What is B Borrow?
B borrow is special fill material. It is used for a variety of purposes. Among them are backfill for overpasses and embankments. The material used for these purposes must be of acceptable quality and contain no wood or large lumps. It is therefore called B borrow. Here are some of its uses: Area outside the highway right-of-way
B borrows, or areas outside the highway right-of-way, are often used for development projects that require a large volume of construction materials. These areas can contain a variety of materials, including soil, rock, and concrete. A decision should be made early in the project development process to determine whether waste disposal is permitted. This decision should be included in the scope of the project and in the construction plan.
When placing a construction or reconstruction project in an area outside the highway right-of-way, the Contractor should follow the Department's rules for b borrows. These requirements include following sound engineering practices, not obstructing highway traffic, and avoiding the need for the use of a utility that is located in the right-of-way. In addition, the Contractor must pay for the costs associated with obtaining a borrow permit. Lastly, the Contractor must notify the Engineer of the borrow area at least 20 days prior to beginning work. The Engineer must approve the borrow area's location, control of material, and perform all necessary tests to ensure that it is safe for use. Special filling for storm sewers
Backfilling storm sewers is the process of adding material to an existing storm sewer system. This material is typically crushed stone or a granular material that is well graded. The material should be compacted to a density that will support the pipe system and any surface loads. The density required will depend on the site, the material used, and the experience of the installer. Backfill for embankments
When constructing an embankment, it is important to use suitable materials and compact them to meet the required density and moisture requirements. This material may come from an excavation on the project site or from a borrow area. It must also meet the required plasticity index. The following are some guidelines for selecting the appropriate backfill for an embankment:
The Engineer determines the amount of material needed based on the cross section and the end area of the embankment. The quantity for which payment is made must not exceed the amount needed to construct the embankment to a neat cross section. The measurement of the embankment must also account for any settlement of the embankment. In some instances, the Engineer may choose to measure the embankment after the selected backfill material or topsoil is spread. In that case, the Engineer can deduct the computed quantities of the selected backfill from the total amount of materials needed for the embankment.
The borrow area provided by the Contractor should be regular in cross section to ensure accurate measurement. It should blend with the existing land forms, and the Contractor must be careful not to encroach on adjoining owners. The Contractor must be diligent in draining surface water in its natural course and complete the excavation in a manner consistent with the natural drainage conditions.
The water content of the special backfill material used shall be less than two percentage points below the optimum moisture level determined by the Engineer. The special backfill material may be processed using an approved pugmill or may be mixed with water on-site. However, the moisture content of the special backfill material must not exceed the limits specified in the contract document. borrow garden tools
Depending on the type of soil used, the Contractor may be required to compensate the Contracting Authority for the amount of material removed from the optional borrow area. The compensation rate will be determined based on the quantity of material removed and replaced, and the cross section measurements. Backfill for overpasses
Overpasses are special structures that are built for traffic purposes. They are often located in urban areas and span high-speed bridges. When a special overpass needs to be demolished, the most common method is the mechanical demolish mode. This requires the use of a bailey support and protection to prevent the structure from being damaged during the process.
In addition to this, it is also necessary to consider the abutment-backfill interactions for highway bridges. The interaction between the two structures is highly influential in seismic risk assessment, particularly at the regional level. To better understand the abutment-backfill relationship, probabilistic backfill models are used. In addition, numerical methods are used to establish the validity of the pushover response of backfills. These methods use advanced plasticity materials in finite element models of soils, which result in consistent backfill force displacement relationships.
Backfill plays an important role in the load-carrying capacity of masonry arch bridges. While backfill is not structural, it transmits live loads and stabilizes the arch barrel when it is under load. Because of this interaction, it is difficult to separate the effects of the backfill from existing assessment codes. To separate these effects, a series of experiments was conducted, including 27 small-scale bridge tests. The experimental peak loads were then compared with those calculated by limit analysis software.
An additional issue in the evaluation of bridge safety is the seat-type abutment-backfill system. While this system contributes to the overall structural system, it is usually ignored in Europe. The reason is that European designers prefer to use joint gaps that are larger than the ones required in design earthquakes. Fortunately, Caltrans Guidelines specify an easy way to account for the interaction between the abutment and backfill. Specifically, Caltrans Guidelines prescribe an abutment-backfill interface with a fully sacrificial approach. In other countries, however, designers detail this interface so that a plastic hinge forms at the base of the backwall.