Evaluation of Geosynthetics Use in Pavement Foundation Layers and Their Effects on Design Methods

This report presents findings of a research effort aimed at reviewing and updating existing Illinois Department of Transportation (IDOT) specifications and manuals regarding the use of geosynthetic materials in pavements. The project consisted of three tasks: evaluate current IDOT practice related to the use of geosynthetics; review research and state of the practice on geosynthetics applications, available products, design methods, and specifications; and propose recommendations for geosynthetic solutions in pavements to modernize IDOT’s practices and manuals. The review of IDOT specifications revealed that geotextiles are the most used geosynthetic product in Illinois, followed by geogrids. Several of IDOT’s manuals have comprehensive guidelines to properly design and construct pavements with geosynthetics, but several knowledge gaps and potential areas for modernization and adoption of new specifications still exist. Based on the review of the available design methods and the most relevant geosynthetic properties and characterization methods linked to field performance, several updates to IDOT’s practice were proposed. Areas of improvement are listed as follows. First, establish proper mechanisms for using geogrids, geocells, and geotextiles in subgrade restraint and base stabilization applications. This includes using shear wave transducers, i.e., bender elements, to quantify local stiffness enhancements and adopting the Giroud and Han design method for subgrade restraint applications. Second, update IDOT’s Subgrade Stability Manual to include property requirements for geogrids, geotextiles, and geocells suitable for subgrade restraint applications. Third, establish proper standards on stabilization, separation, and pumping resistance for geotextiles by incorporating recent research findings on geotextile clogging and permeability criteria. Fourth, promote the use of modern geosynthetic products, such as geotextiles with enhanced lateral drainage, and fifth, elaborate on proper methods for construction/quality control measures for pavements with geosynthetics.

A theory of glacier dynamics and instabilities Part 1: Topographically confined glaciers

We present a theoretical framework that integrates the dynamics of glaciers with and without the topographic confinement. This Part 1 paper concerns the former, which may exhibit surge cycles when subjected to thermal switches associated with the bed condition. With the topographic trough setting the glacier width and curbing the lateral drainage of the meltwater, the problem falls under the purview of the undrained plastic bed (UPB) formalism. Employing the UPB, we shall examine the external controls of the glacial behavior and test them against observations. Through our non-dimensionalization scheme, we construct a 2-D regime diagram, which allows a ready prognosis of the glacial properties over the full range of the external conditions, both climate- and size-related. We first discern the boundaries separating the glacial regimes of steady-creep, cyclic-surging and steady-sliding. We then apply the regime diagram to observed glaciers for quantitative comparisons. These include the Svalbard glaciers of both normal and surge types, Northeast Greenland Ice Stream characterized by steady-sliding, and Hudson Strait Ice Stream exhibiting cyclic surges. The quantitative validation of our model containing no free parameters suggests that the thermal switch may unify the dynamics of these diverse glaciers.

Flow Topology in the Confluence of an Open Channel with Lateral Drainage Pipe

The purpose of this paper is to develop design guidelines for flood control channel height in the vicinity of the confluence of a submerged drainage pipe and a flood control channel. The water exchange in the confluence of an open channel with a lateral drainage pipe produces unique hydraulic characteristics, ultimately affecting the water surface elevation in the channel. An accurate prediction of the water surface elevation is essential in the successful design of a high-velocity channel. By performing several experiments, and utilizing a numerical model (FLOW-3D), this study investigated the impact of submerged lateral drainage pipe discharges into rectangular open channels on flow topology in the confluence hydrodynamics zone (CHZ). The experiments were conducted in different flume and junction configurations and flow conditions. Moreover, the simulations were performed on actual size channels with different channel, pipe, and junction configurations and flow conditions. The flow topology in the CHZ was found to be highly influenced by the junction angle, as well as the momentum ratios of the channel flow and the pipe flow. The findings of this study were used to develop conservative design curves for channel confluences with lateral drainage pipe inlets. The curves can be used to estimate water surface elevation rise in different channel and pipe configurations with different flow conditions to determine the channel wall heights required to contain flows in the vicinity of laterals.

Analysis of the application results of the traditional vacuum preloading method: A case study

The traditional vacuum preloading method is a common way for enhancing the bearing strength of the soft clay layer. In general, a serious of plastic drainage boards are plugged into the soft clay foundation, and a sand layer is covered above the soft clay layer to establish a space for lateral drainage of the clay before applicating vacuum load. This paper analysed the application results of the traditional vacuum preloading method with the help of the data from an engineering case. The in-site testing data of the variation of the pore pressure in clay layer and the settlement are collected to evaluate the benefit of traditional vacuum preloading method.

Geofluid dynamic concept of prospecting for hudrocarbon accumulations in the earth crust

In our paper we produce new evidence of the tectonosphere and hydrosphere structure of oil and gas sedimentary basins and confirm significant influence of geofluid-dynamic processes on formation of hydrocarbon accumulations in the crust at the great depths. In our opinion the theory based on obsolete views on the tectonosphere structure lessen the importance the sedimentary migration theory of hydrocarbon generation. We prognosticate a particular stagnant type of post-elysionic water-drive systems in the crust at the great depths in conditions of increased hydrodynamic isolation. Absence of regionally sustained vertical and lateral drainage layers characterizes geological environment where stagnant type developed, and, corollary, fluids outflow into external environment is practically unfeasible. The subsalt filling complexes of the epicontinental deepwater basins are included into the post-elysionic water-drive systems. These complexes occur at the great depths and possibility of striking unique and large oil and gas fields there is inherent. We propose a system of fluid-dynamic conditions for preserving hydrocarbon accumulations in the lower crust as a result of developing sedimentary-migration theory for oil and gas formation. We consider the refinement of methods for prospecting and exploration large deposits at the great depths will pave the way for expanded reproduction of hydrocarbon reserves in the “old” oil and gas producing regions in our country.

Assessment of Leachate Production from a Municipal Solid-Waste Landfill through Water-Balance Modeling

Mineral temporary capping systems of landfills are required to accomplish the long-term coverage prerequisites or to use them as a basis layer prior to later permanent sealing. Such a capping system for a municipal waste landfill in Rastorf (Northern Germany) was developed and tested for its sealing capability on the basis of observed and simulated water balance components for the period between 2008 and 2015, considering observed local weather data and complemented by the Hydraulic Evaluation of Landfill Performance (HELP 3.95 D) model. The modeling results of this case study could be improved by the correction of previously used global solar radiation data due to the consideration of exposure and inclination angle of landfill surface areas. The model could positively be validated by comparing observed and simulated outflow (surface runoff and lateral drainage) data with R2 values ranging between 0.95 and 0.99, as well as for the leachate rates with R2 values of 0.78–0.87. The statistical-empirical HELP model was found useful in predicting the leachate generation of a temporary landfill capping system for specific soil and site conditions, even if only a restricted set of observed data was available.