Seismic Soil Pressures on Rigid Walls with Sloped Backfills

Wood (1973) provided analytical solutions for the response of a rigid wall retaining elastic uniform soil backfill of finite length subjected to harmonic base excitation. Wu and Finn (1999) proposed a modified shear beam solution and derived closed-form formulations for computing dynamic soil pressures under harmonic loading. However, for rigid walls retaining sloped backfills, analytical solutions are not available for computing seismic soil pressures against the walls. In the current study, seismic soil pressures on rigid walls retaining 2H:1V (27°) sloped backfills have been computed using a total of eight acceleration time histories recorded in past large earthquakes. These records were selected and linearly scaled to three levels of ground motions with a nominal PGA of 0.26g, 0.48g and 0.71g. Nonlinear time-history analyses were conducted using the computer program VERSAT-2D which uses a hyperbolic stress – strain model to simulate the hysteresis response of soil under cyclic loads. Soil pressure diagrams are shown in the paper for horizontal backfills (φ=32°), and for sloped backfills with loose sand (φ=32°) and dense sand (φ=40°) under the three levels of ground motions. A soil pressure coefficient, K0E, has been introduced to represent the total static and seismic pressures on a rigid (or non-yielding) wall. It is found that K0E varies from 1.1, 1.7 to 2.2 for horizontal backfills under ground motions of 0.26g, 0.48g and 0.71g, respectively. K0E increases to 2.7, 3.8 and 4.9 for the 27° sloped backfills under the same three levels of ground motions, respectively. The point of thrust is at about 0.47H above the base of wall for horizontal backfills, but for sloped backfills it increases to 0.53H for loose sand and 0.55H for dense sand

Comparison of 2-D and 3-D Dynamic Analysis of Effective Stress of Earth Dams

Presented in this paper is a comparison between the results of 2-D and 3-D dynamic effective stress analyses of a hypothetical earth dam and two real tailing dams. The study is based on a method of rigorous nonlinear dynamic analysis by taking account the interaction of the fluid and soil phase of the material

Preliminary Studies of Ground Motions at Treasure Island and Yerba Buena Sites During the 1989 Loma Prieta Earthquake

Site response analyses were conducted at the Treasure Island site where surface motions were recorded during the Loma Prieta earthquake. The analyses were conducted using a nonlinear dynamic effective stress method which took into account the effects of the liquefaction that occurred at the site. The rock motions recorded at nearby Yerba Buena Island were used as input motions. Computed and recorded ground motions transverse to the direction of wave propagation and associated response spectra were in good agreement. Agreement was also good in the radial direction, except in certain frequency bands higher than 1.25 Hz. Coherence studies showed that some of these discrepancies may be due to low coherence between the Treasure Island and Yerba Buena motions in these same frequency bands

Fast-growing Larix kaempferi suffers under nutrient imbalance caused by phosphorus fertilization in larch plantation soil

There are significant differences in the morphological and physiological responses of larch species with contrasting growth rates under fertilization. However, little is known about species-specific differences in responses to nutrient imbalance caused by fertilization. Therefore, in this study, the effects of nitrogen (N) and phosphorus (P) fertilization on the morphological, physiological and chloroplast ultrastructural traits of two contrasting larch species, fast-growing Larix kaempferi and slowly-growing L. olgensis, grown in larch plantation soil, were investigated during two growth seasons. It was shown that N and combined N and P (NP) fertilization increased plant photosynthesis, foliar N contents, chlorophyll contents, and dry mass accumulation and partitioning in aboveground organs in both larch species. Although P fertilization enhanced P accumulation, its presence reduced the N content in soluble proteins in the foliage of both larch species. Yet, P fertilization exhibited some differences in the two species: P fertilization increased photosynthesis, chlorophyll content and biomass accumulation of L. olgensis, while it decreased these parameters dramatically in L. kaempfert P fertilization increased foliar N content in L. olgensis, while it reduced it in L. kaempferi. P fertilized L. kaempferi had more damaged chloroplast ultrastructure than L. olgensis. In addition, L. kaempferi exhibited lower acid phosphatase activities, and higher photosynthesis and biomass accumulation than L. olgensis, except under P fertilization. L. kaempferi allocated more biomass into needles, except under P fertilization, while L. olgensis allocated more into stems under fertilization. In conclusion, it was shown that nutrient imbalance caused by P fertilization has greater negative effects on a fast-growing species than on a slowly-growing one, and the negative effects are related to differences in acclimation strategies, N partitioning to photosynthetic components, and P transportation and metabolism in the foliage.Peer reviewe

Acceptance and Preference for COVID-19 Vaccine among Japanese Residents at Early Stage of the Epidemic in Japan

Background: This study aimed to survey the attitudes toward COVID-19 vaccines and their acceptability among the Japanese public as soon as the United States Food and Drug Administration (FDA) authorized vaccines and their rollouts started around the world. Methods: An anonymous cross-sectional survey was conducted in Japan between 4 January and 5 March 2021. A questionnaire was administered to evaluate attitudes toward COVID-19 vaccines according to demographic characteristics, vaccine characteristics, and vaccine production. Results: A total of 1037 completed responses were received. More than half (63.5%) of the participants responded positively (extremely likely/likely) toward COVID-19 vaccines. The highest acceptance to be vaccinated was discovered among the youngest age group. As expected, participants who had never delayed acceptance or refused the vaccine in their history of vaccination had a significantly higher willingness to be vaccinated against COVID-19 (p < 0.001). Females (OR = 2.66, 95% CI: 1.99–3.58) and participants who had ever delayed acceptance or refuse the vaccine (OR = 3.49, 95% CI: 2.42–5.05) had higher odds of COVID-19 vaccine hesitancy. Participants with a postgraduate degree (OR = 0.64, 95% CI: 0.40–1.00) presented the highest willingness to be vaccinated against COVID-19. More than two-thirds (72.9%, 95% CI: 70.4%–75.8%) of the participants did not mind a booster dose required following primary vaccination. A total of 63.2% (95% CI: 60.0%–66.0%) of the participants only accepted a nearly 90% effective or above vaccine at preventing COVID-19. At the same, 86.4% (95% CI: 84.4%–88.4%) of the participants reported only accepting a vaccine with minor side effects. Conclusions: The moderate levels of COVID-19 vaccine acceptance found in the early phase of the pandemic demonstrate that it is important to improve the implementation of effective management for vaccine promotion and the acceptability of the vaccine to slow or delay transmission

The Effect of Central Loops in miRNA:MRE Duplexes on the Efficiency of miRNA-Mediated Gene Regulation

MicroRNAs (miRNAs) guide posttranscriptional repression of mRNAs. Hundreds of miRNAs have been identified but the target identification of mammalian mRNAs is still a difficult task due to a poor understanding of the interaction between miRNAs and the miRNA recognizing element (MRE). In recent research, the importance of the 5′ end of the miRNA:MRE duplex has been emphasized and the effect of the tail region addressed, but the role of the central loop has largely remained unexplored. Here we examined the effect of the loop region in miRNA:MRE duplexes and found that the location of the central loop is one of the important factors affecting the efficiency of gene regulation mediated by miRNAs. It was further determined that the addition of a loop score combining both location and size as a new criterion for predicting MREs and their cognate miRNAs significantly decreased the false positive rates and increased the specificity of MRE prediction

Dynamic soil-structure interaction: pile foundations and retaining structures

This thesis deals with two important topics in soil-structure interaction: seismic earth pressures against rigid walls and the seismic response of pile foundations. These two disparate problems are linked by a common method of solution which is an approximation to the response of the half-space, either linear or non-linear. The approximate formulation permits analytical solutions against rigid walls when the backfill is uniform and elastic. The solution agrees very closely with an existing exact solution. For elastic non-homogeneous backfills and for non-linear soil response the approximate formulation is expressed using the finite element method. An efficient computer program SPAW has been developed to determine dynamic thrusts and moments against rigid walls for arbitrary non-homogeneous soil layers. Results of analyses show that the peak dynamic thrusts are larger for a uniform soil profile than when the shear modulus of the soil varies linearly or parabolically with depth. The program SPAW also possesses the ability of modelling the effect of soil non-linearity on dynamic thrusts. Studies showed that an increase of peak dynamic thrust may be expected due to soil non-linearity, compared with results from a linear elastic analysis. A quasi-3D finite element method of analysis has been proposed to determine dynamic response of pile foundations subjected to horizontal loading. A computer program PlLIMP has been developed for the analyses of elastic response of pile foundations including the determination of pile impedances as a function of frequency. The analysis is conducted in the frequency domain. The program can analyze single piles and pile groups in arbitrary non-homogeneous soil layers. Another quasi-3D finite element computer program PILE3D has been developed for the analysis of non-linear response of pile foundations in the time domain. The program is suitable of dynamic analyses of single piles and pile groups. The soil non-linearity during shaking is modelled using a modified equivalent linear method. Yielding of the soil is taken into account and there is a no-tension option controlling the analysis. The proposed quasi-3D model has been validated using the elastic solutions from Kaynia and Kausel (1982), Novak and Nogami (1977) and Novak (1974), Fan et al. (1991), data from full scale vibration tests of a single pile and a 6-pile group, and data from centrifuge tests of a single pile and a 2x2 pile group under strong shaking from simulated earthquake. Excellent results have been obtained using the proposed method. Time-dependent variations of dynamic impedances of pile foundations during shaking have been evaluated for the model pile foundations used in the centrifuge tests. The analyses quantify the reduction in the stiffnesses of the pile foundations with the increased level of shaking. The translational stiffness Ƙѵѵ decreases the most during strong shaking; the rotational stiffness Ƙθθ decreases the least. However, the damping of pile foundations increases with the level of shaking.Applied Science, Faculty ofCivil Engineering, Department ofGraduat

Seismic induced flow deformation and remediation study of Sardis Dam

Previous investigations of the seismic stability of Sardis Dam indicated that the entire central silt core and a weak clayey silt layer in the dam foundation are susceptible to liquefaction which could result in large losses of shear strengths in these liquefied soils. The post-liquefaction behaviour of Sardis Dam was evaluated using new flow deformation analysis technique which was developed by Finn and Yogendrakumar (1989). The analysis showed the potential for large displacements including a great loss of freeboard during the design earthquake. A strategy of designing remedial measures to limit deformations to a tolerable amount was adopted over the conventional factor of safety approach. Various levels of remediations were investigated using TARA-3FL. The remediation procedure adopted for field trials was anchoring the upstream slope to the foundation using rows of rectangular prestressed reinforced concrete piles. Estimating post-liquefaction deformations for this remediation scheme posed challenging problems in analysis.Applied Science, Faculty ofCivil Engineering, Department ofGraduat