THM-coupled numerical analysis of temperature and groundwater level in-situ measurements in artificial ground freezing

Belarusian Potash salt deposits are bedded under aquifers and unstable soil stratums. Therefore, to develop the deposits a vertical mine shaft sinking is performed using the artificial ground freezing technology. Nowadays, real time observations of ground temperature and groundwater level is applied to control the ground freezing process. Numerical simulation can be used for a comprehensive analysis of measurements results. In this paper a thermo-hydro-mechanical model of freezing of water saturated soil is proposed. The governing equations of the model are based on balance laws for mass, energy and momentum for a fully saturated porous media. Clausius-Clayperon equation and poroelastic constitutive relations are adopted for description of a coupled change in water and ice pore pressure, porosity and a stress-strain state of freezing soil. The proposed model enables us to describe evolution of equivalent water content measured in Mizoguchi’s test and predict frost heave strain in one-sided freezing test. Numerical simulation of ground freezing in the Petrikov mining complex located in Belarus has shown that the model is able to describe field measurements of pore pressure inside a forming frozen wall. Furthermore, the mismatch between hydro- and thermo-monitoring data obtained during the artificial freezing is analyzed

Finite-element simulation of residual stresses induced by laser shock peening in TC4 samples structurally similar to a turbine blade

This study is devoted to the investigation of residual stresses distribution (RSD) in a TC4 sample treated with laser shock peening. The study placed special emphasis on analyzing the RSD at the part of the samples structurally similar to a turbine blade, which is more frequently subjected to damage during service according to the aircraft statistics. Results of simulation showed that low power density of 1.11 GWt/cm2 could not induce compressive residual stress on the surface of a treated object. Furthermore, increasing the overlapping of laser spots does not improve the situation and still fail to induce surface compressive residual stress at a laser intensity of 1.11 GWt/cm2. The compressive stresses occur only with the rise in power density. Reducing the spot size from 3 mm to 1 mm for the power density of 10 GWt/cm2 results in a 20% increase in the magnitude of compressive residual stress in the area of interest. Moreover, applying 35% overlapping further enhances this value. In addition to increasing the magnitude of residual stress, this approach also leads to a more homogeneous RSD of the treated material

Finite-element study of residual stress distribution in Ti-6Al-4V alloy treated by laser shock peening with varying parameters

Laser shock peening (LSP) is used to enhance surface quality of the metallic structures by the generation of compressive residual stresses on it. This work studies the effect of the main LSP parameters on residual stress fields by the finite-element method. The specimen under investigation is a square plate with a thickness of 3 mm made of Ti-6Al-4V. The performed analysis enhances understanding of LSP application to structures manufactured from this material and this information can be useful for a choice of optimal peening parameters. The effect of the spot size and shape, the pulse energy, the number of peen layers, overlapping of spots and temporal variation of the mechanical pressure induced by plasma is considered and analyzed. A 3D finite-element model based on the Johnson-Cook constitutive relation is developed and verified by the results of residual stress measurements performed for the LSP-treated samples under different conditions. From the obtained results the following main conclusions can be drawn: pulse energy provides the more significant effect although the resulting residual stresses profile tends to some saturation curve; temporal pressure pulse shape and its total duration also substantially alter the residual stress field; the least significant parameter is the spot shape

Fatigue life investigation of notched TC4 specimens subjected to different patterns of laser shock peening

The exhaustion of constructive ways for increasing the service life of parts has led to the development of new methods which can improve their material properties during operation under various loading conditions. Laser shock peening (LSP) induces compressive residual stress field which prevents fatigue crack initiation and propagation in components. Characteristics of laser impact and treatment patterns play an important role in efficiency of LSP application for improvement of fatigue properties. This work is devoted to the experimental examination of two LSP patterns to reveal the most optimal scheme from fatigue live improvement point of view. Proposed LSP pattern allowed one to increase the fatigue life of specimens with semi-circular notch by an order of magnitude. The numerical simulation of the LSP was performed to visualize the residual stress field of treated specimen after loading and to give the interpretation of the experimentally observed improvement of fatigue life

Numerical analysis of a caprock integrity during oil production by steam-assisted gravity drainage method

The work is devoted to the investigation of a caprock integrity during oil production by steam-assisted gravity drainage method. An originally proposed thermo-hydro-mechanical model was used for the evaluation of mechanical loading acting on the over-burden. The model includes mass conservation laws, the energy conservation law and the linear momentum balance. Filtration of each phase of the three-phase flow (steam, oil and water) is described by Darcy’s law. Inelastic deformations are described by the phenomenological viscoplastic model based on Drucker-Prager yield criterion.  The effect of  the porosity evolution induced by the propagation of the steam chamber within the reservoir on the oil production rate and the caprock integrity is studied. It has been shown that the oil production rate is strongly depend on the prevailing physical mechanism of the porosity evolution.  Reservoirs characterized by the volumetric strain mechanism of the porosity evolution produce slightly higher values of the mechanical loadings acting on the over-burden

Numerical Simulation of Heavy Oil Recovery by Steam-Assisted Gravity Drainage Method

Steam-assisted gravity drainage method (SAGD) is an efficient technique for a heavy oil recovery which is characterized by values of recovery factor up to 0.8. This work is devoted to the three-dimensional field-scale numerical simulation of SAGD taking into account various kind of non-uniformity induced by technological reasons as well as heterogeneous structure of the reservoir. The proposed coupled thermo-hydro-mechanical model includes conservation laws of momentum, mass and energy which are supplemented by constitutive equations and state laws. Results have shown that oil production rate is significantly affected by the presence of the barrier layers as well as non-uniformity of the steam propagation along the horizontal wellbore

Numerical Simulation of Coupled Thermo-Hydro-Mechanical Processes in Freezing Soils

In the study a thermo-hydro-mechanical model of freezing of saturated soil is presented, with focus on numerical simulation of artificial ground freezing (AGF). Artificial freezing of saturated soils induces such process in the soils as water migration, frost heave and consolidation which can have an effect on the freezing process and surrounding areas. To take into account the important from geotechnical point of view processes the thermo-hydromechanical model was developed. The model is based on the fundamental balance equations of continuum media mechanics. The Clausius-Clapeyron equation and constitutive relations of poromechanics are used for describing a relationship between pore pressure, temperature, stress and strain fields. Also an inelastic strain is included accounting for an effect of frost heave. The equations of the model were implemented in Comsol Multiphysics® software and solved using the finite element method relative to variables of porosity temperature and displacement. Numerical simulation of artificial freezing of a soil stratum for a vertical shaft sinking was carried out. A mesh convergence of numerical solution was analyzed. Results of the simulation have shown the model enables to describe a frozen wall formation with a coupled change of porosity, water pore pressure, volumetric strain and mean stress

Fatigue life investigation of notched TC4 specimens subjected to different patterns of laser shock peening

The exhaustion of constructive ways for increasing the service life of parts has led to the development of new methods which can improve their material properties during operation under various loading conditions. Laser shock peening (LSP) induces compressive residual stress field which prevents fatigue crack initiation and propagation in components. Characteristics of laser impact and treatment patterns play an important role in efficiency of LSP application for improvement of fatigue properties. This work is devoted to the experimental examination of two LSP patterns to reveal the most optimal scheme from fatigue live improvement point of view. Proposed LSP pattern allowed one to increase the fatigue life of specimens with semi-circular notch by an order of magnitude. The numerical simulation of the LSP was performed to visualize the residual stress field of treated specimen after loading and to give the interpretation of the experimentally observed improvement of fatigue life

Tau Neutrinos in the Next Decade: from GeV to EeV

Tau neutrinos are the least studied particle in the Standard Model. Thiswhitepaper discusses the current and expected upcoming status of tau neutrinophysics with attention to the broad experimental and theoretical landscapespanning long-baseline, beam-dump, collider, and astrophysical experiments.This whitepaper was prepared as a part of the NuTau2021 Workshop.<br