Micro trench duct placement
A method of placing cable within concrete or asphalt includes cutting a trench into the concrete or asphalt. The method further includes placing a tubular material having a hollow inner diameter within the trench. The method also includes placing the cable within the tubular material.
The present invention relates generally to outside utility cable placement techniques and, more particularly, to utility cable placement using micro trench ducts.
BACKGROUND OF THE INVENTIONWith the explosion in communication via the Internet in recent years, there has been a corresponding increase in demand for high-speed bandwidth, such as that provided by fiber optic cables. However, provision of fiber optic cabling to the many locations, where it is in demand, has been problematic. Underground provision of fiber optic cabling has been a primary means of providing the cabling to various locations. Underground cable placement, though, requires excavation and, often, considerable surface destruction to permit the placement of the fiber optic cabling. Additionally, when the cable is placed in the ground, it is difficult to repair without having to re-excavate the area so that the cable can be removed. Furthermore, placement of cable directly in the ground leaves the cable in an unprotected state where it is susceptible to injury due to environmental conditions or external events on, or under, the surface of the ground.
Therefore, there exists a need for methods and assemblies for installing subsurface utility cables, such as fiber optic cables, that reduce surface destruction when installing the cables, improves the capability to repair subsurface cables once they are installed, and protects subsurface utility cables so as to reduce damage due to environmental conditions or external events.
SUMMARY OF THE INVENTIONIn accordance with one aspect consistent with the principles of the invention, a method of placing cable beneath a roadway includes cutting a trench in a surface of the roadway and placing a duct in the trench. The method further includes filling the trench with a sealer and placing cable within the duct.
According to another aspect consistent with the principles of the invention, an assembly for carrying cable within a trench cut in concrete or asphalt includes a duct comprising a tubular material having a hollow inner diameter and an outer diameter that is approximately equal to a width of the trench. The assembly further includes cable placed within the hollow inner diameter of the duct.
According to yet another aspect consistent with the principles of the invention, a method of placing cable within concrete or asphalt includes cutting a trench into the concrete or asphalt to a depth of 3.5 to 4.0 inches from a surface of the concrete or asphalt. The method further includes placing a tubular material having a hollow inner diameter within the trench and placing the cable within the tubular material.
BRIEF DESCRIPTION OF THE DRAWINGSThe accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with the description, explain the invention. In the drawings,
The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and their equivalents.
Methods and assemblies consistent with the present invention enable the placement of subsurface utility cables through the use of subsurface micro trenches and micro ducts, installed in roadway concrete or asphalt, that require minimal surface trenching, permit easy repair of the utility cables, and protect the utility cables from environmental conditions or external events. Consistent with one aspect of the invention, micro trenches may be cut approximately three to four inches into a roadway surface, and a micro duct that includes a high load rating material may be placed into the micro trench for carrying the subsurface utility cables. A spacer may be placed on top of the micro duct along the length of the micro trench to enhance structural rigidity and to protect the micro duct. A sealer may then be placed in the micro trench, over the micro duct and spacer, to fill up the trench made in the roadway surface.
Subsurface utility cables may then be inserted in the micro duct subsequent to placement of the micro duct in the micro trench. Subsurface utility cables may, thus, be easily repaired after placement into the micro trench by pulling the cables out through the micro duct via, for example, a hand hole or a manhole. The micro duct and spacer may additionally protect the subsurface utility cables from environmental conditions and external events that may otherwise damage the utility cables.
Exemplary Micro Trench
After the cutting of micro trench 100, a micro duct 125 may be placed in the bottom of micro trench 100. Micro duct 125 may include a hollow tubular conduit for receiving cable 130, such as, for example, any type of utility cable. In one implementation, for example, micro duct 125 may be made of HDPE and may further be HD20 load rated. Micro duct 125 may include an inside diameter that ranges from about 0.35 inches to about 0.40 inches. Micro duct 125 may further include an outside diameter that ranges from about 0.475 inches to about 0.525 inches. In one exemplary implementation, micro duct 125 may include a 0.375 inch inside diameter and a 0.5 inch outside diameter. Cable 130, such as, for example, fiber optic cable, may be installed in micro duct 125 to run through the inside diameter of the duct. Cable 130 may also include any type of utility cable that may fit within the inner diameter of micro duct 125.
After placement of micro duct 125, a spacer 135 may be placed in micro trench 100. Spacer 135 may include a substantially solid tubular member that enhances structural rigidity and provides protection to cable 130 from, for example, moisture and other environmental conditions that exist on the roadway surface 105. Spacer 135 may, for example, be made out of a material that is water impermeable and heat resistant to approximately 400 degrees Fahrenheit. In some implementations, for example, spacer 135 may be placed on top of micro duct 125 at a depth d2 135 below roadway surface 105. Depth d2 135 may be at least 2 inches, but not more than 3 inches. Spacer 135 may have a diameter that is approximately 25% larger than trench width w 120 to ensure a tight seal between micro duct 125 and side surfaces of micro trench 100. In one exemplary implementation, spacer 135 may have a ⅝ inch diameter for a ½ inch trench.
After placement of spacer 135, a sealer 140 may be placed in micro trench 100. Sealer 140 may seal micro trench 100 to protect cable 130 from environmental conditions. Sealer 140 may include, for example, bitumen, though other sealing materials may be used. The thickness of sealer 140 may be between two and three inches, and should overlap the edge of micro trench 100 by about two inches (not shown). The total width of sealer 140 on the roadway surface 105, therefore, should be approximately 4.5 inches (assuming a trench width w 120 of 0.5 inches). Sealer 140 may protrude no more than ¼ inch above the roadway surface 105.
Exemplary Trench Cutting Process
A micro trench 100 may then be cut in the roadway material 115 along the defined trench route [act 215]. For example, standard ½ inch concrete saw blades, turned so that the blade cuts backwards (i.e., upcuts), may be used to cut a micro trench 100 of width w 120 and depth d1 110. The cutting machine may be used without water (i.e., dry cut), with a dust collection and containment system attached to the back of the blade area to catch the debris and dust.
When possible, micro trench 100 may be cut parallel or perpendicular to other pavement attributes (e.g., expansion joints, striping, etc.). The trench depth d1 may be between 3.5 and 4 inches and should be inspected after cutting to ensure gradual transitions are maintained. Transitions in depth at the bottom of micro trench 100 should be smooth and may be achieved with a hand/cut-off saw. Trench width w 120 may be equal to the outer diameter of the micro duct 125 that is to be placed in micro trench 100. For example, if micro duct 125 to be placed has an outside diameter of 0.5 inches, then width w 120 should be 0.5 inches.
If ninety degree turns in micro trench 100 are required, then trench 100 may be cut to each running line, and then a forty-five degree angle may be cut between the two lines. For example, a micro trench ninety-degree turn 300 is illustrated in
For entering hand holes, manholes, or building walls, a core bore may be made through an external surface of the hand hole, manhole or building wall. For example, as shown in
Returning to
For entering hand holes, manholes, or building walls, micro duct 125 may be inserted through a core bore 400 that extends through an external surface of the hand hole, manhole or building wall. For example, as shown in
Spacer 135 may be placed on top of micro duct 125 uni-directionally (i.e., only in one direction in trench 100) [act 915]. Spacer 135 usually should not be placed from two different directions (i.e., bi-directionally) and normally should not be spliced to begin a new piece or to make a repair. Instead of splicing, adjacent spacers 135 may be overlaid by at least six inches. Spacer 135 may be placed on top of micro duct 125 by pressing spacer 135 into micro trench 100 using a steel wheel with sufficient weight to ensure that slack is removed and that there is no space between micro duct 125 and the bottom of spacer 135.
Once all spacers 135 in the trench line are in place, sand may be added to all areas in micro trench 100 where spacers 135 will not protect micro duct 125 from hot sealer 140 [act 920]. The sand should be added such that its height is the same as the top of spacer 135. The sand may be fine grade and dry. After installation, the micro trench 100 may be inspected [act 925]. Micro trench 100 may be inspected, for example, to ensure that the top of spacer 135 or sand, if any, is at depth d2 below the roadway surface 105. Depth d2 may by at least 2 inches, but no more than 3 inches from the surface.
If the trench requires more than 3 inches of sealer, then a spacer or sand may be used to fill the additional void between the top of spacer 135 that is placed on top of micro duct 125. Sealer 140 may be heated to a temperature of between 325 degrees Fahrenheit (F) to about 375 degrees F before placement in micro trench 100. The final pass to place sealer 140 may be made after previously placed sealer has had time to cool and contract [act 1115] and may overlap the edge of micro trench 100 by approximately two inches. Sealer 140 may be placed to include no more than ¼ inch of sealer above roadway surface 105.
After placement of sealer 140, the cable 130 may be placed in micro duct 125 [act 1120]. A pulling method, for example, may be used to pull cable 130 through micro duct 125. Pulling tension, however, usually should not exceed 300 lbs., therefore, a 300 lb. break-away may be used. Cable blowing techniques may also be used to place cable in micro duct 125.
CONCLUSIONConsistent with the invention, a technique may be employed that uses micro ducts that can be placed in micro trenches under roadway concrete or asphalt to carry subsurface utility cables. Micro trenches may be cut approximately three to four inches into the roadway surface and a micro duct that includes a high load rating material may be placed into the micro trench for carrying the subsurface utility cables. Subsurface utility cables may be inserted in the micro duct and may then be easily repaired by pulling the cables out through the micro duct via, for example, a hand hole or a manhole. The micro duct additionally protects the subsurface utility cables from environmental conditions and external events that may otherwise damage the utility cables. Methods and assemblies, consistent with the invention, thus, permit the installation of subsurface utility cables that require minimal trenching, permit easy repair of the utility cables, and protect the utility cables from environmental conditions or external events.
The foregoing description of embodiments of the present invention provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. While series of acts have been described with respect to
No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one” or similar language is used. The scope of the invention is defined by the following claims and their equivalents.
Claims
1. A method, comprising:
- cutting a trench in a surface of the roadway;
- placing a duct in the trench;
- placing a spacer within the trench on top of the duct,
- filling the trench with a sealer;
- placing a first cable within the duct;
- pulling the first cable out of, and through, the duct; and
- placing a second cable within the duct without removing the sealer within the trench.
2. The method of claim 1, wherein the first cable comprises utility cable.
3. The method of claim 1, wherein the first cable comprises optical fiber cable.
4. The method of claim 1, wherein the trench is cut to a depth of approximately 3.5 to 4.0 inches beneath the surface of the roadway.
5. (canceled)
6. The method of claim 1, wherein the duct comprises high density polyethylene (HDPE) duct.
7. The method of claim 4, wherein the trench is cut to a width of approximately 0.5 inches.
8. (canceled)
9. The method of claim 1, wherein the spacer comprises a tubular shape.
10. The method of claim 9, wherein a diameter of the spacer is approximately 25% larger than a width of the trench.
11. The method of claim 1, further comprising:
- placing sand within the trench.
12. The method of claim 1, wherein the sealer comprises bitumen.
13. The method of claim 12,wherein the sealer is heated to between approximately 325 and 375 degrees Fahrenheit before filling the trench.
14-22. (canceled)
23. A method of placing cable within concrete or asphalt, comprising:
- cutting a trench into the concrete or asphalt to a depth of approximately 3.5 to 4.0 inches from a surface of the concrete or asphalt;
- placing a tubular material having a hollow inner diameter within the trench;
- placing a spacer on top of the tubular material, wherein the spacer comprises a water impermeable, heat resistant material:
- filling at least a portion of the trench with a sealer;
- placing a first cable within the tubular material;
- removing the first cable from the tubular material without removing the sealer from the trench; and
- placing a second cable within the tubular material without removing the sealer from the trench.
24. The method of claim 23, wherein the first cable comprises fiber optic cable.
25. (canceled)
26. The method of claim 23, wherein the spacer has an outer diameter that is approximately 25% greater than a width of the trench.
27. (canceled)
28. The method of claim 23, wherein the tubular material comprises high density polyethylene (HDPE).
29. The method of claim 23, wherein the tubular material comprises an outer diameter of approximately 0.5 inches and wherein the inner diameter comprises approximately 0.375 inches.
30. (canceled)
31. The method of claim 23, wherein the sealer comprises bitumen heated to between 325 and 375 degrees Fahrenheit.
32. The method of claim 1, wherein the first cable is pulled out of, and through, the duct without removing the sealer within the trench.
Type: Application
Filed: Feb 26, 2004
Publication Date: Sep 1, 2005
Inventor: Steven Purcell (Richardson, TX)
Application Number: 10/786,298