Non-uniform Soil Research Articles

Compression rings support deep cut : Lalwani, C L Civ Engng, N Y, V52, N12, Dec 1982, P50–51

The plans for building the Cuyahoga Valley Interceptor Lift Station in Cleveland, Ohio, called for 126 ft. (38.4 m) by 105 ft. (32 m) construction, some 80 ft. (24.4 m) below grade. Bracing of this large and deep excavation was done by four reinforced concrete compression ring beams (largest of this kind in the United States). Clear and uncluttered working space within the excavated area was an expedient way to build the concrete framed Interceptor Lift Station. The complex design of the ring beams was done keeping in consideration the uneven loading patterns due to excavation procedures and due to non-uniform soil properties. A close coordination between design assumptions and the Contractor's operations was a must for the success of the project. Inclinometers were installed to monitor the mass movement and the stability of the soil.

Scale Model Studies of Station Grounding Grids

The design and use of scale models for evaluating the performance of grounding grids is described. Construction details of two electrolytic tanks of different sizes and of a number of scale- model grids are discussed, together with the associated instrumentation. Results are presented showing the potential profiles for a number of grids and the effects of the number of meshes, the use of ground rods, and non-uniform soil resistivity.

Alternative compaction specifications for non-uniform fill materials : Pickens, G A Proc 3rd Australia-New Zealand Conference on Geomechanics, Wellington, 12–16 May 1980, V1, P231–235. Publ Wellington: New Zealand Institution of Engineers, 1980

The difficulties that arise in enforcing standard compaction specifications where the fill materials are not uniform, are described. A case is made for alternative specifications that permit much more straightforward and reliable control testing in non-uniform soils. The alternative air voids - strengths approach is described for soils ranging in type from clays to sands.

Study of Driven Ground Rods and Four Point Soil Resistivity Tests

A series of tests has been conducted to compare the apparent soil resistivity of a driven ground rod with the soil resistivity measurements obtained by the four point method. Both uniform and non-uniform soil conditions were encountered. A theoretical analysis is performed for the two test methods in two-layer soil conditions. An equation is derived to enable the calculation of the driven rod apparent soil resistivity based on the four point soil resistivity tests.. The actual test results are analyzed based on two-layer theoretical considerations. Possible limitations of the four point test method are discussed.

Using Check Varieties to Adjust Visual Scores for Nonuniform Soil Drying in Drought Resistance Field Screening

Using Check Varieties to Adjust Visual Scores for Nonuniform Soil Drying in Drought Resistance Field Screening

Solutions of the heat conduction equation in a non‐uniform soil

AbstractA class of analytic, periodic solutions of the heat conduction equation in a non‐uniform soil is derived. The class may be characterized by the fact that the speed of the temperature wave varies according to the square root of the soil diffusivity (a function of soil depth). In addition it is shown that the constant soil solution is the limiting case when the rate of change with depth of diffusivity and thermal conductivity become very small. The solutions may be regarded as general whenever temperature analysis is restricted to small values of depth or whenever the soil parameters vary slowly. For all other cases the class of solutions possess the additional property that the rate of change of conductive capacity varies directly as the product of the bulk density and specific heat of the soil. A particular temperature profile is given for the case when the diffusivity varies as the nth power of depth.

The vertical response of an ocean bottom seismometer: Analysis of the Lopez Island vertical transient tests

A lumped-parameter model was developed to predict the response of an ocean bottom seismometer, resting on relatively non-stiff sediments, to vertical ground-motion. The model predictions were compared with the response of an instrument on a foundation of foam rubber to a sinusoidal input. Comparison of the model data to the measured Lopez Island vertical transient test data showed that bearing pressure of the instrument in a nonuniform vertical soil profile causes certain instruments to experience a shear modulus higher than the mean.

Surface Hydrology: IV°Flow in Sloping, Layered Soil

In a nonuniform soil with rotational symmetry the properties change along a coordinate n that forms an angle \Ia\N with the vertical. During infiltration there will be a flow component in the parallel direction s downstream, which is proportional to the rain itself and the slope. The horizontal flow is proportional to the vertical flow, the slope, and the coefficient of anisotropy. The last has been calculated for a soil made up distinct layers. In the limiting case of very thin layers or near the saturation point, the vertical and horizontal conductivities are, respectively, the expected arithmetic and harmonic means familiar from saturated flow. The coefficient of anisotropy increases with the rate of vertical flow to a power greater than unity. The horizontal flow component can be many times the vertical one. It finds application in pollution problems and in the study of the underground water regime.

The Application of Computer-Aided Grounding Design Techniques to a Pulp and Paper Mill Grounding System

The combination of computer analysis and measurements used to determine the optimum configuration for the grounding system for a large pulp and paper mill which includes three substation grounding grids, each located in a significantly different nonuniform soil, is presented. A thorough analysis and measurement program prior to construction of a new facility which can identify major problems before they occur is shown. Minimum cost solutions to the problems are proposed.

Surface Hydrology: III°Causes of Lateral Flow

Streamlines bend after they enter a nonuniform, sloping soil. On penetrating to a more permeable soil layer they bend downstream. This can occur in unsaturated soil above a sloping water table or in a layer in which water accumulates because of the presence of less permeable underlying layer. We considered the general case of a nonuniform soil with rotational symmetry at an angle to the vertical, i.e., a sloping soil. General proof is provided that the soil generally behaves as a anisotropic medium so that infiltration also invloves a horizontal net flow component. This net flow component is proportional to the slope, the vertical flow, and the coefficient of anisotropy. The existence of such a mechanism can account for the concentration of water in concave spots, possible seepage, and runoff and erosion phenomena at low rates of rainfall. It can also explain how a previous rainfall leads to earlier onset of runoff during the next rain, etc.

Rain Infiltration into Layered Soils: Prediction

A simple model, based on the Green-Ampt approach, for describing one-dimensional vertical water infiltrarion into nonuniform soils under rain application is presented. The model contains three measurable input parameters which are based on properties and initial soil profile conditions. The model performance is compared against another model derived from the general flow theory and a good agreement is found. The comparison is made for different soil profiles and rain intensities. The application of the model is illustrated by numerical examples. Conditions under which soil surface saturation and water ponding occur are examined. The model provides a useful workable tool, in irrigation and hydrology, for approximating infiltration in the field where the soils are seldom uniform.

Transmission Line Tower Grounding Performance in Non-Uniform Soil

Detailed computer analyses of a 765 kV typical transmission tower footing grounding performance during phase-to-ground fault condition are described and discussed. It is assumed the tower is erected on a two-layer earth structure. The tower resistance, worst touch and step potentials, are calculated for various soil conditions described by the top layer height and both layer resistivities. Universal charts are presented to help the engineer in predicting and designing transmission tower ground performance.

Field investigations of structurally nonuniform eluvial soils : Proc International Symposium on the Geotechnics of Structurally Complex Formations, Capri, 1977, Vol 1, P211–217

Field investigations of structurally nonuniform eluvial soils : Proc International Symposium on the Geotechnics of Structurally Complex Formations, Capri, 1977, Vol 1, P211–217

Statistical theory of sampling nonuniform soils : Ratz, M V; Sheinin, V I Proc International Symposium on the Geotechnics of Structurally Complex Formations, Capri, 1977, Vol 1, P359–399

Statistical theory of sampling nonuniform soils : Ratz, M V; Sheinin, V I Proc International Symposium on the Geotechnics of Structurally Complex Formations, Capri, 1977, Vol 1, P359–399

Digital calculation of earthing systems in nonuniform soil

The mathematical model of earthing systems consisting of straight-line elements in the nonuniform soil is developed. The method presented enables the evaluation of all earthing system characteristics by applying a general algorithm, appropriate for digital computing, based upon elementary data of the earthing system and soil configuration.

Error associated with measurement of soil moisture change by neutron probe

For soil moisture estimation by neutron probe, it is shown that field calibration data should be analysed using a regression of moisture content on count ratio. A set of correction factors are derived for use with a probe which account for the sphere of influence penetrating a soil/air interface. These factors limit the uncertainty of soil moisture estimation in surface layers to that associated with non-uniform moisture profiles. Three different techniques are used to determine these factors and the results are compared. Non-uniform soil moisture conditions during collection of calibration data exert a greater influence than does bulk density, on the uncertainty in the relationship between soil moisture content and count ratio. The resulting uncertainty in the regression coefficient must be considered in error analysis of soil moisture change. Calculated and measured estimates of likely errors associated with soil moisture change data are found to agree.

Errors in Gamma‐ray Measurements of Water Content and Bulk Density in Nonuniform Soils

AbstractRecent experimental study of freezing soils has shown gamma‐ray measurements of water content and bulk density are in error when the water content and bulk density are not uniform throughout the gamma‐ray beam. Many gamma‐ray measurements involve nonuniform soils. This study was conducted to determine the magnitude of errors due to nonuniform bulk density and water content. Errors in gamma‐ray water content and bulk density were determined for soil‐water systems with linear and step‐function changes in water content and bulk density and for measurements of water absorption by a nonswelling porous medium. Both single‐energy and dual‐energy gammaray systems were analyzed.Large errors in water content and bulk density determined by dualenergy gamma‐ray measurements can occur for highly stratified soils. The calculated values may fall outside the range of values within the gamma‐ray beam. Relatively small errors occur if the bulk density and water content change linearly in the collimated beam. Both single‐ and dual‐energy systems accurately measure the average water content in the collimated beam if the bulk density of the soil is constant. However, the average water content in the beam may not represent the water content at the middle of the collimated beam and the middle of the preset time period. Errors due to nonuniform soils can be evaluated using the equations and graphs presented.

Bearing capacity of piles in layered soils. Part 1. Clay overlying sand

The paper summarizes investigations on jacked and driven piles in non-uniform soils consisting of clay and sand. Part 1 deals with the bearing capacity of piles penetrating through clay into sand whereas Part 2 discusses the case of piles in a sand stratum overlying clay. Preliminary tests on small model piles have been undertaken to study the effects on the point resistance of parameters such as the strength and thickness of a clay stratum, the strength ratio of soils in the two layers and the geometry of the layers. Based on these results, tests on a 76 mm diameter instrumented steel pile and a 36 mm diameter static cone penetrometer have been carried out for selected combinations of the variables involved.The test results are analysed to determine the influence of clay thickness and strength on the point resistance of piles in sand, expressed by a non-dimensional clay strength factor λ, and parameters influencing λ are discussed. The effect of layering on the shaft friction in sand and the radial stresses along the pile length are studied. The efficiency of small groups of model piles in layered soils is obtained. Field data are analysed, including scale effects, and simple design rules are suggested to estimate the bearing capacity of piles in layered soils.

CORRELATION OF ALFALFA YIELD WITH VARIOUS INDEX OF SALINLLY

ABSTRACT Lysimeter alfalfa yield response to nonuniform soil salinity was related to: D irrigation water salinities, 2) average profile soil salinities. 3) soil water salinities weighted on the basis of water uptake by the crop at the appropriate root-zone depth, and 4) in situ soil water salinities integrated over time. Alfalfa yield correlated best with no. 4. For most field situations, average profile soil salinity would be a useful approximate index of salinity for relating alfalfa yield response under conditions of flood irrigation management.

Soil Water Uptake by Alfalfa1

AbstractWater uptake patterns of alfalfa (Medicago sativa L.) assist us in understanding proposed models governing plant water uptake. The data in this paper are presented to elucidate some details of passive water uptake from profiles with nonuniform soil water distributions. Soil water content under an alfalfa seed crop was monitored with a neutron moisture probe. Alfalfa roots withdraw soil water in the lower portion of the root zone (where soil matric potentials were between −7 and −10 bars), while the upper portion of the profile was above −2 bars. This indicates that for passive water uptake to occur, large water potential differences must exist between the root xylem and the soil in the upper, moist portion of the profile. Plant water potential measurements support passive uptake.