ABSTRACT
The hydraulic properties of expansive soils are affected due to the formation of visible cracks in the dry state. Chemical stabilization coupled with fiber reinforcement is often considered an effective strategy to improve the geotechnical performance of such soils. In this study, hydraulic conductivity tests have been conducted on expansive clay using two different types of fibers (fiber cast (FC) and fiber mesh (FM)) exhibiting different surface morphological properties. The fiber parameters include their dosage (added at 0.2% to 0.6% by dry weight of soil) and length (6 and 12 mm). Commercially available lime is added to ensure proper bonding between clay particles and fiber materials, and its dosage was fixed at 6% (by dry weight of the soil). Saturated hydraulic conductivity tests were conducted relying on a flexible wall permeameter on lime-treated fiber-blended soil specimens cured for 7 and 28 days. The confining pressures were varied from 50 to 400 kPa, and the saturated hydraulic conductivity values (ksat) were determined. For FC fibers, an increase in fiber dosage caused ksat values to increase by 9.5% and 94.3% for the 6 and 12 mm lengths, respectively, at all confining pressures and curing periods. For FM fibers, ksat values for samples mixed with 6 mm fiber increased by 12 and 99.2% for 6 and 12 mm lengths, respectively for all confining pressures at the end of the 28-day curing period. The results obtained from a flexible wall permeameter (FWP) were compared with those of a rigid wall permeameter (RWP) available in the literature, and the fundamental mechanism responsible for such variations is explained.
ABSTRACT
This study investigated shear strength behaviour of compacted sand-clay mixtures used as liners, with 10%, 20%, and 30% clay contents. A natural high-plasticity and highly expansive clay found in the eastern province of Saudi Arabia was used. A series of consolidated undrained triaxial tests and pore water pressure measurements of saturated samples with various clay contents and confining pressures was conducted using a computer-controlled Bishop and Wesley triaxial cell. The unit was equipped with pressure volume controllers and a pressure transducer for measuring sample volume changes and excess pore water pressure. The experimental test results indicate that clay content and confining pressure significantly affect stress strain response curves, pore water pressure generation curves, and steady-state shear strength. Sand-clay mixtures with clay content less than 10% showed a tendency toward contractive behaviour. The failure line slope increased in accordance with clay content increase. The deviator stress versus axial strain of saturated sand-clay mixtures indicated a hyperbolic trend. The stress ratio versus axial strain representation was more informative for the shear strength behaviour assessment. Clay content did not significantly affect critical-state friction angle. Scanning electron microscope images of the sand-clay mixtures with different clay contents are presented.
ABSTRACT
OBJECTIVE: This study was intended to assess the knowledge, attitude and practice of pediatricians and pharmacists about sugar free medications (SFMs) and their impact on oral health. MATERIALS AND METHODS: Self-administered close ended questionnaire was handed out to all pediatricians and pharmacists in five tertiary hospitals in Riyadh (King Khalid University Hospital, King Saud Medical City, King Fahad Medical City, Prince Sultan Medical Military City, Security Forces Hospital) to investigate the knowledge, attitude and practice concerning SFMs. RESULTS: Eighty-five pediatricians and 77 pharmacists participated in this study. The results showed that pediatricians and pharmacists have a good knowledge, but negative attitude toward SFMs. Only (5.9%) of pediatricians had formal undergraduate training which is significantly lower than pharmacists (15.6%) (p = 0.04). One-third of pediatricans and pharmacists prescribe or dispense SFMs. The most influencing factors toward prescription (pediatrician) of SFMs was the medical status of the patient (70.6%), while the most influencing factor of dispensing (pharmacists) SFMs was the availability in the pharmacy (64.9%). Two-third of pediatricians (67%) guide the parents about the risk associated with sugar-containing medications (SCMs) which is significantly higher than pharmacists (p < 0.0001). Also, 53% of pediatricians recommend oral hygiene instructions when prescribing SCMs which is also significantly higher than pharmacists (p = 0.0 02). CONCLUSION: There is a considerable knowledge about SFMs and its impact on dental caries, among pediatricians and pharmacists participated in this study. However, their attitude toward prescribing or dispensing SFMs was not positive and may be linked to the gap in knowledge. Further training and education of healthcare providers regarding the use of SFMs and its negative impact on dental caries has to be reiterated.
