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Topic: Subgrade

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	FM 5-430-00-2 Chptr 12 Airfield Pavement Design
		Since the subgrade is a frost-susceptible soil (frost group F3) and the area is subjected to frost, the total thickness design must be derived from the soil-support index, which is 3.5 (Table 12-12).
		Subgrades known to be NFS to the depth prescribed for subgrade preparation and known to contain no frost-susceptible layers or lenses, as demonstrated and verified by extensive and thorough subsurface investigations and by the performance of nearby existing pavements.
		Consequently, it is not feasible to scarify and recompact the subgrade.
	www.globalsecurity.org /military/library/policy/army/fm/5-430-00-2/Ch12.htm (18846 words)

	FM 5-430-00-1 Chptr 5 Subgrades and Base Courses
		Figure 5-2 demonstrates that the magnitude of the stresses on the subgrade decreases as the flexible-pavement structure is thickened.
		Where subgrade materials meet plasticity requirements but are deficient in grading requirements, it may be possible to treat an existing subgrade by blending in stone, lime rock, sand, or similar materials to produce an acceptable subbase and raise the design CBR value.
		The existing subgrade may meet the requirements for a subbase course, or it may be possible to treat the existing subgrade to produce a subbase.
	www.globalsecurity.org /military/library/policy/army/fm/5-430-00-1/CH5.htm (7307 words)

	Cement Association of Canada - Subgrade and Subbase
		The subgrade on which a slab on ground is to be placed should be well drained, of uniform bearing capacity, level or properly sloped, and free of sod, organic matter, and frost.
		During subgrade preparation, it should be remembered that undisturbed soil is generally superior to compacted material for supporting concrete slabs.
		The subgrade should be moistened with water in advance of placing concrete, but should not have puddles or wet, soft, muddy spots when the concrete is placed.
	www.cement.ca /cement.nsf/ep/73787DEC0A5522C6852568B6004996D1?opendocument (404 words)

	[No title] (Site not responding. Last check: 2007-10-14)
		The subgrade shall be substantially uniform in density throughout the entire width of the subgrade.
		The subgrade shall be constructed to drain surface water to the side ditches and all ditches shall be kept open by the contractor.
		The subgrades shall be checked after rolling and, if not at the proper elevation at all points, sufficient material shall be removed or added and compacted to bring all portions of the subgrade to the required elevation and density.
	www.modot.state.mo.us /design/specbook/documents/Sec0209_001.doc (478 words)

	Section II - Pavement Construction Manual
		Drainage of the subgrade and bases is essential during construction and for the life and strength of the section.
		For rigid pavements, the modulus of subgrade reaction (K) is used to measure the strength of the underlying pavement layers.
		In subgrade construction, it is necessary to insure that the subgrade is built to the proper grade and smoothness and to insure that the density requirements are met.
	www.faa.gov /arp/anm/services/construction/pavement_manual/section_ii.htm (2296 words)

	[No title] (Site not responding. Last check: 2007-10-14)
		The depth of subgrade to be stabilized is 300 mm.
		Continue mixing until the lime-pozzolan has been uniformly incorporated into the subgrade to the required depth with the mixture being homogeneous and friable, and soil clods are broken down to pass a 25-mm screen and at least 60% pass a No. 4 sieve, exclusive of rock particles.
		Protect the subgrade with a minimum of 150 mm of subbase during the winter shutdown period.
	www.jbcassociates.com /employees/408files/patpkpzzln.doc (1850 words)

	Item 206 Lime Soil Stabilized Subgrade
		The subgrade in lime stabilized areas shall be test rolled prior to the addition of lime, with a grader having a minimum weight of 14 metric tons (15 tons).
		The subgrade shall be shaped to the plan lines prior to admixture of lime so as to permit the construction of a uniform compacted course of lime treated soil to the thickness shown on the plans.
		All lime-soil stabilized subgrade shall be compacted to 100 percent of the laboratory maximum dry density.
	www.dot.state.oh.us /spec/206.htm (1092 words)

	Due North Resources - Geotextiles
		If the subgrade soil is subject to persistent or even occasional wet conditions, the geotextile placed over it must be highly permeable to allow rapid drainage of water from the loaded subgrade soils up into the free draining aggregate base.
		Regardless of subgrade strength, the site should first be cleared of all sharp objects, tree stumps, and large stones that could puncture the fabric.
		Over very soft subgrade, care must be taken during aggregate placement to insure the fabric is not moved out of position nor the subgrade overstressed.
	www.cyber-north.com /geotextiles.html (2100 words)

	[No title] (Site not responding. Last check: 2007-10-14)
		The subgrade shall be prepared as specified in Section 212, and shall be free from an excess or deficiency of moisture at the time of placing the selected material.
		The subgrade shall be prepared as specified in Section 212 and shall be free from an excess or deficiency of moisture at the time of placing base course material.
		The subgrade shall also comply, where applicable, with the requirements of other items that may be contained in the Contract that provide for the construction, reconstruction, or shaping of the subgrade or the reconstruction of the existing base course.
	www.ahtd.state.ar.us /Construc/specbk96/ar300.doc (10378 words)

	Comprehensive Monitoring Systems for Measuring Subgrade Moisture Conditions (Site not responding. Last check: 2007-10-14)
		Subgrade resilient modulus is highly dependent on water content, which can vary significantly with a number of environmental factors.
		Multiple-segment TDR probes were placed horizontally in the soil subgrade, in the stone subgrade, and in the asphalt stabilized base, and single-segment probes were placed on the asphaltic concrete of the roadway sections.
		Temperature sensors were installed in the soil subgrade and in the stone base at the same elevations as the TDR probes, and at three elevations in the top 200mm of the pavement.
	www.pubs.asce.org /WWWdisplay.cgi?9903857 (316 words)

	America's Premier Paver - Design Guides: Heavy Vehicular
		It is recommended that the design be undertaken using a subgrade category as described earlier or from the geotechnical report, as the geotechnical consultants will consider these factors when providing their recommendations.
		Subgrade soils or granular material unsuitable for use alone may be treated to produce a stronger layer.
		The subgrade soil may be stabilized by adding portland cement or lime, depending on the quality of the soil.
	www.americaspremierpaver.com /cad/heavy.htm (10401 words)

	[No title] (Site not responding. Last check: 2007-10-14)
		Grading and subgrade preparation shall conform to other sections of these specifications except that a finished subgrade is not required prior to combining the pavement materials.
		The existing pavement materials removed shall be placed on the subgrade in the proportions and to the depth shown on the plans.
		The modified subgrade shall be constructed to the cross section shown on the plans and shall be compacted to the density and stability specified in Section 203 unless otherwise noted on the plans.
	www.fsark.com /Engineering/StandardSpecs/211.html (610 words)

	[No title] (Site not responding. Last check: 2007-10-14)
		The way to minimize subgrade failure in a roadway system is to accurately determine the subgrade soil strength and simply keep the loading applied to the subgrade less than what would cause a bearing capacity failure.
		Gradation analysis, on base course and subgrade samples obtained at different depths, revealed that fines present in the base course were significantly greater in the control and geogrid-stabilized sections than in the geotextile-stabilized section.
		As a result of the gradation analysis of the underlying subgrade, it is believed that the subgrade fines present in the base course may be pumped from a depth greater than 150 mm inside the subgrade.
	www.ctr.vt.edu /index.cfm?fuseaction=DisplayResearchProjects&ProjectID=103 (1793 words)

	Railway Track and Structures: Application and performance of Hot-mix-asphalt trackbed over soft Subgrade: Properly ... (Site not responding. Last check: 2007-10-14)
		As a benchmark, the earlier test showed that with a conventional 18-inch granular layer, the soft subgrade was highly stressed due to 39-ton axle loads, thus leading to higher levels of subgrade deformation and frequent surfacing operations.
		As a result, the measured subgrade stresses were lower for the asphalt trackbeds than for the 18-inch granular track.
		To show how stresses induced by wheel loads are reduced from the hma to the subgrade, Figure 3 shows the dynamic stress results under an actual train operation (40 mph) measured on the eight-inch hma surface, as well as on the subgrade surface.
	www.findarticles.com /p/articles/mi_m0BFW/is_1_98/ai_82134975 (1475 words)

	SPECS APPENDIX A
		Immediately prior to placing the concrete, the subgrade shall be checked for conformity with the cross section shown on the plans by means of an approved template on the side forms.
		The subgrade shall be clean of loose or wet material prior to placing concrete.
		All subgrade testing shall be made not more than 48 hours prior to placement of pavement, unless extreme weather conditions dictate retesting (rain, freezing temperature, excessive temperature, etc.).
	www.boonecountyky.org /bcpc/Specs/a1.htm (1351 words)

	Michigan Concrete Association - Parking Area Subgrade Checklist
		When there are wet areas in the subgrade the water must be removed and a determination made to see if there are any soft spots.
		The areas between dissimilar soils should be excavated to a six (6) inch depth, blended and re-compacted to create a transition of approximately ten (10) feet from one soil type to the other.
		If the subgrade soil is clay, a leveling course may trap water and additional under drainage may be required.
	www.miconcrete.org /page.cfm/139 (666 words)

	Green Section Recommendations For A Method Of Putting Green Construction \| United States Golf Association
		The subgrade should be established approximately 16 inches (400 mm) below the proposed surface grade - 18 to 20 inches (450 to 500 mm) when an intermediate layer is necessary - and should be thoroughly compacted to prevent further settling.
		As an alternative to round pipe placed in a trench, flat pipe placed directly on the prepared subgrade may be employed, provided the flat pipe conforms to ASTM D 7001 (provisional), is a minimum of 12 inches (300 mm) in width, and is not covered by a geotextile sleeve.
		The entire subgrade then shall be covered with a layer of clean, washed, crushed stone or pea gravel to a minimum thickness of four inches (100 mm), conforming to the proposed final surface grade to a tolerance of ±l inch.
	www.usga.org /turf/course_construction/green_articles/putting_green_guidelines.html (2420 words)

	538.00 Subgrade (Site not responding. Last check: 2007-10-14)
		The bottom of the excavation for the pavement, or top of the fill, will be known as the pavement subgrade and will conform to the lines, grades, and cross sections shown on the accepted plans.
		After excavation and embankment is completed and the subgrade brought to final grade, it will be rolled with a rubber-tired roller which is a minimum size of eight (8) to twelve (12) tons and other compaction equipment as required to bring the subgrade to the required density and stability.
		Soft and yielding material and portions of the subgrade which show deflection will be scarified and recompacted or will be removed and replaced with base course material, and compacted as specified herein.
	www.ci.broomfield.co.us /standspec/_DATA/SEC500/530_00_SITE_WORK_AND_EARTHWORK/538_00_Subgrade.html (346 words)

	Subgrade - Wikipedia, the free encyclopedia
		Over US$130,000 has been donated since the drive began on 19 August.
		In highway engineering, subgrade is the native material underneath a constructed pavement.
		Subgrades are commonly compacted before the construction of a pavement, and are sometimes stabilized by the addition of asphalt, portland cement or lime.
	en.wikipedia.org /wiki/Subgrade (82 words)

	Rigid Pavement Design User's Manual
		If Complete Subgrade Protection or Limited Subgrade Protection are desired, the user may enter the Degree-Days and Soil Unit Weight to determine the depth of frost penetration.
		To complete the subgrade data input, the user should enter the subgrade k value and the thickness of all stabilized and non-stabilized layers.
		In addition to the subgrade information, the user is prompted for information regarding the properties and condition of the existing pavement.
	www.faa.gov /arp/engineering/software/manuals/RigidManual.htm (1405 words)

	ACPA Concrete Pavement Progress (CPP) (Site not responding. Last check: 2007-10-14)
		Soil stabilization is sometimes required to facilitate construction by drying a subgrade soil and stabilizing the working platform for the subbase and/or pavement.
		If a pavement design is based on a stabilized subgrade strength value, the long-term durability of the material must be considered (i.e., consider if the stabilized soil will retain its strength for the life of the pavement).
		The key is to provide a uniform, stable subgrade platform for construction equipment, as well as the rest of the pavement structure.
	www.pavement.com /CPP/2005/CPP-January-05.htm (2341 words)

	SELECTION OF SUBGRADE MODULUS FOR PAVEMENT OVERLAY DESIGN PROCEDURES
		This subgrade property is used in the design of new pavement sections as well as in the rehabilitation of existing roadways. Without adequate information on the roadbed soil, a pavement structure will be improperly designed and as a result, it may fail prematurely.
		As a result, the frozen condition was not considered in the analysis. After testing was completed for the undisturbed samples, the disturbed (remolded) samples were prepared by crumbling the sample and re-compacting it to 152-mm (6-in.) using five lifts and static compaction. This procedure is fully described in the specifications (refer to Appendix A).
		Subgrade cores from the spring of 1993 were tested for resilient modulus shortly after obtaining them from the field. Again, two conditions were considered, undisturbed and disturbed (remolded). Unlike the first set of subgrade cores, samples were easily removed from the Shelby tubes and, therefore, they did not require freezing prior to extraction.
	www.ndsu.nodak.edu /ndsu/ugpti/MPC_Pubs/html/MPC94-34.htm (8072 words)

	[No title]
		The lime-treated subgrade shall not be mixed or compacted if the temperature of the lime/soil is below 35(F. 307.05 Preparation of Subgrade Prior to beginning any lime treatment the subgrade shall be constructed and finished to smooth and uniform surfaces conforming to the grades and typical sections specified.
		Soft or otherwise unsuitable subgrade disclosed by proof rolling shall be over-excavated, and replaced to a compacted stable state.
		Throughout this entire operation, the shape of the course shall be maintained by blading, and the surface upon completion shall be smooth and shall conform with the typical section shown on the plans and to the established lines and grades.
	www.dot.state.co.us /DesignSupport/construction/1999SSP/307lts.doc (2604 words)

	Subgrade Performance Study (Site not responding. Last check: 2007-10-14)
		This Pavement Subgrade Performance Study is investigating the performance of full-scale pavements involving several types of subgrade soils tested at several moisture contents.
		The objectives of this Pavement Subgrade Performance Study are to:
		Develop an improved mechanistic subgrade failure criterion (elastic and/or plastic) for new and reconstructed pavements;
	www.crrel.usace.army.mil /research/Pooled_Fund/index_sps.htm (219 words)

	Michigan Concrete Association - Parking Area Subgrade Guide
		The goal is to place concrete parking areas on properly prepared subgrades that are uniform in soil composition and compaction.
		Subgrade is defined the natural ground, graded and compacted, on which the concrete parking area is constructed.
		It is important, however, that subgrade support be reasonably uniform without abrupt horizontal changes from hard to soft, and that the upper portion of the subgrade be of uniform composition and density.
	www.miconcrete.org /page.cfm/138 (232 words)

	LINQ Industrial Fabrics, Inc. - Tech Note #19
		A geotextile should be placed between the aggregate and the subgrade to act as a separator, which prevents the subgrade and aggregate base course from mixing and thus maintains the desired strength of the aggregate base.
		Utilization of a separation geosynthetic minimizes the potential for aggregate being forced down into the subgrade by the action of the applied loads or by the migration of the subgrade up into the base course.
		The solution to contamination of a stone base course by subgrade fines is the use of a geosynthetic functioning as a separator between the soil subgrade and the stone base course (Koerner and Koerner 1994).
	www.linq.com /geotex/technote/tech19.html (688 words)

	CEHNC 1110-1-23, Chapter 7 (Site not responding. Last check: 2007-10-14)
		If the subgrade consists principally of gravel or sand, the filter layer may not be necessary and may be replaced by additional base course if the particle sizes in the will be necessary.
		Hence in frost areas, the compacted subgrade will not be considered part of the layered system of the tank trail, which should be comprised of only the wearing, base, and subbase courses.
		If a compacted subgrade layer is included in the trail section, it should be compacted to the density required in order to produce the CBR value used in design.
	www.hnd.usace.army.mil /rtlp/DSGNMAN/chap7.htm (2958 words)

	Geosynthetic Design & Testing - Pond Liners
		The subgrade materials are dispersive and this interferes with the end use of the water.
		The subgrade that is to receive the liner requires careful preparation.
		The subgrade preparation is required to meet the specification of the liner manufacturers.
	www.geosynthetic.com.au /pond.html (484 words)

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