Yuan chyng Wang

National Taipei University of Nursing and Health Science · Graduate Institute of Long-Term Care

Estimating the damage induced by an explosion around a blast hole has always been a challenging issue in geotechnical engineering. It is difficult to determine an exact dimension for damage zone since many parameters are involved in the formation of failures, and there are some uncertainties lying in these parameters. Thus, the present study adopte...

Rock explosion has always been a complex problem because neither rock characteristics nor explosion waves could be accurately estimated. As such, this imposes a high uncertainty on deterministic methodologies available for damage prediction. In this paper, by defining two damage zones around the blast hole, including crushed and cracked zones, a fi...

The methods proposed by Kezdi' and Sherard' are widely used to assess the internal stability of granular soils due to their simplicity, although their accuracy is questionable, especially for widely graded soils. A modification was thus developed to increase the accuracy of these methods while keeping them as straightforward as possible. A simple g...

Coupled hydro-mechanical (HM) processes are significant in geological engineering such as oil and gas extraction, geothermal energy, nuclear waste disposal and for the safety assessment of dam foundations and rock slopes, where the geological media usually consist of fractured rock masses. In this study, we developed a model for the analysis of cou...

In this study, a numerical manifold method (NMM) model was developed for fully coupled analysis of hydro-mechanical (HM) processes in porous rock masses with discrete fractures. Using an NMM two-cover-mesh system of mathematical and physical covers, fractures are conveniently discretized by dividing the mathematical cover along fracture traces to p...

In this study, a numerical manifold method (NMM) model is developed to analyze flow in porous media with discrete fractures in a non-conforming mesh. This new model is based on a two-cover-mesh system with a uniform triangular mathematical mesh and boundary/fracture-divided physical covers, where local independent cover functions are defined. The o...

Internal instability is associated with geotechnical structures such as earth dams and dikes, and involves movement of fine loose particles through the voids of the main soil skeleton. In this study, some methods to determine the delimiting particle size (DPS) were critically reviewed. The accurate determination of the values of DPS and the diamete...

Numerical manifold method (NMM) is a numerical method known for analyzing continuous and discontinuous mechanical processes in a unified mathematical form. In this study we developed a new second-order NMM model to solve the nonlinear problem of water flow with the free surface priori unknown and the difficulty of modeling drains which could dramat...

Conventional model tests and centrifuge tests are frequently used to investigate seepage erosion. However, the centrifugal test method may not be efficient according to the results of hydraulic conductivity tests and piping erosion tests. The reason why seepage deformation in model tests may deviate from similarity was first discussed in this work....

In the numerical modeling of fluid flow in heterogeneous geological media, large material contrasts associated with complexly intersected material interfaces are challenging, not only related to mesh discretization but also for the accurate realization of the corresponding boundary constraints. To address these challenges, we developed a discontinu...

One major challenge in modeling groundwater flow within heterogeneous geological media is that of modeling arbitrarily oriented or intersected boundaries and inner material interfaces. The Numerical Manifold Method (NMM) has recently emerged as a promising method for such modeling, in its ability to handle boundaries, its flexibility in constructin...

A major challenge of modeling fluid flow in heterogeneous media is to model the material interfaces, which may be arbitrarily oriented or intersected with Dirichlet, Neumann, or other boundaries, making it difficult to mesh and accurately satisfy the boundary constraints. In order to solve these problems, we derived a new continuous approach in the...

SUMMARYA major challenge in seepage analysis is to locate the phreatic surface in an unconfined aquifer. The phreatic surface is unknown and assumed as a discontinuity separating the seepage domain into dry and wet parts, thus should be determined iteratively with special schemes. In this study, we systematically developed a new numerical manifold...

We present an extended multiple interacting continua (Ex-MINC) model of fractured rock masses that uses Oda's crack tensor theory to upscale the hydraulic and mechanical properties. The Ex-MINC concept includes separate connected continua representing active fractures, inactive fractures, and matrix to represent the fracture-matrix system. The crac...

Beltrami–Schaefer stress functions are general solutions of the equilibrium equations of an elastic body without body force. In this paper, the representation of the non-uniqueness of these solutions is deduced by converting the equations into operator matrix form—including an operator matrix and its generalized inverse—and then deriving the repres...

Internal stability against suffusion and filter efficiency are two important issues in geotechnical engineering. To well assess them, the constriction size distribution (CSD) of soil particles must be determined accurately. Both the Silveira model and the modified Silveira model have been widely used to mathematically simulate CSD curves and then t...

Zonal disintegration have been discovered in many underground tunnels with the increasing of embedded depth. The formation mechanism of such phenomenon is difficult to explain under the framework of traditional rock mechanics, and the fractured shape and forming conditions are unclear. The numerical simulation was carried out to research the genera...

The mechanical behavior of deep rock masses differs from that of shallow rock masses. Deep rock masses are classified into alternating fractured and intact zones. This unique geological phenomenon is known as zonal disintegration. It is difficult to explain the formation mechanism of such phenomenon under the framework of traditional rock mechanics...

Beltrami and Schaefer derived solutions for the equilibrium equations of an elastic objective free of body force, and Gurtin proved that the solutions are complete, i.e., proved that Beltrami–Schaefer stress functions are general solutions of the equilibrium equations. In this paper we show that the Beltrami–Schaefer stress functions are not unique...

Field monitoring carried out in a deep tunnel of the Dingji coal mine in China confirmed the zonal disintegration phenomenon by using the borehole TV. Based on field monitoring, an analogical model test was conducted to research the fracture shape and forming conditions of the rock mass in the Dingji mine. To perform the model test, an analogical m...

Internal erosion in river levees and landslide dams has often caused serious damage of the embankment body. As one type of internal erosion, piping erosion is the process in which fine soil particles are detached from the particle skeleton of coarser particles. At microscopic scale, particle composition and migration are the two main issues of pipi...

The deep rock masses show a different mechanical behavior compared with the shallow rock masses. They are classified into alternating fractured and intact zones during the excavation, which is known as zonal disintegration. Such phenomenon is a great disaster and will induce the different excavation and anchoring methodology. In this study, a 3D ge...

Cracks on a natural soil surface provide preferential pathways for water infiltration and contaminant solute transport. Before the mechanical property and permeability of cracked soil can be studied, a crack network model must first be established. Based on statistical analysis of crack geometry from field observations, a new method of representing...

This paper compares numerical modeling of the effect of stress on solute transport (advection and matrix diffusion) in fractured rocks in which fracture apertures are correlated with fracture lengths. It is mainly motivated by the performance and safety assessments of underground radioactive waste repositories. Five research teams used different ap...

A widely accepted method of filter design is the “US Natural Resources Conservation Service” (NRCS, Gradation design of sand and gravel filters, 1994) procedure in which a lot of criteria are suggested to satisfy proper filtration and permeability requirements of the filter and to prevent segregation during construction, yet the internal stability...

The internal stability against suffusion of granular soils and filter which have a primary coarser skeleton and loose finer particles (i.e. bimodal structure) were studied using a semi-empirical method to divide the grain size distribution curve to two components, a primary skeleton and loose particles; the primary skeleton acts as a filter for the...

In this paper, we present a linked multicontinuum and crack tensor approach for modeling of coupled geomechanics, fluid flow, and solute transport in fractured rock. We used the crack tensor approach to calculate effective block-scale properties, including anisotropic permeability and elastic tensors, as well as multicontinuum properties relevant t...

A new group of thin film metallic glasses (TFMGs) have been reported to exhibit properties different from conventional crystalline metal films, though their bulk forms are already well-known for high strength and toughness, large elastic limits, and excellent corrosion and wear resistance because of their amorphous structure. In recent decades, bul...

Cracks appear on natural soil surface due to wetting drying cycles, shearing or other causes. The existence of crack has most important effect on the properties of soil. The crack of the soil has attracted much attention. The description of cracks' geometry is the fundamental work for investigating the cracked soil. It is common to use the cracked...

Landslide is a common failure mode for levee, and the safety of which is always assessed by the value of safety factor. However, the safety assessment using the index of safety factor is usually unreasonable due to the uncertainty of soil characteristics, in contrast, the risk analysis by consideration of such uncertainties is more reasonable. Ther...

The process of surrounding rock crushing and water rushing under excavating or mining contains four phase, Darcy laminar flow in the aquifer, High velocity(relativity) Non-Darcy flow in transitional zone and fracture zone, and the Navier-Stokes turbulence in drift. In this paper, a model was suggested to simulate the process of fluid flows surround...

By means of brief pauses in radiofrequency (RF) sputter deposition between individual layers, ultrathin copper oxide layers were formed through adsorption in the Cu/Cu multilayers. Their mechanical properties were compared with the Cu/Cu(O) multilayers whose oxide layers were deliberately deposited between copper layers. The mechanical hardness val...

The low-energy electronic states and energy gaps of carbon nanocones in an electric field are studied using a single-p-band tight-binding model. The analysis considers five perfect carbon nanocones with disclination angles of 60°, 120°, 180°, 240° and 300°, respectively. The numerical results reveal that the low-energy electronic states and energy...

With unique properties such as high strength, amorphous alloys in the bulk form have been a focus for many studies in recent years. Yet, the amorphous alloys (metallic glass) in the thin film form have not received much attention. In this paper, we will review and report some important and interesting results obtained from these thin film metallic...

The mechanical behavior of multi-walled carbon nanotubes (MWNTs), being fixed at both ends under uniaxial tensile loading, is investigated via the molecular dynamics (MD) simulation with the Tersoff interatomic potential. It is found that Young's modulus of the MWNTs is in the range between 0.85 and 1.16 TPa via the curvature method based on strain...

Motivated by recent experimental works on the modifications of endomorphin-2 (EM2, H-Tyr-Pro-Phe-Phe-NH2) to develop better painkiller, we performed structure-activity-relationship (SAR) studies to investigate modified C-terminal ligands by using molecular dynamics (MD) simulations. Specifically, instead of the CONH2 for the unmodified EM2's C-term...

We investigate the residual strains in a free-standing Cu/Nb multilayer of 30 nm nominal layer thickness with synchrotron x-rays. This material system is characterized by columnar grains of Cu and Nb with incoherent interfaces and a sharp physical-vapor-deposition texture. High energy x-rays were used with an area detector along with multiple sampl...

In this paper, we develop a novel experimental apparatus, referred to as the resonant frequency device, and establish methodology to measure the fatigue properties of thin solid films. Arranging thin-film strips of our specimens into the mechanical setting of a cantilever beam and using state-of-the-art piezo actuators to generate oscillation at th...

Fatigue properties of magnetron sputtered Cu/Nb composite laminates with 40 nm individual layer thickness were determined. Compared to bulk Cu, over an order of magnitude increase in the stress to failure was observed. The ratio of the fatigue endurance limit to the ultimate tensile strength was about 0.35.

Energy dissipation and fatigue properties of nano-layered thin films are less well studied than bulk properties. Existing experimental methods for studying energy dissipation properties, typically using magnetic interaction as a driving force at different frequencies and a laser-based deformation measurement system, are difficult to apply to two-di...

Potential applications of high-damping and high-stiffness composites have motivated extensive research on the effects of negative-stiffness inclusions on the overall properties of composites. Recent theoretical advances have been based on the Hashin–Shtrikman composite models, one-dimensional discrete viscoelastic systems and a two-dimensional nest...

The effect of a negative bulk modulus phase in elastic composites is studied. Negative bulk modulus K<0 is shown to be possible in selected unit cells. In isotropic solids, K<0 can be attained when negative Poisson's ratio is sufficiently small, below the stability limit (for stress control) ¼ À1. Such materials, if used as inclusions, are predicte...

The figure of merit for structural damping and damping layer applications is the product of stiffness E and damping tan δ. For most materials, even practical polymer damping layers, E tan δ is less than 0.6 GPa. We consider several methods to achieve high values of this figure of merit: high damping metals, metal matrix composites and composites co...

When an elastic object is pressed, we expect it to resist by exerting a restoring force. A reversal of this force corresponds to negative stiffness. If we combine elements with positive and negative stiffness in a composite, it is possible to achieve stiffness greater than (or less than) that of any of the constituents. This behavior violates estab...

We present an enhancement of the resonant ultrasound spectroscopy method for the determination of elastic and viscoelastic properties. By using shear transducers rather than the usual compressional ones, signal strength for the fundamental is enhanced by one to three orders of magnitude. This enables simplified determination of shear modulus and da...

Particulate composites with negative stiffness inclusions in a viscoelastic matrix are shown to have higher thermal expansion than that of either constituent and exceeding conventional bounds. It is also shown theoretically that other extreme linear coupled field properties including piezoelectricity and pyroelectricity occur in layer- and fiber-ty...

When a force deforms an elastic object, practical experience suggests that the resulting displacement will be in the same direction as the force. This property is known as positive stiffness. Less familiar is the concept of negative stiffness, where the deforming force and the resulting displacement are in opposite directions. (Negative stiffness i...