AIR-FILLED BLADDER BASED BRIDGING ACROSS WEAK AND COMPRESSIBLE SOLIDS

Abstract

A system for creating a bridge across an expanse of weak and compressible materials (e.g., a lagoon) may include an air bladder, a geosynthetic installed over the air bladder and across the expanse, and fill materials installed over the geosynthetic and across the expanse. In conjunction, the air bladder, geosynthetic, and fill materials may create a bridge across the expanse. The geosynthetic may include a separation geotextile and/or a geogrid or a reactive core mat. The geosynthetic may be installed with a free excess length corresponding to a final expected profile of the geosynthetic after consolidation of underlying materials. The air bladder may be inflated to take up the excess slack in the geosynthetic. After or while fill is consolidated, the air bladder may be deflated in a controlled manner to maintain stability while consolidating the underlying materials. Additional systems and associated methods are also disclosed.

Claims

1. A system for bridging across an expanse of weak and compressible materials, the system comprising: an air bladder; a geosynthetic installed over the air bladder and across the expanse; and fill materials installed over the geosynthetic and across the expanse, wherein the air bladder, geosynthetic, and fill materials, in conjunction, create a bridge across the expanse.

2. The system of claim 1, wherein the geosynthetic comprises a separation geotextile installed over the air bladder and across the expanse.

3. The system of claim 2, wherein the geosynthetic comprises a geogrid installed over the separation geotextile and across the expanse.

4. The system of claim 1, wherein the geosynthetic comprises a reactive core mat installed over the air bladder and across the expanse.

5. The system of claim 1, wherein the geosynthetic is anchored at, proximate to, or beyond a perimeter of the expanse, the geosynthetic provided with a free excess length corresponding to a final expected tensioned profile of the geosynthetic after underlying materials have been consolidated.

6. The system of claim 5, wherein the air bladder is inflatable to take up slack in the geosynthetic represented by the free excess length.

7. The system of claim 1, further comprising a drainage blanket or fill comprised of foamed glass aggregate placed on the geosynthetic.

8. The system of claim 7, wherein the foamed glass aggregate has a dry bulk density that is less than or equal to 15 lb/ft.sup.3, or between 15 and 62.4 lb/ft.sup.3.

9. The system of claim 1, further comprising a drainage blanket placed on the geosynthetic and comprising reactive particles, surfaces or elements to passive treat or polish expressed liquids/water from underlying materials.

10. The system of claim 1, further comprising a fill of stabilized dredged material (SDM) that is created using a variety of techniques with special attention given to pneumatic flow tube mixer (PFTM) technology to avoid or limit trafficking the area during fill placement.

11. A method for bridging across an expanse of weak and compressible materials, the method comprising: installing an air bladder in the expanse; and installing a geosynthetic over the air bladder and across the expanse; and installing fill materials over the geosynthetic and across the expanse, wherein the air bladder, geosynthetic, and fill materials, in conjunction, create a bridge across the expanse.

12. The method of claim 11, wherein installing the geosynthetic comprises installing a separation geotextile or a reactive core mat over the air bladder and across the expanse.

13. The method of claim 12, wherein installing the geosynthetic further comprises installing a geogrid over the separation geotextile or the reactive core mat and across the expanse.

14. The method of claim 11, further comprising installing one or more drainage pipes above the geosynthetic.

15. The method of claim 11, further comprising anchoring the geosynthetic at, proximate to, or beyond a perimeter of the expanse, and optionally in perimeter trenches along the perimeter of the expanse, wherein the geosynthetic is provided with a free excess length corresponding to a final expected tensioned profile of the geosynthetic after underlying materials have been consolidated.

16. The method of claim 15, further comprising inflating the air bladder to take up slack in the geosynthetic represented by the free excess length.

17. The method of claim 11, wherein installing the fill materials comprises uniformly placing fill material from the perimeter concentrically inwards.

18. The method of claim 11, wherein installing the fill material comprises placing a drainage blanket on the geosynthetic, the drainage blanket comprising foamed glass aggregate and/or reactive particles, surfaces, or elements to passive treat or polish expressed liquids/water from underlying materials.

19. The method of claim 11, further comprising creating a fill of stabilized dredged material (SDM) using a variety of techniques with special attention given to pneumatic flow tube mixer (PFTM) technology to avoid or limit trafficking the expanse during fill placement.

20. The method of claim 11, further comprising deflating the air bladder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 illustrates an example system, in a first configuration, for bridging across an expanse of weak and compressible materials.

[0009] FIG. 2 illustrates an example system, in a second configuration, for bridging across an expanse of weak and compressible materials.

[0010] FIG. 3 illustrates an example system, in a third configuration, for bridging across an expanse of weak and compressible materials.

[0011] FIG. 4 illustrates an example system, in a fourth configuration, for bridging across an expanse of weak and compressible materials.

[0012] FIG. 5 illustrates an example fill material for a system for bridging across an expanse of weak and compressible materials.

[0013] FIG. 6 illustrates the fill material of FIG. 5 placed within water.

[0014] FIG. 7 illustrates the fill material of FIG. 5 used to widen a road on soft soils.

[0015] FIG. 8 illustrates the fill material of FIG. 5 used to raise grade without surcharge or pre-consolidation.

[0016] FIG. 9 illustrates an example pneumatic flow tube mixer (PFTM).

[0017] FIG. 10 illustrates an example stabilized dredged material from the PFTM of FIG. 9.

DETAILED DESCRIPTION

[0018] There are a variety of soft compressible soils, and high liquid/water content and/or unconsolidated soil-like and waste media that are characterized very high compressibility, very low strengths, low solids contents, collapse potential and/or thixotropy that make them unable to support any weight. As a result, it is very difficult to initially bridge over these materials in order to support the surface loadings associated with roadways in the case of unconsolidated or high water content clays, sediments and coastal areas, or for the installation of soil caps or other lightweight cover systems on waste and sludge lagoons, mine tailings, ash fills and other repositories where the isolation of these wastes is necessary for environmental protection, to limit exposure, brownfield redevelopment, or other low impact purposes like the creation of parking areas, playing fields or solar farms. Other non-limiting examples of problematic materials to be traversed or covered include peats, boggy soils, liquifiable or collapsible soils and industrial residues such as paper sludges, biosolids, wastewater sludges, silica gels, oil/refinery sludges, drilling muds, oil sands residues, titanium and/or bauxite red muds, off spec paints and pigments, tarry materials, other miscellaneous gelatinous media, and so on, which can range from extreme acidity to alkalinity depending on the reside/waste.

[0019] Advances in geosynthetics in the past 50 years has enabled construction over many such areas. Specifically, high strength geotextiles and geogrids have be used to provide the particle separation and load transfer (strength) functions to enable bridging over these areas so that surface loads may be placed on these media in order to consolidate (densify) them and thus develop strength to gradually support the weight of roadways, soil caps and other loads as desired. A key to success is managing the time dependent consolidation of these media and their corresponding strength gain without overloading them. In some cases, the settlement can be substantial and the initial bridging over these media is very challenging because too rapid and/or non-uniform loading can lead to punching shear, bearing capacity and deep seated rotational geotechnical failures or liquefaction that result in the creation of mud waves or large displacements, any of which can result in the loss of equipment and life. As such, the initial bridging across said media at the leading edge can be very slow to near impossible with risk of excessive settlement or progressive failure, including traversing over/through an overlying water cap that may be on such media which can support no weight whatsoever.

[0020] The use of the geosynthetics in lagoon type settings typically requires that they be anchored on opposite sides of the lagoon plan area much like a trampoline to develop the necessary tensile forces to prevent the applied surface loads from failing the underlying very, soft compressible media. When the repository width is long and the expected settlement is large, the fixed geosynthetics are at risk of tearing, rupturing or pulling out from their anchor locations (e.g. trenches) if too taught, leading to the aforementioned loss of equipment and life. But with insufficient tensioning, there may be too much slack in the geogrid for it to effectively carry and lower the ground pressure to enable initial bridging without excessive deflection or settlement, which may prevent or significantly slow the rate of bridging at the leading edge. Accordingly, there is a need for the gradual controlled, tensioned release of additional lengths of geosynthetic (up to several meters) when traversing very soft/weak and highly compressible media with large plan areas and dimensions. If released (e.g. unrolled/unspooled) from the edge or perimeter of a lagoon or plan area, then there is concern that the geosynthetic will get potentially snared on obstructions or debris in the lagoon and likewise tear and fail also leading to the aforementioned loss of equipment and life. Accordingly, there is a need to release this additional length of geosynthetics where the settlement is expected to be the greatest, which, for example, is often the center of a circular lagoon, along the centerline of the long axis of a rectangular lagoon, or the centroid of an irregular plan area.

[0021] This technology disclosure describes a process by which a sacrificial high strength and thus buoyant air bladder is used (below) in conjunction with high strength geotextiles/geogrids to create the initial bridge across a lagoon as a non-limiting example of its application. Those skilled in the art of geosynthetics and construction with soft compressible media will appreciate the adaption of this approach to other site specific challenges and geometries. First, an inflatable air bladder (or series thereof) is strategically positioned at key locations in the lagoon plan area that correspond to where the maximum settlement is expected to occur. Non limiting examples of how this bladder might be deployed and strategically positioned is through the use of shallow draft boats or barges, pontoon excavators, low ground pressure equipment, cabling systems, air drops, etc.

[0022] A deflated air bladder of a desired size, shape and volume is deployed along with an inflation line/pipe. Overlying this, a separation geotextile may then be placed on the lagoon plan area to prevent migration of the lagoon solids into the subsequentially applied fill materials. Next installed across the lagoon plan area is a high strength geotextile/geogrid. One skilled in the art might alternatively install a geocomposite with separation and strength functions. All geosynthetics are anchored at or just beyond the lagoon perimeter and are provided with a free excess length corresponding to their final and tensioned profiles once the lagoon media has been consolidated to the desired extent. The air bladder is then inflated to the necessary diameter to take up the slack represented by the excess length of the geosynthetics which has the dual purpose of positioning the slack where needed most, e.g., directly above the location where the greatest settlement is expected. Thereafter, fill is uniformly placed from the perimeter concentrically inwards with the first layers placed being preferentially comprised of granular materials to serve as a drainage blanket for the expressed pore fluids from the underlying lagoon solids as they consolidate. Concentric fill placement from the perimeter aids in lateral confinement, settlement and mitigates the potential for lateral movement of the air bladder from uneven tension of the geosynthetics and differential settlement.

[0023] The overburden pressure represented by the fill materials is opposed by the buoyancy of the air bladder which creates the necessary tension in the geotextile/geogrid for it support the fill materials despite its excess length. Controlled depressurization of the air bladder then allows the downward deflection of the geotextile/geogrid and increases the overburden pressure on the lagoon solids forcing their consolidation. Alternating incremental fill placement and depressurization of the air bladder are then managed in such a way as to optimize fill placement while mitigating risks of failure until the final settlement profile is attained.

[0024] In some non-limiting variations of the application, the separation geotextile can be replaced by a CETCO reactive core mat (RCM) or the equivalent containing reactive or sorptive elements to passively treat or polish contaminated pore waters originating from the lagoon solids.

[0025] In some non-limiting variations of the application, a piping manifold can be installed in the drainage blanket to remove consolidation water from the lagoon solids.

[0026] In some non-limiting variations of the application, the drainage blanket and fill materials may be comprised of ultra lightweight foamed glass aggregate (UL-FGA) which is a vesicular, buoyant and coarse aggregate with a specific gravity on the order of 0.25. This buoyancy further acts to offset the overburden pressure of materials placed on top of it.

[0027] In some non-limiting variations of the application, the drainage blanket materials may be comprised of materials that are reactive, have reactive coatings (including UL-FGA) or otherwise contain reactive elements to elements to passively treat or polish contaminated pore waters originating from the lagoon solids.

[0028] In some non-limiting variations of the application, the fill materials can be soil and/or soil-like media, recycled materials, industrial byproducts or other solids such as those treated by stabilization/solidification including stabilized dredged material (SDM) that is created using a variety of techniques with special attention given to the pneumatic flow tube mixer (PFTM) technology that produces a flowable fill that helps avoid or limit trafficking the lagoon during fill placement.

[0029] FIG. 1 illustrates an example system 100, in a first configuration, for bridging across an expanse of weak and compressible materials (e.g., a lagoon 102). In one example, an air bladder 104 may be placed on the lagoon 102, such as where the greatest settlement is expected. A separation geotextile (GT) or reactive core mat (RCM) 108 may be placed on the lagoon 102. The cut length of the GT/RCM 108 may reflect the final expected profile, as described above. A geogrid (GG) 112 may be placed on the lagoon 102. The cut length of the GG 112 may reflect the final expected profile, as described above. The GG 112 and GT/RCM 108 may be anchored in perimeter trench(es) or an equivalent. The air bladder 104 may be inflated to take up slack in the geosynthetics to pretension. Drainage pipes 116 may be installed, as desired. Fill material 120 (e.g., UL-FGA) may be placed on the geosynthetics, such as in a manner as described above. The fill material 120 may be placed uniformly from the perimeter in to prevent mud wave. The fill material 120 may serve as initial (and buoyant) bridging medium and drainage blanket.

[0030] FIG. 2 illustrates the system 100 in a second configuration. In one example, soil fill or stabilized dredged material (SDM) 124 may be placed on the fill material 120, such as in a manner as described above. The soil fill or SDM 124 may be placed uniformly from the perimeter in to prevent mud wave.

[0031] FIG. 3 illustrates the system 100 in a third configuration. In one example, the pressure within the air bladder 104 may be released. As the bladder pressure is incrementally released, the geosynthetics (e.g., GG 112 and GT/RCM 108) settle and maintain tension. The lagoon solids may compress. The bladder pressure release may be balanced with fill addition.

[0032] FIG. 4 illustrates the system 100 in a fourth configuration. In one example, the method may continue to cycle between lagoon solids compression, bladder pressure dissipation, and fill addition. The final configuration may be achieved when the air bladder 104 is eventually deflated.

[0033] FIG. 5 illustrates an example implementation of the fill material 120. The fill material 120 may be an aero-aggregate UL-FGA (ultra-lightweight foam glass aggregate). The fill material 120 may be produced from post consumer recycled glass. The fill material 120 may have 100% recycled material content. The average particle size of the fill material 120 may be between 1.0 inches and 1.5 inches. The fill material 120 may have a dry bulk density of 15 lb/ft.sup.3 (maximum). The fill material 120 may be closed cell (buoyant). The fill material 120 may be chemically inert. The fill material 120 may be nonreactive with chemicals.

[0034] FIG. 6 illustrates the fill material 120 placed within water. In one example, the fill material 120 may be buoyant, with 50% of the fill material 120 above/below a water line 130 when placed within water.

[0035] FIG. 7 illustrates the fill material 120 used to widen a road on soft soils. The fill material 120 may be placed directly on compressible soils and geosynthetics may be placed on the fill material 120. Soil fill or SDM 124 may be placed on the geosynthetics.

[0036] FIG. 8 illustrates the fill material 120 used to raise grade without surcharge or pre-consolidation. FIG. 8 illustrate a proof concept of a New Jersey development where 10 ft of fill material 120 was placed on soils (e.g., WOH soils) to raise grade without surcharge or pre-consolidation. The fill material 120 may also provide stormwater storage in the development.

[0037] FIG. 9 illustrates an example pneumatic flow tube mixer (PFTM) 140. The PFTM 140 may include a PFTM chamber 142 that combines compressed air, DM slurry, and PC grout to produce SDM 124.

[0038] FIG. 10 illustrates an example SDM 124 from the PFTM 140. The SDM 124 from the PFTM 140 may be spread across an area. The SDM 124 may be spread using an energy dissipator 144. FIG. 10 illustrates amended (fresh) dredged material 146 pumped from the PFTM 140 and hardened/cured dredged material 148 as structural fill one day.

[0039] The description of certain embodiments included herein is merely exemplary in nature and is in no way intended to limit the scope of the disclosure or its applications or uses. In the included detailed description of embodiments of the present systems and methods, reference is made to the accompanying drawings which form a part hereof, and which are shown by way of illustration specific to embodiments in which the described systems and methods may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice presently disclosed systems and methods, and it is to be understood that other embodiments may be utilized, and that structural and logical changes may be made without departing from the spirit and scope of the disclosure. Moreover, for the purpose of clarity, detailed descriptions of certain features will not be discussed when they would be apparent to those with skill in the art so as not to obscure the description of embodiments of the disclosure. The included detailed description is therefore not to be taken in a limiting sense, and the scope of the disclosure is defined only by the appended claims.

[0040] From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention.

[0041] The particulars shown herein are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of various embodiments of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for the fundamental understanding of the invention, the description taken with the drawings and/or examples making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

[0042] As used herein and unless otherwise indicated, the terms a and an are taken to mean one, at least one or one or more. Unless otherwise required by context, singular terms used herein shall include pluralities and plural terms shall include the singular.

[0043] Unless the context clearly requires otherwise, throughout the description and the claims, the words comprise, comprising, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of including, but not limited to. Words using the singular or plural number also include the plural and singular number, respectively. Additionally, the words herein, above, and below and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of the application.

[0044] Of course, it is to be appreciated that any one of the examples, embodiments or processes described herein may be combined with one or more other examples, embodiments and/or processes or be separated and/or performed amongst separate devices or device portions in accordance with the present systems, devices and methods.

[0045] Finally, the above discussion is intended to be merely illustrative of the present system and should not be construed as limiting the appended claims to any particular embodiment or group of embodiments. Thus, while the present system has been described in particular detail with reference to exemplary embodiments, it should also be appreciated that numerous modifications and alternative embodiments may be devised by those having ordinary skill in the art without departing from the broader and intended spirit and scope of the present system as set forth in the claims that follow. Accordingly, the specification and drawings are to be regarded in an illustrative manner and are not intended to limit the scope of the appended claims.