Numerical modeling for the coupled thermo-mechanical processes and spalling phenomena in sp Pillar Stability Experiment (APSE)

In this paper, the coupled thermo-mechanical （TM） processes in the AEspoe Pillar Stability Experiment （APSE） carried out by the Swedish Nuclear Fuel and Waste Management Company （SKB） were simulated using both continuum and discontinuum based numerical methods. Two-dimensional （2D） and three- dimensional （3D） finite element method （FEM） and 2D distinct element method （DEM） with particles were used. The main objective for the large scale in situ experiment is to investigate the yielding strength of crystalline rock and the formation of the excavation disturbed/damaged zone （EDZ） during excavation of two boreholes, pressurizing of one of the boreholes and heating. For the DEM simulations, the heat flow algorithm was newly introduced into the original code. The calculated stress, displacement and temperature distributions were compared with the ones obtained from in situ measurements and FEM simulations. A parametric study for initial microcracks was also performed to reproduce the spalling phenomena observed in the APSE.

Numerical study on coupled thermo-mechanical processes in sp Pillar Stability Experiment

This paper presents a study of the full three-dimensional thermo-mechanical （TM） behavior of rock pillar in,Aspo Pillar Stability Experiment （APSE） using a self-developed numerical code TM-EPCA3D. The transient thermal conduction function was descritized on space and time scales, and was solved by using cellular automaton （CA） method on space scale and finite difference method on time scale, respectively. The advantage of this approach is that no global, but local matrix is used so that it avoids the need to develop and solve large-scale linear equations and the complexity therein. A thermal conductivity versus stress function was proposed to reflect the effect of stress on thermal field. The temperature evolution and induced thermal stress in the pillar part during the heating and cooling processes were well simulated by the developed code. The factors that affect the modeling results were discussed. It is concluded that, the complex TM behavior of Aspo rock pillar is significantly influenced by the complex boundary and initial conditions.

Analysis of sp Pillar Stability Experiment: Continuous thermo-mechanical model development and calibration

The paper describes an analysis of thermo-mechanical （TM） processes appearing during the Aspo Pillar Stability Experiment （APSE）. This analysis is based on finite elements with elasticity, plasticity and dam- age mechanics models of rock behaviour and some least squares calibration techniques. The main aim is to examine the capability of continuous mechanics models to predict brittle damage behaviour of gran- ite rocks. The performed simulations use an in-house finite element software GEM and self-developed experimental continuum damage MATLAB code. The main contributions are twofold. First, it is an inverse analysis, which is used for （1） verification of an initial stress measurement by back analysis of conver- gence measurement during construction of the access tunnel and （2） identification of heat transfer rock mass properties by an inverse method based on the known heat sources and temperature measurements. Second, three different hierarchically built models are used to estimate the pillar damage zones, i.e. elas- tic model with Drucker-Prager strength criterion, elasto-plastic model with the same yield limit and a combination of elasto-plasticity with continuum damage mechanics. The damage mechanics model is also used to simulate uniaxial and triaxial compressive strength tests on the ,Aspo granite.

Generation of Accelerated Stability Experiment Profile of Inertial Platform Based on Finite Element

The residual stress generated in the manufacturing process of inertial platform causes the drift of inertial platform parameters in long-term storage condition.However,the existing temperature cycling experiment could not meet the increased repeatability technical requirements of inertial platform parameters.In order to solve this problem,in this paper,firstly the Unigraphics（UG） software and the interface compatibility of ANSYS software are used to establish the inertial platform finite element model.Secondly,the residual stress is loaded into finite element model by ANSYS function editor in the form of surface loads to analyze the efficiency.And then,the generation based on ANSYS simulation inertial platform to accelerate the stability of experiment profile is achieved by the application of the analysis method of orthogonal experimental design and ANSYS thermal-structural coupling.The optimum accelerated stability experiment profile is determined finally,which realizes the rapid,effective release of inertial platform residual stress.The research methodology and conclusion of this paper have great theoretical and practical significance to the production technology of inertial platform.

Numerical modeling of coupled thermo-mechanical response of a rock pillar

Understanding the rock mass response to excavation and thermal loading and improving the capability of the numerical models for simulating the progressive failure process of brittle rocks are important for safety assessment and optimization design of nuclear waste repositories.The international cooperative DECOVALEX-2011 project provides a platform for development,validation and comparison of numerical models,in which the sp pillar stability experiment（APSE） was selected as the modeling target for Task B.This paper presents the modeling results of Wuhan University（WHU） team for stages 1 and 2 of Task B by using a coupled thermo-mechanical model within the framework of continuum mechanics.The rock mass response to excavation is modeled with linear elastic,elastoplastic and brittle-plastic models,while the response to heating is modeled with a coupled thermo-elastic model.The capabilities and limitations of the model for representation of the thermo-mechanical responses of the rock pillar are discussed by comparing the modeling results with experimental observations.The results may provide a helpful reference for the stability and safety assessment of the hard granite host rock in China＇s Beishan preselected area for high-level radioactive waste disposal.

Thermo-mechanical coupling analysis of APSE using submodels and neural networks

The ,Aspoe Pillar Stability Experiment （APSE） is an in situ experiment for investigating the spalling mechanism under mechanical and thermal loading conditions in a crystalline rock. In this study, the thermo-mechanical behaviors in the APSE were investigated with three models： （1） a Full model with rough meshes for calculating the influence of tunnel excavation; （2） a Submodel with fine meshes for predicting the thermo-mechanical behavior in the pillar during the borehole drilling, heating, and cool- ing phases; and （3） a Thin model for modeling the effect of slot cutting for de-stressing around the pillar. In order to import the stresses calculated from the Full model to the Submodel and to define the complex thermal boundary conditions, artificial neural networks （NNs） were utilized. From this study, it was pos- sible to conclude that the stepwise approach with the application of NNs was useful for predicting the complex response of the pillar under severe thermo-mechanical loading conditions.

Preparation and Quality Evaluation of Salicylic Acid Gel

Taking salicylic acid as the active ingredient and 10%sodium hydroxide aqueous solution as the neutralizer,the best matrix for preparing gel was screened,and the salicylic acid aqueous gel was prepared.The properties,pH value and viscosity were determined,and the stability,antibacterial activity and irritation were evaluated.The experimental results showed that the best gel matrix was cellulose,which had the best stability,could increase the solubility of salicylic acid in gel preparations,solved the problem of easy precipitation of salicylic acid crystals,enhanced the antibacterial activity,and reduced irritation,providing a reference for the application of salicylic acid in cosmetics.

Full scale amendment of a contaminated wood impregnation site with iron water treatment residues

Iron water treatment residues （Fe-WTR） are a free by-product of the treatment of drinking water with high concentration of iron oxides and potential for arsenic sorption. This paper aims at applying Fe- WTR to a contaminated site, measuring the reduction in contaminant leaching, and discussing the design of delivery and mixing strategy for soil stabilization at field scale and present a cost-effective method of soil mixing by connnon contractor machinery. Soil contaminated by As, Cr, and Cu at an abandoned wood impregnation site was amended with 0.22% （dw） Fe-WTR. To evaluate the full scale amendment a 100 mtest site and a control site （without amendment） were monitored for 14 months. Also soil analysis of Fe to evaluate the degree of soil and Fe-WTR mixing was done. Stabilization with Fe-WTR had a significant effect on leachable contaminants, reducing pore water As by 93%, Cu by 91% and Cr by 95% in the upper samplers. Dosage and mixing of Fe-WTR in the soil proved to be difficult in the deeper part of the field, and Pire water concentrations of arsenic was generally higher.Despite water logged conditions no increase in dissolved iron or arsenic was observed in the amended soil. Our field scale amendment of contaminated soil was overall successful in decreasing leaching of As, Cr and Cu. With minor improvements in the mixing and delivery strategy, this stabilization method is suggested for use in cases, where leaching ofCu, Cr and As constitutes a risk for groundwater and freshwater.