# Experimental Study on the Bearing Capacity of Gas Oil-Contaminated Coastal Sand
###### Abstract  
Ground hydrocarbon contamination is a grave consequence of fossil fuel consumption, making it increasingly unsustainable. Consequently, researchers worldwide have been compelled to conduct a large number of studies on the geotechnical aspects of hydrocarbon-contaminated soils. Still, the complications arising from the integration of geotechnical complexities with diverse hydrocarbon properties present a substantial research need. The assessment of the foundation bearing capacity in hydrocarbon-contaminated soils is of paramount importance, especially given that numerous contaminated sites either house significant industrial facilities or are earmarked for critical infrastructure projects. This study investigates the shear strength and bearing capacity of gas oil-contaminated coastal sands using laboratory testing and physical modeling, with a special focus on the combined influence of the degree of saturation and relative density. Footing's shear failure mechanisms were analyzed based on predicted and measured bearing capacity values. Findings show a decrease in the friction angle with a contamination increase, while the apparent cohesion initially rises before declining. Furthermore, the study revealed that the foundation's bearing capacity exhibited an increase up to a specific contamination level, followed by a subsequent decrease. This increase is circa 90 and 100 percent at a 5 percent contamination content for loose and dense sand, respectively. Comparing the predicted and measured bearing capacity results shows that the general shear failure mechanism has occurred in the dense subgrade, while the loose subgrade's failure mechanism is more inclined towards local shear failure. contaminated soils; sand; sustainability; environmental geotechnics; bearing capacity 202331245023312450  
In the Republic of Korea, for instance, several oil spill incidents--including the Hebei Spirit crude oil spill in 2007 and the Sea Prince accident in 1955, which contaminated over 200 and 73 km of coastline, respectively--have induced major oil contamination in sites of high industrial prominence [4,5]. These incidents are on top of the numerous oil leakages occurring in terrestrial environments due to industrial and petrochemical activities [6]. In the last decades, a number of reduced-scale physical modeling [7, 8, 9, 10, 11], laboratory element testing [1, 2, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21], and field testing [22] studies have been conducted to study the variations in the mechanical properties of soils contaminated with different types of contaminants. [PERSON] et al. [2] conducted one of the first comprehensive laboratory studies on oil-contaminated soils using Kuwaiti Jahara sand samples. They found a slight reduction in the friction angle compared to clean sand. CBR test results showed a 25% increase with 4% oil content, which then dropped at 6% oil content. In a study by [PERSON] and [PERSON] [7] on contaminated Jumoonjun sand (east coast of the Republic of Korea), they observed a decrease in the bearing capacity as the contamination levels increased. In their 2007 study, [PERSON] et al. [20] examined the impact of crude oil contamination on coastal soil samples from Bushehr, Iran (SM, SP, and CL types). Their results showed that, as the oil content increased, the friction angle and cohesion of the SP and SM samples decreased and increased, respectively. [PERSON] and [PERSON] [10] examined the impact of the contamination type and depth on the bearing capacity of a circular footing. Their findings revealed a reduction in bearing capacity due to oil contamination. Furthermore, [PERSON] et al. [13] investigated the impact of gas oil contamination on SP, ML, and CL soil samples using basic laboratory tests, including unconfined compression strength (UCS) and direct shear tests. Their findings indicated that the friction angle decreased and the cohesion increased with the contamination level. Additionally, the UCS results revealed that the strength of CL samples increased with 3% contamination.