An evolutionary approach to modelling the thermo-mechanical behaviour of unsaturated soils

A new data mining approach is presented for modelling of the stress-strain and volume change behaviour of unsaturated soils considering temperature effects. The proposed approach is based on the evolutionary polynomial regression (EPR), which unlike some other data mining techniques, generates a transparent and structured representation of the behaviour of systems directly from raw experimental (or field) data. The proposed methodology can operate on large quantities of data in order to capture nonlinear and complex relationships between contributing variables. The developed models allow the user to gain a clear insight into the behaviour of the system. Unsaturated triaxial test data from literature was used for development and verification of EPR models. The developed models were also used (in a coupled manner) to produce the entire stress path of triaxial tests. Comparison of the EPR model predictions with the experimental data revealed the robustness and capability of the proposed methodology in capturing and reproducing the constitutive thermo-mechanical behaviour of unsaturated soils. More importantly, the capability of the developed models in accurately generalising the predictions to unseen data cases was illustrated. The results of a sensitivity analysis showed that the models developed from data are able to capture and represent the physical aspects of the unsaturated soil behaviour accurately. The merits and advantages of the proposed methodology are also discussed

Engineering properties of soil /

Bibliography: p. 417-426.Mode of access: Internet

Formation and Dissociation of Methane Hydrates from Seawater in Consolidated Sand: Mimicking Methane Hydrate Dynamics beneath the Seafloor

Methane hydrate formation and dissociation kinetics were investigated in seawater-saturated consolidated Ottawa sand-pack under sub-seafloor conditions to study the influence of effective pressure on formation and dissociation kinetics. To simulate a sub-seafloor environment, the pore-pressure was varied relative to confining pressure in successive experiments. Hydrate formation was achieved by methane charging followed by sediment cooling. The formation of hydrates was delayed with increasing degree of consolidation. Hydrate dissociation by step-wise depressurization was instantaneous, emanating preferentially from the interior of the sand-pack. Pressure drops during dissociation and in situ temperature controlled the degree of endothermic cooling within sediments. In a closed system, the post-depressurization dissociation was succeeded by thermally induced dissociation and pressure-temperature conditions followed theoretical methane-seawater equilibrium conditions and exhibited excess pore pressure governed by the pore diameter. These post-depressurization equilibrium values for the methane hydrates in seawater saturated consolidated sand-pack were used to estimate the enthalpy of dissociation of 55.83 ± 1.41 kJ/mol. These values were found to be lower than those reported in earlier literature for bulk hydrates from seawater (58.84 kJ/mol) and pure water (62.61 kJ/mol) due to excess pore pressure generated within confined sediment system under investigation. However, these observations could be significant in the case of hydrate dissociation in a subseafloor environment where dissociation due to depressurization could result in an instantaneous methane release followed by slow thermally induced dissociation. The excess pore pressure generated during hydrate dissociation could be higher within fine-grained sediments with faults and barriers present in subseafloor settings which could cause shifting in geological layers

Implementing Infection Control and Quality of Life Best Practices in Nursing Homes With Project ECHO: Protocol for a Patient-Centered Randomized Controlled Trial

BackgroundNursing homes in the United States were devastated by COVID-19, with 710,000 cases and 138,000 deaths nationally through October 2021. Although facilities are required to have infection control staff, only 3% of designated infection preventionists have taken a basic infection control course prior to the COVID-19 pandemic. Most research has focused on infection control in the acute care setting. However, little is known about the implementation of infection control practices and effective interventions in nursing homes. This study utilizes Project ECHO (Extension for Community Health Outcomes), an evidence-based telementoring model, to connect Penn State University subject matter experts with nursing home staff and administrators to proactively support evidence-based infection control guideline implementation. ObjectiveOur study seeks to answer the research question of how evidence-based infection control guidelines can be implemented effectively in nursing homes, including comparing the effectiveness of two ECHO-delivered training interventions on key patient-centered outcomes such as reducing the number of residents with a COVID-19 diagnosis. MethodsA stratified cluster randomized design was utilized. Using a 1:1 ratio, we randomly assigned 136 nursing homes to ECHO or ECHO Plus arms. Randomization was stratified by geographic location, baseline COVID-19 infection rate, and facility capacity. The study had two phases. In phase one, completed in July 2021, nursing homes in both study arms received a 16-week infectious disease and quality improvement training intervention via real-time, interactive videoconferencing and the ECHO learning model. Phase one sessions were up to 90 minutes in duration. In phase two, completed in November 2021, the ECHO group was offered optional 60-minute office hours for 9 weeks and the ECHO Plus group received 9 weeks of 60-minute sessions on emerging topics and an additional 8-session refresher series on infection control. ResultsA total of 290 nursing home facilities were assessed for eligibility, with 136 nursing homes recruited and randomly assigned to ECHO or ECHO Plus. Guided by the Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework, we will simultaneously evaluate the study’s effectiveness and implementation outcomes at baseline (intervention start date), and at 4, 6, 12, and 18 months. The primary outcome is the COVID-19 infection rate in nursing homes. Secondary outcomes include COVID-19 hospitalizations and deaths, flu-like illness, and quality of life. Surveys and interviews with participants will also provide data as to the adoption, implementation, and maintenance of best practices taught throughout ECHO sessions. ConclusionsA multipronged approach to improving infection control and emergency preparedness in nursing homes is important, given the toll that the COVID-19 pandemic has taken on residents and staff. The ECHO model has significant strengths when compared to traditional training, as it allows for remote learning delivered by a multidisciplinary team of experts, and utilizes case discussions that match the context and capacity of nursing homes. Trial RegistrationClinicalTrials.gov NCT04499391; https://clinicaltrials.gov/ct2/show/NCT0449939