Buried Cylinder Research Articles

Theoretical analysis on stress distribution characteristics around a shallow buried cylinder Karst cave containing filling in limestone strata

Theoretical analysis on stress distribution characteristics around a shallow buried cylinder Karst cave containing filling in limestone strata

Effects of precipitation change and nitrogen addition on soil net N mineralization in a saline-alkaline grassland of Northern Shanxi Province, China.

To explore the responses of soil net nitrogen (N) mineralization rate to precipitation varia-tion and nitrogen deposition in salinized grassland, we set precipitation manipulation and nitrogen addition experiments in the typical agro-pastoral ecotone saline-alkaline grassland of Northern Shanxi Province, China. The in situ soil net N mineralization rate was determined by top-cover buried PVC cylinder from May to September in 2019. The results showed that there were seasonal dynamics in soil net N mineralization rate. Soil net N mineralization rate was not affected by increase/decrease precipitation (±50%), nitrogen addition (10 g·m-2·a-1) or the combination of nitrogen addition and increase 50% precipitation treatments. The combination of nitrogen addition and 50% reduction of precipitation significantly improved soil net nitrification rate and net N mine-ralization rate by 10.8 and 8.6 times, respectively. Soil net nitrogen mineralization rate was positively related to soil water content, and negatively related to soil pH. The effects of nitrogen addition on soil nitrogen mineralization rate were dependent on precipitation conditions. Soil water content and pH were important factors regulating soil net nitrogen mineralization rate in the saline-alkaline grassland of Northern Shanxi Province. Therefore, to roundly assess the response model of soil N mine-ralization process to global change, it is necessary to consider the interaction of precipitation changes and nitrogen addition, and the soil physical and chemical properties of salinized grassland.

Scattering by Perfectly Conducting Cylindrical Targets Hidden Below a Multilayered Medium

An approach to solve the scattered field by perfectly conducting cylinders with circular cross-section, placed below a multilayered medium, under illumination by a line source, is presented. In principle, the interaction of the field scattered by the targets with the multilayer above leads to an infinite number of scattered fields, excited as multiple reflections in each layer by the interfaces. Nevertheless, the developed theoretical formulation is a very compact one, as only two scattered-field contributions are used in each layer, a down-propagating term, described as scattered-reflected field, and an up-propagating one relevant to the scattered-transmitted field. Suitable basis functions, i.e., cylindrical waves expressed through plane-wave spectra, are employed, which are defined through reflection and transmission coefficients of a multilayered medium. As shown in the numerical implementation, the method can be applied to the modeling of several radar problems of targets in complex environments. For example, the technique can be employed to model buried cylinders in geophysical scenarios, in Ground Penetrating Radar applications. The modeling of scattered field by hidden targets in Through-the-Wall radar surveys is another possible field of use. The multilayer may, indeed, model a stratified masonry, but also a room hiding a target in a buildings’ interior.

A comparison study using particle swarm optimization inversion algorithm for gravity anomaly interpretation due to a 2D vertical fault structure

A new approach to the inversion of gravity data utilizing the Particle Swarm Optimization (PSO) algorithm is used to model 2D vertical faults. The PSO algorithm is stochastic in nature; its development was motivated by the communal in-flight performance of birds looking for food. The birds are represented by particles (or models). Individual particles have a location and a velocity vector. The location vectors represent the parameter value. PSO is adjusted with random particles (models) and searches for targets by updating generations.Herein, the PSO algorithm is applied to three synthetic data sets (residual only with and without noise, residual plus regional, residual plus anomaly generated by a buried cylinder structure) and two field gravity data sets acquired across known faults in Egypt. Assessment of the synthetic data demonstrates that the PSO algorithm generates superior results if a first horizontal gradient (FHG) filter is applied first. The robustness of the PSO inversion algorithm is demonstrated for both synthetic and field gravity data.

Numerical simulation on offshore artificial island cofferdam of Hong Kong-Zhuhai-Macao Bridge

The deep-buried steel cylinder structure has the characteristics of both gravity structure and pile foundation structures. Based on the offshore artificial island of Hong Kong-Zhuhai-Macao Bridge (HZMB), the stability and deformation response of the deep-buried steel cylinder cofferdam was studied throughout the construction process. Stability calculation of the steel cylinder on deep soft foundation was carried out based on the theoretical formula recommended in the technical standards, and the measured values in situ were summarised. The results show that the steel cylinder displacement in 3D simulation model is consistent with the measured data, which is larger than that using theoretical formula. The stability safety derived from the theoretical formula is consistent with the 3D simulation results and measured data. The instability judgment of the buried steel cylinder and the selection criteria of the bottom bearing layer are also given in the paper.

Numerical simulation on offshore artificial island cofferdam of Hong Kong-Zhuhai-Macao Bridge

The deep-buried steel cylinder structure has the characteristics of both gravity structure and pile foundation structures. Based on the offshore artificial island of Hong Kong-Zhuhai-Macao Bridge (HZMB), the stability and deformation response of the deep-buried steel cylinder cofferdam was studied throughout the construction process. Stability calculation of the steel cylinder on deep soft foundation was carried out based on the theoretical formula recommended in the technical standards, and the measured values in situ were summarised. The results show that the steel cylinder displacement in 3D simulation model is consistent with the measured data, which is larger than that using theoretical formula. The stability safety derived from the theoretical formula is consistent with the 3D simulation results and measured data. The instability judgment of the buried steel cylinder and the selection criteria of the bottom bearing layer are also given in the paper.

Scattering from a Buried PEMC Cylinder due to a Line Source Excitation above a Planar Interface Between Two Isorefractive Half Spaces

A solution to the problem of scattering from a perfect electromagnetic conducting (PEMC) circular cylinder buried inside a half-space and excited by an infinite electric line source is provided. The line source is parallel to the cylinder axis, and is located in the other half-space. The two half spaces are isorefractive to each other. The source fields when incident at the planar interface separating the two half spaces, generate fields that are transmitted into the half-space where the cylinder is. These fields then become the known basic incident fields for the buried PEMC cylinder. Scattering of these incidents fields by the cylinder will consequently generate fields at the interface that get reflected back into the same half-space and transmitted frontward into the source half-space, all of which are unknown. Imposing appropriate boundary conditions at the surface of the buried cylinder and at a specified point on the interface, enables the evaluation of these unknown fields. The refection coefficient at the specified point is then computed for cylinders of different sizes, to demonstrate how it varies with the PEMC admittance of the buried cylinder, the intrinsic impedance ratio of the two isorefractive half-spaces, and the burial depth of the cylinder.

Full-wave analysis of the scattering of a pulsed light beam by dielectric cylinders embedded in a homogeneous medium

An approach to study the time-domain scattering by a set of dielectric cylinders with circular cross section, placed in a semi-infinite medium, is presented. The illuminating light comes from a pulsed beam impinging onto the cylinders from outside the medium. The solution is developed in a semi-analytical way, starting from results based on the cylindrical wave approach pertinent to the case of illumination by a monochromatic plane wave. The method is numerically implemented to simulate the scattering response of buried cylinders illuminated by a pulsed Gaussian beam. In the presented results, the different contributions to the total scattered field are recognizable, giving an account of all the interactions between incident field, target and interface. The model adopted is well suited to the study, at optical frequencies, of scattering problems involving biological samples, such as vessels and fibers, embedded in tissues or immersed in fluids, through fast and accurate electromagnetic simulation.

Scattering from a Buried PEMC Cylinder Illuminated by a Normally Incident Plane Wave Propagating in Free Space

A rigorous solution is presented to the problem of scattering by a perfect electromagnetic conducting (PEMC) circular cylinder buried inside a dielectric half-space that is excited by a normally incident transverse magnetic (TM) plane wave propagating in free space. The plane wave incident on the planar interface separating the two media creates fields transmitting into the dielectric half- space becoming the known primary incident fields for the buried cylinder. When the fields scattered by the cylinder, in response to those fields incident on it, are incident at the interface, they generate fields reflected into the dielectric half-space and fields transmitted into free space. These fields, and the fields scattered by the cylinder are expressed in terms of appropriate cylindrical waves consisting of unknown expansion coefficients which are to be determined. Imposing boundary conditions at the surface of the cylinder and at a point on the planar interface, enables the evaluation of the unknown coefficients. This procedure is then replicated, by considering multiple reflections and transmissions at the planar interface, and multiple scattering by the cylinder, till a preset accuracy is obtained for the reflection coefficient at the particular point on the interface. The refection coefficient at this point is then computed for cylinders of different sizes, to show how it varies with the PEMC admittance of the cylinder, its burial depth, and the permittivity of the dielectric half-space.

A Perturbation Method for Scattering by a Dielectric Cylinder Buried in a Half-Space

A simple method is presented for transverse magnetic plane-wave scattering by a dielectric cylinder of arbitrary cross section buried in a half-space. The interface between two semi-infinite dissimilar half-spaces is considered as an infinite aperture, which is represented by a perturbed equivalent magnetic current. Coupled integral equations for the aperture electric field (or equivalent magnetic current) and the equivalent currents on the buried cylinder are obtained from surface equivalence principles and are solved numerically by the method of moments. Data for the electric field at the interface and far field are presented for cases of interest and are compared to the results available in the literature.

Investigating the reduction of cross-polarized Gaussian beam scattering from a PEMC buried cylinder coated with a topological insulator.

An investigation is presented for the reduction of cross-polarized Gaussian beam scattering from a perfect electromagnetic conducting (PEMC) cylinder coated with topological insulator (TI) material and buried in a semi-infinite medium. To calculate the successive reflections of the scattered field from the interface, cylindrical wave functions are written into the spectrum of plane waves. The scattered reflected field is calculated for each plane wave of the spectrum. Near- and far-zone scattered fields are reported for time-reversal symmetry and symmetry-broken TI coating. It is observed that the near-zone scattered field is very helpful to understand why the scattering width (SW) of a cylinder coated with time-reversal symmetry TI material is different from the SW of a cylinder coated with symmetry-broken TI material. The effect of spot size of the Gaussian beam on the scattering pattern is investigated, while the result for a plane wave is served as a reference. It is observed that cross-polarized scattering can be reduced by increasing the thickness of the coating layer. It also decreases as admittance of the PEMC core increases. Moreover, the cross-polarized scattered field becomes significantly small when time-reversal symmetry is broken, irrespective of PEMC or perfect electric conductor (PEC) core.

Estimating geometrical parameters of cylindrical targets detected by ground-penetrating radar using template matching algorithm

In the current research, the ground-penetrating radar (GPR) method has been employed to identify physical and geometrical parameters of buried cylindrical structures using the pattern recognition approach. To achieve this goal, the well-established mathematical relationships between geometrical parameters of cylindrical target (radius, burial depth, and horizontal location) and the associated GPR hyperbolic response characteristics are employed using the template matching method. In order to validate the applicability of the template matching method in providing estimates of such parameters, the method is first examined on GPR responses of synthetic models with known geometrical parameters followed by applying on real data using two different similarity criteria including 2-D spatial convolution and normalized cross correlation in the wave number domain. In the first step, the GPR responses of 71 synthetic models encompassing one, two, and three horizontal cylinders were produced using the improved 2-D finite difference in frequency domain. Then, appropriate preprocessing sequences to reduce random noise caused by forward modeling were applied on synthetic data. The proposed algorithm applied on several synthetic model responses could estimate the known geometrical parameters of the buried cylinders with acceptable accuracy (maximum error of 15%). The template matching algorithm was also used to extract geometrical parameters of water and wastewater pipes buried in Imam Hossein Square, Isfahan city, as real GPR data. Depending on environmental conditions and subsurface host formation, the real GPR data normally contain a variety of noises; therefore, a series of appropriate objective preprocessing and processing stages were designed in order to apply on real GPR images before deploying template matching algorithm. The applicability of the template matching algorithm on real data and validity of the estimated parameters were proved based on assessing the accuracy of the estimated geometrical parameters of respective pipes through GPR response versus the measured parameters. The proposed algorithm was designed in such a way that all steps of estimating geometrical parameters of buried cylindrical targets are automatically carried out.

Buried targets in layered media: A combined finite element/physical acoustics model and comparison to data on a half buried 2:1 cylinder.

Previously, a combined finite element/physical acoustics model for proud targets [K. L. Williams, S. G. Kargl, E. I. Thorsos, D. S. Burnett, J. L. Lopes, M. Zampolli, and P. L. Marston, J. Acoust. Soc. Am. 127, 3356-3371 (2010)] was compared to both higher fidelity finite element models and to experimental data for a proud 2:1 aluminum cylinder. Here that expression is generalized to address the case of a target buried in a layered media. The result is compared to data acquired for the same 2:1 cylinder but half buried in a mud layer that covers the sand sediment (considered here as infinite in extent below the mud layer). The generalized expression reduces to both the previous proud result and to the result for a target buried in an infinite medium under the appropriate limiting conditions. The model/data comparisons shown include both the previous proud model and data results along with the ones for the half buried cylinder. The comparison quantifies the reduction in target strength as a function of frequency in the half buried case relative to the proud case.

Calculation of gravity due to a vertical cylinder using a spherical harmonic series and numerical integration

We developed a spherical harmonic series that represents the gravitational potential and its gravity field due to a buried right vertical cylinder. This series can be used at far- and intermediate-regions, and is fast and accurate, using only a few terms. We compared the values of the fields acquired by this new spherical harmonic series, with ones computed by direct numerical integrations, using a fine-mesh structure for a vertical cylinder. Results of the calculations are shown and performances of the two different methods are compared. Faithfulness of the spherical harmonic series is tested with an inversion example.

Use of chiral coating to reduce RCS of PEC cylinder buried beneath a sinusoidal surface

The reduction in radar cross section (RCS) of a perfect electric conductor (PEC) cylinder coated with chiral media buried below a sinusoidal surface is investigated. Spectral plane wave representation of field (SPRF) is used to account for the interaction of buried cylinder with the sinusoidal surface. Small perturbation method (SPM) is used to observe scattering from the sinusoidal surface. Different scattering scenarios are simulated by changing chirality and thickness of coating layer. It is observed that co polarized RCS is significantly reduced for some values of chirality. The behavior of the scattering coefficients is very useful to understand the dependence of RCS reduction on chirality.

On guided versus deflected fields in controlled-source electromagnetics

Abstract The detection of electrically resistive targets in applied geophysics is of interest to the hydrocarbon, mining and geotechnical industries. Elongated thin resistive bodies have been extensively studied in the context of offshore hydrocarbon exploration. Such targets guide electromagnetic fields in a process which superficially resembles seismic refraction. On the other hand, compact resistive bodies deflect current in a process which has more similarities to diffraction and scattering. The response of a real geological structure is a non-trivial combination of these elements—guiding along the target and deflection around its edges. In this note the electromagnetic responses of two end-member models are compared: a resistive layer, which guides the electromagnetic signal, and a resistive cylinder, which deflects the fields. Results show that the response of a finite resistive target tends to saturate at a much lower resistivity than a resistive layer, under identical survey configurations. Furthermore, while the guided electromagnetic fields generated by a buried resistive layer contain both anomalous horizontal and vertical components, the process of electromagnetic deflection from a buried resistive cylinder creates mainly anomalous vertical fields. Finally, the transmitter orientation with respect to the position of a finite body is an important survey parameter: when the distance to the target is much less than the host skin depth, a transmitter pointing towards the resistive cylinder will produce a stronger signal than a transmitter oriented azimuthally with respect to the cylinder surface. The opposite situation is observed when the distance to the target is greater than the host skin depth.

Simulation of locating buried objects via fringe pattern-based measurements in an optical fiber sensor-integrated continuous-wave ground-penetrating radar system

A new ground-penetrating radar system that can determine the depth and position of a buried metal cylinder, which is the combination of an optical fiber sensor (OFS), continuous-wave transmitter, and optical communication link, is proposed and simulated in the MATLAB and Optiwave program packages. Employing an optical sensor instead of a standard radio frequency (RF) receiver offers the advantage of preventing electromagnetic interference along the sensor's main unit cable and lower amplification noise. In this paper, the electric field distribution at the OFS due to reflections from the soil surface and the buried object is obtained mathematically using Green's function. The OFS's detected electric signal is then simulated. The effects of the cylinder's depth and the RF transmitter frequency are observed. The plots of the OFS output voltages vs. the x-axis distance to the burial point display interference fringe patterns. The position and the depth of the cylinder are determined using the characteristics of these patterns. It is estimated that the burial depth can be ascertained with a maximum 5-cm error for a 1-GHz transmitter frequency.

Seismic simulation of liquefaction-induced uplift behavior of a hollow cylinder structure buried in shallow ground

When designing buried structures using a performance-based framework, it is important to estimate their uplift displacement. A simplified method is proposed for predicting the uplift displacement of a hollow cylinder structure buried in shallow backfill based on the equilibrium of vertical forces acting on the structure during earthquakes. However, this method only provides the maximum value, which frequently is overestimated in practical applications. To offset this limitation, first, the uplift behavior of buried hollow cylinder structures subjected to strong earthquake motions was simulated. Then, two-dimensional effective stress analyses based on the multiple shear mechanism for soil were conducted, and the results were compared with the centrifuge test data. The soil parameters were evaluated based on laboratory test results. The seismic response data from 20g centrifuge tests were analyzed, and the results were generally consistent with the results of centrifuge model tests. In particular, the effective stress model showed a reasonable ability to reproduce the varying degrees of uplift displacement depending on the geotechnical conditions of trench soils adjacent to the hollow cylinder structures buried in shallow ground.

Scattering by a cylinderical shell buried in elastic sediment

Scattering results are presented for the case of cylindrical steel targets buried in elastic sediment with sound incident from the air above. The STARS3D finite element program recently extended to layered, elastic sediments is used to compute the scattering and the resulting normal displacement at the interface since the specific focus here is detection by systems which rely on monitoring the acoustic displacements or displacement-related entities at the fluid-sediment interface. Results are compared for the scattered field produced by the cylinder buried in layered elastic sediment versus in fluid sediment and for the scattered field of a buried cylindrical shell versus a buried solid cylinder. [This work was supported by ONR.]

Closure to “Discussion of ‘Mechanics of Confined Thin-Walled Cylinders Subjected to External Pressure,’” (Vasilikis, D., and Karamanos, S., 2014, Appl. Mech. Rev., 66(1), p. 010801)

The authors would like to thank Prof. Gresnigt for reading their paper and for preparing an extensive commentary, which addresses interesting issues stemming from his long-time experience in pipeline mechanics and behavior. It is the authors’ opinion that his commentary identifies several demanding problems on this subject and can be used as guidance for future research work. Our closure is aimed at complementing the commentary in further discussing those issues.In the course of our study, we examined several parameters that affect buckling behavior of confined thin-walled cylindrical shells. Nevertheless, a few additional parameters are stated by Prof. Gresnigt, namely residual stresses, Bauschinger effect, and heat treatment that may influence the mechanical properties. Residual stresses and the Bauschinger effect are mainly related to the manufacturing process. For large-diameter, thin-walled cylinders (D/t > 100), the most popular manufacturing method is spiral welding of a steel coil. Unfortunately, there exists little information on the residual stresses of such pipes. In the course of a European research program, the authors are currently working on the finite element simulation of spiral-welding pipe-manufacturing process to determine residual stresses, including the effects of decoiling. Furthermore, residual stress measurements are also performed for comparison purposes. By completion of this research, information on the distribution of residual stresses will be available and appropriate stress distribution can be considered as the initial stress state for external pressure analysis under confined conditions.Heat treatment is another factor for external pressure capacity. There exist several publications for the beneficial effects of heat treatment on external pressure buckling of thick-walled offshore steel pipes. On the other hand, there is no information for such effects on the response of thin-walled confined pipes, mainly due to pipe coating. Therefore, more research is necessary on this subject.Prof. Gresnigt also refers extensively to “mechanically lined pipe”, a novel pipe product, very promising for hydrocarbon pipeline applications. When this double-wall pipe is bent, the thick-walled outer cylinder deforms rather smoothly, whereas the thin-walled liner is susceptible to wrinkling under lateral confinement conditions, provided by the outer cylinder, as pointed out by several recent publications, experimental and computational. For lined pipes used in offshore applications, their structural behavior and buckling under external pressure is of particular interest, not given attention in the literature. This problem is somewhat different than the one described in the present paper; external pressure is not applied at the interface between the outer cylinder and the liner, but it is applied at the outer surface of the double-wall lined pipe. This means that both the outer and the liner pipe shrink and eventually buckle, most likely in the form of an oval shape. However, it would be interesting to analyze externally pressurized lined pipes with the numerical tools of the present paper and, in particular, to examine the detachment and the deformation shape of the thin-walled liner.The effects of gravity loading on the structural behavior of buried thin-walled cylinders under external pressure conditions have been examined in Sec. 4.2 of the present paper, referring mainly to buried steel water pipelines, with values of D/t ratio greater than 100. Initial ovalization of the buried pipe due to gravity will reduce its external pressure capacity. Using the finite element models of the present study, it would be helpful to extend the present work in determining a rational allowable value of initial ovalization due to gravity, so that external pressure capacity is not significantly reduced. This would be of significant interest to the water steel pipeline community.In several engineering applications mentioned by Prof. Gresnigt, confined cylinders subjected to external pressure can be made of other materials, and prediction of their buckling and postbuckling behavior under external pressure would require accurate modeling of material behavior. Nevertheless, it is the authors’ opinion that, conducting an elastic analysis similar to the one described in Sec. 3 of our paper and considering a simple criterion for material failure at the critical location, one may obtain reasonable estimates of the ultimate pressure capacity.Finally, we would also point out the lack of adequate experimental evidence on this subject of our paper. It is our understanding that conducting full-scale tests on large-diameter cylinders would be quite difficult and expensive. Nevertheless, a series of tests on appropriately scaled cylinders may be more feasible and helpful towards better understanding of buckling and postbuckling of thin-walled cylinders embedded in a deformable medium.