What is the difference between soil stiffness and soil shear strength?
In general, soil stiffness is determined by soil shear strength. The higher the soil stiffness is, the more fatigue damage may occur in the riser pipe, since vibration frequency and stress ranges will be higher. Secant soil stiffness is generally higher than tangent soil stiffness. It is hence more conservative to use secant soil stiffness.
Why is soil stiffness important in pipe design?
Therefore, when expressing soil stiffness in this form it is important to use units of force/unit deflection/unit length of pipe. Soil stiffness under vertical compressive loading is important for wave-related riser fatigue. An increase in soil stiffness reduces fatigue life.
What is the difference between secant soil stiffness and tangent soil stiffness?
Secant soil stiffness is generally higher than tangent soil stiffness. It is hence more conservative to use secant soil stiffness. However, the actual tangent soil stiffness may yield better accuracy for fatigue prediction because it better represents soil deformation characteristics for fatigue loading. Abolfazl Eslami, ...
How do you calculate the soil stiffness of a beam?
The traditional way of defining soil stiffness for a beam on an elastic foundation is by the Modulus of Subgrade Reaction, Ksu, which can be obtained by re-arranging equation (9.19): (9.20) Ksu = q / δ = E 2 B (1 - v 2) The units of Ksu are Force/length cubed, e.g. kN/m 3.
Why is soil stiffness important?
How is soil stiffness determined?
What is SCR feasibility?
How does liquefaction affect soil?
What is vertical deformation of soils beneath foundation loading called?
Why is the volume of voids in soil time dependent?
Does shear reduce soil stiffness?
See 4 more
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What is stiffness of clay soil?
In fine-grained soils, such as clays, the phenomenon is less aggressive and is known as “cyclic modulus degradation” (Matasovic and Vucetic 1995). As the name suggests, stiffness reduces with continuing cycles of straining, often at a steady rate with respect to the logarithm of the number of cycles.
How is soil stiffness measured?
determined by in-situ and lab tests. Degradation of G-γ curve describes the behaviour of the soil from very small to very high strains. In order to get its shape, it can be estimated from in-situ and laboratory tests.
What is stiffness modulus of soil?
4.6 Stiffness. Soil modulus is a complex parameter in foundation engineering due to different involved conditions. Young's modulus (E) parameter is usually introduced as the deformability parameter for soil relates to linear elastic behavior for geomaterial.
What is soil spring stiffness?
Spring's stiffness is correlated to mechanical properties of the soil, shaft diameter, and pile flexibility factor using curve fitting techniques. It is found that spring stiffness is dependent to shaft diameter.
What is meant by shear strength of soil?
Shear strength of a soil is indicative of its resistance to erosion. Specifically, it is defined as the resistance to deformation by the action of tangential (shear) stress. Soil shear strength is made up of cohesion between particles and resistance of particles sliding over each other due to friction or interlocking.
What is E value of soil?
Typical values of ETypical EOrganic alluvial clays and peats0.1 ~ 0.6 MPaNormally consolidated clays0.2 ~ 4 MPaSteel205 MPaConcrete30 MPa5 more rows
What is a soil modulus?
Soil Young's modulus (E), commonly reffred to as soil elastic modulus, is an elastic soil parameter and a measure of soil stiffness. It is defined as the ratio of the stress along an axis over the strain along that axis in the range of elastic soil behaviour.
What is average density of soil?
As a rule of thumb, most rocks have a bulk density of 2.65 g/cm3 so ideally, a medium textured soil with about 50 percent pore space will have a bulk density of 1.33 g/cm3. Generally, loose, porous soils and those rich in organic matter have lower bulk density.
What does soil plasticity mean?
Then, determine plasticity, that is, the ability of soil materials to change shape, but not volume, continuously under the influence of a constant pressure and to retain the impressed shape when the pressure is removed.
What is soil spring?
It is a complex soil /structure interaction, and soil springs help to find out how the real presures and loadings vary around the box. Soil springs to represent those additional supporting elements help to solve real world applications where the simple is inacurate.
How do you calculate the k value of soil?
k = 40 x SF x qa, where SF is factor of safety considered in bearing pressure calculation and qa is allowable soil bearing capacity. So, you could employ the above equation in determining the Soil Subgrade Modulus.
How do you calculate pile stiffness?
Pile group stiffness may be calculated as product of single pile stiffness and coefficient n0. 5, where n is number of piles in the group. Estimated raft stiffness is Kr = 75 MN/m and pile group stiffness Kp = 143 ∙ 90. 5 MN/m.
What is stiffness physics?
Stiffness is defined as the resistance to a force causing a member to bend.
What is soil modulus?
Soil Young's modulus (E), commonly reffred to as soil elastic modulus, is an elastic soil parameter and a measure of soil stiffness. It is defined as the ratio of the stress along an axis over the strain along that axis in the range of elastic soil behaviour.
What is modulus of subgrade reaction k?
The modulus of subgrade reaction (k) is used as a primary input for rigid pavement design. It estimates the support of the layers below a rigid pavement surface course (the PCC slab). The k-value can be determined by field tests or by correlation with other tests.
What is subgrade modulus?
The subgrade modulus is a lumped constant of integration of the differential equation of a beam supported by elastic springs. It is a function of the following: Soil elastic properties: Modulus of Elasticity, Es, and Poisson's Ratio, νs. Foundation plan dimensions: Length, L, and Width, B.
Soil Stiffness - Structural engineering general discussion - Eng-Tips
I am designing a raft foundation using finite element analysis software. I need to insert a value for the stiffness of the bedding material (ie the soil). Could
(PDF) Determination of soil stiffness properties - ResearchGate
PDF | A good knowledge of the soil stiffness properties is very important for geotechnical engineering. Stiffness parameters are required as input for a... | Find, read and cite all the research ...
Modelling soil stiffness as Spring Support - Structural engineering ...
How did you determine that an allowable bearing pressure will limit the settlement to 10mm? My spacegass user manual which references the bowels textbook states that clayed soils with an ultimate bearing capacity between 200 and 400kPa (which would roughly equate to what you have) a typical modulus of subgrade reaction would be between 24,000 and 48,000kN/m^3.
Calculate Of Soil Spring Stiffness [dvlr2m135pnz]
Steps To Calculate soil stiffness as spring in sap : Stiffness The force that cause unit displacement or unit rotation 1- Bearing Capacity Of Soil =
Who wrote the Great Soil Groups of the United States?
Development and Significance of the Great Soil Groups of the United States (PDF; 5.82 MB) by Charles E. Kellogg; published in 1936
How many orders of soil taxonomy are there?
The Twelve Orders of Soil Taxonomy - poster.
What does "stiff" mean?
stiff, rigid, inflexible mean difficult to bend. stiff may apply to any degree of this condition. stretching keeps your muscles from becoming stiff rigid applies to something so stiff that it cannot be bent without breaking. a rigid surfboard inflexible stresses lack of suppleness or pliability. ski boots with inflexible soles
What does "not easily bent" mean?
1 : not easily bent And because Sarah's clothes were stiff and heavy, the Indian woman made her clothes of deerskin … — Alice Dalgliesh, The Courage of Sarah Noble
What is the consistency of soil?
Consistency varies with the water content of the soil. The consistency of a soil can range from (dry) solid to semi-solid to plastic to liquid (wet). The water contents at which the consistency changes from one state to the next are called consistency limits (or Atterberg limits ).
What determines the state of soil?
The environment into which deposition takes place, and subsequent geological events that take place there, largely determine the state of the soil, (i.e. density, moisture content) and the structure or fabric of the soil (i.e. bedding, stratification, occurrence of joints or fissures, tree roots, voids, etc.)
What is the difference between clay and sand?
Clay particles have a flaky shape . There are major differences in engineering behaviour between SANDS and CLAYS (e.g. in permeability, compressibility, shrinking/swelling potential). The shape and size of the soil grains has an important bearing on these differences. Shape of grains.
How many phases are there in soil?
In natural soils the three phases are intermixed. To aid analysis it is convenient to consider a soil model in which the three phases are seen as separate, but still in their correct proportions.
What are the mechanical properties of soil?
Engineers are primarily interested in a soil's mechanical properties: strength , stiffness , permeability . These depend primarily on the nature of the soil grains, the current stress, the water content and unit weight. Basic characteristics of soils.
How to determine water content of soil?
The most usual method of determining the water content of soil is to weigh a small representative specimen, drying it to constant weight and then weighing it again. Drying can be carried out using an electric oven set at 104-105° Celsius or using a microwave oven.
What is soil engineering?
Soil as an engineering material. The term "soil" means different things to different people: To a geologist it represents the products of past surface processes. To a pedologist it represents currently occurring physical and chemical processes. To an engineer it is a material that can be:
What are the two categories of soil samples?
There are two categories of soil samples, disturbed and undisturbed.
Why do we need soil samples?
Soil samples help provide a general subsurface profile and can be used to measure engineering properties , including those properties indicating the presence of a restrictive soil layer. When a soil boring is performed to determine if a site is suitable for infiltration, the following information should be requested from a soil boring company or geotechnical engineer (see attached Table 2 for greater detail):
How far below the bottom of the soil should boring be?
Caution: It is Highly Recommended that soil borings be extended a minimum of 5 feet below the bottom of the proposed infiltration practice and that the most restrictive soil layer be considered in estimating infiltration rate.
What is soil probe?
Soil Probe. Soil probes are a basic form of soil sampling, used to collect shallow or surface samples by pushing a T-shaped probe into the ground. The probe cuts a core sample smaller than the diameter of the probe body. The sample can also be collected within a liner inside the probe.
Why do we dig trenches?
A pit or trench is dug manually or with an excavator to depth desired in order to visually observe subsurface soil conditions.
Why is soil stiffness important?
Soil stiffness under vertical compressive loading is important for wave-related riser fatigue. An increase in soil stiffness reduces fatigue life. (ii) Suction effects due to riser embedment appear to be less important for riser design, but may in some circumstances need to be accounted for.
How is soil stiffness determined?
In general, soil stiffness is determined by soil shear strength. The higher the soil stiffness is, the more fatigue damage may occur in the riser pipe, since vibration frequency and stress ranges will be higher. Secant soil stiffness is generally higher than tangent soil stiffness.
What is SCR feasibility?
Deepwater SCR feasibility is often a combination of strength and fatigue challenges, each of which is affected by TDP soil stiffness. Several approaches are available in riser analysis software for TDP modeling, representing trenching, suction and lateral friction. The riser TDP locations move when the host vessel changes its draft or moves between near and far positions. Riser fatigue damage is actually spread over a length of the SCR. Hence it is important to account for TDP movement in the calculation of SCR fatigue at the TDP.
How does liquefaction affect soil?
Liquefaction reduces the soil stiffness and the effect on foundations can. (1) reduce the natural frequency of the system and may cause resonance type phenomenon. (2) reduce the foundation stiffness may also increase the deformation of the structure.
What is vertical deformation of soils beneath foundation loading called?
The vertical deformation of soils beneath foundation loading is called settlement . Compressibility of soils involves stress–strain relationships. In this regard, the trend of stress–strain curves plus soil stiffness plays an important role in settlement calculations. Generally, due to static or dynamic loading by foundation and consequence of induced stresses distributed in depth, these types of settlement are diagnosed as following:
Why is the volume of voids in soil time dependent?
It is related to time-dependent change of volume of voids within the soil due to increase of σ z ′ and excess pore pressure dissipation. Accordingly, in saturated soils, the soil particles and fluids in voids are incompressible, and the void volume change occurs if some pore water is squeezed out from the soil mass skeleton in response to external loading. This settlement is dependent on time, and fine-grained saturated soil is the most important source of settlement.
Does shear reduce soil stiffness?
Repeated shear strain may reduce the stiffness of saturated soils. Assuming that the changes in soil stiffness drive the long-term performance, the average strain next to a pile is a governing criterion and must be preserved in order to ensure similar stiffness degradation in both model and prototype.
