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Publication Number: FHWA-RD-07-052
Date: September 2007
This protocol describes a method to determine if a soil is expansive and a method to predict the amount of swell. This protocol is based on AASHTO Designation T 258-81 (1996), Determining Expansive Soils. The test shall be performed in accordance with this standard (AASHTO T 258), as modified herein. Those sections of the AASHTO standard included in this protocol by reference and without modification shall be strictly followed. All other sections of this protocol shall be followed as modified herein.
The referenced test method shall be performed on representative subgrade samples obtained at designated LTPP sampling locations.
This test covers a method to determine if a soil is expansive and a method to predict the amount of swell in the soil. This test is to be conducted in accordance with AASHTO T258-81 (1996), Method II.
2.2 LTPP Protocols
P43 Determination of Atterberg Limits
P49 Determination of the Natural Moisture Content
P51 Sieve Analysis of Subgrade Soils
3.1 The potential expansiveness of a soil may be determined by using the Atterberg Limits of the soil. The Atterberg Limits shall be determined in accordance with LTPP Protocol P43, Determination of Atterberg Limits.
3.2 The soil's potential for expansion may be determined based on Table 1.
|Degree of Expansion||Liquid Limit||Plasticity Index|
|High||> 60||> 35|
|Low||< 50||< 25|
4.1 The amount of swell to be expected in a stratum is determined by an empirical procedure called the Potential Vertical Rise (PVR) Method. The method requires knowledge of the depth of the expansive subgrade.
4.3 PVR Test and Prediction Procedure
4.3.1 The moisture content of the subgrade soils will be determined using samples obtained at intervals of 2 feet (0.6 m) to a total depth of 20 feet (6.1 m) below top of subgrade. Test in accordance with LTPP Protocol P49, Determination of the Natural Moisture Content.
4.3.3 For each sample determine the LL and PI in accordance with LTPP Protocol P43. In addition, determine the percent binder (minus No. 40 [0.425-mm] sieve) in the soil layers in accordance with LTPP Protocol P51, Sieve Analysis of Subgrade Soils.
Note: For SPS-8 projects, a maximum depth of sampling is 20 feet (6.1 m). It is assumed that even if expansive soils exist below the 20-foot (6.1-m) depth, the influence on total PVR will not be significant. Also, if the amount of material retained on the No. 40 (0.425-mm) sieve is less than 25% by weight, then Atterberg Limits will not determined for that sample.
4.3.13 Record the following on Form T60:
Sample identification shall include: Region, State, State Code, Experiment Number, SHRP ID, Field Set Number, and Location Number.
Test identification shall include: LTPP Test Designation, LTPP Protocol Number, and Test Date.
Test results shall include: percent passing the No. 40 (0.425-mm) sieve; natural moisture content; LL; PL; the PVR in inches for each 2-ft (0.6-m) layer, as calculated according to Section 4.3 of AASHTO T 258-81 (1990), and the total PVR for the location.
Comments shall include LTPP standard comment code(s), as shown in Section 4.3 of this Guide and any other note, as needed.
LTPP LABORATORY MATERIAL HANDLING AND TESTING
LABORATORY MATERIAL TEST DATA
DETERMINING EXPANSIVE SOILS
LAB DATA SHEET T60
SUBGRADE SOILS TEST DESIGNATION SS12/PROTOCOL P60
LABORATORY PERFORMING TEST:______________________________________________________________
LABORATORY IDENTIFICATION CODE: __ __ __ __
REGION _________________ STATE ___________________ STATE CODE __ __
EXPERIMENT NO _____ SHRP_ID __ __ __ __
SAMPLED BY: ______________________________________________ FIELD SET NO . __ __
DATE SAMPLED: __ __-__ __-__ __ __ __
1. LAYER NUMBER (FROM LAB SHEET L05B) __ __
2. LABORATORY TEST NUMBER __
3. LOCATION NUMBER __ __ __ __ __
4. TEST RESULTS
|Sample Depth, ft.||p40, %||mc, %||LL||PL||PVR, in.|
|0-2||__ __.__||__ __.__||__ __||__ __||__.__ __|
|2-4||__ __.__||__ __.__||__ __||__ __||__.__ __|
|4-6||__ __.__||__ __.__||__ __||__ __||__.__ __|
|6-8||__ __.__||__ __.__||__ __||__ __||__.__ __|
|8-10||__ __.__||__ __.__||__ __||__ __||__.__ __|
|10-12||__ __.__||__ __.__||__ __||__ __||__.__ __|
|12-14||__ __.__||__ __.__||__ __||__ __||__.__ __|
|14-16||__ __.__||__ __.__||__ __||__ __||__.__ __|
|16-18||__ __.__||__ __.__||__ __||__ __||__.__ __|
|18-20||__ __.__||__ __.__||__ __||__ __||__.__ __|
5. TOTAL PVR, inches __ __.__ __
(a) CODE: __ __ __ __ __ __ __ __ __ __ __ __
(b) NOTE _______________________________________________________________________________
7. TEST DATE __ __-__ __-__ __ __ __
|SUBMITTED BY, DATE||CHECKED AND APPROVED, DATE|
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Topics: research, infrastructure, pavements and materials
Keywords: research, infrastructure, pavements and materials, Asphalt cement, asphalt concrete, field sampling, General Pavement Studies, laboratory testing, LTPP, material properties, pavement layering, Pavement Performance Data Base, portland cement concrete, protocol,Specific Pavement Studies, subbase, subgrade, treated base, unbound base
TRT Terms: research, facilities, transportation, highway facilities, roads, parts of roads, pavements