Soil stiffness k values K includes the effects of texture, mineralogy, organic matter, structure, permeability, and depth to a limiting layer. If a spread footing is assigned a soil capacity explicitly (without the use of a soil table), this value will be used for the design of the spread footing. Pile-Stiffness Factor K The pile-stiffness factor is defined as: Here’s how to approach this question Determine the soil stiffness in k N m 3 or the appropriate units. SOIL PROPERTIES (LPILE & COM624P) p-y Curve Criteria Soil Modulus Parameter k Soil Strain Parameter E50 E50 = Strain at 50% Stress Level of Clay p-y Curve Criteria These criteria are used by LPILE1 to calculate p-y curves internally: In essence, the engineer must know the size of the foundation (and expected deflection) in order to undertake an appropriate test to determine k-values to enter in his foundation calculations. Soils Assigning Soil Properties The default Subgrade Modulus and Allowable Bearing Pressure are entered in the Soil Definitions Spreadsheet. Specifically, the soil spring constants, both at the surface and at a user input embedment depth, are determined in the analysis. 5. Stiffness values are provided for different shell areas. These formulations give the total soil springs stiffness for three translational and three rotational degrees of freedom. Dec 1, 2020 · The ks value given is 17,713kN/m3 which is in line with Bowles. Winkler first proposed the subgrade reaction in 1867 [Ref. All foundations must have a factor of safety applied for design purposes (typically between 2 and 4). Abstract The stiffness of a ground mass is a useful parameter to understand its mechanical behaviour under service. Apr 1, 2007 · The original and modified K -stiffness Method are demonstrated to quantitatively improve the estimate of the magnitude and distribution of reinforcement loads for internal stability design of vertical-faced geosynthetic reinforced soils walls with granular backfills when compared to the current American and Japanese methods. Resilient Modulus is a measure of the elastic response of a soil (e. In addition to the following, it should be noted that exceptions to typical values of soil properties occur often. This cyclical logic underlines the problems in determining k from field testing. I have a rather large mat foundation to design (using a beam on elastic foundation) and the geotech report gives a subgrade modulus in kcf. Researchers This tutorial covers how to obtain the Pile Head Stiffness Matrix and Simplified Spring Constants of a reinforced concrete pile under various loading conditions in RSPile. It quantifies the relationship between the stress applied to the soil and the resulting strain. Modulus of subgrade reaction of soil is considered when the elastic behavior of the soil is used for the analysis. Download Table | Stiffness values of different types of soil for different footing dimensions. The stiffness analysis implemented in STAAD. . " My question is, assume a vertical pile of 40 ft long embeded in sand. (1− 2) Not a fundamental soil property Not readily measured Depends on many factors such as size and shape of footing, type of soil, relative stiffness of footing and soil, vary along footing, vary with time, etc. linear stiffness is equal in all directions). Nov 15, 2010 · Sorry if this has been covered before. The value of spring you should input into SAP2000 is calculated as follows: 1-Determine the soil stiffness in kN/m3 or ton/m3 of lbs/ft3 … View the full answer Previous question Next question Soil-Spring Stiffness K - Free download as PDF File (. The maximum value of stress that may be sustained is termed strength. Usage of correlations for geotechnical design is addressed in the various design sections of the Geotechnical Manual. Settlements are caused by strains in the ground. Soil stiffness is defined as a key soil property characterized by either small-strain shear-wave velocity or small-strain shear modulus, representing the maximum stiffness (G max) of the soil. The apparent lateral stiffness of soil is strongly influenced not only by the soil stiffness but also the geometry and the stiffness of a pile. Apr 15, 2024 · 1. ABSTRACT: Immediate settlement calculations for spread footings supported by clay soils are generally based on displacement influence factors derived from elastic stress fields and soil stiffness estimated from triaxial compression strength tests or correlations to various measureable characteristics such as plasticity, strength, or stress history. The methodology returns equivalent values to the SPT correlation proposed by Scott (1981). 1 1 st Step: Estimation of K CPT stiffness In this first step, the spring stiffness of the 10mm long soil element is estimated. ABSTRACT: The K-stiffness Method is an empirically-developed working stress method used to compute reinforcement loads for the internal stability design of geosynthetic reinforced soil walls under operational con-ditions. 4 and 5: Dec 30, 2021 · Stiffness (F=Kx) is the extent to which an object resists deformation in response to an applied force. 2. Here, k = modulus or coefficient of subgrade reaction; p = applied pressure and s = deformation of soil settlement. 1995) 1. It then calculates stiffness (k) as force over displacement using bearing capacity and shell area. Introduction This support note describes how lateral spring constants should be derived from Standard Penetration Test (SPT) “N” values for use in LUSAS piling analyses where the soil is not modelled explicitly and no information is known regarding the soil stiffness. It has been found that bending moments and the computed soil pressure are not very sensitive to what is used for ks because the structural member stiffness is usually 10 or more times as Basic mechanics of soils Analysis of stress and strain Strength Stiffness Material behaviour Loads from foundations and walls apply stresses in the ground. from publication: Soil Structure Interaction Effects on Pushover Analysis of Short Span RC Bridges In general, the soil stiffness and elastic modulus depends on the consistensy and packing (density) of the soil. The German Institute for Standardization DIN 4018:1974 [13] suggests the value of relative stiffness K to estimate the behaviour of soil-foundation systems. Mar 2, 2005 · Is the Soil Spring Constant the same as Modulus of Subgrade reacton? I argued with a collegue that it is not. Jun 1, 2010 · A good knowledge of the soil stiffness properties is very important for geotechnical engineering. But I am wondering how to calculate it manually. Often retaining structures are analysed representing the soil as merely a load – the stiffness of the soil is not modelled. Just one comment/question: The k value (modulus of subgrade reaction) is not a property of the soils since it depends on the geometry of the loaded area. Case histories are presented to illustrate the method, its perfor Aug 23, 2008 · FACTOR (SOIL ERODIBILITY) accounts for the influence of soil properties on soil loss. The following relationships can be demonstrated (for proofs refer to a text on the strength of materials). Small strain stiffness and nonlinear soil behavior can be determined utilizing SDMT. The Resilient Modulus is a basic subgrade soil stiffness/strength characterization commonly used in structural design of pavements. The design proceeds considering only limiting active and passive lateral earth pressuresa. Peak live load doesn't usually occur for long enough for full consolidation to take place. Jun 13, 2011 · Soil spring coefficients have to be properly assigned in simulating retaining wall behaviors accurately. May 14, 2015 · Thanks for the information. It assumed that the material is elastic and isotropic (i. In real terms this means that for every 12,000kPa applied to the soil (kilonewton per meter squared), the soil is expected to displace or settle 1mm. A higher subgrade modulus indicates a stiffer soil that deforms less under the same load. 3. 1. At present, the stiffness can be easily determined with a soil stiffness gauge (SSG) that is a light and user Jul 22, 2025 · What is Soil Stiffness? Soil stiffness, a fundamental property of soil mechanics, refers to the resistance of soil to deformation under applied load. Nov 17, 2025 · Enter the pressure applied to the soil and the resulting deflection to calculate the subgrade modulus. Introduction For rigid foundations, the analytical solutions of the elastic half-space approach are presented. The subgrade modulus is not constant underneath a foundation. It gives the formula for calculating the coefficient of horizontal subgrade reaction ks based on the undrained shear strength of the soil Su and pile diameter D. , how well a soil is able to return to its original shape and size after being stressed) under repeated loading. Jul 27, 2020 · The modulus of subgrade reaction ks (also called the coefficient of subgrade reaction of soil) is the ratio of the pressure against a flat surface on soil and the settlement at that point. Actually, due to the soil non-linear behavior, the consideration of a constant value for k’, independent of the strain level, corresponds to a rough approximation to the real behavior. Loads from foundations and walls apply stresses in the ground. Jul 17, 2025 · This is where soil spring stiffness comes in – a critical parameter that can make or break the structural integrity of a project. As a result, it produces There is no reliable correlation between the three measures of soil properties-modulus of subgrade reaction, soil bearing capacity, and soil compressibility-because they are measurements of entirely different characteristics of a soil. 1, it can be considered rigid system while it behaves flexible for K-values ≤ 0. Three basic subgrade stiffness/strength characterizations are commonly used in the United States: California Bearing Ratio (CBR), modulus of subgrade reaction (k), and elastic (resilient) modulus. It has been suggested to me a value of 40 times the bearing capacity divided by a factor of safety. pdf), Text File (. Assuming a linear relation in the initial part of the stress-strain curve, the most suited kunc results for design are those that correspond to the points of the tangent elasticity modulus. For different soils at the same relative density, the value of 4)' is affected by particle-size distribution and particle shape. In the case of a continuous footing, where the modulus of subgrade reaction is required to calculate the stiffness of the Aug 20, 2021 · For your vertical stiffness, it would help if you gave values for both sustained and transient loads. Elastic Modulus (E=Stress/Strain) is a quantity that measures an object or substance's resista The soil capacity beneath a footing is calculated from the data that is defined by the user in the Foundation module. A maximum k value of 135 MN/m3 (500 pci) will be used. The theory of elasticity was then used to relate the plate-bearing test to the modulus of soil reaction. Its value may be obtained from the corresponding diagrams illustrated in Figure 5. Jul 17, 2025 · The subgrade modulus (k) is a crucial parameter in geotechnical engineering, representing the soil’s stiffness or resistance to deformation under load. It then CBR and K-value to Modulus of Elasticity (E) conversion For existing pavements originally designed using the California Bearing Ratio (CBR) method, the subgrade modulus can be determined from direct soil testing or using the available CBR values and converting them to an equivalent Modulus of Elasticity using the relationship that appears on the "Aerodrome Design Manual, Part 3 — Pavements Spring Constant for Soil - Free download as PDF File (. Soil Correlations This section of the Geotechnical Manual presents the SPT correlations to be used for friction angle (phi angle) and unit weight. The relationship between a strain and stress is termed stiffness. g. However, that simplicity assumes the footing will The purpose of this paper is to address the determination of site-specific soil stiffness parameters for finite element analyses utilizing in-situ testing methods, as opposed to performing rigorous laboratory testing. I need to insert a value for the stiffness of the bedding material (ie the soil). The theoretical background of the method is summarized, and the interpretation of the results is explained. Lateral springs stiffness are calculated by equating pile head stiffness from FE models to predicted value from beam on elastic support theory. Spring stiffness is important in designing machines, vehicles, and tools to ensure proper motion and load control. The document shows that Ks and the constant K in Winkler's model are identical For a given soil the value of 4)' increases as the relative density increases. 001. 2 SPT blow counts using qc 1. 1995) May 4, 2008 · I have a question about how the subgrade modulus relates to the assumed spring stiffness of a soil. The correlations use Standard Penetration Test (N) values corrected for overburden and hammer efficiency (N160). 05 May 25, 2010 · It said that "If k is the spring constant for the finite element model in units F/L, then k is determined by multiplying the coefficient of variation of horizontal subgrade reaction by the depth of the center of the pile segment and by the length of your pile segment. Depending on the relative stiffness K R, the foundation or structural system will be considered rigid or flexible. txt) or read online for free. The obvious reason is that basic examples given in most text books almost always use bearing capacity to calculate the plan dimension of a footing. Spring’s stiffness is correlated to mechanical properties of the soil, shaft diameter, and pile flexibility factor using curve fitting techniques. By accurately calculating soil spring stiffness, engineers and researchers can better understand soil behavior, optimize design parameters, and reduce the risk of costly failures and damage. Recently, the writers have collected data from Japanese case studies of monitored full-scale geosynthetic reinforced soil walls constructed with different facing batters Jun 11, 2005 · Equation (3) can be applied for non-cohesive soils. Normally we use plate loading tests of correlations to CBR to obtain the k values. Apr 6, 2023 · The Modulus of Subgrade Reaction (k-value) is an important parameter used in the design of foundations for buildings, bridges and other structures. Download Table | The estimated spring Stiffness of raft foundation for three different types of soil from publication: Soil Structure Interaction Analysis for Seismic Response of an Asymmetric RC For both the static and cyclic curves an initial linear section is defined using an initial stiffness which is assumed to vary linearly with depth, from zero at the surface. e. SPT “N” values are used in the calculation of stress-strain modulus, Es which in turn is then transformed into a Using the Nonlinear EI Only Mode computational option (Figure K-2), create the Moment-Stiffness curve for a single pile (Figure K-7). Feb 12, 2018 · We would like to show you a description here but the site won’t allow us. The values tend to decrease as the soil compresses and could become smaller and smaller as the test continues. , stratigraphy) based on ODOT soil classification and consistency (stiffness of cohesive soils or density of granular [non-cohesive] soils). The maximum value of This coefficient is dependent not only on the soil stiffness but also on the pile properties. Use the “Other Documents Websites” link for nurses, physicians, dentists, and others. Feb 16, 2005 · I am designing a raft foundation using finite element analysis software. Es = Eu (undrained) vs E’ (drained) = ∆ = . the stiffness of the foundation that affects the distribution of pressure Determining the subgrade reaction modulus The subgrade reaction modulus can be determined in the following ways: – using a circular slab – using tables of characteristic values and correlations D. Pro is based on the matrix displacement method. , Shear Modulus, G, Poisson's Ration, v It is particularly important to note that K constant is not a soil property since it is dependent on the foundation characteristics (dimensions and stiffness), as well as the loads applied to the foundation. the soil stiffness in the impact zone of the load under the foundation. Figure 5: Base modulus correction factor, R b, for various L/d values Mar 9, 2024 · What soil spring values would I assign to a finite element model assuming the following: Medium dense sand 120 pcf Below water table Friction angle 30 degrees Assume perfect elastic plastic behavior Focus on the elastic portion of the p-y curve at k4 Per the National Frame Building Probably the most widely used value in a soil report is soil bearing capacity. It presents Winkler's linear model for soil pressure-deflection and defines the modulus of subgrade reaction Ks. AI generated definition based on: Journal of Applied Introduction For rigid foundations, the analytical solutions of the elastic half-space approach are presented. Strength and Stiffness Subgrade materials are typically characterized by their strength and stiffness. 0. In the matrix analysis of structures by the displacement method, the structure is first idealized into an assembly of discrete structural components. The linear section is defined by an initial stiffness gradient k. Further, subgrade reaction can also be considered as the representation of the soil-bearing capacity. But, it is not one of the basic soil properties and depends on many parameters including soil stiffness, foundation stiffness, foundation shape, size etc. Typical values of Young's modulus for granular material (MPa) (based on Obrzud & Truty 2012 complied from Kezdi 1974 and Prat et al. 2 Shear modulus of rock Standard penetration tests (SPT) The Standard Penetration Test was developed in the late 1920s, but the test procedure was not standardized until 1958 (see ASTM D1586), with periodic revisions to date. The soil resistance is in units of force per length of pile segment while the deflection is in length units. Overview The purpose of this chapter is to identify, either by reference or explicitly herein, appropriate methods of soil and rock property assessment, and how to use that soil and rock property data to establish the final soil and rock parameters to be used for geotechnical design. This document provides information for calculating the horizontal subgrade reaction for pile analysis in cohesive soils. This document discusses calculating spring constants for foundations and base slabs of structures. Soil spring stiffness values are given for skin resistance of 178,539. The soil properties, pile properties, and calculation method are provided. For low-rise buildings, depth of borings may be specified to be about 6 m below the anticipated foundation level, with at least one boring continuing deeper, to a lesser of 30 m, the least building dimension, or refusal. The stiffness of the soil spring is usually unchanged throughout the analysis. 16]) , Winkler ABSTRACT: In this paper, an integrated methodology is introduced for estimating the static vertical subgrade modulus from CPT for shallow foundations on cohesionless soils. The distributions of the soil’s subgrade reaction and bending moment acting on the pile are shown. It defines bearing capacity, shell areas, and maximum allowable deflection in soil. Tables 1-3 show the results for a 0. 1 Strength of rock 1. The default soil definition will be used for the soil properties in the whole model, except where another soil region is drawn. Because of simplicity and ease of use, this method is still the fundamental soil parameter for foundation design. From the physical point of view, the Winkler The Geotechnical Analysis add-on provides RFEM with additional specific soil material models that are able to suitably represent complex soil material behavior. It is a measure of the stiffness of the soil, and it plays a crucial role in determining the deflection and settlement of the foundation. (250 pci) should be sufficient. The modulus of subgrade reaction has been traditionally used in pavement design as a representation of the stiffness of the subgrade soils under short duration, transient loading. 2. Can anyone point out a rule of thumb for estimating the soil spring stiffness from the bearing capacity. Recent developments and advancements in soil models and computer programs failed to prevent structural engineering to use one the most elementary theories in modeling of the soil-structure Download scientific diagram | Values of modulus of subgrade reaction for different soils Source: [17] from publication: Effect of soil compressibility on the structural response of box culverts Jul 28, 2005 · To be thorough, if you expect your clients to use the subgrade reaction approach for laterally loaded piles, you should recommend a value for K or N (sub h), and state how R or T is to be calculated with your recommended value. It helps engineers design foundations, slabs, and pavements by estimating how much the soil will settle or deform under an applied load. The coefficient of subgrade reaction is expressed in load intensity per unit of displacement. Mar 22, 2022 · An analysis comparing the combined stiffness of the foundation, superstructure framing components, and shear walls with the stiffness of the soil can be used to calculate the approximate rigidity of the structural system. Reference k values of the soil. At any non-zero deflection values, the secant stiffness will be dependent on both the initial tangent modulus and p u, strongly dependent on diameter (Eq. Both Broms's equations and the nondimensional solutions describe the soil resistance by a modulus k, which, as men tioned previously, is a function of the depth and magnitude of the lateral load. Deformation (exaggerated) of a short, free-head, pile subjected to the maximum horizontal load in cohesionless soils. The ultimate soil resistance p u and y 50 are given by Eq. Typical values of soil Young's modulus are given below as guideline. 2 2 nd Step Aug 1, 2021 · The soil stiffness index (SSI) is now measured to estimate the ρ d values and/or design values of soil stiffness more rapidly. Soil classifications A-1-a through A-3a are considered granular soils, and A-5 through A-7-6 are considered cohesive soils. 25 mm (0. Some discipline documents are in the licensing system. Stiffness parameters are required as input for a lot of geotechnical calculations related to Apr 14, 2016 · The soil's role in the problem is that depending on how the soil deforms in response to the stress (its stiffness represented by the parameter k) a different portion of the underside of the slab will be supported and influence the reaction force acting on the bottom of the slab. In this new feature, the program creates curves of incremental loading versus foundation stiffness components K22, K23, K32, and K33, as shown in Figure 1-1. Other correlations We would like to show you a description here but the site won’t allow us. It specifies the soil spring stiffness of 40,000 kN/m3 according to Bowles, an allowable bearing capacity of 250 kN/m2 with a safety factor of 2. The value of spring you should input into SAP2000 is calculated as follows: 1-Determine the soil stiffness in kN/m3 or ton/m3 of lbs/ft3 … View the full answer Previous question Next question A user defined soil model allows the user to input the soil resistance for various soil deflection values to define the p-y curve. The document provides steps to calculate soil stiffness as a spring in SAP2000. The K value is a complex property and is thought of as the ease with which soil is detached by splash during rainfall or by surface flow, or both. To determine the soil stiffness constants in Bekker and Upadhyaya models, a sandy-loam soil reflecting general character of an agricultural soil was selected and multiplate penetration tests were conducted. The subgrade modulus is a measure of the soil’s stiffness and is used in pavement and foundation design. May 23, 2025 · A higher value of k means the spring is stiffer and requires more force to deform. To analyse the conditions within a material under loading, we must consider the stress-strain behaviour. Table- Range of typical values for K value in Universal Soil Loss Equation. 7mm diameter and a 10mm incremental penetration: (2) This conversion is applied for every q c measurement until the final CPT depth. Could anyone give me some advice on how I calculate this value? I have heard that it is the allowable bearing pressure divided by teh In bodies of elastic material the three stiffness moduli (E', K' and G') are related to each other and to Poisson’s ratio (n '). 9). This calculator will determie the spring rates for a foundary placed top various soil conditions - Soil Foundary Spring Calculator Feb 25, 2023 · The soil reaction coefficient, or Winkler coefficient, is normally referred to as K or K S [kgf/cmc]. Soil Spring stiffness and damping values are generally computed with available formulae for circular rigid foundation on the surface of an elastic, homogeneous and isotropic half space. Modeling Soil Reaction to Laterally Loaded Piles TAKAAKI KAGAWA A numerical study was made for linearly elastic soil-pile condi tions to clarify the lateral soil-reaction behavior of a pile. A statistically valid relationship between DCP penetration and R-value is probably feasible in that some soil properties influencing the result are common to both. Rb depends on the L/d ratio, the pile stiffness factor K, and the ratio of the bearing stratum modulus of elasticity, Eb, to the soil’s modulus of elasticity, ES, (Eb/ES). With some judgment, (k) values obtained from field testing can be used for pavement design purposes. Thus attempting to predict R-value from DCP penetration indirectly through the shear strength or stiffness will be very unreliable. Due of soil formation by sedimentation, this is a particularly relevant case for geotechnical engineering, especially for fine grained soils with rather elongated flat particles such as clays. This can do with software. It’s a crucial factor influencing the stability, bearing capacity, and overall performance of various engineering structures built upon or within the soil. Transversal anisotropic stiffness: The stiffness is identical in the two horizontal directions but different from the vertical direction. Typical values for k are shown in the table below: A user defined soil model allows the user to input the soil resistance for various soil deflection values to define the p-y curve. However, if movements/ deflections of the structure are insufficient to mobilise the limiting values, intermediate values of earth pressure occur, as illustrated in Figure 1 below. 1. As per equation 1, the spring stiffness is the cone resistance q c divided by the displacement. The subgrade modulus is a function of the soil stiffness and compressible layer thickness, as well as the foundation dimensions and stiffness. The modulus of subgrade reaction or static stiffness K is a function of the following: Soil Properties (i. Slight empirical adjust ments had to be made in the Please use the simple Keyword Search for the best results. Jan 3, 2025 · The modulus of subgrade reaction (k-value) is used to evaluate the stiffness or load-bearing capacity of soil in structural and geotechnical engineering. Based on expression (3), the value of kh for wall of a unit width can be expressed by Equation (4): Many approaches have been developed to determine the soil-spring stiffness and typical values have been proposed for different types and densities of soil. It is The document provides soil spring stiffness values and properties for modeling a bored pile foundation in a finite element analysis. Thanks in advance. May 1, 2000 · To estimate the behavior of soil–foundation systems (rigid or flexible), the limit values of relative stiffness are first determined for raft foundations on elastic soils with the stiffness e value. If however, we use an A of 100m and B of 26m, actual foundation dimensions, the calculated k value reduces significantly to 3029 kN/m3 Would like some guidance on what is the correct approach. Oct 28, 2018 · The modulus of subgrade reaction (Ks), is a commonly used parameter for a mat foundation analysis. A simple and easily implemented experimental method, the W AK test (wave activated stiffness K test), was proposed by Briaud and Lepert (J) to estimate, on site, the stiffness of the soil under lying a rigid foundation. 4. The relationship between E' and the R-value determined from Hveem's stabilometer test was determined by using an empirical correlation presented by the California Division of Highways between the R-value and the plate-bearing test. Jan 5, 2016 · A feature was added to compute values for a foundation stiffness matrix that may be used in structural analysis models for a certain range of loads. For K-values ≥ 0. I can input this directly in PCA Mat, but I would like Dec 31, 2014 · "SPRING-K" is a spreadsheet program written in MS-Excel for the purpose of determining the soil spring constants for foundations for the vertical direction (Z), as well as for the horizontal directions (X and Y). There is a check box in the Soil Definitions Spreadsheet to determine which soil definition will be used as the default. Despite the advantage provided by the knowledge of the ground stiffness, this parameter was seldom determined in the past, because it required elaborated in situ tests. The subgrade soil scaling factor (SSSF) shows the basic properties of soil such as stiffness, gravimetry, density, and particle distribution, which are Nov 23, 2021 · This is a soil stiffness for a weak clay material given as 12,000kPa/mm. Define the single pile section type, dimensions and material properties (Figure K-3 to K-5). Typical values of k for different soil types and moisture contents are shown in Table 6-1. You can currently search for documents from five agencies. Typically, the modulus of subgrade reaction is estimated from other strength/stiffness tests, however, in situ values can be measured using the plate bearing test. , Shear Modulus, G, Poisson's Ration, v The soil stiffness is represented by the form of values related to each soil condition. However, these typical values ignore the Thus attempting to predict R-value from DCP penetration indirectly through the shear strength or stiffness will be very unreliable. (KN/m3 units) This is for modelling a raft Oct 16, 2014 · This educational webpage, part of the InTeGrate teaching materials, explains the soil erodibility factor (K factor) by examining how soil texture, structure, organic matter, and human activities like mining and tillage influence erosion potential, using real-world examples and supporting resources for undergraduate earth and environmental science instruction. The k-value used for floor-slab design reflects the response of the subgrade under temporary (elastic) conditions and small deflections, usually 1. This technical article is an introduction to show how the stress-dependent stiffness of soil material models can be determined. The proposed methodology relies on fundamental concepts of soil mechanics and foun-dation engineering. In Winkler ‘s model, the subsurface is characterized by a linear relationship between the failure of a point (s) and the contact pressure (p) at the same point: p = K s K is the “background constant” or “coefficient of subgrade reaction”. The document also provides equations to model soil pressure, water Jan 24, 2010 · Therefore, I double this value to calculate the spring constant, which is the bearing pressure which will cause the soil to compress 1" (again, I am working in English units). In case of cohesive soils the value of kH1 becomes the same as the value of parameter kSI established for a beam resting on a horizontal surface of the same kind of soil. 82 kN/m/m, lateral resistance of 25,000 kN/m We would like to show you a description here but the site won’t allow us. 8m diameter pile and Tables 4-6 show the results for a 1m diameter pile, with soil spring constants (ks), horizontal stiffness (K), constrained modulus (K'), and incremental stiffness (Ki) reported at regular depth intervals down the pile. For a CPT with 35. At least one soil boring should be specified for every 230 square metres of the building area for buildings over 12 m height, or having more than three storeys. It is crucial for analyzing ground deformation in engineering earthworks and is assessed using geophysical methods such as surface wave techniques. 3 Like all other soil strength tests, K-value test will not provide a representative measurement of suhgradc strength unless performed under the conditions that wouJd be expected after equilibrium of the subgradc with the environmental influences of moisture, density, frost, drainage and traffic. Nov 24, 2017 · 2. Soil spring properties are often represented by bilinear curves considering stiffness and ultimate ground reaction based on ground surveys. The estimation of the k value is usually a challenge to practicing engineers but is essential to the ac curacy of the solution. A linear stress distribution is assumed, thus, whether the soil substratum is cohesive or cohesionless is not taken into consideration. For large Jul 18, 2025 · Divide the boring log into soil layers (i. Feb 4, 2012 · The soil bearing capacity is 50 KN/m2 and soil is soft clay soil but to analyze this foundation in SAFE I need to know the subgrade modulus “K” value so any one can suggest the conservative K value range for this type of soil and bearing capacity???? What is the modulus of subgrade reaction? To add to the confusion, especially for the novice slab designer, this value has been called by many different names in various publications such as modulus of subgrade reaction, subgrade reaction, subgrade modulus, coefficient of subgrade reaction, Winkler foundation (E. Abstract: Soil stiffness constants govern the soil sinkage and the behavior of soil under load. 4 Stiffness and strength of rock 1. In general, the soil stiffness and elastic modulus depends on the consistensy and packing (density) of the soil. Please tell me I am right! Can anyone give me references where I can get some info about Soil Spring Constant. 3 Soil stiffness 1.