Characterization of Hydraulic Behaviours of Coarse Rock Materials in a Large Permeameter

The hydraulic behaviour of a rock material structure is a major feature for its design and safety assess- ment. Similar to all other physical problems, in order to enclose the governing equations systems and achieve a solution, the hydraulic characteristics of these materials need to be determined experimentally and implemented then into adopted thermo-dynamical models. This paper covers the process of the design, construction and operation of an experimental rig built for this specific purpose. Using the constructed large-scale permeameter, tests have been conducted. The non-linear hydraulic behaviour of various mate- rials under extreme turbulent conditions, where Reynolds number reaches unprecedented values, has not been studied before. Preliminary results are presented and discussed.

Soil hydraulic conductivity as affected by vegetation restoration age on the Loess Plateau,China

The Loess Plateau of China has experienced extensive vegetation restoration in the past several decades, which leads to great changes in soil properties such as soil bulk, porosity, and organic matter with the vegetation restoration age. And these soil properties have great effect on the soil infiltration and soil hydraulic conductivity. However, the potential changes in soil hydraulic conductivity caused by vegetation restoration age have not been well understood. This study was conducted to investigate the changes in soil hydraulic conductivity under five grasslands with different vegetation restoration ages （3, 10, 18, 28 and 37 years） compared to a slope farmland, and further to identify the factors responsible for these changes on the Loess Plateau of China. At each site, accumulative infiltration amount and soil hydraulic conductivity were determined using a disc permeameter with a water supply pressure of -20 mm. Soil properties were measured for analyzing their potential factors influencing soil hydraulic conductivity. The results showed that the soil bulk had no significant changes over the initial 20 years of restoration （P〉0.05）; the total porosity, capillary porosity and field capacity decreased significantly in the grass land with 28 and 37 restoration ages compared to the slope farmland; accumulative infiltration amount and soil hydraulic conductivity were significantly enhanced after 18 years of vegetation restoration. However, accumulative infiltration amount and soil hydraulic conductivity fluctuated over the initial 10 years of restoration. The increase in soil hydraulic conductivity with vegetation restoration was closely related to the changes in soil texture and structure. Soil sand and clay contents were the most influential factors on soil hydraulic conductivity, followed by bulk density, soil porosity, root density and crust thickness. The Pearson correlation coefficients indicated that the soil hydraulic conductivity was affected by multiply factors. These results are helpful to understand the changes in hydrological and erosion processes response to vegetation succession on the Loess Plateau.

Transport of solutes under transient flow conditions–A case study–Yamuna river sub basin(Kosi Kalan to Agra)

The imbalance between incoming and outgoing salt causes salinization of soils and sub-soils that result in increasing the salinity of stream-flows and agriculture land.This salinization is a serious environmental hazard particularly in semi-arid and arid lands.In order to estimate the magnitude of the hazard posed by salinity,it is important to understand and identify the processes that control salt movement from the soil surface through the root zone to the ground water and stream flows.In the present study,Yamuna sub-basin(both sides of Gokul dam site)has been selected which has two distinct climatic zones,sub-humid(upstream of Mathura)and semi-arid region(downstream of Mathura).In the upstream,both surface and ground waters are used for irrigation,whereas in the downstream mostly groundwater is used.Both soils and ground waters are more saline in downstream parts of the study area.In this study we characterized the soil salinity and groundwater quality in both areas.An attempt is also made to model the distribution of potassium concentration in the soil profile in response to varying irrigation conditions using the Soil-Water Infiltration and Movement(SWIM)model.Fair agreement was obtained between predicted and measured results indicating the applicability of the model.

A Comparison of Five Different Techniques to Determine Hydraulic Conductivity of a Riparian Soil in North Bavaria, Germany

Soil saturated hydraulic conductivity(K_s) is a predominant input factor when forecasting the vertical transport of contaminants through the soil or when estimating the flood retention capacity of the soil. Displacement of contaminants in the soil over extended periods of time can be attributed mainly to matrix flow, whereas flow through macropores becomes significant under untypically wet conditions, e.g., during spills or rain storms. To obtain matrix conductivities for a soil, the effects of macropores should be excluded.However, the K_s values of a soil profile are unlikely to be reflected solely by pedotransfer tables based on soil texture and bulk density.In this study, we examined five different methods(pedotransfer table, soil core, borehole permeameter, particle-size distribution curve, and instantaneous profile) to determine K_s values for a mercury-contaminated riparian soil for subsequent simulation of longterm mercury displacement toward groundwater. We found that the determined K_s values increased in the following order: borehole permeameter < particle-size distribution curve < pedotransfer table < instantaneous profile < soil core. The instantaneous profile method yielded K_s values of matrix flow, which additionally reflected the structure-related features of K_s values as provided by the soil core method. Despite being labor intensive and requiring expensive field sensors, the instantaneous profile method may provide the best representative in-situ K_s values for the studied site.