Geosynthetic-Reinforced Retaining Walls with Flexible Facing Subjected to Footing Loading

Geosynthetic-reinforced retaining (GRR) walls have been used as bridge abutments to support shallow foundations. This technology eliminates the need for traditional deep foundations, such as piles, to support bridges. However, limited studies have been conducted so far to evaluate the performance of GRR abutment walls constructed with flexible facing. The objectives of this study were: (1) to evaluate the performance of the GRR walls subjected to static footing loading and (2) to develop methods to predict facing lateral deflections and surface settlement of GRR walls under the footing loading. To fulfill the above research objectives, a comprehensive experimental study and analytical analysis were conducted. In this study, pullout tests were conducted to evaluate the effect of the load application method using an airbag with and without stiff plates on the vertical stress distribution and the pullout capacities and deflections of extensible (geogrid) reinforcement in the soil in a large pullout box. The non-uniform pressure distribution resulting from the airbag with stiff plates reduced the pullout resistance of the reinforcement as compared with that without stiff plates. The test results also show that the displacements in the cross section of the same transverse bar were not equal when the normal load was applied through stiff plates. This study investigated the combined effects of tension, bending, and friction on the measured strains on the upper and lower sides of uniaxial geogrid specimens by wrapping the specimen around a cylinder of different diameters. The test results show the combination of tension, bending, and friction reduced the average upper and lower strains by 28% as compared with the tension only. The cylinder diameter did not have any effect on the measured strains of the geogrid on the cylinder. The experimental study investigated eight reduced-scale GRR abutment walls with wrapped-around and modular concrete block facing subjected to static footing loading in a test box under a plane strain condition. The settlements of the footing, the lateral deflections of the facing, the vertical and lateral earth pressures, the tensile strains along reinforcement, and the failure mode were evaluated. The test results showed that the modular block facing acting as a relatively rigid structural element reduced the footing settlement as compared with the wrapped-around facing. Moreover, the maximum lateral deflection in the wrapped-around facing wall was much larger than that of the modular block facing wall under the same applied footing pressure. The measured maximum vertical stress was larger than the calculated stress from the Boussinesq equation and the 2:1 distribution method at the centerline of the footing. The maximum lateral earth pressure was recorded at the depth of 0.5H-0.7H and 0.9H (H is the wall height) from the top of the walls with modular block and wrapped facing, respectively. The Boussinesq equation was used to calculate the lateral earth pressure induced by footing loading, which approximately matched that measured for the wall with wrapped-around facing, but was quite different from that for the wall with modular block facing. Shallow, middle, and deep slip surfaces were observed in these test models at failure. This study also investigated the effect of footing loading on global stability of GRR walls with wrapped-around and modular block facing. The limit equilibrium methods (i.e., the Bishop modified method and the Spencer method) included in the ReSSA program was used to determine critical slip surfaces and their corresponding factors of safety of the eight reduced-scale experimental models and ten case histories in the literature. Based on the limit equilibrium analyses, the critical slip surfaces identified by Bishop's modified method and Spencer's two-part wedge method reasonably agreed with those observed in the walls under footing loading. The data analysis showed an exponential relationship between the calculated factor of safety using the Bishop method and the maximum lateral facing deflection or the surface settlement of the GRR walls under footing loading

Investigation of the effective parameters on the phenol removal from the groundwater by response surface method

The discharge of industrial waste containing organic pollutants like phenol has caused a surge in environmental complications in water, soil, and air. In recent years, the concentration of phenolic pollutants has risen due to their high toxicity and environmental persistence. This research used geotextile/activated carbon (GTX/AC) adsorbent to purify groundwater contaminated with phenol, owing to its easy availability. A low-cost geotextile carrier was utilized to avoid the dispersion of active carbon in the groundwater. Response surface method (RSM) was used in the present research to design and optimize experimental tests. The results indicate that the initial concentration, pH, and adsorbent dosage are the most significant parameters affecting the geotextile/activated carbon (GTX/AC) adsorbent performance. Maximum adsorption capacity was considered the highest desirability level for the response surface method optimization. The initial phenol concentration equal to 458.8 mg/L, the amount of pH equal to 7, and the dose of adsorbent equal to 5.5 gr were the best conditions for removing phenol from the water. Based on the result of this research, the response surface method can be used for modeling and optimizing phenol adsorption from groundwater, and geotextile/activated carbon (GTX/AC) adsorbent is a suitable choice for the treatment of water polluted with phenol

Using Electro-peroxone Process to Remediate Soil Contaminated with Phenol

Industrial processes are among human activities that cause production of a large volume of wastewater containing organic pollutants such as phenol and its derivatives. Soil remediation is crucial for enhancing environmental quality for both humans and other living organisms. This study investigate the use of an electro-peroxone system to remove environmental pollutants from soil. In conjunction with ozonation, the study employed electrochemically generated hydrogen peroxide using a carbon electrode, addressing concerns about transportation and storage. Experiments were structured using response surface methodology (RSM) with three variables: ozone dosages ranging from 4 to 8 l/h, initial pollutant concentrations from 20 to 50 mg/kg, and treatment durations between 7 and 14 days. The effectiveness of phenol removal from soil was assessed by applying a consistent voltage of 2 V/cm to the soil samples in all experiments. Results revealed a negative correlation between initial pollutant concentration and ozone consumption and a positive correlation between treatment duration and pollutant removal efficiency. Optimal removal efficiency occurred with a 14-day treatment duration, an 8 l/h ozone dosage, and a 20 mg/kg initial pollutant concentration. The electro-peroxone system\u27s application indicates its potential as a sustainable, eco-friendly, and cost-effective approach to soil remediation for pollution

Stress Distributions and Pullout Responses of Extensible and Inextensible Reinforcement in Soil Using Different Normal Loading Methods

Copyright ASTM International. All rights reserved; Wed Feb 17 17:01:32 EST 2021. Downloaded by Kansas University, pursuant to License Agreement. No further reproduction authorized.In design of reinforced soil structures, pullout capacity of reinforcement in an anchorage zone is an important parameter for stability analysis. This parameter is generally quantified by conducting laboratory or field pullout tests. In the laboratory pullout test, the reinforcement is embedded in the soil mass at a normal stress, which is commonly applied by a pressurized airbag or a hydraulic jack through a rigid plate, and then a horizontal tensile force is applied to the reinforcement. This article reports an experimental study conducted to evaluate the effect of the load application method using an airbag with and without stiff wooden plates on the vertical stress distribution and the pullout capacities and deformations of extensible (geogrid) and inextensible reinforcement (steel strip) in the soil in a large pullout box. This study monitored the distributions of the vertical earth pressures at the top and bottom of the soil mass in the pullout box, and at the level of reinforcement using earth pressure cells. The measured earth pressures show that the airbag with stiff plates resulted in a nonuniform pressure distribution, whereas the tests with an airbag directly on the soil had an approximately uniform pressure distribution. The nonuniform pressure distribution resulting from the airbag with stiff plates reduced the pullout resistance of the reinforcement as compared with that using the same airbag without stiff plates. The nonuniform pressure distribution effect was more significant for narrow inextensible reinforcements than wide extensile reinforcements. The test results also show that the displacements in the cross section of the same transverse bar were not equal when the normal load was applied through stiff plates

Analytical Method for Predicting Lateral Facing Deflection of Geosynthetic-Reinforced Soil Abutment Walls

Geosynthetic-reinforced soil (GRS) walls have been recently used as bridge abutments to directly support spread footings on the reinforced soil mass. This application reduces the requirement for using traditional deep foundations, such as piles or drilled shafts, to support bridge beams. GRS abutment walls are generally subjected to high footing loads that are close to the wall facing. Although GRS abutment walls with modular block facing have been the subject of a number of studies, there are limited methods to predict the profile of the lateral facing deflections along the height of the GRS abutment walls. Lateral deflections along the facing of GRS walls are of significant importance and are difficult to predict. In practice, design engineers need numerical modeling or software to predict the deflection profile. The objectives of this study were to develop an analytical approach to estimate lateral deflections of the wall facing along the height of the GRS abutment walls. Two sets of equations were developed, and experimental test results were used for verification of the proposed analytical approach. There is agreement between the results from proposed approach and the measured data. The maximum lateral deflections predicted from the proposed equations are almost identical to the measured data. The facing lateral deflection profiles with depth are within close range of measured data. The proposed analytical equations for determining lateral deflections provide an effective and simple tool in design of the GRS abutment walls

Behavior of buried sliplined corrugated metal pipes subjected to footing loading

Buried structures (e.g., culverts and pipes under roadways) installed several decades ago are reaching the end of their service life. Excavation and replacement of these structures will cause disturbances to the transportation network and require significant funding. Trenchless techniques (e.g., sliplining) have been increasingly employed to rehabilitate deteriorated buried structures (e.g., corroded corrugated steel pipes). Sliplining includes inserting a new pipe (liner) into an existing deteriorated pipe and filling the gap between them with grout. The objective of this study was to evaluate the effect of sliplining on the behavior of buried corrugated steel pipes with different degrees of corrosion under loading. In this experimental study, six footing loading tests were conducted on the unlined and sliplined buried steel corrugated pipes with different degrees of corrosion in soil in a reduced-scale test box under a plane-strain condition. A low-viscosity grout was used to fill the space between the steel pipe and the liner. After the footing loading tests were conducted, the sliplined steel pipes were exhumed from the box for examination and assessment. Then, a series of parallel plate loading tests were carried out on the exhumed rehabilitated pipes using a universal testing machine. The results show that the measured earth pressures induced by footing loading above the crown of the unlined pipe with 0% corrosion were higher than those with 50% and 90% cutout to simulate the degree of corrosion. However, the degree of corrosion did not have a significant effect on the earth pressures induced by footing loading above the crown of the sliplined pipes. From the exhumed pipes, sliplining increased the load-carrying capacities as compared with the unlined steel pipes tested in air

Development of Rail Anchor Testing Through Literature Review of CWR Buckling Resistance Evaluation

Continuously welded rail (CWR) is among the most used railroad systems worldwide with great improvements compared to jointed tracks, including refined ride quality, increased fatigue life of track and rolling stock, and reduced maintenance costs. Rail buckling is one of the key remaining issues for CWRs to further reduce safety hazards and infrastructure deterioration, and save required track retrofit material and efforts. CWR buckling is induced by combined longitudinal, lateral, and torsional forces on the track that are caused by the synergy of rail components, the loading from moving trains, the interaction between track and substructure, and the effect of thermal variations. A systematic evaluation of factors that contribute to rail longitudinal, lateral, and torsional stiffnesses and a thorough investigation of their interactions are critical to understand rail buckling and enhance buckling resistance on CWR. This paper compiles, summarizes, and interprets existing research related to rail buckling resistance, considering parameters such as time-dependent neutral temperature of the tracks, the type of trains, various track resistors (rails, sleepers, and ballasts), and other accessories (anchors and fasteners). A discussion of previous experiments that studied resistors and rail buckling resistances is presented, which guides development of an experimental arrangements as part of an on-going large-scale rail resistance testing project in Edinburg, Tx. The information summarized in this article greatly points out additional needs for experimental and numerical studies, enlightens future research, and provides structured background for prospective improvements on rail buckling and stiffnesses of CWR

Using Electro-peroxone Process to Remediate stabilized clay

Industrial processes are among human activities that cause the production of a large volume of wastewater containing organic pollutants such as phenol and its derivatives. These pollutants are among the substances that are considered a serious threat to the health of the environment, soil and humans. Soil remediation is crucial for enhancing environmental quality for both humans and other living organisms. This study investigated the use of an electro-peroxone system to remove environmental pollutants from soil. In conjunction with ozonation, the study employed electrochemically generated hydrogen peroxide using a carbon electrode, addressing concerns about transportation and storage. Experiments were structured using response surface methodology (RSM) with three variables: ozone dosages ranging from 4 to 8 l/hr, initial pollutant concentrations from 20 to 50 mg/kg, and treatment durations between 7 and 14 days. The effectiveness of phenol removal from soil was assessed by applying a consistent voltage of 1 V/cm to the soil samples in all experiments

Use of a coupled SBR–MBR for treatment of produced water enriched by halophilic bacteria

The performance of a sequencing batch bioreactor (SBR) coupled with a membrane bioreactor (MBR) for treatment of hypersaline produced water by insertion of a halophilic bacterial consortium was tested at three different organic loading rates (OLRs): 1, 2 and 4 (kg chemical oxygen (O2) demand (COD)/m3)/d. Four total dissolved solids (TDS) concentrations (20, 50, 80 and 120 g/l) were investigated in this study. At different TDS concentrations and OLRs, COD removal was found to be efficient at 91·3–99·5% and the amount of mixed liquor suspended solids (MLSS) varied from 4·61 to 9·88 g/l. The amounts of COD removal and MLSS increased with increased OLRs and decreased in hypersaline concentrations. Increases in TDS had a negative effect on membrane flux and fouling rates, but, in this hybrid system, the reduction in flux with increase in TDS was minor, while high-quality treated water was produced from the immersed membrane. </jats:p