Horizontal Tensile Stress Research Articles

Theoretical Rayleigh and Love Waves from Explosions in Nonspherical Cavities and from Tectonic Release in Compressive Stress Fields

Ben‐Menahem and Mikhailov (1995) developed a spherical mapping approximation to compute displacement fields due to explosions in nonspherical cavities embedded in elastic media. The explosion‐generated stress distribution was mapped onto the surface of an equivalent virtual spherical cavity. In this article, we use these techniques to analyze Rayleigh‐ and Love‐wave radiation patterns for a horizontal cylinder cavity, modeling an explosion in a tunnel for diameter‐to‐length ratios ranging from a line source (zero diameter) to that of a disk (zero length). The equivalent tectonic release is that created in a horizontal direction tensile stress field. With this orientation, the Love‐wave radiation pattern is identical to that of a vertical strike‐slip fault with a strike of 45° from the axis of symmetry. Assuming temporal step-function pressures and ignoring near-field nonlinear elasticity, shock waves, and reverberations in the air-filled cavity, we express the displacement fields for either explosion or tectonic release, in terms of a multipole expansion of spherical eigenvectors. This is done for both axisymmetric ellipsoidal and right cylindrical cavities. As in Ben‐Menahem and Mikhailov, at long wavelengths the dominant spherical harmonics are found to be, at most, second order. This is true even for extreme geometries such as the finite-length line source and the disk. For long-period surface waves, the first two terms suffice. At very long periods, the radiation field is the same as that due to the rapid formation of a spherical cavity in the presence of tensile stress, and differs by only a sign in case the initial stress is compressive instead. The two sources differ only in their respective second-order moment tensor time functions.

Origin of transform faults in back‐arc basins: examples from Western Pacific marginal seas

AbstractTransform faults in back‐arc basins are the key to revealing the evolution of marginal seas. Four marginal basins in the Western Pacific, i.e. the South China Sea (SCS), Okinawa Trough (OT), West Philippine Basin (WPB) and Shikoku‐Parece Vela Basin (SPVB), were studied to redefine the strikes and spatial distribution of transform faults or fracture zones. Based on high‐resolution tectonomorphology, gravity and magnetic anomalies, pattern of magnetic lineations, seismic profiles, geometry of basins and palaeomagnetic data, together with analyses of regional geological setting, plate reconstruction and geodynamic analysis, this paper suggests that all the transform faults in the four marginal basins are in general NNE‐trending. Moreover, by comparing with the contemporary structural framework of the East Asian Continental Margin, we propose new models concerning marginal seas spreading and have revised the previous Cenozoic plate reconstruction models related to the East Asian Continental Margin and the Western Pacific marginal seas. There are three possible origins of these NNE‐trending transform faults. 1. Inheriting the orientation of the strike‐slip faults at the rifting continental margin (e.g. the SCS and OT). The real strike of transform faults should not be NW but NNE. The large‐scale NNE‐trending dextral strike‐slip faults distributed in the continental shelf of the SCS control a series of pull‐apart basins of the SCS. Due to a higher degree of pull‐apart, oceanic crust began to open. Then they evolved into the NNE‐trending transform faults in the SCS and could also be regarded as a natural extension of the NNE‐trending strike‐slip faults in the South China Block (SCB). The geodynamic mechanism of the OT is similar to that of the SCS. Consequently, transform faults of the OT should also be NNE‐trending, which is not perpendicular to the spreading axis but instead displays oblique spreading. 2. Izu‐Bonin‐Mariana (IBM) Trench retreat to the NNE and NE. Subduction rollback to the NE and NNE produced the NE‐ and NNE‐striking horizontal tensile stress, resulting in the rifting of the Kyushu‐Palau Ridge (KPR), controlling the spreading of the SPVB and forming the NE‐ and NNE‐trending transform faults. This also involves oblique spreading. 3. The later overall rotation of the Philippine Sea Plate (PSP). Since 25 Ma, the WPB has rotated clockwise about 40°. Therefore the NW‐ and NNW‐trending transform faults that formed at the later spreading stage have rotated to be the near‐N–S‐ or NNE‐striking faults. These transform faults are almost perpendicular to the spreading axis. Copyright © 2016 John Wiley & Sons, Ltd.

Two-step Method of Designing Distribution of Material Stiffness in Perpetual Pavement to Prevent Structural Rutting and Fatigue

A two-step method for stiffness distribution design with application to perpetual pavements is proposed. In the first step resultant stiffness of asphalt concrete layers is estimated using nomograms obtained via solution of three-dimensional problem of a layered half-space. As controlling parameter vertical strain in the soil base is used. In the second step simplified model of composite beam is applied to predict distribution of stiffness within the asphalt layers. In order to derive design formulas, criterion of equality of stiffness of composite beam's cross-section and stiffness of a homogenous reference layer being a part of layered system, and criterion of horizontal tensile stress reduction at critical locations are used. Obtained formulas require input of thicknesses of individual layers and some material properties, including strain endurance limits.

Edge waves in an initially stressed visco-elastic plate

The present study analytically investigates the propagation of edge waves in a pre-stressed homogeneous visco-elastic plate. The plate is initially stressed in horizontal direction only. The solution for potential function and displacement components of the edge wave propagation have been obtained separately. Dispersion equation of edge wave has been established in closed form.The horizontal tensile and compressive initial stress parameters give the remarkable effect on the phase velocity of edge wave propagation.

Theoretical analysis on the deformation characteristics of coal wall in a longwall top coal caving face

Against the background of analyzing coal wall stability in 14101 fully mechanized longwall top coal caving face in Majialiang coal mine, based on the torque equilibrium of the coal wall, shield support and the roof strata, an elastic mechanics model was established to calculate the stress applied on the coal wall. The displacement method was used to obtain the stress and deformation distributions of the coal wall. This study also researched the influence of support resistance, protective pressure to the coal wall, fracture position of the main roof and mining height on the coal wall deformation. The following conclusions are drawn: (1) The shorter the distance from the longwall face, the greater the vertical compressive stress and horizontal tensile stress borne by the coal wall. The coal wall is prone to failure in the form of compressive-shear and tension; (2) With increasing support resistance, the revolution angle of the main roof decreases linearly. As the support resistance and protective force supplied by the face guard increases, the maximum deformation of the coal wall decreases linearly; (3) As the face approaches the fracture position of the main roof, coal wall horizontal deformation increases significantly, and the coal wall is prone to instability; and (4) The best mining height of 14101 longwall face is 3.0m.

Accurate determination of near-surface responses of asphalt pavements

Accurate determination of structural responses plays a critical role in a mechanistic-empirical pavement design. A new distress model, top-down fatigue cracking, has been incorporated in the newly developed Mechanistic-Empirical Pavement Design Guide. The critical response for top-down cracking is the horizontal tensile stress or strain at the pavement surface. However, the poor convergence of analytical layered elastic solutions in the vicinity of the pavement surface may result in large errors in response results. This study uses the Lucas algorithm to effectively solve this problem. The algorithm converts the complicated oscillating behaviour of the product of Bessel functions to regular oscillations by separating the integrand into high- and low-frequency components. Thus, extrapolation techniques can be effectively applied to accelerate the convergence. A computer code is developed to implement the proposed procedure. The computer code is verified against the boundary conditions and finite element results. It is also compared to other layered elastic programs. The results show that the proposed procedure can accurately determine the near-surface responses of asphalt pavements.

Blast response of reinforced concrete pile using fully coupled computer simulation techniques

Pile foundations transfer loads from superstructures to stronger sub soil. Their strength and stability can hence affect structural safety. This paper treats the response of reinforced concrete pile in saturated sand to a buried explosion. Fully coupled computer simulation techniques are used together with five different material models. Influence of reinforcement on pile response is investigated and important safety parameters of horizontal deformations and tensile stresses in the pile are evaluated. Results indicate that adequate longitudinal reinforcement and proper detailing of transverse reinforcement can reduce pile damage. Present findings can serve as a benchmark reference for future analysis and design.

Modelling of 3D response pulse at the bottom of asphalt layer using a novel function and artificial neural network

Fatigue life of asphalt mixes in laboratory tests is commonly determined by applying a haversine or sinusoidal load with a specific frequency. However, the frequency (time duration) and shape of horizontal tensile stress and strain pulses at the bottom the asphalt layer depend on pavement design (thickness and stiffness of layers) and loading specifications (speed and contact radius). The first objective of this paper is to introduce a novel function for a more realistic representation of 3D response (stress and strain pulses in longitudinal, transverse and vertical directions) at the bottom of the asphalt layer. The second objective is to establish a framework for determination of magnitude and shape of 3D response pulse at the bottom of the asphalt layer using artificial neural network. This framework enables designers to predict the shape and magnitude of stress and strain pulses in three directions based on some parameters related to pavement structure and loading specifications.

Implications of thermally-induced fracture slip and permeability change on the long-term performance of a deep geological repository

This paper addresses thermally-induced shear slip, i.e., thermoshearing, and changes in permeability of a deep geological repository in large scale. We present a systematic examination of the thermal stress expected to be generated in the far-field around the repository. The main mechanisms for generation of thermal stress that can affect permeability are; comparatively high horizontal compressive thermal stress at the repository level, vertical tensile thermal stress right above the repository and horizontal tensile stress near the surface, and shear stress at the corners of the repository. Based on thermal loading history, probabilistic shear slip analysis was conducted to investigate the possibility of thermoshearing. Higher probability of shear slip is expected with higher differential thermal stress, and this was highly affected by fracture orientations. Stress paths obtained from the thermo-mechanical analysis were used as stress boundary conditions for Discrete Fracture Network-Discrete Element Method (DFN-DEM) Analysis to investigate the effect of stress changes on permeability. In four out of the six DFN models, normal deformation dominated the closure and opening of fractures, with shear dilation being the dominant factor in the other two models. Changes in permeability caused by shear dilation were not reversed after the repository cooled, which is explained by the irreversible fracture shear deformation after shear slip. This study was conducted on data from the Forsmark site in Sweden, and this analysis has implications for sites that have comparatively large horizontal in-situ stresses and relatively few fractures.

Numerical simulation of the mechanical performance of deep beam

The purpose of this paper is the analysis of the mechanical performance of concrete deep beams. To overcome the shortcomings inherent to the pioneer models, the finite element approximation on a non linear orthotropic model is employed. The obtained results showed that the practiced range on steel reinforcement did not influence, significantly, the beam performance, and one testifies a behavior, in the overall way, pursuant the fashion accepted in the scientific literature on the subject. Nevertheless, it should be detached that the material failure resulted from the concrete crushing on beneath load region, in addition to the occurrence of horizontal tensile stress and "snap back", at the upper edge in the center region, for the beams of greatest height.

Evaluation of hot-mix asphalt susceptibility to temperature-induced top-down fatigue cracking by means of Uniaxial Cyclic Tensile Stress Test

A dominant failure mode in hot-mix asphalt (HMA) layers is material fatigue, occurring when the asphalt layer is repeatedly loaded by tensile stresses. The maximum stress arises at the bottom of the asphalt layer and, in consequence, crack development is initiated at the bottom. Various techniques are known that simulate bottom-up fatigue cracking in the laboratory. Fatigue failure is also observed on top of the pavement. Especially in cold climates, temperature-induced top-down cracking initiated at the pavement surface is a well-known failure mode. Usually, horizontal tensile stresses in the surface layer are smaller than stresses in the bottom layer. At cold temperatures and when temperature falls within a short period of time, the traffic-induced stress is superposed by temperature-induced stress, and the total stress may come up to the tensile strength of the material. In order to test the material's susceptibility to temperature-induced top-down fatigue cracking in the laboratory, the Uniaxial Cyclic Tensile Stress Test (UCTST) was established and recently introduced in European Standards (prEN 12697-46). In this test, a prismatic shaped HMA beam is subjected to a constant tensile load (representing the temperature-induced stress) which is superposed by a sinusoidal tensile load (representing the traffic load). This loading situation results in a visco-elastic strain response on the one hand, and in an accumulation of visco-plastic strain on the other. Different failure modes are observed in UCTST. In this paper, the failure modes occurring in UCTST, i.e. cracking of the specimen, stiffness decrease, and creep, are discussed based on the results from laboratory testing of nine different HMA and on variation of loading conditions.

Mechanical Analysis of Construction Process for Shallow Weaking Surrounding Rock Multi-Arch Tunnel

Based on a practical engineering, considering the characteristics such as shallow,weaking surrounding rock, large span, double-arch of the tunnel, the stress and strain of surrounding rocks, support structure and mid-wall were analyzed by FEM for different excavating procedure. The simulation results were compared with in-situ monitoring results. The crown settlement and convergence displacement are divided two obvious increasing stages. Surrounding rock upper and under the mid-wall generate bigger plastic strain and should be strengthened. Temporary support of the pilot bears bigger load and should be reinforced. Bearing bigger horizontal direction tensile stress and uneven load, the bottom of mid-wall must have enough reinforcing steel bar or employ augment foundation. The analysis results provide a scientific basis and technical guidance for the construction optimization of the tunnel constructed by three-pilot excavation method.

Mechanical Analysis of Construction Process for Shallow Weaking Surrounding Rock Multi-Arch Tunnel

Based on a practical engineering, considering the characteristics such as shallow,weaking surrounding rock, large span, double-arch of the tunnel, the stress and strain of surrounding rocks, support structure and mid-wall were analyzed by FEM for different excavating procedure. The simulation results were compared with in-situ monitoring results. The crown settlement and convergence displacement are divided two obvious increasing stages. Surrounding rock upper and under the mid-wall generate bigger plastic strain and should be strengthened. Temporary support of the pilot bears bigger load and should be reinforced. Bearing bigger horizontal direction tensile stress and uneven load, the bottom of mid-wall must have enough reinforcing steel bar or employ augment foundation. The analysis results provide a scientific basis and technical guidance for the construction optimization of the tunnel constructed by three-pilot excavation method.

Estimating crustal seismic anisotropy with a joint analysis of radial and transverse receiver function data

SUMMARY We developed an integrated technique for estimating crustal anisotropy with a horizontal axis using radial (R) and transverse (T) receiver functions. The technique includes computing three individual and one joint objective function (JOF) and a reliability analysis of the estimated anisotropy. The individual objective functions (IOFs) are designed to: (1) maximize the peak energy of the stacked R receiver function after a cosine moveout correction in the Ps arrival time; (2) to maximize the correlation of the radial receiver functions after a full correction of anisotropy or (3) to minimize the total energy of transverse receiver functions stacked after a removal of crustal anisotropy. The JOF was computed by a weighted average of the three IOFs, and the reliability analysis uses the principle that stacking coherent signals can lead to an increase of signal-to-noise ratio. We applied the technique to synthetic receiver functions generated with 30–60 per cent white noise from a variety of anisotropic and heterogeneous models. The synthetic tests indicate that the proposed technique has good capability to recover the input models. Despite the presence of random and other coherent noises, such as those caused by inhomogeneous structures, in the data, the technique can always provide accurate estimates of crustal anisotropy. We applied the technique to two permanent seismic stations in western China and found significant crustal anisotropy beneath one station located at the northern edge of the Tibetan plateau. The observed fast polarization direction at this station follows the direction of the maximum horizontal tensile stress, suggesting that the observed seismic anisotropy is likely caused by mineral alignment in the lower crust. The station situated in the Sichuan basin, on the other hand, shows little to no seismic anisotropy, which may suggest that the crust beneath the basin is nearly rigid with very little deformation. The developed technique can be applied to any broadband seismic stations that have a good backazimuthal coverage of teleseismic events.

Numerical modelling of thermally induced desiccation of geosynthetic clay liners observed in laboratory experiments

ABSTRACT: A fully coupled model is used to simulate the results of large-scale laboratory tests that investigated the non-isothermal behaviour of geosynthetic clay liners in landfill basal liner applications. Results of numerical simulations of the laboratory tests in terms of water content, capillary pressure, temperature and stress distributions are presented, and encouraging agreement between the numerical and experimental results is achieved. Under the conditions examined, a 25°C/m temperature gradient led to the development of tensile stresses within the GCL, increasing the resultant likelihood of cracking. A Poisson's ratio of 0.25 resulted in predicted horizontal tensile stresses supporting qualitative observation of desiccation cracking in the GCLs. One important implication of the work reported herein is that elevated temperatures need not occur for extended periods to create the risk of desiccation.

Horizontal stresses in the mantle and in the moving continent for the model of two-dimensional convection with varying viscosity

Numerical experiments on studying the spatial fields and evolution of viscous overlithostatic horizontal stresses and pressure in the mantle and in the moving continent are carried out. The continent moves consistently with time-dependent forces, which act from the viscous mantle. By introducing the varying viscosity, we gain the possibility for taking into account the oceanic lithosphere and the difference between the viscosity of the upper and the lower mantle in the context of a purely viscous model. The typical overlithostatic horizontal stresses in the main part of the mantle are ±(7–9) MPa (70–90 bar); in the highly viscous regions and, particularly, in the subduction zones they are at least three times larger. The descending mantle flows in the depth interval from approximately 50 km to about 300 km are more sharply pronounced in the pressure field than in the field of horizontal stresses. At the considered stages of motion and in different parts, the continent is characterized by the following typical values of stresses: the overlithostatic pressure ranges from −5 to +15 MPa; the horizontal overlithostatic tensile stress amounts up to −4MPa (−40 bar); and the compressive stress in case of the overriding of the subduction zone attains +35 MPa (350 bar).

Numerical modeling of the distribution of horizontal stresses in a moving continental plate

The distribution and time evolution of overlithostatic horizontal stresses in the vertical cross-sections of the model of a solid continent are studied in terms of a 2D numerical model. The continent is moving self-consistently with time-varying mantle flows. Over a period of 50 Ma, the continent, which had been initially located at a distance of about 1500 km from the downward mantle flow (subduction zone), first overlays the region of the marginal sea, then thrusts over the zone of subduction, thus making it inclined and deforming it. It is found that the horizontal tensile stresses observed at the initial stages are succeeded by compressive stresses, especially at the leading edge (up to 40 MPa). This is caused by the change of the dragging action of the subduction zone into the retarding action during the continent crossing over this zone. The dependence of the calculated stresses on the Rayleigh number and on the thickness of the model of the continent is estimated. It is obtained also that the distribution of horizontal stresses along the strike of the continent is rather distinctly indicative of the locations of upward and downward flows in the subcontinental mantle. With the considered values of the model parameters, the tensile stresses in the near-to central regions of the continent may be twice to thrice the tensile stresses at its margins. Hence, in the simplest case of a homogeneous continent, its division will occur in the zone directly above the upward subcontinental flow. Detachment from the continent of the fragments of its edge adjacent to the marginal sea implies that the thickness of the continental plate in that part and/or its strength is considerably lower than in the center of the continent.

The effect of stiffness and duration parameters to the service life of the pavement structure

The goal of this article is to determine the effect of various material parameters to the fatigue life of the pavement structures. Nowadays many types of mixtures can be built in the pavements, with different stiffness moduli. However, the Hungarian asphalt pavement design method can not handle that. The main cause of failure of the asphalt layers is supposed to be caused by the strains coming from the horizontal tensile stresses at the lowest level of layers. Many calculations were made with various attributes of the layers of the pavement structures i.e. subgrade, base course, binder course and surface course. After these calculations, we can clearly see which parameter of which layer is the most important to build a pavement with long fatigue life.

Modelling Tensile Strain Response in Asphalt Pavements

ABSTRACT Traditionally, HMA pavement designs and modeling methods have historically been based on the fundamental assumption that fatigue cracking generally initiates at the bottom of the HMA layer due to excessive tensile stresses/strains, and then propagates upwards to the surface. However, fatigue cracking can either be bottom-up or top-down initiated depending on the location of the maximum horizontal tensile stresses and strains in the HMA layer. Various factors such as the pavement structure and wheel/tire loading configurations influence both the location and magnitude of the fatigue crack-related tensile strains that are induced in the HMA layer. In this study, the influence of these factors on the tensile strains responses and potential location of fatigue crack initiation in HMA pavements was investigated. To address the non-uniformity distribution of the tire-pavement contact pressure (TPCP), including the vertical tire-pavement contact pressure and horizontal tire-pavement stress, a three-dimensional finite element program was utilized for the computational simulations and numerical analyses. Specifically, the actual TPCP of different tire types and tread patterns measured under variable load levels and tire inflation pressures were utilized to evaluate and analyze the potential locations of maximum tensile strains in terms of fatigue crack initiation. The results showed that the longitudinal and low latitudinal tire-pavement stress hardly influence the maximum tensile strains in the HMA layer; and that the maximum tensile strains can occur either at the top or bottom (or both) of the HMA layer, thus inducing top-down and/or bottom-up fatigue crack initiation. Just like heavy-truck tire loading, the study also demonstrated that light-truck tire loading can induce excessive fatigue crack-related tensile strains in the pavement.

Transconductance Enhancement by Utilizing Pattern Dependent Oxidation in Silicon Nanowire Field-Effect Transistors

Transconductance (gm) enhancement in n-type and p-type nanowire field-effect-transistors (nwFETs) is demonstrated by introducing controlled tensile strain into channel regions by pattern dependant oxidation (PADOX). Values of gm are enhanced relative to control devices by a factor of 1.5 in p-nwFETs and 3.0 in n-nwFETs. Strain distributions calculated by a three-dimensional molecular dynamics simulation reveal predominantly horizontal tensile stress in the nwFET channels. The Raman lines in the strain controlled devices display an increase in the full width half maximum, and a shift to lower wavenumber confirming that gm enhancement is due to tensile stress introduced by the PADOX approach.