Full-Scale Lateral Load Testing of Deep Foundations Using Blast-Induced Liquefaction

To improve our understanding of the lateral load behavior of deep foundations in liquefied soil, a series of full-scale lateral load tests have been performed at the National Geotechnical Experimentation Site (NGES) at Treasure Island in San Francisco, California. The ground around the test piles was liquefied using explosives prior to lateral load testing. The goal of the project is to develop load-displacement relationships for bored and driven piles and pile groups in liquefied sand under full-scale conditions for improved and non-improved ground. The results of this investigation confirmed that controlled blasting techniques could successfully be used to induce liquefaction in a well-defined, limited area for field-testing purposes. Excess pore pressure ratios greater than 0.8 were typically maintained for 4 to 10 minutes after blasting. Data were collected showing the behavior of laterally loaded piles before and after liquefaction in non-improved ground. Following liquefaction, the stiffness of the soil-foundation system typically decreased by 70 to 80% of its pre-liquefaction value non-improved ground. Ground improvement with stone columns was then performed prior to an additional series of tests. Lateral load tests were again conducted before and after blasting to induce liquefaction. Cone penetration testing following the installation of stone columns found that the density was improved significantly. As a result, the stiffness of the foundation system following blasting was 2.9 to 3.6 times that in the liquefied soil. Subsequent tests involving more than twice as many piles or 50% larger piles provided less than 50% of the increased resistance produced by stone column treatment alone. This study provides some of the first full-scale quantitative results on the improvement of foundation performance due to ground improvement in a liquefiable deposit

Ground Improvement for Increasing Lateral Pile Group Resistance

Lateral load tests were performed on a full-scale pile cap in untreated clay along with pile groups involving (a) excavation and replacement with sand backfill, (b) a soilcrete wall along the side of the pile group, and (c) a jet grouted zone below the pile cap. The average compressive strength of the soft, plastic clay increased from an average of 50 kPa to an average of about 1000 kPa with soil mixing (10% cement) and to 3000 kPa with jet grouting (20% cement). Excavation and replacement only increased resistance by about 20%; however, the soil mixed wall increased resistance by 60%, and jet grouting increased resistance by 160%. For the soil mixed wall, essentially all of the increased resistance can be explained due to passive pressure and side/base shear against the soil mixed wall. However, for the jet grout treatment, additional resistance can also be attributed to increased structural resistance of the composite soilcrete volume under the cap. Soil mixing and jet grouting provide a means to significantly increase the lateral resistance of existing pile group foundations with relatively little investment of time, effort, and expense relative to the addition of more piles

Soil Amplification at Treasure Island During the Loma Prieta Earthquake

The Loma Prieta Earthquake ground motions recorded on Treasure Island, a man-made fill in San Francisco Bay were considerably greater than on the adjacent Yerba Buena rock outcrop. The Yerba Buena motions were used as input to the computer program SHAKE90 for computing soil amplification at Treasure Island. Shear wave propagation velocities were obtained by seismic cone penetration testing. Reasonable agreement was observed between the computed and recorded accelerations at the strong motion recording station. The maximum computed accelerations around the island ranged from 0.13 to 0.20 g\u27s. The degree of damage at various locations on the island correlated somewhat with the maximum computed accelerations

Liquefaction Hazard Mitigation by Prefabricated Vertical Drains

Liquefaction has typically been mitigated by in-situ densification; however vertical composite drains offer the possibility of preventing liquefaction and associated settlement while reducing the cost and time required for treatment. Three case histories are presented which describe the use of vertical drains to mitigate liquefaction hazard and techniques to control the flow of water exiting the drains. In addition, results from a test case are presented where controlled blasting techniques were used to evaluate drain performance in-situ. Blasting was successful in liquefying loose sand in an untreated test site. Similar blast charges were then detonated at adjacent sites treated with drains. Measurements demonstrated that the drains significantly increased the rate of pore pressure dissipation. In addition, the installation process typically densified the surrounding soil, thereby decreasing the liquefaction potential. Computer analyses successfully matched the measured response and suggest that the drains could be effective for earthquake events

Liquefaction source layer for sand blows induced by the 2016 megathrust earthquake (Mw 7.8) in Ecuador (Boca de Briceño)

Numerous sand boils were generated in the alluvial plain at the mouth of the Rio Brice˜no valley (Ecuador) during the Mw 7.8 earthquake of April 2016. The area is characterized by a series of raised marine terraces formed as a consequence of the rapid tectonic coastal uplift during the Quaternary. Boreholes and geotechnical investigations were carried during post-earthquake surveys and for the purpose of mitigating the liquefaction effects. Five lithological units were identified at a site of embankment, which represented continental-marine and transitional sedimentation since the Last Glacial Maximum. A comprehensive study of texture and petrographic composition of sand boils has been performed and compared with sandy silts and silty sands of the buried sedimentary sequence in order to identify the source levels for liquefaction. The petrographic components, in particular the low content of bioclasts and carbonate fragments of the sand boils, allow to pinpoint a source layer made up of fine-grained silty sands located between 2 and 4.5 m depth (Unit 2) whereas the deeper marine sands, richer in bioclasts, were not involved. The results support the idea that earthquake-induced liquefaction phenomena are not restricted to clean sands and well-sorted deposits, but may affect sand layers with significant amount of nonplastic silt

Composite Ground Modification System: Vibroreplacement and Dynamic Compaction, Salt Lake County Detention Center, Utah

The site for a new Adult Detention Center currently under construction in Salt Lake City, Utah, is underlain by loose sands and soft clayey lake deposits. Due to bearing capacity, static settlement, and liquefaction concerns, a hybrid ground improvement program consisting of both dynamic compaction and vibroreplacement was implemented. Stone columns were concentrated under spread and wall footings; dynamic compaction was performed over the whole site. A comprehensive quality assurance/ quality control program was executed, with a significant number of cone penetration tests, standard penetration tests, 10 plate load tests, and deceleration readings taken with an accelerometer mounted on the dynamic compaction weight. This large body of data enabled the authors to assess the effectiveness of the ground improvement program, as well as analyze the results of the experimental deceleration readings

CONFRONTO DEI PARAMETRI GEOTECNICI E GEOFISICI PRE E POST BLAST TEST PRESSO IL SITO SPERIMENTALE DI MIRABELLO (FE)

L'articolo presenta alcuni risultati preliminari derivanti dal primo esperimento di liquefazione indotta tramite blast test realizzato in Italia, presso Mirabello (FE), comune fortemente colpito da fenomeni di liquefazione durante la sequenza sismica verificatasi in Emilia-Romagna nel 2012. In particolare diverse indagini in sito con tecniche invasive e non invasive sono state eseguite prima e dopo le detonazioni per confrontare la variazione dei parametri geotecnici e geofisici nel tempo

HYBRID HETEROGENEOUS CATALYSTS FOR HYDROGENATION OF CARBON DIOXIDE

HYBRID HETEROGENEOUS CATALYSTS FOR HYDROGENATION OF CARBON DIOXIDE Lucia M. Petkovic, Harry W. Rollins, Daniel M. Ginosar, and Kyle C. Burch Idaho National Laboratory P.O. Box 1625 Idaho Falls, ID 83415-2208 Introduction Anthropogenic emissions of carbon dioxide, a gas often associated with global warming, have increased considerably since the beginning of the industrial age.1 In the U.S., stationary CO2 sources, such as electricity generation plants, produce about one-third of the anthropogenic CO2 generation. Reports2 indicate that the power required to recover 90% of the CO2 from an integrated coal-fired power-plant is about 10% of the power-plant capacity. This energy requirement can be reduced to less than 1% if the recovered CO2 is applied to the production of synthetic fuels. However, the lack of efficient catalysts along with the costs of energy and hydrogen has prevented the development of technologies for direct hydrogenation of CO2.3 Although the cost of hydrogen for hydrogenating CO2 is not economically attractive at present, the future production of hydrogen by nuclear power sources could completely change this scenario.2 Still, an efficient catalyst will be essential for commercial application of those processes. The objective of the work presented here was the development of hybrid catalysts for one-step carbon dioxide hydrogenation to liquid fuels. The hybrid catalysts, which were prepared by two novel techniques, included a copper/zinc oxide catalytic function distributed within an acidic zeolitic matrix. Results of catalyst activity and selectivity studies at atmospheric pressure are presented in this contribution. Experimental Catalysts were prepared by two novel techniques and under several different conditions to produce copper/zinc oxide/zeolite materials. Once synthesized, samples were pelletized and the fraction between 40-60 mesh was utilized for the experiments. Two hundred milligrams of catalyst were loaded in a U-tube stainless steel reactor and a flow of 100 cm3/min of a 10:90 H2:Ar mixture was passed through the catalyst bed while the temperature was increased from room temperature to 513 K at 1.8 K/min and held at 513 K for 15 h. A reactant gas mixture composed by 10 cm3/min of CO2 and 30 cm3/min of H2 was then passed through the catalyst bed and the reaction products monitored by on-line gas chromatographic analyses using an SRI Multiple Gas Analyzer #2 equipped with 3 columns (MoleSieve 13X, Hayesep-D, and MXT-1) and 3 detectors (TCD, FID, and FID-methanizer). This GC system allowed for quantification of inert gases, CO, CO2, methanol, dimethylether, higher alcohols, water, and hydrocarbons up to C20. One hundred milligrams of a commercial syngas-to-methanol catalyst along with the same amount of a commercial zeolite catalyst was utilized under the same reaction conditions for comparison purposes. These catalysts were utilized either in two-layers (Com1) or mixed together (Com2). Results and Discussion Under the conditions applied in this study, the main reaction products were CO, CH3OH, CH3OCH3, and H2O. Methanol and dimethylether production rates and selectivities with respect to CO formation are presented in Figures 1 and 2, respectively. Although the activity of the synthesized catalysts did not surpass the commercial catalysts, the selectivity to oxygenates with respect to CO on most of the synthesized catalysts were better than on the commercial catalysts. For example, ca

DIRECT DECOMPOSITION OF METHANE TO HYDROGEN ON METAL LOADED ZEOLITE CATALYST

The manufacture of hydrogen from natural gas is essential for the production of ultra clean transportation fuels. Not only is hydrogen necessary to upgrade low quality crude oils to high-quality, low sulfur ultra clean transportation fuels, hydrogen could eventually replace gasoline and diesel as the ultra clean transportation fuel of the future. Currently, refinery hydrogen is produced through the steam reforming of natural gas. Although efficient, the process is responsible for a significant portion of refinery CO2 emissions. This project is examining the direct catalytic decomposition of methane as an alternative to steam reforming. The energy required to produce one mole of hydrogen is slightly lower and the process does not require water-gas-shift or pressure-swing adsorption units. The decomposition process does not produce CO2 emissions and the product is not contaminated with CO -- a poison for PEM fuel cells. In this work we examined the direct catalytic decomposition of methane over a metal modified zeolite catalyst and the recovery of catalyst activity by calcination. A favorable production of hydrogen was obtained, when compared with previously reported nickel-zeolite supported catalysts. Reaction temperature had a strong influence on catalyst activity and on the type of carbon deposits. The catalyst utilized at 873 and 973 K could be regenerated without any significant loss of activity, however the catalyst utilized at 1073 K showed some loss of activity after regeneration

CONFRONTO DEI PARAMETRI GEOTECNICI E GEOFISICI PRE E POST BLAST TEST PRESSO IL SITO SPERIMENTALE DI MIRABELLO (FE)

L’articolo presenta alcuni risultati preliminari derivanti dal primo esperimento di liquefazione indotta tramite blast test realizzato in Italia, presso Mirabello (FE), comune fortemente colpito da fenomeni di liquefazione durante la sequenza sismica verificatasi in Emilia-Romagna nel 2012. In particolare diverse indagini in sito con tecniche invasive e non invasive sono state eseguite prima e dopo le detonazioni per confrontare la variazione dei parametri geotecnici e geofisici nel tempo