Rock Mechanics
Ebrahim Ebrahimnezhad Sadigh; Kazem Badv
Abstract
Understanding the rheological behavior of soft marine and lacustrine sediments is crucial for the success of geotechnical and civil engineering projects. Coastal and offshore structures such as artificial islands, lake causeways, piers, and oil platforms directly interact with these sediments. Their ...
Read More
Understanding the rheological behavior of soft marine and lacustrine sediments is crucial for the success of geotechnical and civil engineering projects. Coastal and offshore structures such as artificial islands, lake causeways, piers, and oil platforms directly interact with these sediments. Their safe and stable performance depends on accurate characterization of sediment behavior under complex loading conditions. This study investigates the rheological properties of soft sediments from Lake Urmia, Iran, through a combined experimental and numerical approach. Two key tests were performed: extrusion tests and unconfined compression tests. The extrusion tests were conducted on both undisturbed and remolded samples under various conditions, including different loading rates, moisture contents, and discharge orifice sizes. For the numerical simulation, the Bonded Particle Discrete Element Method (BPDEM) was employed, with the model's micro-parameters calibrated using experimental extrusion test data. The numerical results showed excellent agreement with experimental data: the force-displacement curve was replicated with less than 2% error. The calibrated model also successfully simulated the unconfined compression test, reproducing the stress-strain curve with less than 2% deviation from laboratory results. These findings demonstrate the accuracy of BPDEM in modeling soft sediment behavior. The results indicate that integrating laboratory methods with BPDEM modeling provides a powerful tool for analyzing soft sediments. This approach is particularly effective for Holocene and Late Pleistocene soft to ultra-soft sediments, offering reliable predictions of rheological and mechanical behavior in geotechnical applications.
Environment
Mehdi Soleymani Gharegol; Kazem Badv; Behzad Nemati akhgar
Abstract
This paper carried out the study on removing cyanide from aqueous solutions by modified zeolite with hexadecyltrimethylammonium bromide. After determining the properties of the prepared adsorbent by the XRD, SEM, FTIR, and BET techniques, the effect of parameters such as the initial concentration of ...
Read More
This paper carried out the study on removing cyanide from aqueous solutions by modified zeolite with hexadecyltrimethylammonium bromide. After determining the properties of the prepared adsorbent by the XRD, SEM, FTIR, and BET techniques, the effect of parameters such as the initial concentration of cyanide, pH, contact time, temperature, and the ionic strength of cyanide was examined by batch tests, and the effects of bed depth and flow rate on the performance of cyanide adsorption was investigated by column process. The XRD analysis showed the presence of clinoptilolite mineral in the structure of the raw zeolite, and the surface coating of raw zeolite by surfactant was detected by the SEM method. The FT-IR results confirmed the adsorption of cationic surfactant on the surface of the modified zeolite. The Langmuir, Freundlich and Tamkin adsorption models showed an excellent ability to describe the cyanide adsorption isotherm using the studied adsorbent. The adsorption capacity of cyanide by modified zeolite was 3.97 mg/g, significantly increased compared to the maximum adsorption capacity of raw zeolite cyanide (0.54 mg/g). The pseudo-second-order model has an excellent ability to describe the adsorption kinetics of cyanide contaminants using natural and modified zeolites. Maximum cyanide uptake capacity was achieved at pH value 8. Cyanide removal decreased with increasing pH and ionic strength of the stock solution and increased with an increase in solution temperature. Column study results confirmed that the adsorption capacity increased with the increasing bed depth, and decreased with increasing flow rate. Yoon-Nelson curves are closer to the experimental curves with high R2 values.
