When excavating while biological degradation for example, attack by insects or other depressing ground water, ensure the ground water is below the biological forms as necessary, and against decay if above bottom of cut at all times to prevent washout from behind ground water. Maintain NOTE 6Certain preservative and protective compounds may react control of water in the trench before, during, and after pipe adversely with some types of thermoplastics, and their use should be installation, and until embedment is installed and sufficient avoided in proximity of the pipe material.
To preclude loss of soil support, employ dewatering methods that 6. Movable supports should not be used below 6. Before mov- mining of the trench bottom or walls, the foundation, or other ing supports, place and compact embedment to sufficient zones of embedment. Provide dams, cutoffs or other barriers depths to ensure protection of the pipe.
As supports are moved, periodically along the installation to preclude transport of finish placing and compacting embedment. Backfill all trenches after the 6. Fill voids left blankets for transport of running water to sump pits or other on removal of supports and compact all material to required drains.
Use well graded materials, along with perforated densities. The space between the pipe and trench wall must be wider than the 7. Installation compaction equipment used in the pipe zone. Minimum width 7. Protect the end of the Table 2. If full NOTE 7Installation of pipe in areas where significant settlement may be anticipated, such as in backfill adjacent to building foundations, and in entry is not achieved, disassemble and clean the joint and sanitary landfills, or in other highly unstable soils, require special reassemble.
Use only lubricant supplied or recommended for engineering and are outside the scope of this practice. Do not exceed manufacturers recommendations for angular joint deflection axial align- 7.
Provide a firm, stable, and uniform bedding for the 7. Provide a joints, follow recommendations of both the pipe and solvent minimum of 4 in. If full entry is not achieved, disassemble specified. Allow freshly made joints to 7. Use a suitably graded 7. Place and compact foundation the pipe.
Work in and tamp the haunching material in the area material in accordance with Table 2. For severe conditions, the between the bedding and the underside of the pipe before engineer may require a special foundation such as piles or placing and compacting the remainder of the embedment in the sheeting capped with a concrete mat.
Control of quick and pipe zone. Follow recommendations for compaction given in unstable trench bottom conditions may be accomplished with Table 2. Do not permit compaction equipment to contact and the use of appropriate geofabrics. Use compaction equipment and techniques 7. Before using heavy compaction or construc- utilities or subsurface structures, or whenever there are special tion equipment directly over the pipe, place sufficient backfill foundations such as concrete capped piles or sheeting.
Provide to prevent damage, excessive deflections, or other disturbance a cushion of bedding between the pipe and any such point of of the pipe. See 7. Higher or lower compatible foundation or bedding material and compact to a densities than those recommended in Table 2 may be appro- density not less than the minimum densities given in Table 2. In the absence of an engineering evalua- 7. They are based on attaining an average modulus of 7. Provide bell holes in pipe bedding, no sionless material by watering jetting or puddling should only larger than necessary, in order to ensure uniform pipe support.
In engineer. At all times conform to the lift thicknesses and special cases where the pipe is to be installed to a curved minimum densities given in Table 2. When pipe laying is interrupted, secure engineer based on an evaluation of specific project conditions. For embedment 7. Push least 24 in. Where construction loads may be excessive for structures.
Prevent the should be monitored by the engineer at a frequency appropriate direct transfer of thrust due to surface loads and settlement, and to project requirements. Leakage testing specifications, while ensure adequate support at points of connection to main lines.
When excavating for a service line connection, excavate material from above the top of the existing pipe before 8. Inspection, Handling, and Storage removing material from the sides of the pipe. Materials and 8. Reject noncon- whichever is more stringent. If not NOTE 8Special construction techniques and considerations are re- returned to supplier, dispose of legally.
Accordingly, key considerations in the de- loads applied to the pipe load-induced deflection , and time sign and execution of a satisfactory installation of buried dependent soil response deflection lag. Construction and load flexible thermoplastic pipe that provided a basis for the induced deflections together constitute initial pipe deflection.
Additional time dependent deflections are attributed primarily to changes in embedment and in-situ soils, and trench settle- X1. The sum of initial and time dependent deflections equately investigated prior to construction, in accordance with constitutes total deflection. Practice D , as a basis for establishing requirements for foundation, embedment and backfill materials and construction X1.
The type of pipe selected should be suited for the job Construction deflections are induced during the process of conditions. The magnitude of con- X1. This interaction of uniformity of embedment support, pipe out-of-roundness, and pipe and soil provides a pipe-soil structure capable of support- installation workmanship in general.
These deflections may ing earth fills and surface live loads of considerable magnitude. Compaction The design, specification and construction of the buried flex- of the side fill may result in negative vertical deflections that ible pipe system should recognize that embedment materials is, increases in pipe vertical diameter and decreases in hori- must be selected, placed and compacted so that pipe and soil zontal diameter.
Approaches given in Practice D provide act in concert to carry the applied loads without excessive allowances for construction deflection. Embedment density requirements should be determined by X1. It is the total of construction deflections and characteristics of the in-situ soil and compactibility character- load-induced deflections. The minimum densi- X1. These degree of compaction. For particular installations, the project changes typically add to initial deflections; the time involved engineer should verify that the density specified meets perfor- varies from a few days to several years depending on soil mance requirements.
Time dependent factors are traditionally accounted for by adjusting load- X1. The deflection for specific types of materials depends on the methods used to lag factor is the ratio of final load-induced deflection to initial impart compactive energy. Coarse-grained, clean materials load-induced deflection. Selection of a deflection lag factor is such as crushed stone, gravels, and sand are more readily considered in Practice D In pipe trenches, small, hand-held or walk-behind factors.
As examples, as limits for the design and acceptance of buried flexible pipe vibratory plate tampers work well for coarse grained materials installation.
Deflection limits for specific pipe systems may be of Class I and Class II, whereas hand tampers or air driven derived from both structural and practical considerations. Gas or diesel powered strength, strain, and local distortion.
Practical considerations jumping jacks or small, walk-behind vibratory rollers impart include such factors as flow requirements, clearance for inspec- both vibratory and kneading or impact force, and hence are tion and cleaning, and maintenance of joint seals. Initial and suitable for most classes of embedment and backfill material. When local distortions may be significant, the engineer or after construction when permeable underdrain or embed- needs to establish methods for controlling and monitoring distortion levels.
Field experience shows that migration can result in X1. The gradation and relative size of the deflections and, in any event, to maintain installed deflections embedment and adjacent materials must be compatible in order within specific limits.
Methods of placement, compaction, and to minimize migration see X1. In general, where moisture control should be selected based on soil types given significant ground water flow is anticipated, avoid placing in Table 1 and on recommendations given in Table 2.
The coarse, open-graded materials, such as Class IA, above, below, amount of load-induced deflection is primarily a function of the or adjacent to finer materials, unless methods are employed to stiffness of the pipe and soil embedment system.
Other factors impede migration such as the use of an appropriate stone filter that are important in obtaining deflection control are outlined or filter fabric along the boundary of the incompatible materi- below. To guard against loss of pipe support from lateral migration X1. This criterion need not apply if the coarser material is X1. Live loads applied by following criterion may be used in lieu of X1.
Where external loads are deemed to for nominal pipe sizes 8 in. To allow required to ensure that adequate embedment stiffness is devel- for stabilization of the pipe soil system, deflection tests should oped to support the pipe.
Current presumptive values for x containing crushed stone are based on few, or no, physical soil tests. This research will develop constrained modulus and Duncan-Selig design values for crushed stone and common granular backfill soils for culvert installations.
Historical Version s — view previous versions of standard. In addition to the naturally mined materials, designers are in need of constrained modulus values for recycled concretes and other manufactured embedment materials. Link to Active This link will always route to the current Active version of the standard. This research will develop a test method to determine those values as currently one does not exist.
It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Gravel, crushed rock and granular fill materials i.
Many of the presumptive values are based on testing only one type of soil and extrapolating the data for other soil types. A commentary on factors important in achieving a satisfactory installation is included in Appendix X1. The project will include four objectives. Specific paragraphs in the appendix are referenced in the body of this practice for informational purposes. Little is known about the required lateral forces to provide adequate confining pressure of the crushed stone. Terms of Use and Privacy Statement.
Emphasis will be placed on coordination between the tested samples and the requirements of the LRFD design specifications. Accurately characterizing the relationship between the density and stiffness of crushed stone will enable these soil-structure interaction systems to be designed more cost effectively. Follow-on research may require field validation of installed pipe and buried bridges designed with the results of this research and d ability to achieve good compaction levels in confined areas.
The information may be helpful to the sponsoring committee in keeping the statement up-to-date. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
The second objective in this study is to determine M s and Duncan-Selig parameters for a range of granular fill materials typically used or considered for use as bedding or backfill for buried structures.
Construction Design Materials Geotechnology Bridges and other structures. This determination is necessary qstm define the minimum level of lateral support to be provided by native soils or the required minimum trench width. Cuando la parte superior del ademe deba cortarse, debe nivel de agua se mantenga debajo del fondo del corte para evitar hacerse a 1. Se que se lleve parte de las paredes de la zanja. Se deben rellenar todas las zanjas 6. En el encamado removidos y compactar todo el material a la densidad requerida.
Se debe usar solamente los lubricantes 7. Use un material graduado adecuado donde las adecuados. Se debe 7. Antes de usar un equipo pesado de evitar el movimiento vertical o lateral. No utilice compactadores 8. Si no se regresa al fabricante, debe ser desechada ingeniero. Los X. Las deflexiones distorsiones locales. Deflexiones adicionales dependientes del la limpieza y el mantenimiento del sello de las uniones. NOTA X. La magnitud de las uniformidad en la rigidez del recubrimiento o por cargas concentradas.
Otros X. Material limpio y granulado pueden ser usados en lugar de X1. Por ejemplo, apisonadoras de planchas mm hasta mm. Estas condiciones se presentan donde la resistencia lateral del suelo in-situ es insignificante, tal como un X.
La presencia de estos materiales en el X. Donde se X. La X2.
0コメント