STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable to this application.

BACKGROUND

Field

Example embodiments in general relate to a system and method for installing a membrane-lined wall.

Related Art

Any discussion of the related art throughout the specification should in no way be considered as an admission that such related art is widely known or forms part of common general knowledge in the field.

Levees have been in use for many years, and levee repair systems and methods for just about as long. Cutoff walls are one way to reinforce and prevent leakage in levees, but permeability of materials used (such as concrete) and soil contamination of the concrete during the curing process can reduce the integrity and strength of the cutoff wall. Further, without reinforcement, cutoff walls may be susceptible to seismic and other forces.

SUMMARY

An example embodiment is directed to a system and method for installing a membrane-lined wall. The membrane-lined wall is formed in-place in a trench, typically a narrow, deep trench, formed by excavating the trench, typically along the top of a levee, although the wall system and the method for constructing it is particularly suitable for forming membrane-lined walls on the slope of a levee, as needed for localized problem areas.

In addition to levee reinforcement, the membrane-lined wall is also useful for stopping or preventing levees from leaking, for preventing pollution due to the migration of water or liquid contaminants, such as around the perimeter of waste disposal sites, coal slurry impoundments, and any other sites where groundwater movement should be stopped to prevent water contamination.

The membrane-lined wall comprises cementitious material, such as concrete, that fills the trench. The membrane-lined wall is formed by excavating a trench in the earth, the trench having two sides, a bottom, and a length. Next, a liner, which may be a low-permeability geomembrane, is installed in the trench along the length of the trench, the liner forming a continuous barrier between the two sides and the bottom of the trench and an interior portion of the liner in at least one dimension. After the liner is installed, a reinforcement mat is also installed within the interior portion of the liner, the reinforcement mat having a length aligned with the length of the trench, and having a height aligned with the two sides of the trench. As an example, the reinforcement mat may be a galvanized steel mesh, such as grade 40 galvanized wire mesh with rectangular openings. Other types of reinforcement, or reinforcement in addition to the mesh, may also be used.

The next step comprises filling at least part of the interior portion of the liner with a cementitious material that surrounds the reinforcement mat within the interior portion of the liner, wherein the weight of the cementitious material forces the liner into close contact with the sides of the trench, and then allowing the cementitious material to harden. The cementitious material, or concrete, can surround the reinforcement mat on three sides (such as both vertical sides and the bottom), or on all sides.

To add structural integrity, the reinforcement mat may come in sections, which are then joined together once they are in place in the trench to form a substantially continuous structure. In such an embodiment, the mat sections are joined together at a vertical edge between sections, so that the resulting reinforcement is aligned linearly along the length of the trench. For deeper trenches, multiple vertical sections of reinforcement mat may be required, and in such case, the sections may also be joined along the horizontal edges between them. The sides of the trench may be vertical in some example embodiments.

In an example embodiment, vibration, such as by an internal vibrator, may be applied to the cementitious material before it hardens. The vibration during the hardening process can remove air in the cementitious material and prevent honeycombing, which can weaken the wall.

In an example embodiment, the geomembrane liner comprises two layers of the low-permeability membrane, an inner layer adjacent to the interior portion of the liner, and an outer layer adjacent to the sides and the bottom of the trench. The inner layer of the liner may comprise multiple sections, wherein each section forms an overlap with an adjacent section along a first edge. Such multiple sections may also have an adhesive layer or coating applied at their edges between each adjacent section of the inner layer of the liner.

Further, the outer layer of the liner may comprise multiple sections, wherein each section of the outer layer forms an overlap with an adjacent section of the outer layer along a second edge. In such an embodiment, each overlap of the inner layer may be spaced apart from each overlap of the outer layer in a direction along the length of the trench.

In an example embodiment, forming the membrane-lined wall may further comprise positioning a roll of liner material over one side of the trench, positioning and clamping a lengthwise edge of the liner material over a side of the trench opposite the roll of liner material, and lowering a weight into the trench along the length of the trench to cause the liner material to unroll from the roll of liner material and extend into the trench. In using this method, the liner may then be cut from the roll, lengthwise, so that both edges of the liner (either one or two layers) are at the top of the trench, with a “pocket” of the liner extending down into the trench.

In addition to the preceding method of installing a liner, an example embodiment may further comprise positioning a second roll of second liner material over one side of the trench, and positioning and clamping a lengthwise edge of the second liner material over a side of the trench opposite the second roll of second liner material, and lowering a lengthwise weight into the trench to cause the liner material and the second liner material to unroll and extend into the trench. As with previous embodiments, the cementitious material may comprise concrete.

In another example embodiment, the liner of the membrane-lined wall comprises two layers of a low-permeability membrane, an inner layer adjacent to the interior portion of the liner, and an outer layer adjacent to the sides and the bottom of the trench.

Other example embodiments include a method of excavating the trench that provides for forcing the sides of the trench away from the interior portion of the trench, which can compress the soil of the sides and reduce the tendency of the sides to collapse. The method includes excavating a first depth of the trench extending from a surface of the ground to a first distance; applying an outward force from the interior portion against the two sides along the first depth of the trench; and excavating a second depth of the trench below the first depth such that the two sides extend to a second distance.

The method may further comprise maintaining the outward force against the two sides while excavating the second depth. For example, the second depth may be excavated using an excavator having a boom that extends under an apparatus (such as an air-lift cushion or plates with hydraulic rams between them) that applies the outward force from a position beyond the apparatus along the length of the trench. The excavation method may further comprise applying a force against the two sides along the second depth—that is, below the first depth of the trench.

Once the trench has been excavated, using any method, the membrane-lined wall may be formed as described herein. In addition, a moisture detector can be inserted in the wall, such as in the interior portion, so that if moisture penetrates the membrane, a signal can be produced and sent alerting users to that fact. For example, the moisture detector can be placed proximate the bottom of the trench, inside the liner, and as a further example, it may be a wired sensor that is placed prior to applying cementitious material to the trench. Of course, more than one sensor can be used, and for efficient processing, sensors can be embedded in the reinforcing material or in the liner itself. Once placed, the moisture sensors may be electrically connected to a control unit, which may be actively monitored or which may send radio or cellular signals indicating the presence of moisture detected by the sensor.

In an example embodiment, the liner membrane may be installed quickly and efficiently with a liner installation sled. The liner installation sled may be adapted for being positioned above a trench having a length, and the liner installation sled may comprise a frame and at least two support members mounted on the frame, the at least two support members adapted to movably support the frame on a surface over the trench. The liner installation sled may also include a liner roller rotatably mounted on the frame, the liner roller adapted to hold a roll of a liner above the surface on a first side of the trench when the liner installation sled is in an installation position relative to the trench, wherein a longitudinal axis of the roll of liner can be aligned with the length of the trench.

The liner installation sled includes a weight suspension system mounted on the frame and adapted to movably suspend an elongated weight that can be lowered into the trench and raised out of the trench, and the liner installation sled also may have an elongated liner edge holder mounted on the frame to hold an edge of the liner above the trench, wherein the liner end clamp is mounted so that it is alignable with the length of the trench, wherein the elongated weight is usable with the weight suspension system to force a portion of the liner between the liner end clamp and the liner roll into the trench as described above and herein. The liner end clamp may be or comprise a cylindrical shaft, adapted to clamp and hold a free edge of liner material above the surface on a second side of the trench when the liner installation sled is positioned in the installation position relative to the trench.

In some example embodiments, the liner installation sled further comprises a positioning roller mounted on the frame and positionable above the trench such that a portion of the liner will move from the liner roll and over the positioning roller when the elongated weight is lowered into the trench. The positioning roller can be rotatably mounted on the frame such that it can rotate due to the liner moving over the positioning roller. In addition, the elongated weight can be rotatably suspended from the weight suspension system such that the elongated weight can rotate when the elongated weight is lowered due to the liner moving around the elongated weight.

The weight suspension system may comprise two reels, one at each end of the frame, wherein each reel is adapted to raise and lower a cable attached to an end of the elongated weight. Each cable may be rotatably attached to the elongated weight, for example with a bearing or bushing, such that the elongated weight can rotate when the elongated weight is lowered due to the liner moving relative to the elongated weight.

In some example embodiments, the at least two support members are adjustably mounted on the frame such that the frame can be supported on the surface when the surface is sloped, wherein the frame is alignable by adjustment of at least one of the at least two support members such that a centerline of the frame is above the trench when the liner installation sled is positioned in the installation position relative to the trench. The at least two support members may comprise skids to allow movement of the liner installation sled on the surface over the trench. The may also comprise wheels or tracks for use with different surface types.

The liner installation sled may be used for lining a trench that has two sides and a bottom. The method may include positioning the liner installation sled in the installation position relative to the trench such that the longitudinal axis of the liner roller is aligned with the length of the trench above the surface on the first side of the trench, wherein the edge of the liner is held in position and aligned with the length of the trench by the liner end clamp, above the trench. The method further includes forcing a portion of the liner between the edge and the roll into the trench using the elongated weight such that the liner is supplied from the roll and extends into the trench to form a continuous, seamless barrier between the two sides and the bottom of the trench and an interior portion of the liner.

Example embodiments of the liner installation sled may further comprise a second liner roller rotatably mounted on the frame, the second liner roller adapted to hold a second roll of liner above the surface on the first side of the trench, wherein a longitudinal axis of the second roll of liner is aligned with the longitudinal axis of the liner roller, wherein the liner end clamp also holds a second edge of the second liner above the trench. In this embodiment, the elongated weight is also usable to force a portion of the second liner into the trench.

There has thus been outlined, rather broadly, some of the embodiments of the membrane-lined wall in order that the detailed description thereof may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional embodiments of the membrane-lined wall that will be described hereinafter and that will form the subject matter of the claims appended hereto. In this respect, before explaining at least one embodiment of the system and method for installing a membrane-lined wall in detail, it is to be understood that the system and method for installing a membrane-lined wall is not limited in its application to the details of construction or to the arrangements of the components set forth in the following description or illustrated in the drawings. The system and method for installing a membrane-lined wall is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.

