Optimizing Fiber Parameters Coupled with Chemical Treatment: PROMETHEE Approach

In order to combat issues related to expansive soils, chemical stabilization augmented with use of synthetic fibers is gaining focus in recent times. However, in most of these applications, the practicing field engineers face difficulty in selecting the right mix of fiber size, fiber dosage and stabilizer content. The decision becomes more typical, as the target is to achieve or enhance multiple geotechnical properties which differ with fiber dosage and stabilizer content based on governing mechanisms. Addressing these issues, in this study an attempt is made to present an approach for selecting fibre dosage and lime mix for a typical expansive semi-arid soil. In this article, the effect of randomly oriented polypropylene fiber inclusion in enhancing various geotechnical properties of a typical expansive semi-arid soil is studied. The addition of lime is considered in order to ensure proper bonding between clay particles and discrete fiber elements. PROMETHEE is adopted in order to assist in multi-criteria decision-making process. The approach evaluates multiple geotechnical properties for possible alternatives viz., untreated soil; lime treated soil and other including combinations of fiber dosage and fiber size in the presence of lime. The response measures being the targeted geotechnical properties which include, linear shrinkage tests, unconfined compression strength test, California Bearing Ratio behavior, compressibility characteristics and hydraulic conductivity. The study revealed the best possible alternative considering all the selected response measures

Evaluating Shallow Mixing Protocols as Application Methods for Microbial Induced Calcite Precipitation Targeting Expansive Soil Treatment

Expansive soils, also known as swell-shrink soils, undergo substantial volumetric changes due to moisture fluctuations from seasonal variations. These volumetric changes cause millions of dollars in damages annually. Microbial Induced Calcite Precipitation (MICP) is a promising soil improvement technique, which uses urease producing bacteria to precipitate calcium carbonate. In this study, a stabilization alternative for expansive soils was studied using MICP. Specifically, indigenous bacteria were stimulated by mixing enrichment and cementation solutions with expansive natural soils to precipitate calcium carbonate and make soil stronger and less expansive. This study examined three expansive soils with varying plasticity and mineralogical characteristics. Two protocols for shallow mixing were studied. In Protocol-1, soil samples were mixed with enrichment solutions at optimum moisture content and allowed to mellow for 1, 2, 3, and 4 days. In Protocol-2, soil samples were mixed with enrichment solutions at moisture content corresponding to 95% of maximum dry unit weight on the wet-side of a standard Proctor curve. Moisture was allowed to escape from the mix during the mellowing period under both protocols. Following the mellowing periods, the lost moisture is replaced with cementation solution to reach optimum moisture content, and the soil sample was compacted to its maximum dry unit weight. Unconfined compression strength test was used to evaluate the strength improvements due to treatments. The treatment effectiveness was also evaluated with measurements of calcium carbonate precipitation. The results show promise for this method as an alternative to current shallow stabilization methods. An increase in mellowing period for low and medium plastic soils was determined to be beneficial. The current results also showed that the presence of higher amounts of enrichment solution and addition of less cementation solution is not advantageous for this procedure based on the performance of Protocol-2

Effect of Fiber Reinforcement on CBR Behavior of Lime Blended Expansive Soils: Reliability Approach

Use of synthetic fibers as reinforcement to stabilize expansive soils is gaining momentum. As a contribution towards this growing field of research two different types of synthetic fibers, Fiber Mesh® and Fiber Cast®, were evaluated as a stabilization alternative for expansive soils in the presence of lime. California Bearing Ratio (CBR) is chosen as a performance indicator as it is a good pointer towards pavement effectiveness. Variables such as length and amount of the fibers as well as curing period were studied. Both deterministic and probabilistic (or reliability) analysis is presented in this paper. While the deterministic analysis helps in understanding the measured experimental data, the probabilistic approach accounts for the stochastic nature of the experimental data and provides a better rationale for the design methods. The deterministic approach showed that the improvement in CBR increased with higher fiber contents and longer lengths and the effect was prominent when lime was used as a stabilizer. There were some exceptions to this behavior, which were noted in the paper. The probabilistic analysis showed that the amount and lengths of fibers were important factors in CBR strength. It was also determined that the variation in the target CBR value had considerable effect on optimizing the length and amount of the fibers

Shrinkage and Consolidation Characteristics of Chitosan-Amended Soft Soil: A Sustainable Alternate Landfill Liner Material

Kuttanad is a region that lies in the southwest part of Kerala, India, and possesses soft soil, which imposes constraints on many civil engineering applications owing to low shear strength and high compressibility. Chemical stabilizers such as cement and lime have been extensively utilized in the past to address compressibility issues. However, future civilizations will be extremely dependent on the development of sustainable materials and practices such as the use of bio-enzymes, calcite precipitation methods, and biological materials as a result of escalating environmental concerns due to carbon emissions of conventional stabilizers. One such alternative is the utilization of biopolymers. The current study investigates the effect of chitosan (biopolymer extracted from shrimp shells) in improving the consolidation and shrinkage characteristics of these soft soils. The dosages adopted are 0.5%, 1%, 2%, and 4%. One-dimensional fixed ring consolidation tests indicate that consolidation characteristics are improved upon the addition of chitosan up to an optimum dosage of 2%. The coefficient of consolidation increases up to seven times that of untreated soil, indicating the acceleration of the consolidation process by incorporating chitosan. The shrinkage potential is reduced by 11% after amendment with 4% chitosan and all the treated samples exhibit zero signs of curling. Based on the findings from consolidation and shrinkage data, carbon emission assessments are carried out for a typical landfill liner amended with an optimum dosage of chitosan. In comparison to conventional stabilizers like cement and lime, the results indicate that chitosan minimized carbon emissions by 7.325 times and 8.754 times, respectively

Coupled Effect of Granite Sand and Calcium Lignosulphonate on the Strength Behavior of Cohesive Soil

This paper assesses the significance of stabilizing clay soil with calcium lignosulphonate (CLS) and granite sand (GS). Unconfined compressive strength ( (Formula presented.) ) and hydraulic conductivity (K) are taken as performance indicators and the effect of varying dosages of GS (30%, 40%, and 50%) and CLS (0.5%, 1%, 1.5%, and 2%) at different curing periods on (Formula presented.) and K are examined. The best fit regression equations have been proposed to relate (Formula presented.) and K of untreated clay soil and stabilized clay using GS and CLS. The proposed nonlinear regression equations provide details of experimental data and aid in estimating (Formula presented.) and K very efficiently and reliably for targeted geotechnical applications from a sustainable perspective. © 2022 by the authors

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Geotechnical and Physico-Chemical Characterization of Low Lime Fly Ashes

In order to explore the possibility of using low-lime fly ashes, the physical and chemical properties which have a direct bearing on their geotechnical and geoenvironmental behaviors have been investigated. In this paper, two types of low-lime fly ashes, originating from India, have been used. A brief account of various methods adopted in characterizing their physical, chemical, and geotechnical properties is presented. The relative importance of each of these properties in enhancing the bulk applicability of fly ashes has been brought out