Моделирование напряжённо-деформированного состояния трубопровода в зоне оползня грунта

روستای هاونان در 15کیلومتری جنوب غرب بیرجند و در دامنه شمالی رشته‌کوه باقران واقع شده و تاریخ اولین حرکت اصلی لغزش در منطقه در سال 1364 و تاریخ آخرین حرکت اصلی در سال 1385 است. در این مقاله پهنه‌بندی حساسیت به لغزش و تحلیل پارامترهای فیزیکی- هیدرولوژیکی و تکتونیکی به‌منظور شناسایی بیشتر وضعیت شکل‌گیری توده‌های لغزشی منطقه و تحلیل پایداری دامنه‌ها به کمک مدل فرآیندی SINMAP انجام‌شده است. این مدل نشان می‌دهد بخش اندکی از پهنه لغزشی هاونان در محدوده رطوبتی اشباع قرار می‌گیرد و کمتر از 30 درصد آن دارای حساسیت متوسط تا بالا به لغزش است؛ لذا بایستی در این محدوده به دنبال علل خارجی تأثیرگذار در پدیداری لغزش بود. محدوده هاونان متأثر از سه سری گسل اصلی با روندهای مختلف می‌باشد و در اثر تقاطع این سه سری گسل، واحدهای سنگی (اسپیلیت ها، پریدوتیت ها و گابروها) به‌صورت بلوک‌های گسلی کشیده درآمده و در اثر ادامه فرآیند برش، این بلوک‌ها متحمل تغییر شکل، جابجایی و چرخش شده‌اند. ترکیب سنگ‌شناسی (قرارگیری اسپیلیت بر روی سرپانتینیت) و وجود دو سری شکستگی به‌موازات گسل‌های هاونان و مزار مهم‌ترین عوامل ناپایداری هستند. علاوه بر این برخاستگی رشته‌کوه باقران باعث افزایش تدریجی نشیب دامنه و رخداد زمین‌لرزه‌ای ادواری نیز موجب تشدید لغزش می‌گردد.

The topic of this thesis is the quantification of the influence of preferential flow on landslide-triggering in potentially unstable slopes. Preferential flow paths (e.g., cracks, macropores, fissures, pipes, etc.) commonly exists in slopes. Flow velocities in preferential flow paths can be significantly larger than in the matrix. Under large rainfall or snow-melt events, preferential flow can bypass the adjacent soil matrix and directly reach the groundwater table. The fast pressure build-up caused by preferential flow can reduce the effective stress and shear strength, which is an important triggering factor for landslides. Single-permeability models can not appropriately simulate preferential flow. Hence, hydro-mechanical models of landslide need the inclusion of preferential flow. Preferential flow also affects tracer transport in subsurface flow systems. The celerity in unsaturated flow represents the maximum water velocity in a soil, and it may be used to predict the first arrival time of a conservative tracer. The celerity function is derived from the soil hydraulic conductivity function for unsaturated flow, and is used to derive the breakthrough curve of a conservative tracer under advective transport. Analysis of the bimodal hydraulic function for a dual-permeability model shows that different parameter sets may result in similar soil hydraulic conductivity behavior, but distinctly different celerity behavior. In Chapter 4, a 2D hydro-mechanical model is developed using COMSOL multi-physics modeling software to couple a dual-permeability model with a linear-elastic model. Numerical experiments are conducted for two different rainfall events on a synthetic slope. The influence of preferential flow on slope stability is quantified by comparing the simulated slope failure area for single-permeability model and dual-permeability models. The single-permeability model only simulate regular wetting fronts propagating downward without representing the preferential flow. In contrast, the dual-permeability model can simulate the influence of preferential flow including the enhanced drainage that facilities pressure dissipation under low-intensity rainfall, as well as the fast pressure build-up that may trigger landslides under high-intensity rainfall. The dual-permeability model resulted in a smaller failure area than the corresponding single-permeability model under low-intensity rainfall, while the dual-permeability model resulted in a larger failure area and earlier timing than the corresponding single-permeability model for high-intensity rainfall. In Chapter 5, a parsimonious 1D hydro-mechanical model is developed for field application by coupling a 1D dual-permeability model with an infinite slope stability analysis approach. The numerical model is benchmarked against the HYDRUS-1D for the simulation of non-equilibrium flow. In Chapter 6, the model is applied to simulate the pressure response in a clay-shales slope located in northern Italy. In the study area, preferential flow paths such as tension cracks and macropores are widespread. Intense rain-pulses in the summer can cause nearly-instant pressure responses which may reactivate landslide movement. The water exchange coefficient of the dual-permeability model is calibrated for two single-pulse rainfall-events in the summer, while all other parameters are obtained from field investigations. Results from the dual-permeability model are compared to previously published outcomes using a linear-diffusion equation, where the diffusion coefficient was calibrated for each rainfall event separately. The dual-permeability model explicitly accounts for the influence of both matrix flow and preferential flow on water flow and pressure propagation in variably saturated soils, and is able to simulate the measured pressure response to multi-pulse rainfall-events quite well even in the winter time. Results indicate that the dual-permeability model may be more appropriate for the prediction of landslide-triggering when the pore water pressure response is influenced by preferential flow under high-intensity rainfall.

The pulse-tube refrigerator (PTR) is a rather new device for cooling down to extremely low temperatures, i.e. below 4 K. The PTR works by the cyclic compression and expansion of helium that flows through a regenerator made of porous material, a cold heat exchanger, a tube, a hot heat exchanger and an orifice, in series. In a Stirling-type PTR compression and expansion are generated by a piston. The compression increases the temperature of the helium in the tube and makes it flow towards the orifice; the expansion decreases the temperature and makes the helium flow backwards to the regenerator. The net effect of warmer helium flowing in one direction and colder helium in the opposite direction is that of cooling power at the cold heat exchanger. Three PTRs are inter-connected aiming to obtain the desired 4 K lowest temperature. The conservation laws of mass, momentum and energy, and an equation of state, are simplified using asymptotic analysis based on low Mach-numbers. The regenerator is modelled one-dimensionally with Darcy’s law for flow resistance. The tube is modelled either one-dimensionally without resistance or two-dimensionally with axisymmetric laminar viscous flow. The heat transfer in the porous medium of the regenerator and in the solid tube wall is taken into account. The gas can be either ideal or real. All the material properties, including viscosity and conductivity, are taken temperature and pressure dependent. Three single-stage PTRs are connected with the regenerators in series and the tubes in parallel and six flow possibilities at the junctions are considered. Three by-passes (double-inlets) are used to enhance and tune the performance. The governing equations are numerically solved with a finite-difference method of nominally second-order accuracy in space and time. Pressure correction, flux limiter, 1D-2D connections and domain decomposition are the keywords here. Special attention is paid to suitable initial conditions, high resolution in the boundary layers and to the correct calculation of the three-way junctions in multi-stage PTRs. The model describes the fluid dynamics and thermodynamics of the pulse tubes and regenerators. The heat exchangers are assumed to be ideal in the whole analysis. The equation of state for real gas and other real properties of gas and regenerator material, which are temperature and/or pressure dependent, are applied in the three-stage PTR which works with extreme low temperatures, where the ideal gas law does not hold. The numerical methods require special attention. Typically for flow problems we deal with various length scales. Straight forward discretisation will result in unnecessary fine grids and therefore unacceptable computational time. We developed robust and efficient algorithms to deal with boundary layer problems. The employed domain decomposition technique allows for using coarse grids in areas where the solution does not change significantly. It also decouples a larger system into smaller ones, leading to smaller complexities. The objective of computing accurately and efficiently the steady oscillatory flow and heat transfer in a PTR has been achieved. In particular the tiny viscous and thermal boundary layers of a PTR operating at high frequency (20 Hz) could be resolved. The simulated three-stage PTR was able to cool down close to 5 K. The developed software is intended for use in design and optimisation of multi-stage PTRs.

STUDY OF HYPERBOLIC SYSTEM OF EQUATIONS TO STUDY TRAVEL TIME FOR TRAFFIC MODELLING by Anuj Nayyar 〈Dr. Hongtao Yang〉, Examination Committee Chair Associate Professor of Mathematical Sciences University of Nevada, Las Vegas In this thesis we study the travel time problem based on the known traffic density model. Using the conservation law, we model the travel time function by a boundary value problem of a non homogeneous linear hyperbolic equation. The equation is transformed into an initial value hyperbolic equation, and the well-posedness of the problem is discussed. The mathematical analysis for both density and travel problems are given. We also derive the analytic solutions for several special cases of traffic density. Numerical schemes are proposed for solving for travel time problem. Several numerical examples are presented and error analysis on the solutions obtained is performed to illustrate the rates of convergence of the numerical schemes.

In this paper, the material point software(Anura 3D) is used to set up the contact algorithm and fluid-solid coupling. Based on the M-C strength criterion, the whole process of the true submarine landslide in the South Mediterranean is simulated and back-analyzed. The coefficient of friction is 0.052. The landslide starts at the foot of the slope and gradually develops to the interior to form a whole landslide body. The whole body of the landslide accelerates and slides along the slope. At the 15th second, the maximum speed is 14.52ms-1,after which the friction is due to friction. ResistanceSlide force, the landslide body begins to decelerate. At the 21st second, the landslide body slides into a gentle section(slope is 1.1),the sliding force is close to 0, and the speeds of different particles are different, so the diffusion occurs in the horizontal direction. In the 57s, the speed drops to 0 and the sliding stops, The final sliding distance is 420.3m. The concept of the comprehensive friction coefficient() of the contact surface of the submarine landslide was put forward, and the phenomenon of soil softening and hydroplaning caused by seawater mixing during the sliding process of the submarine landslide was characterized by , and applied to the submarine landslide movement.

In March 2015, exceptional meteoric events occurred in southern Piedmont caused a remarkable rise of the rivers water level of the Tanaro Basin with flooding and many landslides. The engineering geological study reported here, concerns a triggering of a previous landslide occurred in 1982 in the hills, shaped in the marine sedimentary succession (Lugagnano Clay, lower Pliocene) of the southern Asti Reliefs, near San Martino Alfieri village. Detailed geological, morphological and topographic surveys of this landslide, with the aim to recognize the morphological features linked to the previous landslide and those connected to the triggering of it, have been carried out. The reactivation of the landslide was highlighted by the presence of a main scarp with minor escarpments and tracks. The mechanism activation of the main landslide is due to a rotational movement. To define the engineering geological model of the landslide body, standard cone penetration tests. rotary drilling borings with S.P.T. and geotechnical laboratory tests were performed. Through surveys, both main slip surface and deep-water seepage have been detected. In details, failure mechanism in OC clays was caused by: a) rapid increase in the bulk density or volume weight during rainfall events; b) rise of interstitial pressures along the sliding surface with reduction of normal stress and consequent reduction of the shear strength along this surface (progressive failure); c) reduction of cohesion and friction angle, due to clay softening. The results of the study have highlighted the need, as a primary factor of slopes consolidation, to install sub-horizontal drainage pipes in order both to avoid subsoil imbibition and to control the changes of interstitial pressure. The consolidation works focused on the construction of containment structures with deep consolidation and the execution of drainage works in the landslide area.

A first, we used our knowledge of Fourier series to solve several interesting boundary value problems by the method of separation of variables. The success of our method depended to a large extent on the fact that the domains under consideration were easily described in Cartesian coordinates. In this paper/research we address problems where the domains are easly described in polar and cylindrical coordinates. Spesifically we consider boundary value problems for the wave, heat, Laplace and Poisson equation over disks or cylinders. Upon restating these problems in suitable coordinat systems and separating variables, we will encounter new ordinary differential equations, Bessel’s equation, whose solutions are called Bessel function in ways analogous to Fourier series expansions. The vibrations of the membrane are governed by the two-dimensional wave equation, which will be expressed in polar coordinantes, because these are the coordinates best suited to this problem. Finally, we will solve the two dimensional wave equation in polar coordinates (general case).

<p>The spatial impact of a single shallow landslide is small compared to a deep-seated, impactful failure and hence its damage potential localized and limited. Yet, their higher frequency of occurrence and spatio-temporal correlation in response to external triggering events such as strong precipitation, nevertheless result in dramatic risks for population, infrastructure and environment. It is therefore essential to continuously investigate and analyze the spatial hazard that shallow landslides pose. Its visualisation through regularly-updated, dynamic hazard maps can be used by decision and policy makers. Even though a number of data-driven approaches for shallow landslide hazard mapping exist, a generic workflow has not yet been described. Therefore, we introduce a scalable and modular machine learning-based workflow for shallow landslide hazard prediction in this study. The scientific test case for the development of the workflow investigates the rainfall-triggered shallow landslide hazard in Switzerland. A benchmark dataset was compiled based on a historic landslide database as presence data, as well as a pseudo-random choice of absence locations, to train the data-driven model. Features included in this dataset comprise at the current stage 14 parameters from topography, soil type, land cover and hydrology. This work also focuses on the investigation of a suitable approach to choose absence locations and the influence of this choice on the predicted hazard as their influence is not comprehensively studied. We aim at enabling time-dependent and dynamic hazard mapping by incorporating time-dependent precipitation data into the training dataset with static features. Inclusion of temporal trigger factors, i.e. rainfall, enables a regularly-updated landslide hazard map based on the precipitation forecast. Our approach includes the investigation of a suitable precipitation metric for the occurrence of shallow landslides at the absence locations based on the statistical evaluation of the precipitation behavior at the presence locations. In this presentation, we will describe the modular workflow as well as the benchmark dataset and show preliminary results including above mentioned approaches to handle absence locations and time-dependent data.</p>

The present paper focuses on a comparison of cubic equations of state (EoS) with accurate Span-Wagner (SW) EoS. Aungier Redlich-Kwong (ARK) EoS, Soave Redlich-Kwong (SRK) EoS and standard Peng-Robinson (PR) EoS were chosen as the basic EoS implemented into ANSYS CFX commercial solver. Furthermore, modeling of transport properties was also considered. Rigid Non Interacting Sphere (NIS) and Interacting Sphere (IS) viscosity models were chosen for a comparison with REFPROP data. Analytically calculated density and viscosity were compared with the REFPROP values for 1 polar (ethanol) and 2 non-polar (R245fa, MDM) fluids at the first part of the investigation. This part showed no significant difference between compared EoS for the non-polar fluids and slightly lower accuracy of PR EoS for the polar fluid. A significant difference between NIS and IS models was showed. 2D CFD simulations of VKI LS-89 cascade were performed for both MDM and MD4M siloxanes at the second part. It was showed that a preliminary analysis of the fundamental gasdynamic derivative behavior for isentropic expansion is needed for choosing of an appropriate cubic EoS. The choice of NIS or IS transport models does not show a significant effect on the obtained results.

The impact of land use- and climate change on the managed eco-geomorphic balance in the Alps

Thermodynamic and Gasdynamic Aspects of a Boiling Liquid Expanding Vapour Explosion

Load bearing capacity of subgrade soil is of great importance to the integrity of pavement. Soaked CBR of subgrade soil is used as a design parameter for determining the total thickness of a pavement for an estimated ESAL. However, determination of soaked CBR values for pavement design involves soaking a large number of representative soil samples for four days. This is both time consuming and economically discouraging. Establishment of mathematical models for determining soaked CBR values for different types of soils using their index properties, dry densities and unsoaked CBR values is likely to aid design more quickly. With this background in mind, in this study soil samples were collected from sub-grade of an existing flexible pavement in Savar Cantonment Area, Dhaka, Bangladesh. The soil samples were then tested and the index properties were determined. The tested soil samples were identified as Lean Clay and CBR test was performed both in soaked and unsoaked conditions at different densities. The test results of the sample soil have led to the formulation of three empirical equations for predicting soaked CBR values. Index properties of soil from grain size analysis, Atterberg limits test and compaction characteristics from CBR test are used in the first equation to predict soaked CBR value of this lean clay soil. The second equation relates dry density with soaked CBR whereas the third equation relates unsoaked CBR with soaked CBR values for a varying range of dry densities. These equations may be used to predict soaked CBR value where the sub-grade consists of Lean Clay.

Slope movements are among the most widespread and damaging natural hazards in Hungary and worldwide. In recent decades, the occurrence and impact of landslides and related mass movements have markedly increased, a trend commonly linked to ongoing climate change. This study presents a landslide hazard assessment of climate-sensitive slope processes affecting the Danube riverside built structures and houses at the Dunaszekcső high bank, Hungary (Central Europe), focusing on the loess bluff area, where several slope failures and erosional events have been documented in recent decades. The study area is located on the steep Danube-facing slopes of the settlement high bank, composed mainly of Pleistocene loess, loess-derived paleosols, and interbedded sandy and clayey sediments. These lithologies exhibit strong variability in cohesion, permeability, and moisture sensitivity and are covered by shallow soils, resulting in high susceptibility to surface erosion, earth slides, and loess collapses. Steep slopes, locally sparse vegetation, and unfavourable slope exposure further increase landslide hazard. The applied methodology integrates detailed field mapping, geomorphological and engineering geological analysis, and evaluation of long-term and event-based precipitation data. Special attention was given to the identification of active sliding areas and the trigger mechanism. The results indicate that both short, high-intensity convective storms and prolonged rainfall events can initiate landslides. Under current and projected climatic conditions, slope failures and sediment mobilisation are expected, highlighting the urgent need for integrated landslide risk mitigation strategies. These include continuous slope monitoring, rainfall-based early-warning systems, and targeted structural and non-structural protection measures. The paper benefited from the results of GeoNetSee project “An AI/IoT-based system of GEOsensor NETworks for real-time monitoring of unStablE tErrain and artificial structures”, which is financed through the Interreg Danube Region programme, contract DRP0200783.

Abstract. The Umbria Region of Central Italy has a long history of mass movements. Landslides range from fast moving rock falls and debris flows, most abundant in mountain areas, to slow moving complex failures extending up to several hectares in the hilly part of the Region. Despite landslides occurring every year in Umbria, their impact remains largely unknown. We present an estimate of the impact of slope failures in the Umbria region based on the analysis of a catalogue of historical information on landslide events, a recent and detailed regional landslide inventory map, and three event inventories prepared after major landslide triggering events. Emphasis is given to the impact of landslides on the population, the transportation network, and the built-up areas. Analysis of the available historical information reveals that 1488 landslide events occurred at 1292 sites in Umbria between 1917 and 2001. In the same period 16 people died or were missing and 31 people were injured by slope movements. Roads and railways were damaged by slope failures at 661 sites, and 281 built-up areas suffered landslide damage. Three event inventories showing landslides triggered by high intensity rainfall events in the period 1937–1941, rapid snow melting in January 1997, and earthquakes in September–October 1997, indicate the type, abundance and distribution of damage to the population, the built-up areas and the transportation network caused by typical landslide-triggering events. Analysis of a geomorphological landslide inventory map reveals that in some of the municipalities in the region total landslide area exceeds 25%. Of the more than 45 700 landslide areas shown in the geomorphological inventory map, 4115 intersect a road or railway, and 6119 intersect a built-up area. In these areas slope failures can be expected during future landslide triggering events.

List of Examples Preface 1. Introduction. Boundary Value Problems for Ordinary Differential Equations Boundary Value Problems in Applications 2. Review of Numerical Analysis and Mathematical Background. Errors in Computation Numerical Linear Algebra Nonlinear Equations Polynomial Interpolation Piecewise Polynomials, or Splines Numerical Quadrature Initial Value Ordinary Differential Equations Differential Operators and Their Discretizations 3. Theory of Ordinary Differential Equations. Existence and Uniqueness Results Green's Functions Stability of Initial Value Problems Conditioning of Boundary Value Problems 4. Initial Value Methods. Introduction. Shooting Superposition and Reduced Superposition Multiple Shooting for Linear Problems Marching Techniques for Multiple Shooting The Riccati Method Nonlinear Problems 5. Finite Difference Methods. Introduction Consistency, Stability, and Convergence Higher-Order One-Step Schemes Collocation Theory Acceleration Techniques Higher-Order ODEs Finite Element Methods 6. Decoupling. Decomposition of Vectors Decoupling of the ODE Decoupling of One-Step Recursions Practical Aspects of Consistency Closure and Its Implications 7. Solving Linear Equations. General Staircase Matrices and Condensation Algorithms for the Separated BC Case Stability for Block Methods Decomposition in the Nonseparated BC Case Solution in More General Cases 8. Solving Nonlinear Equations. Improving the Local Convergence of Newton's Method Reducing the Cost of the Newton Iteration Finding a Good Initial Guess Further Remarks on Discrete Nonlinear BVPS 9. Mesh Selection. Introduction Direct Methods A Mesh Strategy for Collocation Transformation Methods General Considerations 10. Singular Perturbations. Analytical Approaches Numerical Approaches Difference Methods Initial Value Methods 11. Special Topics. Reformulation of Problems in 'Standard' Form Generalized ODEs and Differential Algebraic Equations Eigenvalue Problems BVPs with Singularities Infinite Intervals Path Following, Singular Points and Bifurcation Highly Oscillatory Solutions Functional Differential Equations Method of Lines for PDEs Multipoint Problems On Code Design and Comparison Appendix A. A Multiple Shooting Code Appendix B. A Collocation Code References Bibliography Index.