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Remedial ground densification is commonly used to reduce the liquefaction susceptibility of loose, saturated sand deposits, wherein controlled liquefaction is typically induced as the first step in the densification process. Assuming that the extent of induced liquefaction is approximately equal to the extent of ground densification, the purpose of this research is to assess the feasibility of using earthquake liquefaction data in remedial ground densification design via energy-based concepts. The energy dissipated by frictional mechanisms during the relative movement of sand grains is hypothesized to be directly related to the ability of a soil to resist liquefaction (i.e., Capacity). This hypothesis is supported by energy-based pore pressure generation models, which functionally relate dissipated energy to residual excess pore pressures. Assuming a linearized hysteretic model, a "simplified" expression is derived for computing the energy dissipated in the soil during an earthquake (i.e., Demand). Using this expression, the cumulative energy dissipated per unit volume of soil and normalized by the initial mean effective confining stress (i.e., normalized energy demand: NED) is calculated for 126 earthquake case histories for which the occurrence or non-occurrence of liquefaction is known. By plotting the computed NED values as a function of their corresponding SPT penetration resistance, a correlation between the normalized energy capacity of the soil (NEC) and SPT penetration resistance is established by the boundary giving a reasonable separation of the liquefaction / no liquefaction data points. NEC is the cumulative energy dissipated per unit volume of soil up to initial liquefaction, normalized by the initial mean effective confining stress, and the NEC correlation with SPT penetration resistance is referred to as the Capacity curve. Because the motions induced during earthquake shaking and remedial ground densification significantly differ in amplitude, duration, and frequency content, the dependency of the derived Capacity curve on the nature of the loading needs to be established. Towards this end, the calibration parameters for energy-based pore pressure generation models are examined for their dependence on the amplitude of the applied loading. The premise being that if the relationship between dissipated energy and pore pressure generation is independent of the amplitude of loading, then the energy required to generate excess pore pressures equal to the initial effective confining stress should also be independent of the load amplitude. However, no conclusive statement could be made from results of this review. Next, first order numerical models are developed for computing the spatial distribution of the energy dissipated in the soil during treatment using the vibratory probe method, deep dynamic compaction, and explosive compaction. In conjunction with the earthquake-derived Capacity curves, the models are used to predict the spatial extent of induced liquefaction during soil treatment and compared with the predicted spatial extent of improvement using empirical expressions and guidelines. Although the proposed numerical models require further validation, the predicted extent of liquefaction and improvement are in very good agreement, thus giving credence to the feasibility of using the Capacity curve for remedial ground densification design. Although further work is required to develop energy-based remedial densification design procedures, the potential benefits of such procedures are as follows. By using the Capacity curve, the minimum dissipated energy required for successful treatment of the soil can be determined. Because there are physical limits on the magnitude of the energy that can be imparted by a given technique, such an approach may lead to improved feasibility assessments and initial designs of the densification programs. / Ph. D.

The assessment of the shear strength of soil deposits after the occurrence of large strains is an important issue for geotechnical engineers. One method for doing so, the steady state approach, is based on the assumption that the steady state undrained shear strength is a unique function of the in situ void ratio and effective stress. This method, which has been applied to liquefaction and flow failures, has been criticized because it may overestimate the in situ shear strength. The key to the steady state approach is accurate determination of the relationship between void ratio and effective stress at steady state. This is typically accomplished using conventional isotropically consolidated undrained (ICU) triaxial tests. The triaxial test was developed for measuring peak strengths, which typically occur at small strains, but steady state conditions typically occur at much larger strains. At large strain levels, the suitability of conventional triaxial testing procedures and error corrections is uncertain. The measured response at large strains may be inaccurate due to the influence of various testing errors. Furthermore, the true material response in the test specimen at large strains may not accurately represent in situ material behavior at large strains. This research effort consisted of an experimental and analytical study to examine the validity of steady state undrained shear strength determination using conventional ICU triaxial tests. The analytical study addressed triaxial testing errors and conventional corrections that are applied to test data and their influence on the measured steady state parameters. Finite element analyses were conducted to investigate the influence of variations in restraint at the end platens on stress distributions in the sample and measured stress-strain response. The finite element analyses incorporated axisymmetric interface elements to model the friction characteristics between the end platens and the specimen ends. The experimental study focused on several sands that are susceptible to liquefaction. An interface direct shear test program was conducted in order to evaluate various schemes for reducing end platen friction. ICU triaxial tests were conducted on each material using both conventional and lubricated end platens. / Ph. D.

M.S.

M.S.

Earthquake-induced liquefaction of saturated soils and seismic compression of unsaturated soils are major sources of hazard to infrastructure, as attested by the wholesale condemnation of neighborhoods surrounding Christchurch, New Zealand. The hazard continues to grow as cities expand into liquefaction- and seismic compression-susceptible areas hence accurate evaluation of both hazards is essential. The liquefaction evaluation procedure presented herein is based on dissipated energy and an SPT liquefaction/no-liquefaction case history database. It is as easy to implement as existing stress-based simplified procedures. Moreover, by using the dissipated energy of the entire loading time history to represent the demand, the proposed procedure melds the existing stress-based and strain-based liquefaction procedures in to a new, robust method that is capable of evaluating liquefaction susceptibility from both earthquake and non-earthquake sources of ground motion. New relationships for stress reduction coefficient (r_d) and number of equivalent cycles ($n_{eq}$) are also presented herein. The r_d relationship has less bias and uncertainty than other common stress reduction coefficient relationships, and both the $n_{eq}$ and $r_d$ relationships are proposed for use in active tectonic and stable continental regimes. The $n_{eq}$ relationship proposed herein is based on an alternative application of the Palmgren-Miner damage hypothesis, shifting from the existing high-cycle, low-damage fatigue framework to a low-cycle framework more applicable to liquefaction analyses. Seismic compression is the accrual of volumetric strains caused by cyclic loading, and presented herein is a "non-simplified" model to estimate seismic compression. The proposed model is based on a modified version of the Richart-Newmark non-linear cumulative damage hypothesis, and was calibrated from the results of drained cyclic simple shear tests. The proposed model can estimate seismic compression from any arbitrary strain time history. It is more accurate than other "non-simplified" seismic compression estimation models over a greater range of volumetric strains and can be used to compute number-of-equivalent shear strain cycles for use in "simplified" seismic compression models, in a manner consistent with seismic compression phenomenon. / Ph. D.

Magnitude Scaling Factors (MSF) account for the durational effects of strong ground shaking on the inducement of liquefaction within the simplified liquefaction evaluation procedure which is the most commonly used approach for assessing liquefaction potential worldwide. Within the context of the simplified procedure, the spatial variation in the seismic demand imposed on the soil traditionally has been assumed to be solely a function of the spatial variation of the peak amplitude of the ground motions and the characteristics of the soil profile. Conversely, MSF have been solely correlated to earthquake magnitude. This assumption fails to appreciate the inverse correlation between the peak amplitude of ground motions and strong ground motion duration, and thus MSF would seemingly vary spatially. The combination of well-documented liquefaction response during the Darfield and Christchurch, New Zealand, earthquakes, densely-recorded ground motions for the events, and detailed subsurface characterization provides an unprecedented opportunity to investigate the significance of the spatial variation of MSF on the inducement of liquefaction. Towards this end, MSF were computed at 15 strong motion recording station sites across Christchurch and its surroundings using two established approaches. Trends in the site and spatial variation of the MSF computed for both the Darfield and Christchurch earthquakes are scrutinized and their implications on liquefaction evaluations are discussed. / Master of Science

Laboratory tests were performed to investigate the liquefaction susceptibility of uncemented calcareous sands. A series of isotropically consolidated undrained monotonic and cyclic triaxial tests were performed using the Playa Santa sand from Porto Rico. Playa Santa sand is a poorly graded calcareous clean beach sand composed of angular particles with large intra-granular voids. A series of consolidated undrained triaxial tests were performed with the Playa Santa sand remolded to a variety of relative densities and consolidated under a range of confining pressures. In addition, cyclic triaxial tests were performed at a confining pressure of 100 kPa and three sets of relative densities (20%, 40% and 60%). Generation of excess pore pressure under different levels of cyclic loading was established. As a result, relationships were developed to relate the number of cycles required for triggering of liquefaction to cyclic stress ratio. It was seen that the Playa Santa sand was less susceptible liquefaction than quartzitic sands of the same relative density remolded and tested under similar conditions. / Master of Science

The Tamakoshi Dam in Nepal experienced 19 cm of settlement due to three earthquakes that took place from December 14, 2014 to May 12, 2015. This settlement caused massive damage and halted construction and was believed to have been caused by seismic compression. Seismic compression is the accrual of contractive volumetric strain in sandy soils during earthquake shaking for cases where the generated excess pore water pressures are low. The purpose of this case study is to investigate the settlements of the dam intake block relative to the right abutment block of the dam during the three earthquakes. Towards this end, soil profiles for the dam were developed from the boring logs and suites of ground motions were selected and scaled to be representative of the shaking at the base of the dam for the two of the three earthquakes which were well documented. Equivalent linear analysis was completed for the suites of ground motions to produce shear strain time histories which were then utilized in the Jiang et al. (2020) proposed procedure for seismic compression prediction. The results were found to not align with the settlement that was observed in the field, so post-liquefaction consolidation was also considered to be a possible cause of the settlement. The results from that analysis also showed that consideration of post-liquefaction consolidation did not yield settlements representative of those observed in the field. More detailed studies are recommended to assess the settlements that were observed at the dam site, particularly analyses that take into account below and above grade topographic effects on the ground motions and settlements at the ground surface. / Master of Science / The Tamakoshi Dam in Nepal experienced 19 cm of settlement due to three earthquakes that took place from December 14, 2014 to May 12, 2015. This settlement caused massive damage and halted construction and was believed to have been caused by seismic compression. Seismic compression is the accrual of contractive volumetric strain in sandy soils during earthquake shaking for cases where the generated excess pore water pressures are low. The purpose of this case study is to investigate the settlements of the dam intake block relative to the right abutment block of the dam during the three earthquakes. Representative soil profiles were developed based on data collected from the site for analysis of the settlement. Two approaches were used to compute predicted settlement, one which considered only seismic compression as the cause of settlement and a hybrid method that considered both seismic compression and post-liquefaction consolidation. Both approaches predicted settlement values that were less than what was observed in the field. It was found that the ground motion prediction equations used in the analysis were not representative of the tectonic setting in Nepal and thus was the main reason for the under-prediction. The relevance of this research lies in using methodology developed in academia to analyze a real world event and draw conclusions about the methodology's applicability.

On the basis of the results obtained in this investigation, the following conclusions were drawn: 1. Midlothian coal was 31.3 percent liquefied by hydrogenation at atmospheric pressure and 185°C after 72 hours of reaction in a tetralin vehicle and using stannous sulfide as a catalyst. 2. The liquid product of the hydrogenation of Midlothian coal consisted of approximately 50 percent light oil boiling below 200°C., 20 percent middle oil, boiling from 205°C. to 235°C., and 30 percent heavy oil or tar residue. 3. The light oil fraction of the hydrogenated product of Midlothian coal consisted of 5 to 10 percent each of olefins and saturated hydrocarbons, with the remainder being aromatic compounds. 4. The rate of liquefaction of Midlothian coal by hydrogenation researched a nearly constant value of 0.41 grams of liquid product produced per 100 grams of coal per hour after 24 hours of reaction. 5. During the first 24 hours period of hydrogenation, the volatile matter content of the carbonaceous residue increased by 5.0 percent after which the volatile matter decreased by 6.2 percent during the following 48 hour period. 6. During the hydrogenation reaction of 72 hours the fixed carbon content of the coal was reduced by 18 percent. 7. During the latter 48 hours period of reaction, 65 percent of the liquefaction was from the volatile matter constituents and 35 percent of the liquidation was from the fixed carbon components. / M.S.