WICK ASSEMBLY AND METHOD FOR INSTALLING AN UNDERDRAIN
A wick assembly for installation under a roadway according to the invention includes a perforated drain pipe, an inner sheet of a wicking fabric disposed on the perforated drain pipe in a manner effective to cover the perforations therein, an outer sheet of a wicking fabric, and a layer of filter aggregates confined between the inner and outer wicking fabric sheets to form a wick drain in combination with the perforated drain pipe. Water passes through the sheets and filter aggregates in order to enter the perforated drain pipe through the perforations therein. The wick drain may be disposed inside an outer pipe with the outer fabric sheet in slidable contact with the inner periphery of the pipe casing. The outer pipe casing serves to protect the wick drain during installation and is later removed once the wick drain is in position.
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This application is a continuation of U.S. Pat. No 13/665,456 filed on Oct. 31, 2012, and issued as U.S. Pat. No. 8,545,130 on Oct. 1, 2013, which is a divisional of U.S. patent application Ser. No. 11/640,782, filed on Dec. 18, 2006, and issued as U.S. Pat. No. 8,303,215 on Nov. 6, 2012, which is a continuation-in-part of U.S. patent application Ser. No. 11/087,305, filed on Mar. 23, 2005, now abandoned, which claims priority to U.S. Provisional Patent Application No. 60/556,536 filed on Mar. 26, 2004. These applications and patents are incorporated herein by reference in their entirety and for any purpose.
TECHNICAL FIELDThis invention relates to methods and systems for the installation of underdrains beneath roads and other structures.
BACKGROUND OF THE INVENTIONHighways and other paved or concrete roadways can be damaged by water or other accumulated liquids under the roadway. The formation of bumps or frost heaves begins as water seeps under the roadway. As the water freezes and expands in cold weather, the resultant ice pushes up the roadway and forms bumps in the road. These road bumps require considerable cost and time to cut out the damaged areas and repave or reapply concrete. Further, such roadway repairs require additional costs in closing down traffic and providing traffic control.
Haas U.S. Pat. No. 4,808,024, Feb. 28, 1989, provides a method for installing a pavement underdrain wherein underdrains in the form of perforate pipes, preferably covered with a geotextile sock as a filter, are disposed transversely to the lengthwise direction of the roadway in close proximity to faults, cracks, joints and other fissures in the roadway. The underdrains conduct water away from such fissures thereby preventing roadbed particulate material from being pumped upwardly through the fissures together with water which collects below the concrete roadway. However, these underdrains have a relatively limited life in the field, such as 5 years or so, due to the, tendency for the filter fabric to become clogged. The present invention provides a wick drain having a much greater useful life, as well as a method for installing such a wick drain in situations where open cutting or trenching is impractical.
SUMMARY OF THE INVENTIONA wick assembly for installation under a roadway according to the invention includes a perforated drain pipe, an inner sheet of a wicking fabric disposed on the perforated drain pipe in a manner effective to cover the perforations therein, an outer sheet of a wicking fabric, and a layer of filter aggregates confined between the inner and outer wicking fabric sheets to form a wick drain in combination with the perforated drain pipe, such that water passes through the sheets and filter aggregates in order to enter the perforated drain pipe through the perforations therein. The wick drain may be disposed inside an outer pipe with the outer fabric sheet in slidable contact with the inner periphery of the pipe casing. As described further, the outer pipe casing serves to protect the wick drain during installation and is later removed once the wick drain is in position.
The invention further provides a method for installation of a wick drain in the ground. First, if necessary, a passageway is formed through the ground having an entry opening and an exit opening. A wick drain such as the one described above disposed inside a pipe casing is drawn into the passageway until the wick drain is positioned inside the passageway. Then the pipe casing is removed from the passageway by sliding it off of the wick drain, leaving the wick drain in the passageway in a position that allows accumulated liquids to be drawn into the wick drain and drain out of the passageway. The method can be used with a preexisting passageway, although most commonly a new passageway will be drilled using a directional drilling machine. To aid in removing the pipe casing while leaving the wick drain in place, it is preferred to secure the wick drain against lengthwise movement inside the passageway prior to removing the pipe casing, such as by tying it at one end to an anchoring object and pulling on the pipe casing from the other end.
The foregoing method can be practiced with a horizontal directional drilling machine such as the Vermeer Navigator. Using an HDD machine, a pilot hole is drilled from the entry opening to the exit opening, and a back reamer is then connected to the distal end of the drill string, which back reamer is in turn connected to the pipe casing. The HDD machine then pulls the back reamer and pipe casing with the wick drain inside. back through the pilot hole to fully form the passageway. If there is an existing pipe or drain in place, then the step of drilling the pilot hole is omitted, and the back reamer can be provided with pipe bursting capability so that existing pipe is burst as the pipe casing and wick drain are drawn in. One such pipe bursting pipe puller is described in Wentworth et al. U.S. Patent Publication 20040218982, Nov. 4, 2004, the contents of which are incorporated herein by reference.
The invention further relates to an underdrain for a railroad bed comprising a railroad track and bed on which the track is built. The underdrain includes an elongated perforate pipe for collecting water from the railroad bed, which, pipe is disposed in the railroad bed directly below the track and runs along the lengthwise direction of the track, preferably along the centerline of the bed or close to it. At least one outlet pipe is in communication with the perforate pipe, which outlet pipe extends laterally from the perforate pipe and has an outlet opening on one side of the railroad bed which conducts water from the underdrain out of the railroad bed. The invention further provides a method for installing the foregoing railroad underdrain using a directional drilling machine. This and other aspects of the invention are set forth in the detailed description which follows.
In the accompanying drawings:
In a preferred form of a wick 20 according to the invention as shown in
A series of 20 foot sections of HDPE pipe are fused together end-to-end to the desired length to make the pipe casing 24, which preferably has a length which is about the same as the length of hole 32. A rope or nylon cord is blown through pipe 24 (or fed through by tying a weight to the end) and tied to one free end of cord 17. Wick 20 is then pulled inside casing 24 using the rope so that it assumes the position shown in
When the casing 24 and wick drain 20 are fully installed as shown in
The hydraulic wick apparatus and method of the invention avoid the expense of cutting the highway, traffic control, and repaving or reapplying concrete to repair the roadway. The installation of the hydraulic wick may be performed while traffic is traveling on the roadway, therefore minimizing impact to traffic. Only limited traffic control is needed to ensure driver and road crew safety.
While the invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. The aggregate could, for example, be filled into geotextile sleeves forming sandbags which are then wrapped around the inner perforate pipe side by side along its length, eliminating the need for long, quilted blanket having the same length as the perforate inner pipe. These sandbags could wrap all the way around the perforate pipe or only part way around, as long as the perforations are adequately covered. There and other modifications and combinations of the illustrative embodiments will be apparent to persons skilled in the art upon reference to the description. Such variations and additions are specifically contemplated to be with the scope of the invention. It is intended that the appended claims encompass any such modifications or embodiments.
Claims
1. A wick assembly for installation under a roadway, comprising:
- a perforated drain pipe;
- a first sheet of a wicking fabric disposed on the perforated drain pipe in a manner effective to cover the perforations therein;
- a second sheet of a wicking fabric; and
- a layer of filter aggregate disposed between the first and second wicking fabric sheets to form a wick drain in combination with the perforated drain pipe to allow water to pass through the sheets and filter aggregates in order to enter the perforated drain pipe through the perforations therein.
2. The wick assembly of claim 1, further comprising one or more lengthwise seams at which the first and second sheets are secured together, subdividing the layer of filter aggregate into a plurality of lobes.
3. A method of forming a wick drain, the method comprising:
- sandwiching a layer of filter aggregate between a first sheet of fabric and a second sheet of fabric to form a wick layer;
- wrapping the wick layer around a perforated drain pipe such that the wick layer covers the perforations therein; and
- securing the wick layer to the perforated drain pipe.
4. The method of claim 3, further comprising subdividing the filter aggregate into two or more partitions.
5. The method of claim 4, wherein the two or more partitions are lobes defined between seams securing the first sheet to the second sheet along a lengthwise direction.
Type: Application
Filed: Oct 1, 2013
Publication Date: Jan 30, 2014
Applicant: Harr Technologies, Inc. (Anchorage, AK)
Inventor: Robert E. Harr (Kasilof, AK)
Application Number: 14/043,795
International Classification: E01F 5/00 (20060101); E02B 11/00 (20060101);