Numerical Analysis of Settlement Response of Shallow Footing Subjected to Heavy Rainfall and Flood Events

The US and many parts around the world have experienced prolonged periods of heavy rainfall, severe floods, and droughts over the past 50 years. This study investigates the impacts of extreme hydrological events such as heavy rainfall and flood on the settlement behavior of continuous footing installed in unsaturated soil using a coupled Geotechnical-Hydrological finite element software, PLAXIS 2D. Initially, the effect of different degrees of saturation on the settlement behavior of the continuous footing of widths 1.5 m, 3.0 m, and 4.5 m was analyzed by applying a mechanical load. Then the settlement behavior of the footing was analyzed by applying heavy rainfall of intensity 102 mm/day for six days. Finally, the settlement behavior of the footing was analyzed by applying a flood head of 2.5 meters for seven days. The results indicated that the wetting front movement during heavy rainfall and flooding led to the weakening of soil strength and stiffness and induced additional settlements. The additional settlement induced by the flood was significantly higher than the heavy rainfall. The differential settlement was higher when the rainfall was applied on one side of the footing. The rebound of the elastic settlement was uniquely noticed when the flood head receded with time. The results indicated that not all the settlements were induced by the soil saturation but also due to the hydrostatic loading due to the flood head. The settlements induced by the flooding exceeded the allowable settlement of 25 mm, resulting in failure. These additional settlements caused by heavy rainfall and flood will lead to poor serviceability of the structures and cause the failure of the footing.

Potential of Sunflower to Extract Heavy Metals from Leachate

The effectiveness of sunflower to extract harmful heavy metals from landfill leachate using phytoremediation technique was studied in this paper. A case study of Phursungi garbage dump yard located in Phursungi village in Pune, India was taken for this study as the residents have to deal with contaminated water throughout the year which induces diseases like dysentery, cholera, hepatitis, and heavy metal poisoning related diseases. There are various methods in phytoremediation, among which phytoextraction was used for this study. An experiment was carried out to test the removal efficiency of BOD, COD, TS, and heavy metals namely As, Hg and Pb from the soil by sunflowers with and without the addition of Vesicular Arbuscular Mycorrhizal (VAM) fungi. These fungi were used in soil to accelerate the process of extraction. Leachate diluted with 60% water was supplied such that the Hydraulic Retention Time (HRT) was more than 15 days (19 days achieved). The values of contaminants were checked for permissible limits according to standards for land disposal of treated leachates given in Municipal Solid Waste Management (MSW) rules, 2016 and Central Pollution Control Board (CPCB), India. The removal efficiency of Pb from soil was almost the same for plants supplied with VAM (67.92%) and plants without VAM (66.67%). Arsenic (As) removal efficiency was 100% for plants with and without VAM. For mercury (Hg), it was more for plants without VAM (96.29%) than plants with VAM (77.78). Thus, it was concluded that VAM was ineffective. Cd and Cr concentrations in leachate samples were observed to be within the permissible limits. Hence, they were discarded for calculation of removal efficiency.