Tubular sock module with integrated geogrid extensions for constructing stabilized-earth walls and slopes

Abstract

A self-supporting earth facing module has a tubular sock to be filled with compost or fill material and a geogrid sheet which wraps around the circumference of the tubular sock with upper and lower extensions extending lengthwise to one side of the sock. The geogrid sheet is joined by a high-strength seam to the circumference of the sock. The module forms an integrated unit that can be used to form sequenced horizontal earth layers and serve as facing for a geosynthetically stabilized earth wall or slope. The sock may be vegetation-supportive and have built-in connectable irrigation tubing. The modules are installed in consecutive vertical lifts with a granular interlock zone to provide a connection medium for tying adjacent modules to each other and to the reinforced soil zone, and which may include connection to supplemental geogrids that extend the width of the reinforced zone for taller slopes and walls.

1 . A self-supporting earth facing module comprising:
 (a) a tubular sock made of a selected fabric material having a hollow interior volume which is to be filled with a compost or fill material so as to form a semi-rigid sock facing of a given sock diameter and a given sock length extending in a widthwise direction of the module; and   (b) a geogrid sheet made of a geosynthetic sheet material and having a sheet width in the widthwise direction of the module and a sheet length sufficient to extend around the circumference of the tubular sock with upper and lower extensions of given extension lengths extending in a lengthwise direction of the module to one side of the tubular sock,   wherein the geogrid sheet material is joined by a high-strength seam to the fabric material of the tubular sock at a juncture point where at least the lower extension of the geogrid sheet adjoins a circumferential point of the tubular sock,   whereby said module forms an integrated unit that can be used to form a sequenced horizontal earth layer of a plurality of layers and serve as facing for a geosynthetically stabilized earth wall or slope.   
     
     
         2 . A self-supporting earth facing module according to  claim 1 , adapted for forming a vegetative facing wall, wherein the tubular sock is formed with two different high-strength fabrics for containing organic infill, including an inner fabric of a porous nonwoven material with small pore openings to contain organic fines but coarse enough to allow germinated seedlings to grow through the material, and an outer fabric of high-strength netting that provides tensile constraint to contain compost or fill material tightly packed into the sock to form a dense infilling. 
     
     
         3 . A self-supporting earth facing module according to  claim 1 , wherein the sheet material of said geogrid sheet is joined by upper and lower high-strength seams to the sock material of the tubular sock at upper and lower juncture points where the upper and lower extensions of the geogrid sheet adjoin circumferential points of the tubular sock, respectively. 
     
     
         4 . A self-supporting earth facing module according to  claim 1 , wherein the sheet material of said geogrid sheet is joined to the sock using a double-stitched seam, with a resultant wide-width tensile strength that exceeds the wide-width tensile strength of the geogrid sheet. 
     
     
         5 . A self-supporting earth facing module according to  claim 4 , wherein the sheet material is a large-aperture geogrid material, and a high-strength backing tape is used for stitching the seam. 
     
     
         6 . A self-supporting earth facing module according to  claim 1 , wherein the sheet material is a single, rectangular piece of polymeric geogrid material with a width approximately equal to the extension length of the assembled module. 
     
     
         7 . A self-supporting earth facing module according to  claim 1 , wherein the geogrid sheet material has an overall sheet length equal to about 10 to 15 times the diameter of the tubular sock. 
     
     
         8 . A self-supporting earth facing module according to  claim 1 , wherein the tubular sock is formed in modular sock units that are connected in line serially to form a sock facing row. 
     
     
         9 . A self-supporting earth facing module according to  claim 8 , wherein each modular sock unit has a built-in drip irrigation tubing with male/female interconnection ends that can be connected serially end-to-end for a continuous row of facing with irrigation support for each horizontal earth layer. 
     
     
         10 . A self-supporting earth facing module according to  claim 1 , adapted for durable applications, wherein the geogrid sheet material is made of high-tenacity knitted polyester yarns with high molecular weight and covered with a polymeric coating. 
     
     
         11 . A self-supporting earth facing module according to  claim 1 , adapted for environmentally sensitive applications, wherein the tubular sock of the module is made of natural and biodegradable fabric material, such as a coir blanket woven from coir twines made of bristle coir obtained from freshwater cured coconut husks. 
     
     
         12 . A method of construction of a mechanically stabilized earth (MSE) wall or slope comprising the steps of:
 (a) providing a plurality of self-supporting earth facing modules, each comprising a tubular sock made of a selected fabric material having a hollow interior volume which is to be filled with a compost or fill material so as to form a semi-rigid sock facing, and a geogrid sheet made of a geosynthetic sheet material which extends around the circumference of the tubular sock with upper and lower extensions extending in a horizontal direction of the module to one side of the tubular sock, wherein the sheet material of the geogrid sheet is joined by a high-strength seam to the sock material at a juncture point of at least the lower extension of the geogrid sheet with a circumferential point of the tubular sock,   (b) placing a first row of one or more modules of tubular sock facing on a gravel leveling pad along a prescribed wall alignment, with the lower geogrid sheet extension of each module pulled out flat on top of the gravel pad, and with the upper geogrid sheet extension laid loosely back over the module in the opposite direction, and where the end of each module adjoins an adjacent module, overlapping the excess lower geogrid sheet extension onto the lower geogrid sheet extension of the adjacent module after first spreading a thin layer of granular fill onto that lower geogrid sheet extension to prevent the two geogrid sheet extensions from being in direct contact with each other;   (c) with the row of tubular sock facing in place, filling granular backfill on top of the lower geogrid sheet extension of each module of tubular sock facing to provide a vertical lift as high as the module height, and compacting the lift of backfill material to form a reinforced zone;   (d) pulling the upper geogrid sheet extension of each module of the row of tubular sock facing back over the module and laying it flat on top of the compacted backfill lift, then spreading a thin layer of granular fill across the top of each upper geogrid sheet extension; and   (e) placing a next row of one or more modules of tubular sock facing on and slightly offset behind the first row of tubular sock facing to form a sloping set-back in the wall face, and repeating steps (a) to (d) to form a next vertical lift of tubular sock facing; and   (f) repeating step (e) for placing each next row of tubular sock facing for the next vertical lift until a desired height of the facing wall is reached.   
     
     
         13 . A method for construction of an MSE wall or slope according to  claim 12 , adapted for forming a vegetative facing wall, wherein the tubular sock of each module is pre-seeded or hydroseeded and provided with irrigation support to form a vegetated MSE wall or slope. 
     
     
         14 . A method for construction of an MSE wall or slope according to  claim 12 , adapted for durable applications, wherein the geogrid sheet material is made of high-tenacity knitted polyester yarns with high molecular weight and covered with a polymeric coating. 
     
     
         15 . A method for construction of an MSE wall or slope according to  claim 12 , adapted for environmentally sensitive applications, wherein the tubular sock of each module is made of natural and biodegradable fabric material, such as a coir blanket woven from coir twines made of bristle coir obtained from freshwater cured coconut husks. 
     
     
         16 . A method for construction of an MSE wall or slope according to  claim 12 , adapted for forming a vegetative facing wall, wherein live vegetation in the form of sprigs or live cuttings are inserted between lifts. 
     
     
         17 . A method for construction of an MSE wall or slope according to  claim 12 , wherein the rows of tubular sock facing are laid to form a curved wall having one of (a) a concave shape with the geogrid sheet extensions being cut perpendicular to the axis of the tubular modules to allow spreading of the geogrid sheet extensions to form concave curves, and (b) a convex shape with the geogrid sheet extensions being cut perpendicular to the axis of the tubular modules to allow overlapping of the geogrid sheet extensions to form convex curves. 
     
     
         18 . A method for construction of an MSE wall or slope according to  claim 12 , wherein to assure optimal granular interlock between the backfill and the geogrid sheet extensions, the backfill material consists of granular, well-graded sand or sandy gravel with less than 15 percent by weight passing the No. 200 sieve, and with a maximum particle size of 0.75 inch (19 mm). 
     
     
         19 . A method for construction of an MSE wall or slope according to  claim 12 , wherein the extension length of the geogrid sheet extensions in a granular interlock zone behind the facing modules is at least twice the diameter of the tubular sock modules. 
     
     
         20 . A method for construction of an MSE wall or slope according to  claim 12 , wherein a tall wall is constructed using supplemental geogrid extensions to widen the geosynthetic stabilized earth zone with the supplemental geogrid extensions being sandwiched in-between the geogrid extensions of the tubular sock facing modules.