in Xiamen Island. (3) Among the impacts of land subsidence due to different land transformed construction land, the original water area total land subsidence is the most obvious. The longer the completion time, the greater the amount of subsidence. After the original cultivated land conversion into high-rise buildings, the settlement obviously occurred. With the extension of the construction time, the settlement increases gradually. The settlement of the original garden and forest land only occurs in a small number of areas and there is no significant difference from the completion time. (4) Xiamen Island can be used in urban construction areas where 53.34% of it is above the risk level of land subsidence. In addition, the effective suggestions and measures are also given to prevent the risk of urban land subsidence in this study. The results of this study can provide important data support for land subsidence monitoring, planning, design and decision-making in the urbanization process of Xiamen City, and provide a scientific basis for the sustainable development of the cities. The results can also provide theoretical basis and reference significance for the land subsidence monitoring analysis and sustainable development research for other cities at home and abroad. 参考文献 相似文献 引证文献

Simulation of the influence of dynamic loading on the stress-strain state of the natural and geoengineering environment

The paper provides numerical simulation of the influence of dynamic loading on the stress-strain state of the natural and geoengineering technogenic environment taking into account the soil basis for forecasting its use as the basis of the structure. Paper demonstrates the impact of static and dynamic loading on the subsidence of the landfill. To take into account the liquid phase of the waste and the viscoplastic medium, Darcy's law is used as an equation of balance of forces. The body of the landfill is modeled by weak soil taking into account the creep, using the Soft Soil Creep model. The covering and underlying soil layers are described by the Coulomb – Mohr model. An effective method for calculating the sedimentation of natural and geoengineering environment on the example of a solid waste landfill, based on numerical modeling of the stress-strain state of the landfill and underlying soil using finite elements is developed. It is demonstrated that the largest subsidence is experienced by the landfill with sand, as the base soil, but in percentage terms the amount of subsidence with the maximum load relative to the initial subsidence without loading is the largest in clay (33.7%). The obtained results must be taken into account when using landfills as a basis for buildings, structures, routes, recreational areas, etc.

Geomorphology, Stratigraphy and Tectonics of the Mesopotamian Plain, Iraq: A Critical Review

The Mesopotamian Plain is part of the Mesopotamia which extends for vast area bigger than the plain. The plain is almost flat and vast lowland, which has clearly defined physiographic boundaries with the other surrounding physiographic provinces. The plain is a huge accumulation geomorphologic unit, where the fluvial, lacustrine, and the Aeolian landforms prevail; the fluvial units being the abundant among others. However, estuarine and marine forms also are developed, but restricted to the extreme southeastern reaches of the plain. The Mesopotamian Plain is covered totally by Quaternary sediments among which the fluvial origin is the most prevailing and more specifically the flood plain sediments. The flood plain sediments are the Holocene in age, whereas the Pleistocene sediments are restricted to alluvial fan sediments and river terraces. The flood plain sediments cover majority of the Mesopotamian Plain, whereas the alluvial sediments are restricted to the northern–eastern, western and southern peripheral parts only. Different geomorphological features indicate the Neotectonic activity in the plain, such as migrations of rivers due to growing of subsurface anticlines. The extreme southeastern part is covered by the tidal flat and sabkha sediments. Marshes and shallow depressions are also covered by the Holocene sediments which are contaminated by the Aeolian sediments. Mesopotamian Plain is a part of the Mesopotamian Foredeep which is a part of the Zagros Foreland Basin including the Zagros Fold-Thrust Belt. It is large continuously subsiding basin since the Upper Miocene (11.62 Ma). The plain shows no structural features on the surface, except the main fault escarpment representing the part of Abu Jir Active Fault Zone. However, the rolling topography, in the northern parts of the plain indicates subsurface anticlines that are still growing up, such as Balad, Samarra, Tikrit and Baiji anticlines indicating the Neotectonic activity. Moreover, many buried subsurface anticlines are present in different parts of the plain. All of them are growing anticlines and have caused continuous shift to Tigris and Euphrates rivers and their distributaries indicating the Neotectonic activities. The minimum and maximum subsidence amounts in the plain since the Upper Miocene are zero and –2500 m, respectively.

Incidence of Femoral Stem Subsidence Following Aseptic Hip Revision Using Tapered, Fluted Titanium Stems

Background and Hypothesis: Implant design in revision total hip arthroplasty (rTHA) has evolved such that tapered, fluted titanium (TFT) femoral stems have become the gold standard. However, there is a paucity of data on TFT stem subsidence rates following aseptic rTHA. Subsidence can lead to stem loosening, hip instability, leg length discrepancy, and gait impairment in which patients experience great physical challenges requiring undesirable repeat revision surgery. This study assessed the incidence of subsidence in aseptic rTHA performed with TFT stems. &#x0D; &#x0D; Design/Methods: 102 TFT femoral stems implanted between 2011 and 2020 at a single center were retrospectively reviewed. Stem subsidence was measured on digital radiographic images taken immediately after surgery, at 4-weeks and 1-year postoperatively, and at subsequent follow-up clinic visits. Patient characteristics and risk factors for subsidence, revision etiology, and surgical details (stem type, size, etc.) also were extracted from the electronic medical record. &#x0D; &#x0D; Results: 102 aseptic rTHAs were analyzed. 21.8% (22/101) of stems subsided between the immediate postoperative and 4 week follow-up period. 43.1% (22/51) of stems subsided between 4 weeks and 1 year postoperatively, and 39.3% (11/28) of stems subsided between 1 year and latest follow-up (&gt;12 months post-op). At all three time periods, the amount of subsidence was &lt;3 mm in a majority of cases (77% to 96%) which is considered to be an acceptable amount of stem subsidence or “settling.” Only seven TFT stems had subsided more than 3 mm. Two of these stems subsided 10 or more mm but had not required revision at latest follow-up of 4 and 8 years. &#x0D; &#x0D; Conclusion and Potential Impact: The incidence of significant TFT stem subsidence requiring repeat revision surgery was relatively low in this cohort. Further research is warranted to identify specific risk factors for subsidence of TFT femoral stems.

Evaluation of land subsidence in Kashmar-Bardaskan plain, NE Iran

The development of agriculture and industry and the increase of population in countries with arid to semi-arid climates have led to more harvesting of groundwater resources and as a result land subsidence in different parts of the worlds. Decades of groundwater overexploitation in the Kashmar-Bardaskan plain in the north-east of Iran has resulted substantial land subsidence in this plain. The plain is considered as an arid to semi-arid zone and facing a negative water balance. The average annual precipitation in the plain is around 191 mm and the evaporation rate is 3956 mm. According to the unit hydrograph of the plain, the annual decline of water level is 1.12 m. In this study, the velocity of subsidence has been determined using Interferometric SAR technique (In-SAR) and radar images of Envisat ASAR and Sentinel-1 for a time period from 2003 to 2017. The results of an InSAR time series analysis indicated that an area of 1200 km2 with different speeds of 5 to 26 cm/year in the satellite line of sight (LOS) is subsiding. The results showed that in addition to the decline of groundwater level, subsurface conditions such as sediments types (fine-grained layers) and their thickness also affect the occurrence and amount of land subsidence.

Research on the temporal-spatial evolution of ground pressure at short-distance coal seams

To study the temporal-spatial evolution of ground pressure at short-distance coal seams, this paper studied the displacement law of overlying strata and the temporal-spatial evolution of ground stress by analog simulation experiments. The results show when the upper coal seam is mined, overlying strata of the stope form three zones: the caved zone, the fractured zone and the bending subsidence zone. The caved zone which subsided in the largest quantity showed an irregular subsidence curve. The fractured zone where the maximum subsidence amounts are basically located in the middle of the goaf had approximately parabolic subsidence curves. The bending subsidence zone underwent the least subsidence as it was controlled by the key layer. In the coal mining process, stress concentrated in front of both the opening-off cut and the working face. When the working face advanced to 150 m, bearing stress of the opening-off cut and the working face was up to 20 MPa, with a stress concentration coefficient of 1.98. When the lower coal seam was mined, the immediate roof kept caving as the mining proceeded, with no obvious initial weighting or periodic weighting in the main roof. Only the roof stress within the mining area demonstrated greater fluctuations as the mining moved on. Pressures at the opening-off cut and the stopping line remained high in the whole process, so it is suggested to pay special attention to pressure detection during the first cut and make sure the roof is well supported for the mining of lower coal seam.

Deformation and Failure Characteristics and Control Technology of Roadway Surrounding Rock in Deep Coal Mines

With the increase in mining depth, the problem of the floor heave of a roadway is becoming increasingly prominent. Solving this problem for a deep high-stress roadway is the key to ensure safe supply and utilization of coal resources in China. This study investigates the floor heave of a horizontal transportation rock roadway at the depth of 960 m at the Xieyi Mine. A four-way loading simulation test frame similar to the Xieyi Mine was used to reproduce the high-stress environment of a deep roadway by loading different pressures on the roof, floor, and two sides of the roadway. The experimental results show that after the tunnel had been excavated, the surrounding rock failure could be divided into three stages: the initial deformation stage, fissure development stage, and mild deformation stage. The destruction time periods of these stages were 0–0.5 h, 0.5–2 h, and 2–6 h, and the destruction ranges were 0.4 m, 1 m, and 1.5 m, respectively. The amount of roof subsidence, the displacement of the two sides, and the floor heave influence each other, and the range of the bearing ring (5.6 m) of the floor is larger than that of the roof (3.4 m) after the surrounding rock has been damaged. The findings suggest that the floor should be supported first, before the two sides and the roof; then, the support of the key parts (roof and floor corners) should be strengthened. The roof, floor, and two sides are considered for controlling the deformation of the surrounding rock in a coupled trinity support mode. Because of the unfavorable conditions in the area, overexcavation backfill technology was used. The new support was successfully applied during the subsequent construction of the rock tunnel. Based on the long-term monitoring results of the surrounding rock deformation, the floor heave control yielded satisfactory results and maintained the long-term stability of the roadway. Therefore, this study can serve as a reference for preventing floor heave in similar high-stress roadways in the future.

238. Interbody spacers and instability: is there a difference in subsidence and range of motion between various cages for osteotomy techniques?

BACKGROUND CONTEXT Several types of spine osteotomy techniques have been described to maintain sagittal alignment, varying regarding degree of deformity correction and invasiveness. Intradiscal osteotomy (IDO) is an alternative osteotomy technique for correcting thoracolumbar deformity. Lordotic interbody spacers provide anterior column support and act as a fulcrum around which an osteotomy can be reduced. Partial removal of the posterior endplate during IDO may increase subsidence risk. PURPOSE The purpose of this cadaveric study was to compare the biomechanical stability of bilateral IDO with static and expandable oblique interbody spacers to that of standard Smith-Petersen osteotomy (SPO) with transforaminal lateral interbody fusion (TLIF) using a static, banana-shaped spacer, pre- and postsubsidence. STUDY DESIGN/SETTING Biomechanical cadaveric study PATIENT SAMPLE N/A OUTCOME MEASURES N/A METHODS Eighteen cadaveric functional spine units (FSU) were divided into three equal groups (n=6): SPO-TLIF, bilateral IDO and static cage (sIDO), or bilateral IDO and expandable cage (eIDO). Bilateral pedicle screws were placed proximally and distally for all specimens. Subsidence was created by cyclically loading between 400N and 1200N compression for 20000 cycles at 2Hz, and was defined as the amount of implant settling between the first 1200N cycle and last 1200N cycle. Range of motion (ROM) was captured for flexion/extension (FE), lateral bending (LB), and axial rotation (AR), pre- and postsubsidence. RESULTS ROM in FE, LB, and AR was similar for all three groups, with no significant differences in motion pre- or post-subsidence (p>.05). The eIDO group had the largest loss of stability following subsidence, with motion increasing by 111.9±50.7% in FE, 91.4±42.6% in LB, and 65.5±29.9% in AR. Motion following subsidence was significantly higher than pre-subsidence for eIDO for all three bending planes (p=.003). sIDO motion increased by 103.0±104.3% in FE, 70.3±71.4% in LB, and 73.9±72.8% in AR. SPO-TLIF motion increased by 42.0±33.9% in FE, 27.7±20.1% in LB, and 19.4±17.8% in AR. Motion following subsidence was significantly higher than pre-subsidence for SPO-TLIF for LB (p=.037). CONCLUSIONS In this cadaveric model of a single FSU, IDO with both static and expandable interbodies showed similar biomechanical stability to SPO-TLIF both pre- and postsubsidence. Motion in the eIDO group significantly increased following subsidence in all three bending modes, while sIDO did so in none, and SPO-TLIF did so in only LB. This may be due to larger amounts of subsidence in the eIDO group. Expandable spacers in the eIDO group may have been overexpanded, causing endplate damage upon reducing the osteotomy. Further studies are required to elucidate clinical significance. FDA DEVICE/DRUG STATUS RISE (Globus Medical Inc.) (Not approved for this indication), SUSTAIN (Globus Medical Inc.) (Not approved for this indication), SIGNATURE (Globus Medical Inc.) (Not approved for this indication)