46 research outputs found
Estimating Dynamic Properties from Static Tests
The applicability of various types of constitutive models to estimating dynamic material properties for soils from the results of static shear tests is briefly reviewed. The primary obstacle to making such predictions is the limiting resolution of conventional static tests. A simple procedure using empirical relationships to interpolate beyond the limit of the static shear tests is suggested for use in preliminary analysis and in cases where cyclic test data is not available
Performance of Landfills Under Seismic Loading
The record of performance of landfills in earthquakes is excellent. However, the advent of geosynthetic liner and cover systems has increased the susceptibility of modern landfills to seismically-induced instability and deformations. Analyses used to assess the performance of landfills in earthquakes include site response, limit equilibrium stability, and Newmark deformation analyses. Well documented case histories of the behavior of landfills subject to seismic loading are necessary to improve knowledge of the parameters required for these analyses and thereby enhance the reliability of seismic performance evaluations for landfills
Effective Stress Analyses of Seismic Stability
The factors involved in performing effective stress analysis of seismic stability problems are examined. The advantages of using a stochastic model for pore pressure generation are discussed. A simplified analysis of a hypothetical case is outlined to illustrate the factors involved in performing effective stress stability analysis
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Durable and ductile double-network material for dust control
Dust generation is a world-wide issue due to its serious deleterious effects on the environment, human health and safety, and the economy. Although various dust suppression methods have been used for decades, some critical drawbacks in state-of-the-art technology still remain unsolved, such as short-lasting, ground water impact, and prone to water. This work reports a soil stabilizer based on non-toxic material and forms a ductile and durable double-network in soil, namely “D3 soil stabilizer”, which not only improves soil mechanical toughness of surface soil but also suppresses dust generation. A copolymer comprising hydrophilic and hydrophobic components combined with enzyme-induced carbonate precipitation is utilized as an in-situ gelation binder to soil particle. The tunable hydrophobic-to-hydrophilic component ratio minimizes undesirable soil matrix expansion and mechanical strength loss upon experiencing wet-dry processes, while still retains good water affinity. We further demonstrated controllable treatment depth by fine-tuning precursor composition, which is essential to minimize environmental impact. The double-network morphology with carbonate precipitate embedded uniformly in polymer matrix is observed via microscopic imaging. The nature of outstanding ductility, high durability against water, and good long-term stability were supported by systematic unconfined compressive strength (UCS) measurements on treated soil, which show strong inter-particles binding, good retention of peak strength, increased strain at peak strength, and increased toughness after soil samples have experienced wet-dry processes
Solid Waste Landfill Performance During the 1994 Northridge Earthquake
The performance of 22landfills in the Los Angeles area during the January 17, 1994 Northridge earthquake has been investigated. Observations of damage at these landfills indicate that the overall performance of solid waste landfills was encouraging. None of the surveyed landfills showed any signs of major damage. However, one geosynthetic-lined landfill experienced two tears in the geomembrane liner. Most landfills within 30 km of the zone of energy release experienced some form of cracking in the soil cover. Beyond approximately 40 km from the zone of energy release, little to no damage was observed
A multi-phase biogeochemical model for mitigating earthquake-induced liquefaction via microbially induced desaturation and calcium carbonate precipitation
A next-generation biogeochemical model was developed to
explore the impact of the native water source on microbially induced
desaturation and precipitation (MIDP) via denitrification. MIDP is a
non-disruptive, nature-based ground improvement technique that offers the
promise of cost-effective mitigation of earthquake-induced soil liquefaction
under and adjacent to existing structures. MIDP leverages native soil
bacteria to reduce the potential for liquefaction triggering in the short
term through biogenic gas generation (treatment completed within hours to
days) and over the longer term through calcium carbonate precipitation
(treatment completed in weeks to months). This next-generation
biogeochemical model expands earlier modeling to consider multi-phase
speciation, bacterial competition, inhibition, and precipitation. The
biogeochemical model was used to explore the impact of varying treatment
recipes on MIDP products and by-products in a natural seawater environment.
The case study presented herein demonstrates the importance of optimizing
treatment recipes to minimize unwanted by-products (e.g., H2S
production) or incomplete denitrification (e.g., nitrate and nitrite
accumulation).</p
Development of a numerical model for performance-based design of geosynthetic liner systems
Enhancement of Pervious Concrete Pile Subjected to Uplift Load Using Microbial Induced Carbonate Precipitation
Landfill redevelopment
Landfill redevelopment plays a significant role in efficient land use management acting as a catalyst in sustainable planning: the demand of more room for city growth makes abandoned landfills a sort of “recycled” resource that can upgrade spaces and activities in terms of city form, land value and environment features. Risk’s issues concern environmental, social, financial and political aspects of redevelopment. Moreover risk could be determined by a single topic but it rapidly involves the whole project (see risk definition below). Risk is not only a technical matter regarding engineering solution or environment vulnerability: it is more a general issue that decides the failure in terms of social and financial expectation and political credibility. It represents the main obstacle in order to promote redevelopment policies by public sector. So to enhance redevelopment, it’s important to improve the decision process by an innovative approach, concerning not only the engineering solution but also social and financial aspects of redevelopment that involve a quantity of subjects that play a role in the project course: public sectors, developers, site residents, associations, and expert’s lead decision process toward a flow that needs a continuous feedback among the different stages of knowledge, assessment and decision