Soil Mechanics Laboratory Manual Pdf Free Download

This manual presents procedures for performing advanced laboratory tests on fine-grained soils. It covers characterization tests, which determine soil composition and quantify the individual components of a soil, and behavioral tests, such as the Atterberg Limits tests that demonstrate how the fines fraction of a soil reacts when mixed with water and the Linear Shrinkage Test that demonstrates how much a soil shrinks.

The material goes beyond traditional evaluation of basic soil behavior by presenting more advanced laboratory tests to characterize soil in more detail. These tests provide detailed compositional characteristics which identify subtle changes in conditions and vertical variations in the soil, and which help to explain unusual behavior.

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Course content:

Independent performance of geotechnical field and laboratory tests: standard laboratory tests, determination of stiffness parameters of soils (compression tests), determination of strength parameters of soils (triaxial and frame shear tests), determination of permeability coefficient; plate load test, handling of evaluation programs.

Soil mechanics is a subdiscipline within civil engineering and geological engineering that is based on engineering mechanics, engineering geology, and soil physics (Mayne et al. 2002). Engineering mechanics is the field of study of forces acting on bodies and the response of those bodies in terms of motions, stresses, strains, and deformations (NAVFAC 1986). It is based fundamentally on physics and mathematics, with emphasis placed on solving problems and supporting engineering design. Mechanics of materials initially addresses ideal materials that are homogeneous, isotropic, linear, and elastic, and then includes nonideal materials, such as composite materials. Soil is a natural composite material consisting of solid, liquid, and gaseous phases; it is heterogeneous, anisotropic, nonlinear, and plastic to brittle depending upon whether it is completely dry, fully saturated, or partially saturated. Soil may exhibit elastic behavior over a small range of stress, but it also...

Origin, development, and properties of soils. Classification of soilsand applications of engineering mechanics to soils as an engineeringmaterial. Water in soils. Soil-testing methods. Compaction,stabilization, consolidation, shear strength, and slope stability.Prerequisites: CENG 20 and 44A. Corequisite: CENG 121AL. (3 units)

Origin, development, and properties of soils. Classification of soils and applications of engineering mechanics to soils as an engineering material. Water in soils. Soil-testing methods. Compaction, stabilization, consolidation, shear strength, and slope stability. Prerequisites: CENG 20 and 44A. Corequisite: CENG 121AL. (3 units)

The developer wishes to thank the user for providing a detailed report on the initial use of the FHWA soil material model. The insights provided by a novice user of the soil model enabled the developer to incorporate needed improvements. However, it is the developer's opinion that the user's soil model evaluation revealed no substantial problems with the model. Instead, the evaluation exposed mainly what appears to be a misunderstanding of continuum mechanics material models and their use in finite element analysis.

- The large deformation honeycomb model analysis presented is entirely irrelevant with respect to the soil direct shear test simulation. The latter involves material failure, separation, and development of a sliding interface, while the honeycomb example only illustrates crushing of a material block without generation of new material surfaces or significant shearing. Material type 126 is essentially just large springs (see note 4 in the SECTION_SOLID chapter of the LS-DYNA manual). ALE could be available for the soil material model if LSTC elects to allow it.

- This is not true for soil mechanics theories that involve strain softening. The amount of dilation (volume expansion) increases for a constant strain increment as the angle of internal friction increases. Strain softening (damage) is dependent on the dilation (i.e., as the dilation increases, so does the damage). Therefore, more damage occurs as the angle of internal friction increases. This increase in damage causes the apparent decrease in shear force as the angle of internal friction increases. The implication of these dependencies is that the damage input parameters must be changed in conjunction with the value of the internal angle of friction.

- There are data for some of the mentioned parameters in the literature (Eccen, Pwksk). As mentioned in the soil model manual, the author is not aware of any damage theory or damage data for soils. The parameters for damage (Vdfm, Dint, Damlev, epsmax) must be set based on user experience. The other parameters are obtained using laboratory test data (e.g., the triaxial compression test (see figure 6) provides data from which parameters An and Et can be obtained).

The soil model is a continuum mechanics material model. It is designed to model the material response of the continuous soil material. Upon being used in the direct shear test simulation, it should predict the initial increase of the driving force in the experiment to peak value and the decrease of the force as the soil sustains damage. The soil model did this in the user's simulation (as seen in figure 6). It should also indicate material damage and separation (fracture) at the same force-displacement point observed in the experiment. The developer thinks that the soil model would have done this in the direct shear test simulation if the damage parameters had been properly adjusted.

On page 23, the comment, "This result is counter to conventional soil mechanics theories" is only correct if there is no strain softening (damage). The amount of dilation (volume expansion) increases for a constant strain increment as the angle of internal friction increases. The strain softening (damage) is dependent on the dilation (i.e., as the dilation increases, so does the damage). Therefore, more damage occurs as the angle of internal friction increases. This increase in damage causes the apparent decrease in shear force as the angle of internal friction increases. The implication of these dependencies is that the damage input parameters must be changed in conjunction with the value of the internal angle of friction.

The instabilities in the DS-4 simulation are caused by a combination of the strain softening/erosion used in the material model and the element formulation. The FHWA soil material model includes strain softening (damage); once the element has been fully damaged, the model sets a flag to erode (eliminate) the element. This must be done because, at full damage, the element has no stiffness (internal forces). In the currentversion of LS-DYNA, the S/R solid element (8 gauss integration points) is eroded when the first gauss point is fully damaged. However, there are still internal forces associated with the eroded element because the other gauss points are not fully damaged. When the element is eroded, these internal forces are suddenly eliminated. This causes large unbalanced forces at the nodes of the eroded element, which, in turn, cause the shooting nodes behavior mentioned in this report. If damage/erosion of elements is not used because of this problem in the current version of LS-DYNA, then the well-known shear locking behavior dominates the simulation. The shear locking behavior manifests itself when the elements have large distortions (see note 4 for the *SECTION card in the LS-DYNA user's manual). The use of ALE may be used to overcome these problems. However, at long simulation times, the analysis becomes a simulation of almost two separate bodies separated by a slide surface with friction, which is not really a test of the FHWA soil material model.

In many areas of the report, it is mentioned that the authors where unaware of any physical testing or theoretical means for determining the input parameters. In some of these cases, there are direct means (e.g., the Eccen parameter (see figure 2 of the soil model user's manual)).(2) For other cases, indirect methods, such as parameter fits, will need to be made using the material model. An example of this would be to use drained and undrained triaxial compression tests to determine the pore-water effects. In a few cases, there exists no theory. This is the case for the parameters involving strain softening (damage). With other materials, such as steel, concrete, and wood, there are parameters based on theory (fracture energy). To the developer's knowledge, such a theory does not exist at this time for soil. As mentioned in the soil model user's manual,(2) a method was developed for the FHWA soil material model that is similar to the fracture energy theory used for other materials. A second example of limited theory is pore-water (moisture) effects. To fully take into account the effects of pore water, a coupled fluid flow, solid mechanics analysis method is needed. However, the FHWA soil model makes an assumption that the soil deformation times are much shorter than fluid flow though the soil. Therefore, the moisture content (and other input parameters) is assumed to be constant for the simulation times used in vehicle impacts.

The user's assessment of the performance of the soil material model in their direct shear simulation is erroneous. They appear either to have not thought out in detail the nature of the soil response in the direct shear test (and how to prepare a simulation capable of capturing that response) or are exhibiting a considerable misunderstanding of what is to be expected from continuum mechanics material models (of which the soil model is a member). Justification of these observations is provided in the following paragraphs.

The following questions were posed by an expert in soil mechanics from the user's team and were answered by the developer. The questions were posed by the user following a review of the developer's Manual for LS-DYNA Soil Material Model 147.(2) The questions resulted in changes to the soil model where appropriate. e24fc04721