{"id":19789,"date":"2025-08-20T17:17:38","date_gmt":"2025-08-20T15:17:38","guid":{"rendered":"https:\/\/navier-lab.fr\/?p=19789"},"modified":"2025-08-20T17:18:02","modified_gmt":"2025-08-20T15:18:02","slug":"phd-defense-hassan-al-mais","status":"publish","type":"post","link":"https:\/\/navier-lab.fr\/en\/phd-defense-hassan-al-mais\/","title":{"rendered":"PhD Defense \u2013 Hassan Al Mais"},"content":{"rendered":"<section class=\"kc-elm kc-css-654950 kc_row\"><div class=\"kc-row-container  kc-container\"><div class=\"kc-wrap-columns\"><div class=\"kc-elm kc-css-166989 kc_col-sm-12 kc_column kc_col-sm-12\"><div class=\"kc-col-container\"><div class=\"kc-elm kc-css-235930 kc_text_block\"><\/p>\n<p style=\"text-align: justify;\">Hassan Al Mais, a PhD candidate in the Geotechnics team, will defend his dissertation titled <em>&#8220;Effect of pore fluid chemistry on the hydro-mechanical behaviour of Boom Clay: C-H-M coupling of Boom Clay\"<\/em> on <strong>Monday, September 1st, at 2:00 PM<\/strong>, in the Bienven\u00fce amphitheater.<\/p>\n<p><strong>Composition of the jury:<\/strong><\/p>\n<ul type=\"disc\">\n<li data-ogsc=\"black\"><span data-ogsc=\"\" data-olk-copy-source=\"MessageBody\">Prof. Olivier CUISINNIER (Universit\u00e9 de Lorraine) \u2013 Reviewer<\/span><\/li>\n<li data-ogsc=\"black\"><span data-ogsc=\"\">Prof. Jian-Fu SHAO (Universit\u00e9 de Lille) \u2013 Reviewer<\/span><\/li>\n<li data-ogsc=\"black\"><span data-ogsc=\"\">Prof. Anne-Catherine DIEUDONN\u00c9 (TU Delft) \u2013 Examiner<\/span><\/li>\n<li data-ogsc=\"black\"><span data-ogsc=\"\">Prof. Bertrand FRAN\u00c7OIS (Universit\u00e9 de Li\u00e8ge) \u2013 Examiner<\/span><\/li>\n<li data-ogsc=\"black\"><span data-ogsc=\"\">Dr. S\u00e9verine LEVASSEUR (ONDRAF\/NIRAS) \u2013 Examiner<\/span><\/li>\n<li data-ogsc=\"black\"><span data-ogsc=\"\">Dr. Elie VALCKE (SCK CEN) \u2013 Examiner<\/span><\/li>\n<li data-ogsc=\"black\"><span data-ogsc=\"\">Prof. Yu-Jun CUI (\u00c9cole des Ponts ParisTech) \u2013 Supervisor<\/span><\/li>\n<li data-ogsc=\"black\"><span data-ogsc=\"\">Prof. Fr\u00e9d\u00e9ric COLLIN (Universit\u00e9 de Li\u00e8ge) \u2013 Co-supervisor<\/span><\/li>\n<li data-ogsc=\"black\"><span data-ogsc=\"\">Dr. Temenuga GEORGIEVA (EURIDICE) \u2013 Co-supervisor<\/span><\/li>\n<li data-ogsc=\"black\"><span data-ogsc=\"\">Dr. Suresh SEETHARAM (SCK CEN) \u2013 Co-supervisor<\/span><\/li>\n<\/ul>\n<p>The defense will be broadcasted live on Microsoft Teams. You can follow it here: <span lang=\"pt-BR\"><a href=\"https:\/\/teams.microsoft.com\/l\/meetup-join\/19%3ameeting_YWUzZGI1YmMtNWJkOS00NTRhLThhYzMtYjdkNWZjODViZmMx%40thread.v2\/0?context=%7b%22Tid%22%3a%22cbc292d3-d274-4204-9169-16847b678004%22%2c%22Oid%22%3a%224e8a1eae-8039-44cb-83f2-cad610d7ce2d%22%7d\">Teams Link<\/a><a id=\"LPlnk597974\" title=\"https:\/\/www.youtube.com\/live\/Np1YNzuLjdw\" href=\"https:\/\/www.youtube.com\/live\/Np1YNzuLjdw\" target=\"_blank\" rel=\"noopener noreferrer\" data-auth=\"NotApplicable\" data-linkindex=\"0\" data-ogsc=\"\"><\/a><\/span><\/p>\n<p>\n<\/div><div data-closeall=\"true\" class=\"kc-elm kc-css-635020 kc_accordion_wrapper\">\n    <h3 class=\"kc-accordion-title\">Abstract<\/h3>\n<div class=\"kc-elm kc-css-865887 kc_accordion_section group \"><h3 class=\"kc_accordion_header ui-accordion-header\"><span class=\"ui-accordion-header-icon ui-icon\"><\/span><a href=\"#show-the-abstract\" data-prevent=\"scroll\"><i class=\"\"><\/i> Show the abstract<\/a><\/h3><div class=\"kc_accordion_content ui-accordion-content kc_clearfix\"><div class=\"kc-panel-body\"><div class=\"kc-elm kc-css-149022 kc_text_block\"><\/p>\n<p style=\"text-align: justify;\">Deep geological disposal is one of the technological options for the long-term management of radioactive waste by isolating harmful radionuclides from the biosphere through a system of engineered and geological barriers. In Belgium, Boom Clay is considered a reference host formation due to its low permeability, high retention capacity, self-sealing behavior, and favorable mechanical properties. Among the waste forms intended for disposal, Eurobitum waste, produced by bituminization of reprocessing effluents, contains high concentrations of (Na,Ca)NO3. Under repository conditions, the bitumen matrix gradually absorbs water and swells, resulting in the progressive release of the embedded salts that diffuse into the surrounding clay formation. This hypersaline plume induces chemical perturbations that can affect the hydro-mechanical behavior of Boom Clay by altering its microstructure, swelling capacity, and strength.<\/p>\n<p style=\"text-align: justify;\">This thesis presents an investigation of the influence of salinity (Ionic Strengths: 0.015 M, 1.0 M, and 2.0 M) and sodium occupancy (60% and 90%) on the hydro-mechanical behavior of Boom Clay by combining a dedicated experimental campaign with the development of a chemo-mechanical constitutive modeling approach. The experimental program includes swelling pressure measurements under constant-volume conditions, salinization and desalinization tests under oedometric conditions, high-pressure oedometric tests, undrained shear strength tests, and microstructural analyses using mercury intrusion porosimetry. The results demonstrate that increasing salinity leads to a reduction in swelling pressure, an increase in shear strength, and modifications of the aggregate structure, especially at high ionic strengths, which also result in increased hydraulic conductivity. While the observed effects of ionic strength are qualitatively consistent with findings reported for other clay materials, the study provides new insights into the role of sodium occupancy\u2014particularly its potential influence on interlayer spacing\u2014in shaping the chemo-hydro-mechanical response of Boom Clay.<\/p>\n<p style=\"text-align: justify;\">To interpret and predict these coupled effects, a chemo-mechanical constitutive model named ACC2-Chem was developed. The starting point was the ACC-2 elasto-plastic model, initially formulated under in-situ pore water conditions (Ionic Strength = 0.015 M), by introducing a cohesion parameter into both the yield surface and the plastic flow rule to better represent the mechanical response of Boom Clay. In parallel, a new chemo-elastic volumetric strain model was developed to describe the elastic deformations induced by changes in ionic strength and sodium occupancy. This chemo-elastic model was then coupled with ACC-2, resulting in the integrated ACC2-Chem model that captures the chemo-hydro-mechanical interactions in Boom Clay. The model was implemented in the finite element code LAGAMINE and calibrated using set of laboratory data. Its validity was verified by reproducing the main trends observed in salinization\/desalinization and triaxial tests at the laboratory scale.<\/p>\n<p style=\"text-align: justify;\">Finally, 2D repository-scale simulations were conducted to evaluate the long-term chemo-hydro-mechanical behavior of Boom Clay under high salinity perturbations using a decoupled approach. The simulations capture the phenomenological evolution of the repository through four sequential phases: (1) an initial excavation phase lasting one day, (2) a 100-year operational phase under drained conditions, (3) a 300-year post-operational equilibrium phase, and (4) a 500-year swelling and\/or diffusion phase simulating long-term interactions between Eurobitum waste and Boom Clay.<\/p>\n<p style=\"text-align: justify;\">The above findings have contributed to the current understanding of the behavior of Boom Clay under short term exposure to chemically perturbed environments, and has provided theoretical underpinning for a mathematical framework that may support safety and performance assessments for the geological disposal of bituminized radioactive waste in Belgium.<\/p>\n<p>\n<\/div><\/div><\/div><\/div><\/div>\n<\/div><\/div><\/div><\/div><\/section>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":158,"featured_media":19793,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[251,291],"tags":[],"class_list":["post-19789","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-annonces-en","category-annonces-geotech-en"],"acf":[],"_links":{"self":[{"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/posts\/19789","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/users\/158"}],"replies":[{"embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/comments?post=19789"}],"version-history":[{"count":2,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/posts\/19789\/revisions"}],"predecessor-version":[{"id":19796,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/posts\/19789\/revisions\/19796"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/media\/19793"}],"wp:attachment":[{"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/media?parent=19789"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/categories?post=19789"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/navier-lab.fr\/en\/wp-json\/wp\/v2\/tags?post=19789"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}