(A) On completion of the grading operations, a stabilized roadbed shall be constructed. The roadbed shall be stabilized to a firm and unyielding subgrade having the required bearing value specified in the plans.
(B) When the stabilizing is designated as Type B, the specialty engineer will determine compliance with the bearing value requirements by the Limerock Bearing Ratio (LBR) method. If approved by the specialty engineer and only for materials requiring an LBR value of 40, the specialty engineer may omit Sections 6.0 and 6.1 of Florida Method of Test for Limerock Bearing Ratio (FM 5-515) and perform an Unsoaked LBR Test. The engineer or the contractor may request to use this method. If the Unsoaked LBR Test results in a failing test, then the specialty engineer will perform a standard Soaked LBR Test.
(C) The required bearing value shall be obtained either by constructing the roadbed of selected materials from the roadway or by stabilizing the roadbed material by the addition and mixing-in of suitable stabilizing materials. Such work shall be constructed in accordance with these specifications and in accordance with the lines, grades and thickness shown on the plans.
(D) The subgrade to be stabilized may be processed in one course, unless the equipment and methods being used do not provide the required uniformity, particle size limitation, compaction and other desired results, in which case, the processing shall be done in more than one course.
(E) When additive stabilizing materials are required, they shall be spread uniformly over the area to be stabilized.
(F) When the use of materials from an existing base is required as all, or a portion of the stabilizing additives, the engineer will direct the location, placement, and distribution of such materials. Perform this work prior to the spreading of any additional commercial or local materials. Do not remove any section of existing base until the need for it in maintaining traffic is fulfilled.
(G) The mixing shall be done with rotary tillers, or other equipment meeting the approval of the engineer. The contractor may mix the materials in a plant of an approved type suitable for this work. The area to be stabilized shall be thoroughly mixed throughout the entire depth and width of the stabilizing limits. The mixing operations will be required regardless of whether or not the existing soil has the required bearing value without the addition of stabilizing materials.
(H) Regardless of the character or bearing value, all materials remaining after the mixing operations that will not pass a 3-1/2-inch ring shall be removed or broken down to a size not larger than 3-1/2 inches.
(I) Bearing value samples will be obtained and tested at completion of satisfactory mixing of the stabilized area. For any area where the bearing value obtained is deficient from the value specified in the contract documents, additional stabilizing material shall be spread and mixed.
(J) This reprocessing shall be done for full width of the roadway being stabilized and longitudinally for a distance of 50 feet beyond the limits of the area in which the bearing value is deficient.
(K) After mixing operations have been completed and the requirements of bearing value, uniformity and particle size have been satisfied, the stabilized area shall be compacted to the specified density. The materials shall be compacted at a moisture content permitting the specified compaction. If the moisture content of the material is improper for attaining the specified density, either water shall be added or the material shall be permitted to dry until the proper moisture content for the specified compaction is reached.
(L) Within the entire limits of the width and depth of the areas to be stabilized, the minimum density acceptable at any location will be 98% of the maximum density as determined by Florida Methods (FM) 1-T 180 Method “D”. Attainment of the minimum density specified is not required within the upper six inches of areas to be grassed under the contract. These areas shall be compacted to a reasonable firm condition as directed by the engineer.
(M) Use the following undertolerances from the specified bearing value, as based on tests performed on samples obtained after completing mixing operations:
Specified Bearing Value | Tolerance |
LBR 40 | 5.0 |
LBR 35 | 4.0 |
LBR 30 (and under) | 2.5 |
(N) The following unsoaked bearing value requirement is based on tests performed on samples obtained after completing mixing operations:
Specified Bearing Value | Unsoaked Bearing Value Required | Tolerance
|
LBR 40 | LBR 42 | 0.0 |
(O) The completed stabilized subgrade shall be shaped to conform to the finished lines, grades, and cross-section indicated on the plans.
(P) After the stabilizing and compacting operations have been completed, the subgrade shall be firm and substantially unyielding to the extent that it will support construction equipment and will have the bearing value required by the plans. All soft and yielding materials, and any other portions of the subgrade, which will not compact readily, shall be removed and replaced with suitable materials and the whole subgrade brought to line and grade, with proper allowance for subsequent compaction.
(Q) After the subgrade has been completed as specified above, the contractor shall maintain it free from ruts, depressions, and any damage resulting from the hauling or handling of materials, equipment, tools, and the like. It shall be the contractor’s responsibility to maintain the required density until the subsequent base or pavement is in place. Such responsibility shall include any reports, replacement, and the like, of curb and gutter, sidewalk and the like, which might become necessary in order to re-compact the subgrade in the event of underwash or other damage occurring to the previously compacted subgrade. Any such work required for re-compaction shall be at the contractor’s expense. Ditches and drains shall be constructed and maintained along the completed subgrade section.
(2000 Code, § 58-253) (Ord. 88-01, passed 5-24-1988; Ord. 2010-05, passed 4-27-2010) Penalty, see § 10.99