Subgrade modulus of laterally loaded piles in clays daniel 0. Soil subgrade modulus subgradesubbase strength soil bearing capacity, soil compressibility, and soil modulus of subgrade reaction are various measures of strengthdeformation properties of soil. Soilpropertybased subgrade resilient modulus estimation. Structural elements such as concrete pavements used in highways or foundations of buildings are continuously supported by the underlying soil. The inverse analysis was carried out using measured data from the initial loading phase at loading levels 0. Guidelines for the stabilization of subgrade soils in. Subgrade reaction modulus k s can be considered as an appropriate interface between the geotechnical and structural engineers. The results from plt can be used to directly estimate the settlement of a footing and some geotechnical parameters may be derived too. In engineering design of structures, the subsoil can be simulated by a much simpler system called subgrade reaction model. Effective parameters on modulus of subgrade reaction in.
For each test, the pavement surface deflections were measured at the distance of 0, 8. The displacement diagram shows a dishing effect as discussed earlier. According to this model, the modulus is proportional to a power law of the confinement stress. In this way for calibrating model, the studied case is based on results of 0. The modelling of the soil as springs comes forth out of the winkler foundation model. In addition to the twelve possible classifications shown on figure 32. Evaluation of modulus of subgrade reaction ks in gravely. Jan 22, 2018 very important tutorial which shows how to assign different soil subgrade modulus in different areas of mat. As more and more engineers will use software to design foundations, it is essential for engineers to have a fundamental understanding of this soil. Pdf effect of soil subgrade modulus on raft foundation. In a fifth and sixth part, the soil modulus is compared to the soil stiffness and to the soil coefficient of subgrade reaction respectively.
Subgrade reaction modulus k s of clayey soils based on field tests. Subgrade modulus of laterally loaded piles in clays. However, these computer programs often ask for an input called modulus of subgrade reaction. In table 1 are the values of the soil stiffness modulus of soil reaction, e found to represent the types of soils and degrees of compaction for buried flexible pipe. The modulus of subgrade reaction is a calculation expedient, and nothing more. And one of the major functions of a highway pavement is to reduce the. The nature and properties of subgrade soils must be considered in struc tural pavement design. One of the most important engineering challenges in the design of structure, is the reaction of soil in contact with structure.
Soil classification, gradation, moisture limits, lift thickness limits, compaction. Effect of soil subgrade modulus on raft foundation behavior article pdf available in matec web of conferences 120. However, in arid regions or regions where the water table is. By carefully examining the soil, it can be divided into its gravel, sand, and fine silt and clay combined components. Soilpropertybased subgrade resilient modulus estimation for flexible pavement design kevin 0. Soil water in unsaturated soil is under suction, which is known to influence the mechanical and hydraulic properties of the soils. This paper presents the procedure of evaluation of the modulus of elasticity e and the modulus of subgrade reaction k s value based on the california bearing ratio cbr tests and fem analysis.
Once a subgrade modulus is known, the behavior of a laterally loaded pile may be eval. The following methods may be used in the field to estimate the soil s texture, which is defined as the relative size and proportion of the individual grains in a given soil type. Thompson subgrade soils play an integral part in pavement performance. Soil modulus correlations foundation engineering in the. And one of the major functions of a highway pavement is to reduce the stresses transmitted to the subgrade to a level which the soil will accept without significant deformation. Modulus of subgrade reaction of soil is considered when the elastic behavior of the soil is used for the analysis. Wong pilesoil interaction of laterally loaded piles may be characterized by either linear subgrade modulus methods or the nonlinear load transfer relationships, termed py curves. The modulus of subgrade reaction is not a soil property. For this exercise, the software default value for the modulus of subgrade reaction was used.
The influence of some important factors on the shear modulus of soils such as. Design subgrade resilient modulus for florida subgrade soils. What is the value of the modulus of subgrade reaction of. This manual is a revised version of the subgrade stability manual ssm which was first published in march 1982.
Many engineers are not familiar with this term and often try to compare it with bearing capacity. Limitations of winkler model a number of studies in the area of soil structure interaction have been conducted on the basis of winkler hypothesis for its simplicity. Correlation between soil bearing capacity and modulus of. Evaluation of resilient modulus of subgrade and base. Subgradesubbase strength soil bearing capacity, soil compressibility, and soil modulus of subgrade reaction are various measures of strengthdeformation properties of soil. Hence the performance of the pavement is affected by the characteristics of the subgrade. Unsaturated soil, shear modulus, bender elements, shear strength. The soil bearing capacity is 50 knm2 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. The stiffness of both structure and soil has an important role when modelling the interaction. The common theory for calculating the modulus of subgrade reaction is the winkler theory, which cannot take the effect of elasticity and plasticity of soils. Youngs soil modulus, e s, may be estimated from empirical correlations, laboratory test results on undisturbed specimens and results of field tests. Pdf effect of soil subgrade modulus on raft foundation behavior.
A tentative correlation between in situ test results and maximum shear modulus gq of cohesionless soils is proposed. However, the strain modulus is determined by the curve fitting method for the overall normal stresssettlement data. Information includes modulus of elasticiity calculations, typical elastic modulii values, average youngs modulus values with relation to soil type, including clay, sand, silt, and gravel, calculations for modulus of elasticity using undrained shear. Type the allowable soil settlement corresponding to the allowable soil bearing capacity, in the selected units. This article brings out the whole analysis procedure to obtain the k horizontal value. Using nondimensional parameters for the analysis of a slab on a layered soil medium, a method is developed to evaluate an equivalent modulus of subgrade reaction k to be used in the winkler model. The modulus of elasticity or youngs modulus of a soil is an elastic soil parameter most commonly used in the estimation of settlement from static loads. Modulus of subgrade reaction which one should be used. June 1979, after the draft finalized by the soil engineering and rock mechanics sectional committee had been approved by the civil engineering division council. Evaluation of subgrade stabilization on pavement performance. Smallstrain shear modulus and shear strength of an. It has been revised to present the current state of practice at the illinois department of transportation idot, and to include any developments in test procedures or treatment methods that may have taken place over the past two. It is important to consider how these parameters apply to the design of floor slabs.
Determination of basics mechanical properties in a tropical clay soil. Resilient modulus for new hampshire subgrade soils for use in mechanistic aashto design vincent c. Use the soil profile along the roadway alignment to relate resilient modulus to each type of subgrade soil encountered. Evaluation of subgrade stabilization on pavement performance louisiana transportation research center mark morvant, p.
Bureau of reclamation usbr conducted soil tests to determine modulus of soil reaction values for a wide variety of soils having differing compaction levels. As a result, it cannot be determined using a cbr test, plate load test or any other test, for that matter. Guidelines for the stabilization of subgrade soils in california authors. Introduction the american association of state highway and transportation officials aashto pavement design procedure is an empirical design method. The elastic modulus of soil, also referred to as soil modulus or youngs modulus, is a soil characteristic that measures how much it can be stretched or squeezed and must be taken into account, particularly in construction, engineering and landscaping projects.
Modelling the interaction between structure and soil for. Estimation of subgrade resilient modulus using the unconfined. Method of determination of modulus of subgrade reaction kvalue of soils in field. Calculation of subgrade reaction modulus considering the. Harvey partnered pavement research center pprc contract strategic plan element 3. Youngs modulus for soil on the geotechnical information. The structural engineers need an appropriate way to represent the soil in the structural analysis. Basic mechanics of soils university of the west of. Calculate subgrade modulus from soil bearing capacity dialog. Currently use empirical techniques for pavement design and other geotechnical structures.
The subgrade reaction modulus is determined as the ratio between the normal stress and the settlement from 0 to 1. The model soil was classified as an stype soil because it was sandy, uniformly compacted, and homogeneous. Sep 09, 2017 however, these computer programs often ask for an input called modulus of subgrade reaction. Evaluation of modulus of elasticity and modulus of. The chapter continues by describing the interaction between structure and soil. Click to assign the calculated value for subgrade modulus into the selected row for a meshed region. The soil classification is determined by locating the point of intersection of the gradation. Design pamphlet for the determination of design subgrade in. Initial values for the horizontal subgrade reaction coefficient. Estimation of horizontal subgrade reaction coefficient by. Design curves of equivalent subgrade modulus versus a dimensionless lateral load factor are developed. This paper describes how many agencies still use empirical correlations developed to determine design subgrade resilient modulus based on california bearing ratio cbr, rvalue or soil support value for pavement design projects.
Relationships among youngs modulus, shear modulus, constrained modulus, and bulk modulus are defined so that correlations for any of these various measures. The modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabsonground. This modulus depends on some parameters like soil type, dimension, shape, embedment depth and type of foundation flexible or rigid. Experimental study of resilient modulus of unsaturated. Department of civil and environmental engineering, the hong kong university of science and technology, clear water bay, kowloon, hksar. The subgrade reaction modulus, that indicates the relation between soil pressure and deflection, is one of the most efficient parameter that is used for structural analysis of foundation members. The modulus of subgrade reaction, which is defined as the ratio between an applied pressure q and the deflection. Youngs modulus and poissons ratio are measured directly in uniaxial compression or extension tests, i. Resilient modulus for new hampshire subgrade soils for use in. The subgrade reaction coefficient of a foundation soil in an open pier has been identified using an extended kalman filter ekf based on measurements taken during in situ horizontal loading tests on a pile.
Resilient modulus, ultimate shear strength, dielectric permittivity, and shear and. Subgrade soil properties gravel g stones pass 75 mm sieve, retained on 2 mm 0 excellent 5075 a1 gpgm 70 assumed sand sa will form a cast when wet. Guidelines for the stabilization of subgrade soils in california. The modulus of subgrade reaction is a conceptual relationship between soil pressure and deflection that is widely used in the structural analysis of foundation members. Variations in shear strength, yongs modulus, internal friction angle, soilmetal friction angle, cohesion and adhesion were determined at different experimental. Soil subgrade reaction civil engineering community. For many construction projects, it is common to find that the preliminary design is based on soil parameters. Youngs modulus for soil on the geotechnical information website. Soilpropertybased subgrade resilient modulus estimation for.
The pressuredisplacement response of the soil in the cbr mould is simulated using cosmosworks fem model where the soil, the load plunger, and the steel mould of cbr are represented. If we know the modulus of subgrade reaction, elastic behavior of the soil can be model. The fundamental problem with the use of this model is to determine the stiffness of elastic springs used to replace the soil below foundation. It is used for continuous footing, mats and various types of piling. The theory of subgrade reaction assumes that the unit soil reaction p with respect to a laterally loaded pile increases linearly with the lateral deflection y, as expressed in the fol lowing equation. Factors influencing the modulus and related to the state of the soil 3. Determine the insitu resilient modulus for each major soil type encountered.
It is clear that both the cyr and shear modulus are fairly constant, which indicates that the homogeneity of. Pdf determination of subgrade reaction modulus of two. Examine the boring logs, soil profiles, and classification tests and select representative soil layers for laboratory testing. A correlation model to estimate the resilient modulus from uc test results and other soil properties was developed. Among them the stressstrain modulus youngs modulus, es, and the subgrade reaction.
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