Sanjay Kumar Shukla

ABSTRACT The analysis of laterally loaded piles is generally carried out by idealizing the soil mass as Winkler springs, which is a crude approximation; however this approach gives reasonable results for many practical applications. For more precise analysis, the three- dimensional finite element analysis (FEA) is one of the best alternatives. The FEA uses the modulus of elasticity of soil, which can be determined in the laboratory by conducting suitable laboratory tests on undisturbed soil samples. Because of the different concepts and idealizations in these two approaches, the results are expected to vary significantly. In order to investigate this fact in detail, three-dimensional finite element analyses were carried out using different combinations of soil and pile characteristics. The FE results related to the pile deflections are compared with the closed-form solutions in which the modulus of subgrade reaction is evaluated using the well-known relationship. In view of the observed discrepancy between the FE results and the closed-form solutions, an improved relationship between the modulus of subgrade reaction and the elastic constants is proposed, so that the solutions from the closed-form equations and the FEA can be closer to each other.

ABSTRACT Background/Question/Methods Enhancing ecosystem services provided by agricultural lands is of much interest, but little research has examined how management for specific services affects others. We evaluated trade-offs among ecosystem services in an existing payment for ecosystem services (PES) pilot program in the Northern Everglades that is paying ranchers to retain water on their lands. In addition to water storage, ranchlands offer multiple ecosystem services, including forage production, a mosaic of wetland and upland habitats, and associated biodiversity. Our objectives were to: (1) quantify biodiversity and forage production on four ranches participating in the Florida Ranchland Ecosystem Services Project (15 wetlands); (2) evaluate whether enhanced water storage created synergies or trade-offs for the ecosystem services of biodiversity or forage production; and (3) determine whether enhancing water services affects stressors such as pests (mosquitoes) and invasive plants and animals, thus detracting from services provided. Ultimately, our data will refine decision tools to evaluate trade-offs among multiple ecosystem services at scales relevant to ranchers and decision makers. Results/Conclusions We used an information criterion approach to evaluate models describing the association between water storage, primarily measured as water depth; invertebrate and vertebrate abundance; plant richness; non-native plant cover; and wetland forage cover. We predicted that diversity of most organisms peaks at intermediate water depths, except fish, which were expected to become more abundant with increasing depth. Total abundance of macroinvertebrates, amphibians, and fish generally increased with water depth and peaked at intermediate to high depths, ~10-35 cm. Non-native vertebrates were too rare to compare with water availability. Plant richness decreased with increasing water depth in all wetlands. Plants associated with short-hydroperiod, diverse wet prairies declined with increasing water depths. Significant quadratic relationships between water depth and non-native plant cover were found in four of 15 wetlands. Our prediction that upland forage cover would decline with water depth was supported for all wetlands, but decreases in wetland grass cover (forage species) was not found at deeper depths. Our results suggest that managing for water services may create synergies and trade-offs with diversity depending on which organisms are considered.

Experiments were conducted on calcareous and sandy soils to investigate the effects of organic amendments for vegetable production on groundwater nitrogen (N) concentration in south Florida. The treatments consisted of applying yard and food residuals compost, biosolids ...

ABSTRACT This paper presents the details of an experimental study on the electrical resistivity of iron ore mine tailings produced in Western Australia. In the study, an experimental set-up is developed based on the Wenner Array, and has been used for determining the electrical resistivity of the tailings at different relative densities in dry and fully saturated conditions. The apparent electrical resistivity of the iron ore mine tailings ranged from 11 kΩm for a very dense state to 19 kΩm for a very loose state in dry condition; while for the fully saturated condition, the resistivity ranged from 20 to 31 Ωm for very dense state to very loose state, respectively. The results are discussed for their practical applications such as identifying weak zones in tailing embankments, extent of corrosion in buried steel pipelines, and extent of degree of compaction in structural fills.

ABSTRACT When the water table rises in a granular soil mass, a large additional settlement of footing resting on such a soil mass is commonly expected. Laboratory model tests show that when the water table rises to the footing level, there can be an additional 400 to 500% of the settlements compared to when the soil is dry. To understand the mechanics of the additional settlements of footings resting on the granular soil masses caused by water table rise, an investigation into the change in the Young's modulus of soil was therefore made using oedometer tests. A relation between the saturated and the dry Young's moduli of the granular soils is presented for use in the elastic analysis of footing settlements. The findings of the investigation were then used to predict the additional settlements of a model footing when subjected to a water table rise, using elastic analysis. The theoretical predictions of the additional settlements are lower than the actual additional settlements observed in the settlement tests conducted in the laboratory using model tests. The model tests show that the additional settlements are larger in loose sands than in dense sands.

ABSTRACT Background/Question/Methods Over the past five years the Florida Ranchlands Environmental Services Project (FRESP) has been field testing a payment for environmental services program in the Northern Everglades with the goal of providing water retention and nutrient removal services on working ranchlands to restore sensitive downstream ecosystems. Designs for site specific on-ranch water management projects in the pilot program included wetland rehydration, flow-through nutrient removal, and pasture water control. Real-time hydrologic monitoring equipment recorded data to allow documentation of stage, discharge, rainfall, pump volume, and nutrient concentrations. The pilot project was implemented through a collaboration of state and federal agencies, ranchers, scientists, and environmental groups and is now in the process of transitioning to a watershed scale payment for environmental services (PES) program. In the emerging PES program there will be a requirement to estimate the services provided as a basis for creating a PES contract. Results/Conclusions One of the largest hurdles was developing a method to predict the provision of the services provided by individual landowner projects. A user-friendly potential water retention model (PWRM) was developed to estimate the expected water retention at each site over ten years. The challenge of information exchange between agencies and land owners was met with field team communication and the development of an internet based database. The use of wireless (cellular and radio) telemetry increased efficiency in budget, personnel resources, and data quality. Remote monitoring reduced data loss due to equipment malfunction and enabled problems to be fixed quickly. Preliminary data show site visits were reduced by approximately 50% and the percentage of reliable data increased by 16% when comparing sites with telemetry and sites without. Wireless technology was integral to maintaining multiple streams of data monitoring for environmental services. Advanced tools for environmental monitoring, data transmission, and site management reduce costs and facilitate estimation of environmental services in large, complex PES programs.

FS factor of safety against sliding (dimensionless) H height of the rock slope (m) kh horizontal seismic coefficient (dimensionless) kv vertical seismic coefficient (dimensionless) q surcharge pressure (N/m2) q* nondimensional surcharge (= q/γH) (dimensionless) T stabilizing ...

Abstract Spatial variability of citrus yield is very common in Florida, but very little has been done to identify the responsible soil factors. Our objective was to characterize variations in soil physical properties in sandy soils where citrus is produced in Florida. A citrus grove ...

This paper introduces a novel meta-heuristic for resolving resource-constrained project scheduling problems (RCPSP), a well known NP-hard problem in operations research. In RCPSP the activities of a project have to be scheduled with the objective of minimizing the total makespan subject to both temporal and resource constraints. The proposed algorithm, named improved immune algorithm (IIA), is based on the traits of an artificial immune system. IIA is different from the traditional immune algorithm in its initialization and hypermutation mechanism. Initialization in IIA is done by using chaotic generator (Logistic, Tent, and Sinusoidal) instead of conventional random number generator (RNG). And hypermutation is performed by parallel mutation (PM) operator rather than point mutation. Parallel mutation comprises two mutation strategies viz. Gaussian and Cauchy. Gaussian strategy is utilized for small step mutation and Cauchy strategy for large step mutation. In order to demonstrate the efficacy of the proposed algorithm on RCPSP, Patterson's test suites are worked out. This study aims at developing an alternative and more efficient optimization methodology and opening the application of variants of artificial immune system for solving the RCPSP.

Abstract The graft copolymerization of poly (methyl methacrylate)[PMMA] onto wool initiated by the potassium persulfate-thiomalic acid (TMA) redox couple has been investigated in the presence of atmospheric oxygen. The percentage of grafting efficiency and polymerization ...

Rock slope stability analysis has been a challenging problem for civil and mining engineers. This is mainly due to the presence of joints/discontinuities within the rock mass. There are several types of rock slope failures observed in different field situations; a plane failure is ...

Abstract : Rock slope stability analysis has been a challenging problem for civil and mining engineers. There are several modes of failure in which a rock slope can fail; a plane failure is one of them. In recent past, a generalised expression has been presented for the factor of ...

This technical note presents an analytical derivation of the expression for the total dynamic active thrust on a retaining wall from the c–ϕ soil backfill considering both horizontal and vertical seismic coefficients. The derivation is based on the Coulomb sliding wedge concept, and it considers tension cracks, wall adhesion, and surcharge in order to make the expression useful for practical applications. It is found that the special cases of the general expression result in the expressions for total static and dynamic active thrusts presented by earlier researchers for different field conditions of soil backfills with and without seismic loadings.

ABSTRACT In the past, the beneficial effects of prestressing the geosynthetic in reinforced soil foundations have been studied mathematically. It is timely to experimentally investigate the degree of improvement generated by prestressing the geosynthetic layer for several embedment depths of a footing resting on a reinforced sand bed. Therefore, laboratory physical model tests and finite element analyses were conducted to study the behaviour of prestressed geotextile-reinforced sand bed supporting a loaded circular footing. The addition of prestress to the geotextile reinforcement results in significant improvement to the settlement response and the load-bearing capacity of the foundation. For a surface footing, the load-carrying capacity at 5 mm settlement for the prestressed case (with prestress equal to 2% of the allowable tensile strength of the geotextile) is approximately double that of the geotextile-reinforced sand without prestress. The beneficial effects of the prestressed geotextile configuration were evident for greater footing depths, in comparison with unreinforced and reinforced (without prestress) counterparts. Experimental and numerical results were also used to validate a few empirical relationships, which are commonly used for solving soil-structure interaction problems. The results obtained from finite element analysis using the program, PLAXIS are generally found to be in reasonabaly good agreement with experimental results.

This technical note presents an analytical expression for the total passive pressure on a retaining wall from the c–ϕ soil backfill subjected to both horizontal and vertical seismic inertial forces. The developed expression has been analysed for the special cases, and the results have been found identical to those proposed by earlier researchers on the subject. A numerical example, presented to illustrate the steps for the calculation of total dynamic passive pressure using the developed general expression, shows that the design value of total dynamic passive pressure as a resistance to the retaining wall movement should be obtained with upward vertical seismic inertial force in combination with the direction of horizontal seismic force towards the backfill.

... Enhanced fluoride removal from drinking water by magnesia-amended activated alumina granules. Shihabudheen M. Maliyekkal a , Sanjay Shukla a , Ligy Philip Corresponding Author Contact Information , a , E-mail The Corresponding Author and Indumathi M. Nambi a. ...

The effects of organic amendments on vegetable crop production, phosphorus (P), and trace element (Zn, Cu, Mn, B, Cd, Pb, Ni) concentrations in groundwater were investigated on calcareous and sandy soils in south Florida. Treatments consisted of applying yard trash and food ...