Embankment seismic fragility assessment: A case study on Xi’an-Baoji expressway (China)

Although embankment seismic damages are very complex, there has been little seismic fragility research yet. Researches on seismic fragility of bridges, dams and reinforced concrete (RC) structures have achieved fruitful results, which can provide references for embankment seismic fragility assessment. Meanwhile, the influencing degrees of retaining structures, such as retaining walls on the embankment seismic performances are still unclear. The K1025+470 embankment of the Xi’an-Baoji expressway was selected as the research object, and the finite difference models of the embankment fill-soil foundation system and embankment fill-soil foundation-retaining wall system were established. The ground-motion records for Incremental Dynamic Analysis (IDA) were selected and the dynamic response analysis were conducted. Probabilistic Seismic Demand Analysis (PSDA) was used to deal with the IDA results and the seismic fragility curves were generated. Based on the assessment results, the influences of the retaining wall on the embankment seismic fragility were further verified. The research results show that regardless of which seismic damage parameter is considered or the presence or absence of the retaining wall, larger PGAs always correspond to higher probabilities of each seismic damage grade. Seismic damages to the embankment fill-soil foundation-retaining wall system are always lower than those of the embankment fill-soil foundation system under the same PGA actions, thus, the retaining wall can decrease the embankment seismic fragility significantly.

Energy transfer and influencing factors in soil during compaction

In China, large-area excavation and filling engineering has increased rapidly with the expansion of construction land. The quality of filling engineering is the most important guarantee for the stability of building structures. Among all research on fill soil, the compaction characteristics are significant for indicating the strength and stability of filling engineering. In this paper, two layers of loess fill soil were compacted by a self-manufactured test system with three different compaction energies. Based on the variation in the soil bottom pressure obtained in the tests, the influence of the compaction parameters on the soil bottom pressure was investigated. The results show that the compaction curve can be used instead of the curve of the change in soil bottom pressure with water content; as the soil density increases, the soil bottom pressure increases to the maximum. The relation of the energy consumption ratio of the soil bottom (σ/σz) and the number of soil layers is exponential and reveals the stability of the soil skeleton formed during compaction. This paper describes the compaction characteristics of loess fill soil from the perspective of energy transfer, and the conclusions provide a theoretical basis for soil filling engineering.

Assessing the Risk Probability of the Embankment Seismic Damage Using Monte Carlo Method

There are few systematic studies on the risk probability assessment, although embankment seismic damages are extremely serious. Meanwhile, retaining walls and other retaining structures play positive roles in improving the embankment seismic performance, but relevant quantitative study is rarely reported. In particular, there are few existing studies on the seismic damage characteristics of the embankment fill-soil foundation system and the retaining structure-embankment fill-soil foundation system under different seismic actions. In view of this, the Xi’an-Baoji expressway K1125 + 470 embankment was taken as the research object, the risk probability assessment of the embankment seismic damage was conducted on the basis of the seismic fragility and seismic hazard assessment, the positive role of the retaining wall in improving the embankment seismic performance was verified, and the seismic damage evolution processes of the retaining wall-embankment fill-soil foundation system and the embankment fill-soil foundation system were analyzed. The research results show that the risk probabilities of the severe damage and destruction of the embankment fill-soil foundation system are 29.07% and 7.62% in the next 50 years, while of the retaining wall-embankment fill-soil foundation system are 19.30% and 3.46% and are reduced by 33.61% and 54.60%, respectively. The influence of the retaining wall on the embankment seismic performance mainly occurs at the middle stage of a violent earthquake, but the seismic damages of the retaining wall itself are also very serious, and the engineering disturbance of the retaining wall is reduced greatly or even lost completely at the final stage of the violent earthquake.

Effects of Fertilizer Type and Rate on the Quality and Nutrient Concentrations of Three Species of Field-grown Shrubs in South Florida

Three species of tropical shrubs, bush allamanda (Allamanda schottii), ixora (Ixora ‘Nora Grant’), and surinam cherry (Eugenia uniflora), were planted into a native sand soil and a calcareous fill soil in south Florida and were fertilized with a 24N–0P–9.2K (24–0–11) turf fertilizer or an 8N–0P–10K–6Mg plus micronutrients (8–0–12) palm fertilizer at rates of 10 or 20 g of nitrogen (N) per shrub four times per year. Two additional treatments using a 0–0–13.3K–6Mg plus micronutrients (0–0–16) palm fertilizer were applied at equivalent rates of potassium (K) (12.5 or 25 g/shrub of K) to that applied in the two 8–0–12 palm fertilizer treatments. Shrub size measurements, nutrient deficiency severity ratings, number of flowers, and shrub density ratings were determined at 6 months after planting (establishment period) and at 3 years after planting (maintenance phase). Data from these measured variables were subjected to principal component analysis to obtain a single measure of overall quality, namely, the scores for each plant on the first principal component. During the establishment period, ixora fertilized with the high rate of 8–0–12 had the highest quality on the sand soil, but there were no differences among treatments on the fill soil for this species or on either soil type for allamanda and surinam cherry. After 3 years of growth, ixora showed no differences in quality on either soil in response to the fertilizer treatments. On the sand soil, allamanda receiving the high rate of 24–0–11 or the low rate of 8–0–12 had significantly higher quality than unfertilized control plants, and the low rate of 8–0–12 produced the highest quality plants on the fill soil. Surinam cherry grown on sand soil had the highest qualities when fertilized with the high rates of either 24–0–11 or 8–0–12. In general, leaf nutrient concentrations were inversely correlated with overall shrub quality, with largest, highest quality plants having the lowest nutrient concentrations because of dilution effects. However, leaf manganese (Mn) concentrations were consistently within deficiency ranges for all species under most treatments, suggesting that Mn deficiency was stunting shrub growth on both soil types.

Nitrogen and Potassium Requirements for Field-grown Areca and Mexican Fan Palms

Potassium (K) deficiency is a widespread problem in palms growing in sandy or calcareous soils in southeastern United States. Its symptoms are highly conspicuous, reduce palm aesthetic appeal, are difficult to correct, and can be exacerbated by nitrogen (N) fertilization. The objective of this study was to determine the optimum fertilization rates and ratio for N and K in areca palm [Dypsis lutescens (H. Wendl.) Beentje & J. Dransf. and Mexican fan palm (Washingtonia robusta H. Wendl.) growing in a calcareous sandy fill soil. Both species had their highest quality when fertilized with 12.2 g·m−2 N and 12.2 g·m−2 K from controlled-release (2–3 month release) sources every 3 months. Actual N and K application rates were better predictors of palm quality than N:K ratio at the highest fertilization rates that would be recommended for field nursery production. However, at lower application rates more typical of those used for landscape palm maintenance, palm quality improved as the N:K application ratio was decreased.

Seismic Damage Investigation of Residential Fill Ground in the Eastern Part of Kyoto Basin

Several earthquakes record that the residential fills always suffer severe damages. In order to know the seismic damage mechanism and evaluate the damage extent of residential fill ground, research is carried out on two fill grounds in the eastern part of Kyoto basin. The research includes field survey about terrain condition, geological condition, development history, disaster condition during 1995 Kobe earthquake and surface wave explorations. Some remarkable conclusions are summarized as follows: In Jyodo-ji area, it is a residential fill on soft alluvium ground. The geological condition is back swamp. The thickness of surface fill soil is about 1~4 meters. In Kiyomizu-dera area, it is a valley filled ground. The geological condition is hilly platform.