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- All Subjects: Civil Engineering
- Creators: Kavazanjian, Edward
- Resource Type: Text
Description
This study evaluates the use of plant-extracted silica solution as a bio-based grout material for improvement of granular soils. Although silicate grout is a very well-established and popular technique in the ground improvement market, efforts have been initiated to replace chemically-synthesized silicate grout with plant-extracted silica grout. This initiative will increase the level of sustainability and consequently improve the existing market acceptability. The silica-rich plant source used for extraction was rice husk, which is an abundantly produced agricultural waste. The extraction method includes acid-leaching, temperature-controlled rice husk ash production and the preparation of an aqueous sodium silicate solution from the ash through an alkaline leachate method. Silica ash was in amorphous form containing 95% of silica content which is suitable for soil treatment. Gelation time was controlled in the absence and presence of sand under different pH values. Bio-based silica grouting showed an improvement of the shear strength of the soil as well as the hydraulic conductivity reduction.
ContributorsSayed Mostafa, Ahmad (Author) / Zapata, Claudia (Thesis advisor) / Khodadaditirkolaei, Hamed (Thesis advisor) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2019
Description
This document presents the assessment of the swelling behavior of expansive clay stabilized with bio-based silica gel and subjected to wetting and drying cycles. The expansive clay used in this research was obtained from Anthem, Arizona. Rice husk is a rich silica by-product of rice production with commercial uses and applications in the industry. Rice husk ash from two different sources -California (named ASU) and India- were subjected to chemical characterization. Fourier Transform Infra-red Spectroscopy was used to verify the functional groups of the gel formed. Results showed differences between the ashes from different sources and confirmed the presence of silica structure bonds. X-Ray Diffraction (XRF) results showed that the ASU ash contained more amorphous silica than the Indian ash.One dimensional swell and consolidation tests were performed to investigate the volume change behavior of the untreated and silica gel treated remoulded samples. The free swell of the clay decreased from 12.3% (untreated sample) to 7.2% (ASU sample) and 11.4% (Indian sample). The effect of the wet and dry cycles on the swelling and consolidation characteristics of the untreated clay demonstrated that the treatment is irreversible after three cycles. Swelling of clay treated with ASU ash was reduced after the first cycle, while that of the clay treated with Indian ash was reduced after three cycles. This was due to the gelation time difference between treatments. Scanning Electron Microscopy images showed that the structure of the untreated clay was discontinuous, flaky and without aggregations whereas particles in the treated samples were aggregated and new bonds were created, decreasing the surface area. The X-Ray Diffraction (XRF) results showed that the main mineral responsible for expansive behavior of the clay studied was illite. The d-spacing of the illite decreased from 4.47Å for the untreated clay to 3.33Å for the treated clay. This study demonstrates a promising technique for clay swelling reduction and a more sustainable solution than that available to current practicing engineering.
ContributorsBogere, Limon (Author) / Zapata, Claudia E (Thesis advisor) / Kavazanjian, Edward (Committee member) / Khodadaditirkolaei, Hamed (Committee member) / Arizona State University (Publisher)
Created2020
Description
This report analyzed the dynamic response of a long, linear elastic concrete bridge subject to spatially varying ground displacements as well as consistent ground displacements. Specifically, the study investigated the bridge’s response to consistent ground displacements at all supports (U-NW), ground displacements with wave passage effects and no soil profile variability (U-WP), and ground displacements with both wave passage effects and soil profile variability (V-WP). Time-history ground displacements were taken from recordings of the Loma Prieta, Duzce, and Chuetsu earthquakes. The two horizontal components of each earthquake time-history displacement record were applied to the bridge supports in the transverse and longitudinal directions. It was found that considering wave passage effects without soil profile variability, as compared with consistent ground displacements, significantly reduced the peak total energy of the system, as well as decreasing the maximum relative longitudinal displacements. The maximum relative transverse displacements were not significantly changed in the same case. It was also found that including both wave passage effects and soil profile variability (V-WP) generally resulted in larger maximum transverse relative displacements, across all earthquake time-histories tested. Similarly, it was found that using consistent ground displacements (U-NW) generally resulted in larger maximum longitudinal relative displacements, as well as larger peak total energy values.
ContributorsSeawright, Jordan Michael (Author) / Hjelmstad, Keith (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2019
Description
Expansive soils pose considerable geotechnical and structural challenges all over the world. Many cities, towns, transport systems, and structures are built on expansive soils. This study evaluates stabilization of expansive soils using silicate solution extracted from rice husk taking advantage of an agricultural material waste. Rice husk ash production was optimized considering several factors including rinsing solution, rinsing temperature, burning time, and burning temperature. Results indicated that washing the rice husk with HCl (1M) produced an ash with surface area of 320 m2/g and 97% of silicon oxide. Two local soils were treated with sodium silicate solution, silica gel at pH 1.5, and silica gel at pH 4 to evaluate its mechanical properties at curing times of 1 day, 7 days, and 14 days. Results indicated that sodium silicate solution reduced the one-dimensional swell by 48% for Soil A, however, swell for soil B remained about the same. Silica gel at pH 1.5 reduced the one-dimensional swell by 67% for soil A and by 35% for soil B. Silica gel at pH 4 did also reduce the free swell by 40% for soil A and by 35% for soil B. Results also indicated that the swell pressures for all treated soils increased significantly compared to untreated soils. Soils treated with sodium silicate solution showed irregular compaction curves. Silica gel-treated soils showed a reduction in the maximum dry unit weight for both soils but optimum water content decreased for soil A and increased for soil B. Atterberg limits were also reduced for sodium silicate and silica gels-treated soils. Swelling index for bentonite showed a reduction by 53% for all treated bentonites. Soil-water characteristics curves (SWCC) for sodium silicate-treated soils remined almost the same as untreated soils. However, silica gels-treated soils retain more water. Surface area (SSA) decreased for sodium silicate-treated soil but increased for all silica gels-treated soils. It was concluded that curing times did not show additional improvement in most of the experiments, but the results remained about the same as 1-day treatment. The study demonstrated that silicate solution is promising and sustainable technique for stabilization of expansive soils.
Contributorsalharbi, hani (Author) / Zapata, Claudia (Thesis advisor) / Kavazanjian, Edward (Committee member) / van Paassen, Leon (Committee member) / Khodadaditirkolaei, Hamed (Committee member) / Arizona State University (Publisher)
Created2020
Description
Bridge scour at piers is a major problem for design and for maintaining old infrastructure. The current methods require their own upkeep and there may be better ways to mitigate scour. I looked to the mangrove forests of coastal environments for inspiration and have developed a 2D model to test the efficacy of placing a mangrove-root inspired system to mitigate scour. My model tests the hydrodynamics of the root systems, but there are additional benefits that can be used as bioinspiration in the future (altering the surrounding chemistry and mechanical properties of the soil).Adding a mangrove inspired minipile system to bridge piers changes scour parameters within my 2D COMSOL models. For the volume of material added, the minipiles compare favorably to larger sacrificial piles as they reduce A_wcz and 〖τ'〗_max by similar (or even better) amounts. These two parameters are indicators of scour in the field. Within the minipile experiments, it is more beneficial to place them upstream of the main bridge pier as their own ‘mangrove forest.’ The value of A_wcz and 〖τ'〗_max for complex 2D models of scour is unclear and physical experiments need to be performed. The model geometry is based on the dimensions of the experimental flume to be used in future studies and the model results have not yet been verified through experiments and field trials. Scale effects may be present which cannot be accounted for in the 2D models. Therefore future work should be conducted to test ‘mangrove forest’ minipile systems in 3D space, in flume experiments, and in field trials.
ContributorsEnns, Andrew Carl (Author) / van Paassen, Leon (Thesis advisor) / Tao, Junliang (Thesis advisor) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2021
Description
Some subterranean animals, such as mole-rats, can burrow underground, sense the environment around them, and communicate with each other. Inspired by the mole-rats, this dissertation is dedicated to developing an active wireless underground sensor network (WUSN) for active underground exploration. Special attention is paid to two key functions: wireless underground data transmission, and underground self-burrowing. In this study, a wireless underground communication system based on seismic waves was developed. The system includes a bio-inspired vibrational source, an accelerometer as the receiver, and a set of algorithms for encoding and decoding information. With the current design, a maximum transmission bit rate of 16–17 bits per second and a transmission distance of 80 cm is achieved. The transmission range is limited by the size of container used in the laboratory experiments. The bit error ratio is as low as 0.1%, demonstrating the robustness of the algorithms. The performance of the developed system shows that seismic waves produced by vibration can be used as an information carrier and can potentially be implemented in the active WUSNs. A minimalistic horizontal self-burrowing robot was designed. The robot mainly consists of a tip (flat, cone, or auger), and a pair of cylindrical parts. The robot can achieve extension-contraction with the utilization of a linear actuator and have options for tip rotation with an embedded gear motor. Using a combined numerical simulation and laboratory testing approach, symmetry-breaking is validated to be the key to underground burrowing. The resistance-displacement curves during the extension-contraction cycles of the robot can be used to quantify the overall effect of asymmetries and estimate the burrowing behavior of the robots. Findings from this research shed light on the future development of self-burrowing robots and active WUSNs.
ContributorsZhong, Yi (Author) / Tao, Junliang (Thesis advisor) / Kavazanjian, Edward (Committee member) / Martinez, Alejandro (Committee member) / Arizona State University (Publisher)
Created2023
Description
This Master's thesis presents an experimental testing program conducted to assess the properties of coarse tailings from two Arizona copper mine heap leach pads. This testing program was motivated by recent failures in tailings impoundments, which has prompted a re-evaluation of tailings deposit stability worldwide. The testing was conducted using a unique large-scale Direct-Simple Shear (LDSS) device at Arizona State University (ASU). Prior to testing the tailings, the LDSS device had to be rehabilitated, as it had not been used for several years. The testing program included one-dimensional compression testing, shear wave velocity measurement, and monotonic shearing under constant volume conditions. The test results demonstrate the effectiveness of the LDSS device in obtaining representative data for tailings under monotonic loading. Recommendations for future improvements of the LDSS include enhancing the connection of monitoring instruments, utilizing more sophisticated software for shear wave velocity measurements, and optimizing the control system. The thesis contributes to geotechnical engineering by improving understanding and evaluation of tailings properties, thereby enhancing safety and environmental sustainability in the mining industry.
ContributorsHarker, Jack Michael (Author) / Kavazanjian, Edward (Thesis advisor) / Zapata, Claudia (Committee member) / Razmi, Jafar (Committee member) / Arizona State University (Publisher)
Created2023