Prediction Of Soil Behavior Research Articles

Using Piezocone Tests for Analysis of Phreatic Water Conditions and Prediction of Soil Behavior in Tailing Dams

Using Piezocone Tests for Analysis of Phreatic Water Conditions and Prediction of Soil Behavior in Tailing Dams

Koni Penetrasyon Testi (CPT) İle USCS Zemin Sınıfının Belirlenmesi ve Değerlendirilmesi

In all geotechnical studies the classification of soil is important both for correct foundation design and prediction of soil behavior. In practice, determination of the soil class can be carried out by drilling or research pit works in the field. Besides, approaches to determine of soil classes from Cone Penetration Test (CPT) data are used. This study was carried out to correlate the predicted USCS soil groups by CPT tests with actual test results which were carried out on the samples taken from field. For this purpose, 15 exploration drillings and 15 CPT test data which were carried out on an alluvial soil were used. The results obtained by the experimental data on the samples taken from the research drillings were compared with the soil classes by CPT tests and correlated together. The findings revealed that the experimentally determined soil classes are considerably different from the soil classes determined by CPT end resistance values. The CPT method, which is insufficient to determine the plasticity of the soil, caused the SM group to be defined as “Sand – Clay”. Same situation was evaluated for SC group it was observed that CPT data were defined this group as “Clay”. This clearly demonstrates that soil classes that cannot be identified by in-situ sampling can lead to erroneous evaluations.

Study of mining tailings geotechnical parameters obtained from SCPTu tests carried on dry and saturated layers

The correct interpretation of in situ and laboratory test results is an important step in the design of mining tailing containment structures. This study aims to analyze the Seismic Cone Penetration Test (SCPTu) results obtained into a mining tailing reservoir composed of two material layers: a thick-dry and a tick-saturated. It is possible to observe that in a same tailing reservoir, the CPTu test interpretation can lead to a classification of each layer as a different soil with specific behavior and properties. This condition demonstrates that tailings with intermediate permeability (10-5 m/s < k < 10-8 m/s) may present partial drainage conditions during a standard cone penetration test (CPTu) (v=20 mm/s), if saturated conditions are verified. The effects of partial drainage can affect test results, and can induce to errors in the prediction of soil behavior and geotechnical parameters. To evaluate the possible effects of partial drainage, in situ test results were compared to laboratory tests results. It was possible to verify that estimated behavior of dry layers, obtained from in situ tests results, present more similarity to the results from laboratory tests. Probably, the partial drainage effects verified through the interpretation of dissipation tests, distorted the estimated behavior of the saturated layer material.

Impact of gasoline contamination on mechanical behavior of sandy clay soil

Oil leakage causes soil contamination and induces changes in the physical and mechanical properties of soils. In areas contaminated with oil products such as gasoline, the implementation of civilian operations requires determination and prediction of soil behavior in the existing conditions. In this research work, the effect of oil contamination by gasoline obtained from the National Oil Company in the Yazd Province is considered to investigate the effect of contaminants on the geotechnical properties of fine-grained sand. In order to examine the geotechnical characteristics of contaminated soil, compaction, undrained triaxial (CU), and consolidation tests are conducted. The tests are carried out on the samples of clean soil and contaminated soil with 1, 3, and 5% gasoline. The results obtained show that added gasoline reduces the optimum moisture content and increases the maximum dry density. In addition, based on the results of the triaxial test, the amount of friction angle and the cohesion of clay sand decrease by 21% and 14% with increasing contamination up to 5%, respectively, compared to the clean soil sample. Furthermore, adding gasoline significantly increases the compressibility and compression index.

Estimating undrained cyclic behavior of compacted mixed clayey soils by statistical tools

Cyclic loading-induced pore water pressure and degradation in the stiffness and strength of saturated soils are most important in dynamic stability analyses of soil structures, because they highly influence the behavior of soils. Conducting laboratory tests for the study behavior of soils is time-consuming, requires huge effort, and is usually expensive. Thereby, the prediction of soil behavior using analytical models can be utilized in the feasibility studies of projects, early decisions in the field, parametric analytical evaluations, etc. Therefore, some efforts have been made to model the excess pore water pressure and degradation characteristics of sandy and clayey soils due to cyclic loading; however, mixed clayey soils have not been examined in detail. This article offer regression analysis-based models to determine the cyclic loading-induced pore water pressure and degradation index of mixed clayey soils using laboratory tests data. The major parameters of the models are the number of loading cycles, cyclic strain amplitude, granular material content, and effective confining pressure. To establish functional relationships between variables, some linear and nonlinear regression tools are used. Residual analyses of the models illustrate that they are superior in establishing meaningful correlations and can be employed effectively, in practice, in the range of parameters used in conducting laboratory tests.

Development of nonlinear cross-anisotropic model for the pre-failure deformation of geomaterials

Nonlinearity and anisotropy of a stress–strain response have been accepted as important factors influencing the pre-failure characteristics of soils. To predict this complex behavior of soils, a simplified soil model was developed using the property of cross-anisotropic elasticity to represent the anisotropic stiffness of soils and the Ramberg–Osgood model to simulate nonlinear stress–strain curves. A hypo-elastic formulation of the stress–strain relationship can describe the directional stiffness as a function of the current stress in a given direction. The model employs the separate formulations of the initial and equivalent elastic moduli for describing the stress-dependency of elastic response of soils. The reliability and usefulness of the model were verified by applications of hollow cylinder tests and triaxial tests on silts. Predictions of soil behavior using this model were compared with representative stress–strain data. The close agreement confirmed that the model reasonably well predicted the nonlinear response of anisotropic deformation at the pre-failure state of soils.

Sample collection procedures for laboratory analysis in the United States soil survey program

Abstract The United States National Cooperative Soil Survey Program has prepared soil maps for much of the country. Both field and laboratory data are used to design map units and provide supporting information for scientific documentation and predictions of soil behavior. Coordination of mapping, sampling site selection, and sample collection in this program contributes to the quality assurance process for laboratory characterization. Requisites to successful laboratory analysis of soils occur long before the sample is analyzed. In the field, these requisites include site selection, descriptions of site and soil pedon, and careful sample collection. A complete description of the sampling site not only provides a context for the various soil properties determined, but it is also a useful tool in the evaluation and interpretation of the soil analytical results. Landscape, landform, and pedon documentation of the sampling site serves as a link in a continuum of analytical data, sampled horizon, pedon, lands...

Stress state-permeability relationships for fine-grained soils

This Technical Note investigates the possibility that stress state- permeability relationships might be developed for clays within the framework of generalisations already made in the analysis and prediction of soil behaviour. Consolidation and permeability tests carried out on red, brown, black cotton and bentonite soils, chosen for their varying liquid limits, are described. The results are presented and interpreted. For a given void ratio the experimental and predicted permeability coefficients showed a good correlation. The interchangeability of stress state and permeability is discussed.

Prediction of soil behaviour. Part IV — partly saturated soils : Nagaraj, T S; Murthy, B R S; Vatsala, A Indian Geotech JV21, N3, July 1991, P237–248

Prediction of soil behaviour. Part IV — partly saturated soils : Nagaraj, T S; Murthy, B R S; Vatsala, A Indian Geotech JV21, N3, July 1991, P237–248

Prediction of soil behaviour. Part III — cemented saturated soils : Nagaraj, T S; Murthy, B R S; Vatsala, A Indian Geotech JV21, N2, April 1991, P169–186

Prediction of soil behaviour. Part III — cemented saturated soils : Nagaraj, T S; Murthy, B R S; Vatsala, A Indian Geotech JV21, N2, April 1991, P169–186

The role of soil spatial variability investigation in the management of the Chad Basin vertisols of N.E. Nigeria

The Chad Basin of North-Eastern Nigeria is endowed with a vast expanse of vertisols that are not only rich in plant nutrient elements but also have a high water-holding capacity. These soils therefore are capable of supporting a large-scale production of food and forage crops alike. The ability of the soils to support large scale cultivation of forage crops is particularly significant in view of the fact that the North-East is the leading producer of livestock in Nigeria. Prediction of soil behaviour and crop productivity are conventionally based on soil test results. The reliability of soil test results on which management decisions are based cannot be greater than the reliability of the soil samples from which the results are obtained. The samples collected from the field must therefore be representative of that field. A procedure for obtaining representative soil samples, based on an adequate assessment of the soil spatial variability, is therefore presented. Surface soil samples (0–15 cm) were collected from 100 locations spaced at regular intervals of 2 m within a transect sited in the middle of a 2 ha field in the Chad Basin of North-Eastern Nigeria. The samples were analysed for exchangeable cations, saturation extract electrical conductivity (EC e ), particle size distribution, bulk density, organic carbon and pH. All the soil properties investigated were found to be normally distributed. Estimated sample autocorrelograms suggested that the observations of Exchangeable Na + , Exchangeable sodium percentage (ESP), EC e , Bulk density and silt content were spatially independent. Exchangeable Potassium and Magnesium, pH, percent sand and percent clay exhibited fairly strong spatial dependence while exchangeable calcium and organic carbon exhibited weak spatial dependence. The implications of the spatial dependence or independence of these soil properties in selecting appropriate soil sampling plans are discussed. Sample size calculations revealed that while it requires only one sample to estimate the mean values of clay content and pH within ±10% of the population means of these properties at the 95% confidence level, 696 samples would be required to estimate the mean value of exchangeable magnesium for the study area at the same precision level. The implications of these estimates of sample number requirements in obtaining reliable soil test results for improved management and enhanced productivity of these vertisols are discussed.

Settlement predictions in complex sabkha soil profiles

Sabkha soils are coastal and inland saline sediments of arid climates, commonly occurring in Middle Eastern and North African countries. They form heterogeneous and complex soil profiles with poor mechanical properties and appreciable organic content. In sabkha soils, prediction of soil behaviour is difficult due to the composite nature of the soil profiles. Geotechnical properties of a typical sabkha formation from the west coast of Saudi Arabia is studied. The settlement predictions based on statistical average of laboratory-determined compressibility parameters are compared with settlements measured in an instrumented test embankment. The predicted magnitudes of the settlements are found reliable and comparable to field measurements. Analysis based on laboratory determined parameters, however, highly overestimate the in situ settlement-time behaviour.