This modular is the cumulative of modulus of subgrade reaction from plate load test k and additional modulus of subgrade reaction due to pile installing. For this exercise, the software default value for the modulus of subgrade reaction was used. The corrected maximum subgrade reaction p u corr z of the py curves shown in fig. Pdf the structural design of concrete pavements according to aashto and pca methods makes use of modulus of reaction k from the. Determining additional modulus of subgrade reaction based. Historical modulus of subgrade reaction kvalue primary subgrade design variable for concrete pavement design in the good old days westergaard models pca design procedure, etc. Determining the deformation and strength characteristics. Modulus of subgrade reaction for insulation boards under. In highway formations the subgrade layer, where acts as a pavement foundation should be well designed.
Key words subbase material, erosion, field performance, concrete pavement, kvalue, gpr, fwd, dcp, static plate load test 18. Prediction of subgrade reaction modulus of clayey soils. Reduction of pile resistance is one of aspects that need to be. Soil subgrade modulus subgradesubbase strength soil bearing capacity, soil compressibility, and soil modulus of subgrade reaction are various measures of strengthdeformation properties of soil. The modulus of subgrade reaction kvalue is defined as that measured or estimated on top of the finished roadbed soil or embankment upon which the base. Used to evaluate the subgrade modulus based on soil bearing capacity, allowable soil settlement, and safety factor. A sdvosb service disabled veteran owned small business. Measure of soil resistance to vertical pressure pressure deflection k 18. The modulus of subgrade reaction is an often misunderstood and misused concept for.
However, it is recommended that a k value be established for the subgrade. The plate load test plt has been a traditional in situ test to. The data developed in the static load test is used in the calculation of the modulus of subgrade reaction in section 6. An introduction to engineering properties of soil and rock.
The k value can be determined by field tests or by correlation with other tests. Estimation of subgrade resilient modulus using the. I have one reference but i theres a typo on the page as. Probably the most widely used value in a soil report is soil bearing capacity. This corrected k eff is the value to be used for design. Westergaard also suggested that deflection measurements of the slab surface could be used for backcalculation of the kvalue rather than load tests on the subgrade. The modulus of subgrade reaction k is used as a primary input for rigid. The proposed methodology relies on fundamental concepts of soil mechanics and foundation engineering applicable to flexible foundations. Adjustment to k for fill thickness and rigid layer. The conversion from resilient modulus of the subgrade to kvalue was updated in the fall of 2011 to better reflect published test results. Pdf models to estimate k subgrade reaction modulus values. In this paper the results of spt and plt tests on gravely soils of tehran alluvium are evaluated. Subgrade reaction an overview sciencedirect topics.
June 1979, after the draft finalized by the soil engineering and rock mechanics sectional committee had been approved by the civil engineering division. Pdf subgrade reaction modulus k s of clayey soils based on. Senior research scientist virginia center for transportation innovation and research wan soo kim, ph. The correlation between subgrade reaction modulus k s, modulus of elasticity e s and corrected standard penetration test blow counts n are presented for clayey deposits of the qazvin alluvium. One of the parameters obtained from the field plate load test is the spring constant modulus of subgrade reaction, k. Subgrade characterization plays a key role in the thickness design of airport pavements. The influence of the thickness of the insulating material to the kvalue is represented, proving that calculating the kvalue from modulus of elasticity can lead to mistakes in common approach of the design. The k value is best estimated based on previous experience or by correlation. For our example, the equivalent modulus of subgrade reaction was determined to be 80 pci. Pdf models to estimate k subgrade reaction modulus.
The 80 psi would be 35 % 80 pci230 pci x 100 % of the plate subgrade reaction value. The 80 pci would have both the reduction of wide area loading and the reduction for longterm soil consolidation. The reported correlations between mr values and the modulus of subgrade reaction k of roadbed soils. The modulus of subgrade reaction k is used as a primary input for rigid pavement design.
In this paper, an integrated methodology is introduced for estimating the static vertical subgrade reaction modulus from cpt for shallow foundations on cohesionless soils. The structural design of concrete pavements according to aashto and pca methods makes use of modulus of reaction k from the subgrade and subbasesubgrade system as parameter to calculate slab. So, even for a bearing capacity calculation, an allowable soil settlement is. Modulus of subgrade reaction a k a k 1 1 corrections. Modulus of subgrade reaction kvalue, pci design value conservative selection e can be estimated from k valuee 20. The kvalue can be determined by field tests or by correlation with other tests. Plate bearing test accordingly to din 189 4 is used to estimate the values of modulus of subgrade reaction. Using figure 527 and table 545, correct the effective modulus of subgrade reaction k eff for loss of support due to subbase erosion. 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. Conventionally, the kvalues must be determined through ndt testing that is expensive and lengthy. The test involves pressing a steel bearing plate into the surface to be measured with a hydraulic jack. California bearing ratio cbr, plate load test plt, modulus of elasticity e, modulus of subgrade reaction k. Facilities development manual wisconsin department of. Stressstrain modulus modulus of elasticity and poissons ratio.
A comprehensive laboratory study was undertaken to determine engineering properties of cementitiously stabilized common subgrade soils in oklahoma for the design of roadway pavements in accordance with the aashto 2002 mechanisticempirical pavement design guide mepdg. Pdf correlation between subgrade reaction modulus and. Experimental evaluation of subgrade modulus and its. For the design of rigid pavements in those areas where no previous experience regarding pavement performance is available, the modulus of subgrade reaction k to be used for design purposes is determined by the field platebearing test. It estimates the support of the layers below a rigid pavement surface course the pcc slab. Indian standard method of determination of modulus of subgrade reaction kvalue of soils in field 0. I fill material will be placed above the natural subgrade, andor 2 a rigid layer e. Army corps of engineers engineer manual, settlement. Due to the results obtained the correlation between spt results n 1 60 and modulus of subgrade reaction k s are also presented for gravely soils. Cbr, rvalue and index tests were performed on tropical residual soils from four locations on the island of oahu in the state of hawaii. In order to promote public education and public safety, equal justice for all, a better informed citizenry, the rule of law, world trade and world peace, this legal document is hereby made available on a noncommercial basis, as it is the right of all humans to know and speak the laws that govern them. Estimation of the static vertical subgrade reaction. This is hardly a surprise as, by definition, the modulus of subgrade reaction ks is a. Opens when the calculate subgrade modulus from soil bearing capacity button is clicked on the soil property form is clicked.
Fol rigid pavements, a rational method for including department of civil engineering, university of arkansas, fayetteville, ark. Modulus of subgrade reaction which one should be used. The subgrade reaction modulus is determined as the ratio between the normal stress and the settlement from 0 to 1. To evaluate the subgrade strength is important during construction and design stage. Table 546 summarizes the recommended design values for the modulus of subgrade reaction from the lowvolume road section of the 1993 design guide. The plate load test see figure 1 and 2 can be used to measure the modulus of subgrade reaction for in situ material. The structural design of concrete pavements according to aashto and pca methods makes use of modulus of reaction k from the subgrade and subbase subgrade system as parameter to calculate slab thickness. A nomograph was developed for adjustment of the seasonally adjusted, effective subgrade kvalue if.
Soils engineer materials division virginia department of transportation introduction. Manual computation of flexible analysis could be challenging and, in almost all. September 2014 test procedure for determining modulus of subgrade reaction k value txdot designation. It represents the load in pounds per square inch on a loaded area, divided by the deflection in inches of that loaded area, psiinch. Westergaards modulus of subgrade reaction k is used in this procedure to express the supporting capability of the subgrade soil. Introduction to rigid pavement design ced engineering. The reported correlations, if any, between the results of simple tests such as atterberg limits, grain size distribution, pocket penetrometer, and hand held shear vane and the mr values of the roadbed soils. Determining modulus of subgrade reaction k value test procedure for determining modulus of subgrade reaction k value txdot designation. Engineering properties of stabilized subgrade soils for. Correlation between soil bearing capacity and modulus of. It is determined on the basis of the loadsettlement curve obtained from the first loading cycle cf.
It is important to consider how these parameters apply to the design of floor slabs. The displacement diagram shows a dishing effect as discussed earlier. Based on the test results, five correlations were developed to estimate the rvalue. The modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabsonground. The foundation modulus k value should be assigned to the material directly beneath the concrete pavement. Finally, the relation between kvalue and slab behavior is discussed. Tex125e figure 1a graphic presentation of k values for all compactable subgrades. Calculate subgrade modulus from soil bearing capacity dialog. The modulus of subgrade reaction, which is defined as the ratio between an applied pressure q and the deflection.
However, the strain modulus is determined by the curve fitting method for the overall normal stresssettlement data. Evaluation of modulus of subgrade reaction ks in gravely. Legally binding document step out from the old to the newjawaharlal nehru invent a new india using knowledge. Subgrade modulus of laterally loaded piles in clays. The modulus of subgrade reaction, k s, is a parameter expressing the elastic reaction of a soil under a surface load.
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