01-Moisture Content and Specific Gravity (original) (raw)

Comparison of techniques for measuring the water content of soil and other porous media

1999

A thesis submitted in the fulfillment of the requirements for the degree of Master of Science in Agriculture MCMXCIX Chapter 1-Review of the literature 1 Chapter one A review of the literature concerning the measurement of water in porous material 1.1. MEASURING MOISTURE STATUS OF POROUS MATERIALS There are three common ways of measuring the moisture in porous materials viz gravimetric, potential and volumetric measurements. The preferred determination depends on how the information required will be employed. For example, a plant biologist may prefer to discuss moisture with respect to potential, as this is how a plant responds to moisture in the soil-plantair continuum. Gravimetric determination, more correctly termed wetness, is the most widely utilised technique (across disciplines) for moisture content determination, as it is simple and well understood. Conversely, volumetric moisture content is most commonly used in irrigated agriculture as the reported figures can readily be converted to volumes of water required for optimum growth. With the development of electronic instrumentation for soil moisture determination, the volumetric basis of soil moisture measurement is now the most utilised of the methodologies. However, the relationship between the methodologies, the soil moisture characteristic (Section 1.1.4.2), requires explanation to allow a comparison between available in situ technologies. Figure 1-1 Schematic representation of soil matrix indicating relationship between air (A), soil particles (B) and water (C). Soil, as a porous medium, can be considered with respect to moisture status, a combination of three components: air, solid, and water. The relationship between the three components as shown in Figure 1-1 determines how water in soil moves, its ability to act as a solvent and its availability to plants. 1.1.1 Wetness The most common method for determination of moisture in soil is by removing a physical sample from the site in question. The sample is weighed, dried in an oven at 100 °C to 110 °C for 24 to 48 hours, and then re-weighed (Reynolds, 1970a; 1970b; Gardner, 1986). The gravimetric moisture content, termed wetness (w), is then determined: θ (1-6) Where a and b are constants for the identified soil sample. Equation 1-6 is limited in use especially in dry soil due to (potentially) large error.

A Proposed Approach for Evaluating Soils Optimum Moisture.pdf

Science Publishing Corporation, 2018

The processing of optimum moisture content for specific soils as indicated by ASTM D698 specifications detail relies upon developing the fitting third or second degree bend connection between dampness content versus soil dry unit weight on a fitting bend, the registered optimum moisture substance may contrast for a similar soil as for fitting bend figure and its position. The main objective of this study is to evaluate the optimum moisture content value based on computing average moisture content adapted from standard or modified Proctor compaction test trials and compared it with respect to the computing optimum moisture content using standard method. The research deals with a (52) compaction tests results with a wide range of optimum moisture content and dry unit weight to explore the relationships between them. The study also explores the maximum dry density values which versus standard optimum moisture content and average adopted moisture content. Statistical part depends on evaluating many statistical function values for standard and research method starts by evaluating significance of normality using Kolmogorov-Smirnov test. The average differences between standard optimum moisture content and an average value (this study depends) for moisture content was about (-0.20) and an average of differences for dry unit weight values was (0.261).

Determination of Saline Soils Specific Gravity

The existence of salts as part of the solid phase of the soil or dissolved within the pore fluid may cause significant errors in the values of specific gravity of such soils by using conventional determination methods. Errors may arise from effects of wrong measurements of weights or volumes that take place due to dissolution of the salt during testing, precipitation during drying or dehydration of the crystals of certain salts such as gypsum. To overcome this confusion, the standard procedure for specific gravity determination is reconsidered and the calculation methods are reanalyzed. Suggestions for a more adequate procedure for gypseous or other types of saline soils are presented and corrections required for computations are derived.

An indirect determination of the specific gravity of soil solids

Engineering Geology, 2018

The specific gravity of soil solids, , is a significant material property in geomechanics. It is determined in the laboratory by water, gas or kerosene pycnometer, following a rather complex procedure. This Note suggests an original, simple and quickalbeit not empirical-method, which only requires knowledge of the soil unit weight γ sat and the water content w in fully saturated conditions and allows one to obtain the soil solids specific gravity as a derived quantity. The method can be also used for unsaturated soils, provided that they (or a paste made of the soil itself) are previously fully saturated. G s values obtained applying this method to a variety of soils ranging from pure clays to fine-medium sands are in very close agreement with those determined using the pycnometer standard method. As a by-product, the method is a applicable also for assessing the in-situ unit weight of a saturated soil sample  sat , even of cohesionless fine-medium sandy soil, however disturbed it may be. The proposal method is not intended as a substitute for the standard pycnometer method, but as a simple and useful addition to the tool-bag for the characterization of ordinary soils.