f682aff184 Typical values for each property are also summarized. Table 5-37 summarizes recommended design values for the modulus of the fractured slab, Efs, for Level 3 characterization in the NCHRP 1-37A Design Guide. Methods for determining the MR value for each time interval include: laboratory measurement at the estimated in-situ water content for the time interval. When a section of a strip has been grouted thoroughly, allow it to dry completely before performing additional work. Scarifying, reworking, and rolling these soils in cut areas may reduce the soil's load-bearing capacity. Determine gradation of the proposed material using mechanical analysis. Estimate a relative damage ur corresponding to each seasonal modulus value using the empirical relationship: (5.11) uf = 1.18 108 ( MR )-2.32 Compute the average relative damage uf as the sum of the relative damage values for each season divided by the number of seasons.
While a precise value of bedrock stiffness is seldom required, the effect of high bedrock stiffness must nonetheless be incorporated into the analysis. (5.11): (5.12) MR = 3015 ( uf )-0.431 This procedure can also be used to incorporate seasonal variations into the effective base and subbase MR values used to estimate structural layer coefficients in the 1993 AASHTO Guide (see Section 5.4.5). This initial strain is unmeasured in the test, but it is assumed the same in all directions for isotropic material behavior. The stress-dependent MR model implicitly included in the 1993 AASHTO Guide for granular base and subbase materials is (see Section 5.4.5 for more details): (5.9) MR = k1 θk2 in which q=bulk stress = σ1 + σ2 + σ3 (psi) k1, k2=material properties Guidance is provided in the 1993 AASHTO Guide for estimating the values of k1 and k2 for unbound base and subbase layers. [There should be a set of navigation buttons here, but your browser does notsupport inline frames or is currently configured not to display framesYou can still use the text-based navigation facility at the top of the page, though.]. These values, which are functions of the fracture method used and the nominal fragment size, were developed by applying conservatism to the relationship of Efs versus nominal fragment size published in the 1986 AASHTO Design Guide and NAPA IS-117. This is a plot of a typical soil sample values of CBR against moisture content. The bearing capacity of silts, very fine sands, and rock flour (predominantly USCS ML and SC groups) is reasonably good if properly compacted within the specified moisture range. All base courses require a final surface finish. A complete investigation should be made to determine the location and characteristics of all natural materials suitable for base-course construction.
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