Dynamic Soil Properties for Construction Site Investigation Using Geophysical Methods

Mechanical properties of yttria-stabilized zirconia: A study by ReaxFF molecular dynamics simulations

Poisson's ratio and Young's modulus are two important material constants for isotropic elastic materials, but there are usually very difficult problems regarding Poisson's ratio since high accuracy is required for its measurement. And also, for orthotropic elastic materials it is required that these material constants will be determined in line with the respective principal structure direction.In this paper, we describe the methods of measuring Young's moduli and Poisson's ratios for isotropic elastic material and orthotropic elastic materials using biaxial tensile tester. For isotropic elastic materials the Young's modulus and Poisson's ratio can be measured by strip biaxial testing, where the stretch ratio is variable to the axis of X1 and the stretch ratio to the axis of X2 is kept in unity. And the material constants are given by the following equations.E=1/e1σ1(σ12-σ22)ν=σ2/σ1where E is Young's modulus, ν is Poisson's ratio, σ1, σ2 are stress to the axis of X1, X2 and e1 is strain to the axis of X1. For orthotropic elastic materials these material constants are measured by three operations, that is, the strip biaxial tensile testings where the extension direction is selected to 0°(Lateral), 90°(Transverse) and 45°from one of structure principal axis. And the material constants are given by the following equations.EL=1/eL(σL-σTσL'/σT') ET=1/eT(σT'-σL'σT/σL)νLT=σL'/σT'ET/EL and GLT=σθ1/eθ1-EL(1+2νTL)+ET/4(1-νLTνTL)where EL, ET are Young's moduli of lateral and transverse directions respectively, νLT is Poisson's ratio, GLT is shearing modulus, σL, σT are stresses in lateral and transverse axis and eL, eT are the strains. And the prime means the case of transverse direction tensile, and suffix θ1 indicates the case of 45°direction tensile.

New models for effective Young's modulus of particulate composites

Influences of changes in mechanical properties of an overcored sample on the far-field stress calculation

MP66-11 COMPARISON OF THE BIO-MECHANICAL PROPERTIES OF HUMAN AND BABOON’s TUNICA ALBUGINEA

The effects of thermo‐mechanical auxetic foam conversion parameters on the Young's modulus and Poisson's ratio of open‐cell polyurethane foam are related to changes in chemical bonding and cell structure. Applied volumetric compression, conversion temperature, and duration are reported on foam Young's modulus, Poisson's ratio, and structural stability. Fourier transform infrared spectral analysis on samples converted at and above 160 °C strongly indicates a hydrogen bond interaction increase in urea groups (C=O‐‐‐H‐N) and an increase in hydrogen bonding population. Spectral changes inferred soft segment degradation following extensive heat exposure (200 °C, 180 min), specifically a shift and intensity change in CH2and C‐O‐C polyol bands and a broad baseline increase between 3600 and 2400 cm−1. These changes are linked to (i) resistance to dimensional recovery over time and during re‐heating; (ii) Poisson's ratio becoming negative, then zero in tension or marginally positive in compression; (iii) Young's Modulus reducing then increasing; (iv) mass loss, evidenced by thermogravimetric analysis increasing from 150 °C. The minimum mean values of Poisson's ratio of ≈−0.2 (to 10% compression/tension) are comparable to other studies. All samples that retain their imposed compression over time are isotropic, with near constant Young's moduli and Poisson's ratio (to 10% compression/tension).

This paper presentsa novel in-situ test structure for determining Young's modulus and Poisson's ratio of polysilicon thin films, based on electrostatic driving mechanism. The test structure manufactured with polysilicon surface processes, include two parts, one is used for the measurement of Young's modulus, and the other is used for the measurement of Poisson's ratio. By monitoring the deflection of polysilicon beams under the electrostatic force, the Young's modulus and Poisson's ratio can be obtained analytically. Validation and accuracy of the extracting method have been verified by FEM simulation andexperiments. The main advantage of this approach lies in the avoidance of the pull-in phenomena. The test structure can be widely used in MEMS process monitoring and the in-situ extraction of material properties.

Shale oil reservoir characterization is conducted in Western Depression of Liaohe Oilfieid of China. The major storage space is fracture which is preferably developed in shale with high content of silica, calcite or dolomite. A workflow of integrating rock physics models, amplitude preserved processing, and pre-stack inversions is developed and implemented which provides elastic parameters such as Young's modulus, Poisson's ratio and fracture density and orientation. These parameters are used to characterize brittleness of shale and preferable drilling locations for such kind of reservoir. In order to accurately estimate velocity in shale, a better rock physics model called AS-Xu-White is integrated in the workflow especially for guidance of interpretation, which is modified from Xu-white model. Fluid discrimination in fracture with newly developed anisotropic rock physics model is also employed in this work. Introduction Shale constitutes about 75% of sedimentary rocks (Vernik and Liu, 1996). It is not only the major source and seal, but also serves as reservoirs. A large amount of shale gas/oil has been discovered since last century. The rapid development of exploiting techniques increases the unconventional shale gas/oil output greatly, which also lead to growing proportion in hydrocarbon yield. Thus, shale reservoirs exploration has drawn more and more attention. In this paper shale oil reservoir characterization is conducted in Western Depression of Liaohe Oilfieid of China. The hydrocarbon-rich shale in Sha3 member of Shahejie formation in Chenjia sag is selected for the case study (the location is shown in Figure 1). The dark shale in Sha3 member is deposited in semideep-deep lacustrine sedimentary environment, which is very thick and has high ability to generate hydrocarbon with abundant organic matter. The major applications of 3D seismic data in the study of shale reservoir focus on the following three aspects:identifying the faults and karst to direct drilling (Norton et al, 2011);predicting natural fractures indirectly by geometric attributes such as coherence and curvature calculated from post-stack data (Guo et al, 2010), and directly by anisotropic inversion of AVAZ and VVAZ (Ruger, 1998; Goodway et al, 2007);mapping geo-mechanical brittleness and horizontal stress directions for effective hydraulic fracture stimulation (Goodway et al, 2010; Sena et al, 2011). In this paper the shale oil in the target member is not from tight rocks but mainly from natural fractures. Thus the study should focus on identifying fracture-prone zones. An integrated and comprehensive workflow for shale oil reservoir prediction is implemented which provides elastic parameters such as Young's modulus, Poisson's ratio and fracture density and orientation. Before pre-stack inversion, a modified Xu-white model is introduced to simulate the complex fracture system of shale, which leads to better estimate velocity. Since brittleness and fractures are two major factors that control reservoir quality, reservoir prediction could be accessed by identifying fracture-prone brittle areas and detecting the natural fractures, where the isotropic and anisotropic inversion are both used. As a result, the brittle shale distribution determined by crossploting Erho (i.e. a parameter constructed by Young's modulus and density) and Poisson's ratio is in a good agreement with both the well production data and the latest drilling data. On the other hand, fractures predicted by improved anisotropic inversion using limited azimuthal data coincide well with that from the FMI, and are proven to be reasonable from geologic analysis. Fluid discrimination in fracture with newly developed anisotropic rock physics model is also employed in this work. Combining the results with geological analysis, the favorable area is proposed finally.

When blending rubbers into polymers, different rubber distribution status and fraction due to different mechanical property. In this research, effective mechanical properties of rubber-toughened polymers with four blending fraction in six kinds of particle distribution status are simulated numerically by using finite element method. Rubber particle distribution model include four 2D models and two 3D models. Typical effective mechanical properties such as yield stress, Young's modulus, Poisson's ratio and stress-strain curve of each status are obtained. The Results show that all models Young's modulus and Poisson's ratio decrease with rubber particle volume fraction increasing. Young's modulus and Poisson's ratio of three-dimensional body-centered cubic and face-centered cubic models are in a close magnitude range, it means rubber particle volume fraction has less effect on 2D models and two 3D models. As we all known, Matrix yielding, crazing and interface debond. All play an important role in the toughening process of rubber-toughened polymers. So in this paper we also study on toughening mechanism using same models. Our simulation takes use of stress concentration factor, yield ratio and interface elements' strain difference which is related with matrix yielding, crazing and interface debond to study the toughening mechanism. Simulation shows that the maximum stress concentration factor increases with particle volume fraction. The shear yielding occurs first at the equator of rubber particle, and then yield region expands from the equator to the pole of the particle with loads increasing.

Knowledge of the Young's modulus distribution of an atherosclerotic artery allows for differentiation between its components. Intravascular elastography generates an artifactual image of this Young's modulus distribution. A finite element model (FEM) can assist in interpreting the elastogram and give its Young's modulus distribution by inverse problem solution. Intravascular ultrasound (IVUS) measurements were performed on a hard phantom with soft eccentric plaque and an atherosclerotic coronary artery. The complex FEM geometry and Young's modulus distribution were defined using a custom-made graphical user interface. Next elastograms were calculated from IVUS data and compared with FEM elastograms. IVUS and FEM elastograms showed excellent agreement in case of the phantom and a similar pattern in case of the artery. Strain values in the FEM elastogram appeared highly sensitive for variations in the Young's modulus but not in the Poisson's ratio.

Time-dependent behavior of porcine periodontal ligament: A combined experimental, numeric in-vitro study.

Because measuring the frequency dependence of elastic properties in the laboratory is a technical challenge, not enough experimental data exist to test the existing theories. We report measurements of three fluid‐saturated sandstones over a broad frequency band: Wilkenson, Berea, and Bentheim sandstones. Those sandstones samples, chosen for their variable porosities and mineral content, are saturated by fluids of varying viscosities. The samples elastic response (Young's modulus and Poisson's ratio) and hydraulic response (fluid flow out of the sample) are measured as a function of frequency. Large dispersion and attenuation phenomena are observed over the investigated frequency range. For all samples, the variation at lowest frequency relates to a large fluid flow directly measured out of the rock samples. These are the cause (i.e., fluid flow) and consequence (i.e., dispersion/attenuation) of the transition between drained and undrained regimes. Consistently, the characteristic frequency correlates with permeability for each sandstone. Beyond this frequency, a second variation is observed for all samples, but the rocks behave differently. For Berea sandstone, an onset of dispersion/attenuation is expected from both Young's modulus and Poisson's ratio at highest frequency. For Bentheim and Wilkenson sandstones, however, only Young's modulus shows dispersion/attenuation phenomena. For Wilkenson sandstone, the viscoelastic‐like dispersion/attenuation response is interpreted as squirt flow. For Bentheim sandstone, the second effect does not fully follow such response, which could be due to a lower accuracy in the measured attenuation or to the occurence of another physical effect in this rock sample.

Pile foundations placed until hard soil layer and passed through a liquefied layer can be a mitigation effort against liquefaction hazards to buildings. Nevertheless, liquefaction can still impact the stability of the pile. The Anutapura Medical Center (AMC) building at the Anutapura General Hospital complex, Palu city, is a building that is planned to be built on potentially liquefied soil. The foundation of the building was planned to use bored pile foundations to mitigate the possibility of liquefaction. This study aims to analyze and compare the stability of the bored pile group foundation of the AMC building under non-liquefaction and liquefaction soil conditions. The study was conducted by manually calculating the bearing capacity of the bored pile based on soil data. Further analysis was carried out by modeling the pile foundation using Geo5 Pile Group to determine the deformation and internal forces acting on the pile group. The analysis was carried out in 2 cases, i.e., non-liquefaction and liquefaction conditions. The results show differences in the bearing capacity, deformation, and internal forces in non-liquefaction and liquefaction soil conditions. The study results are expected to be a reference and consideration in designing pile foundations in liquefaction-prone locations.

An approximate method is proposed for the analysis of a pile under low or high-amplitude dynamic lateral loading applied at the pile head. The soil-pile system is modeled by the vibrations of a beam on elastic half- space. The uncoupled spring factor (k) and damping coefficient (c) of the foundation medium are defined. Appropriate dynamic soil properties are introduced to determine k and c considering both geometric and material damping. The governing equation of motion of the pile is a fourth order, non-linear, partial differential equation. Difference equation techniques with an iterative process were used in the solution of this equation for various boundary conditions. A computer program was developed for practical application of the proposed method. Comparison of computed results with those measured in instrumented, small-scale, pile tests in clay and sand is generally acceptable. INTRODUCTION Pile foundations in numerous applications are subjected to dynamic, lateral loading at the soil surface ranging from low to high-amplitude. Soil response to low-amplitude dynamic loading may be generally considered linear; therefore, the soil spring factor (k) and coefficient of damping (c) can be assumed constant. Under this soil condition, material damping effects are insignificant and consideration of only geometric damping in the soil to determine dynamic pile response may be justified. However, under high-amplitude dynamic loading, Boil behavior is non-linear. Thus, k and care strain-dependent and not constant. In this case, consideration of soil material damping in determining the behavior of the soil-pile system under dynamic loading is important and should not be disregarded. In an earlier publication (2), the authors introduced an approximate, yet rational approach for the analysis of a laterally-loaded pile subjected to low-amplitude, dynamic surface loading. The soil-pile system was represented by vibrations of a beam on an elastic half-space. The constant discrete, uncoupled spring factor and coefficient of damping were determined using the appropriate dynamic soil properties in accordance with the elastic half-space theory. Soil response was assumed linear and the computation was based only on consideration of geometric damping in the soil medium, while material damping was disregarded. The present paper extends the aforementioned analytical solution of the vibrating pile problem to the range of high-amplitude dynamic loading, which may be experienced in offshore situations. Soil behavior in this case is non-linear. Expressions for the soil k and c as functions of the shear modulus (G), Poisson's ratio, and density of the soil are developed taking into consideration geometric damping in the soil as well as its material damping characteristics. Values of k and c are strain-dependent and thus, variable, since G in this case is a function of the level of stress or strain. The governing equation of motion of a laterally vibrating pile embedded in an elastic half-space is shown in this case to be. a fourth order, partial differential equation with non-linear coefficients. As in previous work (2 & 4), Difference Equations techniques with iterative processes were adopted in the solution of the pile's equation of motion under several boundary conditions.

The aim of this study is to review the geophysical investigations in civil engineering and urban planning by some case histories in Turkey. Geophysics deals with a wide array of earth phenomena, including the temperature distribution of the earth's interior (the source, configuration and variations of the geomagnetic field) and the large-scale features of the terrestrial crust, such as rifts, continental sutures and mid-oceanic ridges. From the geophysical point of view, civil engineering and urban planning includes several geophysical topics used to investigate the physical properties, the physical techniques for regional and local land use planning or micro-zonation, the natural disaster risk estimation studies, etc. In this study, the geophysical approach, regarding civil engineering and urban planning against the natural or artificial disaster risk in macro (human/nature) and micro (society/earth) scales, is given. Geophysical methods provide solutions to a wide range of geotechnical problems: Slope stability, soil liquefaction and amplification studies, site investigations and testing, water works, subways, etc. In this study, an evaluation of the geophysical methods applied to geotechnical problems related to the soils is presented. Soils consist of the products of physical and chemical weathering of the rocks of the earth’s crust. As a part of the engineering design, the aim of a site/soil investigation is to provide the basic data to evaluate the interaction of the natural environment with the proposed structure. As it is known, using physical measurements in geophysics, it is studied as the natural and artificially generated physical fields of the earth. Key words: Geotechnical engineering, geophysics, earthquake engineering, soils, soil dynamics.