Classifications

• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
  • E02D3/12—Consolidating by placing solidifying or pore-filling substances in the soil
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D35/00—Straightening, lifting, or lowering of foundation structures or of constructions erected on foundations

Definitions

• An advantage of elevation of terrain and structures using subterranean injection of solids is that there is no disturbance of the actual use or characteristics of the existing structures when elevation or subterranean mechanical enhancement is done. Additionally, structures can be elevated a little at a time as needed once the rate of sea level rise is understood or more accurately predicted. This spreads the cost of protecting structures over potentially many years rather than requiring that the entire cost be borne at one time.
• the invention is defined by as set out in the appended independent claims.
• the present disclosure relates to an apparatus and process to protect structures and terrain from inundation as well as to gain potential improvements in seismic performance during earth tremors. Expansion of terrain or island formation is also enabled by the systems and methods disclosed herein. Aspects of the disclosed systems and methods include selection of depth, spacing and diameter of holes to be drilled. Other aspects of the disclosed system include selection, formulation, preparation, concentration and injection of lignocellulosic-based slurries into subterranean spaces. Measurement and adjustment of surface altitude, site monitoring and the techniques used to achieve desired final surface topography are also important aspects.
• lignocellulosic material may gain advantages such as the alteration of the mechanical character of the ground to improve seismic performance. Such injection may offer protection against hazards the lignocellulosic material might otherwise pose such as risk of fire or decomposition to release atmospheric pollutants such as methane, nitrous oxide, carbon dioxide or noxious odors.
• Lignocellulosic material may also be injected into a subterranean space to provide a space to accept fluid or gas.
• the lignocellulosic material comprises a molecular density of approximately 1.45 to about 1.55 g/cc.
• the lignocellulosic material is selected from a group consisting of saw dust, divided wood, plant material, wood chips, wood pulp, rice husks, corn stover, wood ash, biochar, trimmings, leaves, grasses, grass trimmings, phytoplankton, algae, and biomass materials.
• a method of subterranean injection of lignocellulosic material comprises the steps of selecting a suitable location for terrain protection, accomplishing surface elevation documentation, and placing surface elevation and inclination change sensors on a surface.
• step 30 surface elevation documentation is next accomplished in conjunction with the placement of surface elevation and inclination change sensors.
• step 30 the process proceeds to step 40 where a determination of the desired depth and orientation of prospective subterranean solids is done by evaluation of soil borings or other information about local geotechnical character of the site.
• step 50 a determination of the number of subterranean injection locations is done which will best accomplish the elevation of ground and contouring of surface or alteration of local soil mechanical properties as desired.
• This sealing may often be accomplished through the use of cementitious sealing plugs, polymer foams, reactive grouts or inflatable plugs that isolate the fluid and pressure at the base of the hole from that of the well bore. Placement of equipment to monitor the subterranean conditions such as a pressure transducer may also be done as needed. Connection of the well to the fluid preparation, pressurization, movement, monitoring and control systems is done.
• step 70 creation of a subterranean aperture is accomplished by injection of fluid under pressure into the subterranean space.
• This step may involve the use of high-pressure jets to help direct the shape of formation of the aperture or additives to increase the fluid viscosity and reduce aperture leak off of injection fluid.
• step 80 expansion of the subterranean aperture is next accomplished by the injection of fluid under pressure.
• step 90 placement of lignocellulosic materials in the aperture is completed with the injection of an aqueous slurry.
• release of excess liquid from the aperture is next allowed which is called relaxation.
• This may be done by allowing fluid to leak out into adjacent subterranean structures or the fluid may be removed at the surface by release of pressure or by controlled pumping.
• the aperture surface settles over the included solid fill and can compact the subterranean solid fill.
• This relaxation allows the included solids to bear the weight of the overburdening earth rather than for the fluid surrounding the solids to bear this weight. With time subterranean fill will also become more thoroughly saturated with fluid increasing the density of individual fill particles and potentially causing them to swell.
• the minimum volume also exceeds this minimum value because a given volume of solids when measured as delivered to the surface location will compact and densify after placement in a subterranean space and exposure to compaction forces such as the mass of the soil overburden the solids will support.
• a low-cost mineral fill material for example the dredge spoils and sediment referenced by Germanovich and Murdoch would contain unwanted coarse and problematic materials, for example large rocks, metal cans, rope and branches as may have accumulated at the bottom of navigational channels or elsewhere.
• dredge spoils are pumped, very large centrifugal slurry pumps are needed to pass the majority of these large contaminants.
• the large foreign materials would require removal before subterranean injection. This removal could be done in either a dilute aqueous vibratory screening operation or in stagewise cyclonic or gravity settling equipment.
• a slurry of fine particles (8-20 micron) magnetite is observed to form a solid-like plate and cannot be resuspended without recrushing and intense shearing. This behavior may be characterized as partial cementation.
• a mineral slurry is a minus 40 mesh clinoptilolite zeolite which also compacts after settling and partially cements. Hard physical scraping and agitation is enough to partially resuspend this material.
• additives which increase the viscosity must often be used.
• Common additives for hydraulic fracturing slurries used to deliver mineral proppants into petroleum well geological structures include polyacrylamide and polysaccharides such as guar gum.
• the particle size of the proppants must be small and the viscosity of the fluid sufficient to enable transport of the proppant horizontally into the fracture without proppant settling or screening out.
• Additives such as guar gum, xanthan gum or fine particle size clay minerals that increase the fluid viscosity may reduce the rate that gases can migrate through the fluid by reducing convective currents and by immobilizing gas bubbles so that they may not freely move in the fluid.
• decomposition by manipulating the pH of the wood chip environment or by adding inhibitors or biocides.
• Another mode to reduce decomposition would be to enrich the environment with the products of decomposition whether those products are organic acids, CO 2 , methane or other constituents.
• Some decomposition of wood chips is inevitable, and this may result in the presence of vapor bubbles in the subterranean space from accumulation of CO 2 and methane to accompany any residual nitrogen or other constituents of residual air. If decomposition reaction products are retained in the wood environment and not allowed to exit, the degradation rate must ultimately decline. Saturation with reaction products such as hydrogen sulfide gas in the case of near-anaerobic decomposition by sulfur utilizing microorganisms can ultimately stop degradation and poison microorganisms responsible for decay.
• reaction rate decline due to the buildup of reaction products is fermentation of sugar-containing fluids by yeast. Elevation of alcohol content in wine or beer will ultimately stop further biological decomposition of sugars to alcohol. Limiting availability of necessary reactants or nutrients and buildup of reaction products will both limit decomposition of lignocellulosic materials in a subterranean environment.
• the solubility of gases such as oxygen, carbon dioxide, and methane in the aqueous fluid surrounding submerged lignocellulosic particles is an important determinant of decomposition reaction rate.
• the quantity of reducible reactants such as oxygen for aerobic decomposition or sulfate, iron, manganese and nitrate ion for partially anoxic decomposition determines whether the whole lignocellulosic material can be decomposed and to a large extent how rapidly that decomposition will occur.
• lignin component of lignocellulosic materials does not degrade and the rate of decomposition of holocellulose which is the combination of the carbohydrates cellulose and hemicellulose that makes up cell walls in plant material is greatly reduced.
• Anoxic decomposition of carbohydrates involves methanogens consuming low molecular weight acidic molecules that are produced by other microbes.
• Anoxic decomposition produces a mixture of carbon dioxide and methane gas. If the reaction products are allowed to accumulate the reaction may be slowed or stopped, as mentioned earlier. In a subterranean environment the condition is effectively always anoxic below the water table or more than a meter underground if dense soils are present.
• Coastal or riparian areas subject to inundation are often anaerobic due to close proximity to the subterranean water table.
• Lignocellulosic materials pumped into a subterranean space of adequate depth or below the local water table are generally only subject to anaerobic decay assisted by methanogenic microbes once initial oxygen available in pore spaces are consumed. This anaerobic decay can only proceed to the extent that reaction products (wastes) can exit the subterranean space.
• Carbon dioxide and methane can migrate as gases through subterranean spaces. Gases such as oxygen, methane and carbon dioxide are significantly less soluble in water when sodium chloride and other salts are present. Because of this brackish water like sea water can slow delivery of reactants and removal of wastes for microbes decomposing lignocellulosic materials and thus increase the longevity of these materials in a subterranean space.
• lignocellulosic particles will resist decomposition longer and thus it is desirable to pump larger Lignocellulosic particles into subterranean spaces.
• Green waste and wood chipping operations create a range of particle sizes.
• Uniformly fine lignocellulosic materials such as sawdust of perhaps 2 mm length by 1 mm width can be quite easy to suspend in an aqueous slurry.
• Sawdust requires more energy to produce and thus once limited supplies of "waste" sawdust materials are exhausted, sawdust would be a much more expensive form of lignocellulosic materials for slurries than coarse chips.
• a 100 mm thick aperture filled with a sawdust slurry might thus need to lose much water during the relaxation stage mentioned in the sequence of steps for injection to place materials in a subterranean aperture.
• This relaxation step allows the injected solids to begin to support the full weight of the overburdening earth.
• the quantity of water lost from the aperture during relaxation by a wood chip slurry with average particle size of 20 mm might be half that lost in a similar relaxation conducted on a sawdust slurry of average particle size 2 mm if both slurries were formed with a similar dry volume of sawdust and woodchips.
• the ability to slurry and inject large particles of lignocellulosic materials has the advantages of significantly lower size-reduction costs, slower degradation in a subterranean environment, lower water required to form slurries, and consequently lower water loss requirement during relaxation of the filled subterranean aperture space.
• the near-neutral buoyancy of lignocellulosic materials is advantageous in this regard. It is expected that particles up to or indeed in excess of 25 mm in any dimension may be pumpable with appropriate pump systems such as progressive cavity or piston pumps that include large check valves. Well piping diameter must be at least four times the diameter of the largest particles.
• Subterranean apertures may be of any orientation, vertical, inclined, horizontal or any complex intermediate shape. Horizontal apertures when filled serve most effectively to elevate the surface of the ground. Slurry flow in a horizontal space poses important challenges. As the fluid flows in a horizontal direction, solids denser than the fluid (which usually has a density close to that of water) will sink until they reach the floor of the aperture. To reduce the rate at which solids settle the viscosity of the fluid may be increased or the size of the solids may be reduced. As the viscosity of the suspending fluid increases, the requisite difference in pressure between the starting point of the fluid and its ultimate endpoint along a horizontal plane increases. Pumping more viscous fluids requires more energy than less viscous fluids over a similar path. A more viscous slurry will prevent solids from settling and also from excessive contact friction with edges of solids such as encountered in sharp pipe bends or tight underground spaces.
• Additives such as guar or xanthan gum or mixtures of the two as well as fine clay materials like sodium bentonite clay can increase the viscosity of fluid and help avoid screen outs or immobilization of solids at tight transitions or bends.
• a mineral solid slurry must be maintained at an adequate agitation velocity or the solids will settle unless the solids content is high enough to result in a thick paste or mud.
• the thin slurry will fill the subterranean aperture with a large volume of water which will still contain fine clay particles and be quite dirty in appearance and potentially able to pollute surface water. Though the thin slurry is quite pumpable it will not carry adequate solids to prop up the terrain and the extra water will require a long period to escape the aperture. Relaxing the aperture so that the solids are bearing the weight of the overburden may take a long time. Reuse of a given aperture space may be challenging because the fine clay particle may clog the pores of the space around the solids as the additional water attempts to exit during relaxation. Therefore, relaxation may take progressively longer and eventually the aperture may not function for additional injections.
• the thick mud will result in a high pressure differential between the injection point and the peripheral extent of the aperture.
• This pressure differential results from the Bingham plastic rheological nature of the mud and may distort the shape of the aperture.
• the distorted shape may result in the central or material entry portion of the aperture filling with a disproportionate quantity of the solids while the periphery has much less material.
• a thick mud is also potentially a major contamination issue for the surface area around the well in the inevitable event of a spill.
• Lignocellulosic slurries by comparison are quite easy to sort, manage and use in a subterranean injection operation. They may be preselected to include only particles of a certain size range with trommels or vibratory screeners without need for drying or fines management systems. Lignocellulosic materials are not generally considered problematic or contamination when spills occur on the surface. They may often be removed with rakes, brooms, leaf blowers, or vacuums. They may also be intentionally placed on the surface to act as a weed controlling mulch or landscaping material. When structures are elevated, the surface placement of residual lignocellulosic mulches, for example wood and bark mixes, creates a particularly beneficial habitat for methanotrophic bacteria.
• the water used to produce a lignocellulosic slurry does not generally become contaminated as water that is used to make a mud or mineral slurry is observed to become filled with fine muddy clay particles. If freshwater is used for slurry formation, there is generally no contamination issue on the surface in the case of slurry water spills and therefore no reason to expend effort avoiding surface water spills. Mineral slurry systems would require surface protection systems to trap the water and recover and potentially haul it away after use. This activity adds substantially to the cost of using the mineral slurry for terrain elevation. No such cost is associated with the use of a lignocellulosic slurry except perhaps in unusual cases.
• Figure 1 illustrates a method 10 of Protecting Structures with Subterranean Injection of Lignocellulosic Solids.
• FIG. 1 illustrates a method for preparing lignocellulosic materials. As illustrated, the process starts at step 200 and proceeds to step 210, where the materials are pre-selected to include the variety or varieties of lignocellulosic materials that are most desirable and those other constituents of the slurry to be formed subsequently.
• step 220 the slurry is formed, an optional post-selection process may be utilized and the slurry is brought to the desired solids level.
• step 230 the slurry is pressurized.
• the pre-selection process at step 220 is guided by knowledge of how different materials contribute to the slurry formation and subsequent solids placement using the slurry.
• Lignocellulosic materials may be selected based on species of plant material, size or shape of plant material, porosity of plant material, degree of water saturation, or degree of decomposition. Additional slurry components such as finely divided mineral solids, chemicals, binding agents and viscosity adjustment agents such as guar gum, cross-linkers and breakers, which are used in hydraulic fracturing, may also be beneficial in the slurry or may be desired in the ultimate solid mass to be placed in a subterranean location.
• Peat soils are notoriously poor at supporting structures. Peat is a decomposed form of lignocellulosic material, Fibric peat soils are less decomposed and contain fibers that serve to enhance their shear strength. The normal force applied to the sample compacts the fibric peat and its shear strength as measured by the direct shear test also rises. At or near the surface where there is little compaction pressure the shear strength of peat soils is very low and so these soils are problematic for structure foundations. However, at depths of 5 meters the compaction pressure arising from support of the overburdening soil would make the soil shear strength adequate for fibric peats in some circumstances. Less aged lignocellulosic materials would be expected to follow a similar pattern. More fibrous materials may be desirable at shallow depths and less fibrous materials may be selected for deeper injections.
• the slow, partial anaerobic decomposition of lignocellulosics will produce methane and carbon dioxide.
• Most soils contain plant roots that decompose anaerobically and the methane produced feeds methanotrophic organisms in the upper, more oxygenated layer of the soil.
• Most of the soil produced methane from subterranean plant decomposition does not enter the atmosphere but is instead consumed by methanotrophic microbes before this occurs. Underneath some structures there would be little to no methanotrophic activity and so lower methane emissions are desirable underneath structures in comparison to under adjacent open or plant covered terrain.
• the slurry formation process is a key aspect of the art which this disclosure enables.
• advanced slurry formation technology that is well-known to those with skill in the art which enable time-dependent control of slurry viscosity to enable low viscosity at the surface, that rises to higher viscosity when viscosifying agents are crosslinked to thicken the slurry and break open formations and entrain heavy solid proppant particles to drag them into subterranean formations.
• Chemical "breakers” then chop up the polysaccharides and other long chain molecules that once thickened the slurry to bring the viscosity back down near that of water. The low viscosity liquid can be drawn back out of the formation leaving the proppants behind.
• the presently disclosed systems and methods exploit the unique capabilities of lignocellulosic material subterranean injection to protect structures can be most efficacious when used at the very lowest cost because many billions of cubic meters of injection solids must be placed to protect many millions of structures. Doubtless lignocellulosic materials will be used with chemical viscosity control as important embodiments but it is the enablement of the simplest and lowest cost slurries which in the end will be a primary contribution of the presently disclosed systems and methods.
• the slurry formation apparatus blends the lignocellulosic materials which may have minor contaminants as mentioned herein with the water which may optionally be brackish and any desired additives such as viscosity control agents or others mentioned earlier to form a slurry with a controlled solids content for presentation to a pump.
• Option A is a batch system in which fixed amounts or solids and the liquid are blended with an agitator, ribbon mixer or by tumbling as in a batch cement mixer. The batch is pumped into the aperture, the valve is closed and a new batch is prepared.
• Slurry formation Option B illustrates the use of a novel device called a centrifugal concentrator for floats.
• the concentrator allows delivery to the injection pump of lignocellulosic materials that float in water (at surface pressure conditions) and enables control over the slurry concentration.
• the concentrator creates a spinning mass of wet lignocellulosic material that remains in place above the pump suction.
• the raw solids and any additives are delivered to a fluid level-controlled tank.
• a self-priming slurry pump as illustrated in the figure or (other pump variety) then delivers wetted materials that are entrained in the water to the concentrator positioned above the injection pump suction and flowing through a preferably pneumatic pinch valve.
• Slurry formation Option C includes all the equipment of Option B with the addition of a hydrocyclone on the tangential return line from the floats concentrator.
• This hydrocyclone removes dense solids that sink in the aqueous fluid.
• the sink materials will typically contain small diameter particles and particles with high aspect ratio. Sand, gravel and coarse heavies will also deliver at this location. Smaller diameter lignocellulosic materials will typically saturate with water more quickly and their density will rise.
• These sinking particles may be delivered to a second pump, for example a progressive cavity pump.
• Both a floats and a sinks stream can be delivered simultaneously to different well locations in dual product mode. These locations may optionally feed different apertures or may feed an expanded aperture in different locations as explained later.
• the dual outlet configuration can be used in conjunction with a grinding circuit.
• the floats product (coarse) that delivers to the apex of the first centrifugal concentrator can be dewatered and returned to a grinder for further size reduction.
• the denser and more fine sinks product may be delivered in a concentrated state to a slurry pump for injection. This creates a safer and less energy intensive way to produce fine particles for a slurry. It reduces overgrinding and dust generation as well as energy use while still creating a reliable fine particle concentrated slurry at the hydrocyclone discharge.
• the cone angle of the hydrocyclone may be made larger, for example from an industry standard 20 degree included angle to a higher included angle such as 30-90 degrees. The larger this angle the larger will become a rotating bed of dense material awaiting discharge from the apex.
• a level sensor in the small feed cone above the dense discharge pump may be used as a control signal to adjust the diameter of the pneumatic apex.
• a low pump feed level would result in a signal to increase the apex diameter by reducing the air pressure in the pneumatic apex of the hydrocyclone.
• As the discharge volume decreases, more rotating material in the bed will instead be re-entrained by the flow of fluid exiting the vortex of the hydrocyclone with residual float solids in the feed and will report back to the initial slurry tank.
• a unique character of this slurry formation option operating in dual product mode is that the relative amount of production of both the floating (coarse) material and the denser sinking material will vary to a significant extent with the relative rate of their withdrawal by their respective pumps. Therefore, if more dense material is required the dense removal pump rate may be increased and this will have the effect of raising the percentage of the feed that reports to dense material because the size of the rotating bed of material is smaller and more solids will join the bed at the margin of material close to the sink/float cut point of the feed.
• apex or vortex diameter in the floats selection concentrator and the cone angle, vortex finder diameter, and apex diameter of the dense selection hydrocyclone enables controlled partition of many varieties of lignocellulosic feeds.
• Each variety of Lignocellulosic material may be partitioned into a more buoyant light (and often coarse) fraction and a more dense heavy (and often fine) fraction over a wide range of ratios of floats/heavy flow splits.
• the floats concentrator can be bypassed and the dilute slurry pump made to feed only the hydrocyclone as shown in slurry formation apparatus option D. If the hydrocyclone is used as in this option a sinking particle stream alone is available and any floats will be returned to the dilute slurry tank. This optional configuration is useful when only fully saturated fine products that sink are desired in the slurry placement and this mode is a single product mode.
• the level of concentration of the slurry depends on the variety of the pump to be used in addition to the flow rate required to open the subterranean aperture and the requisite pressure.
• a centrifugal slurry pump is an attractive option if injection pressures measured at the surface are 500 kpa or lower.
• Centrifugal pumps will have significant pressure limitations when high pressures are required to create fractures but the pressure required to fill an open aperture is often significantly lower than that required to create a fracture.
• Centrifugal pumps work well in situations where the formation aperture to be filled with solids is quite porous and at a depth shallower than 23 m. Centrifugal pumps work better on lower solid volume fraction and so more water per given volume of solids placed in the aperture must escape the structure to allow the solids to carry the overburden.
• a head box can also be used in unusual situations where a 20-50 m high tower or hillside is immediately adjacent to the injection location.
• the water and the solids are combined in a box opening at the top of a vertical pipe. This avoids the problem of solids passing through a mechanical pump but is only useful when a large supply of water and solids are available at an altitude significantly above the injection altitude.
• a head box is not useful to supply the usually high pressures of fracture formation as mentioned above for centrifugal pumps
• a positive displacement pump enables higher injection depths with higher slurry solids loadings.
• Piston pumps such as those used to pump concrete and stucco are quite suitable for injection with solids up to perhaps 25 mm in size for very large pumps but more frequently around 15 mm.
• Progressive cavity pumps are a very good choice if solids are perhaps up to around 10 mm.
• Progressive cavity pumps can be reversed to pull fluid out of a well while still providing backpressure to the fluid. In this way, they can be used to meter flow out of a pressurized aperture. Still other pumps available to those skilled in the art may prove useful for this purpose.
• a pneumatically compressed bladder subsequent to the pump may be a particularly effective check valve variety for trouble-free passage of large solid particles.
• the pneumatic bladder may be inflated after the pump positive stroke to reseal the subterranean pipe from backflow and the bladder may be deflated to enable the passage of a subsequent charge of slurried solids. This may be carefully and automatically timed for best effect.
• the Option B placement strategy illustrated in Figure 5 is directional bulk flow with backpressure.
• an array of wells may be used to create a large horizontal aperture under an area where adjacent wells are in hydraulic communication with the same subterranean space. In this way the overburdening earth can rise and fall as a slab in the ideal case.
• Slurry solids in Germanovich and Murdoch mineral solids are described
• the substitution of porous lignocellulosic slurry particles enables the ensuing invention of a different way to utilize the array of wells.
• the water may be removed from the aperture as the pressure of the formation is rapidly released by slowly drawing water up each well until the pressure falls satisfactorily at each well or excessive solids appear in the fluid at that well. This accelerates the relaxation process for the system of wells.
• Directional bulk flow enables wells to place solids toward one side in greater amount.
• the well can be near the edge of a one-sided filling aperture rather than generally in the middle of the solid fill of an aperture. This improves the ability to demarcate edges of elevated areas more precisely.
• Solids are swept toward one side of the well by adjacent wells which pull fluid and so direct the flow of placed solids. This is useful for example when a highway is to be elevated but the surrounding terrain is not. It is also helpful to shrink the area of uplift produced on a land parcel and avoid the tilting of adjacent structures which are not to be elevated.
• Directional bulk flow also enables better economy with injection solids consumption.
• Option C Directional bulk flow with backpressure and material interchange. This option has the same capabilities as Option B with the enhancement that it can inject either a floats-concentrated product or a sinks-concentrated product because a preselection process has created these two available lignocellulosic feeds.
• Option C produces a concentrated dense (sinks) product and a concentrated buoyant (floats) product, as described earlier. If the initial well, for purposes of illustration, injects floats, the adjacent wells can inject sinks.
• the subterranean injection of lignocellulosic material has substantial novel benefits including: Improvement in the seismic performance of elevated structures, Very long term sequestration of atmospheric carbon which has been incorporated into plant solids, Elimination of fire and pollution risk associated with combustion of plant lignocellulosic material, and Potential Seismic Benefits.
• the fundamental mechanical character of the ground structure beneath a construction can be altered with these characteristics in mind.
• the strategic application of wood chip layers in different orientations such as vertical, horizontal, inclined, cupped or bent can represent one variable to be engineered.
• the stacking of these planes or shapes in any given dimension can create intricate distributed reinforcement.
• the porous layer of wood chips may be used to provide a protective channel through which water is directed around, underneath or away from an area.
• the thickness of the layer or in various parts of a given layer and the variety of biomass within regions will materially alter the stress and strain behavior and porosity of a body of wood chips. This may be thought of as adjusting the spring constant of the ground for various applications of stress.
• the center of a layer may be of one character while the periphery is of a different character.
• Controlling the extraction of reaction products as mentioned above can be used as a mechanism to regulate decomposition rate and the formation of new gas bubbles.
• Controlling the extraction of reaction products as mentioned above can be used as a mechanism to regulate decomposition rate and the formation of new gas bubbles.
• In addition to adding oxygen, or required nutrients such as fixed nitrogen or phosphorus may be expected to maintain desirable gas bubbles in a subterranean wood chip area to enable continued protection from ground movement or rapid increase in pore water pressure.
• areas may be simultaneously protected from rising sea level or subsidence of land below sea, lake or river levels as well as from ground movement events and liquefaction of soil. Elevation of areas protects from rising relative water levels while altering soil mechanical nature gives additional protection from ground movement such as earthquakes.
• the eight wells were drilled and a 100 mm well pipe was cemented and sealed in place with a capillary pressure transducer placed at the base of each pipe to allow accurate measurement of aperture pressure.
• a level controlled tank on one edge of the yard supplied seawater for well slurry preparation and injection.
• a batch slurry preparation area for the partially dehydrated algae which was collected from a beach on the lagoon at a distance of 150 meters from the resort was used for the 20 meter injections.
• a common piping system for the four algae wells was buried in a shallow trench running to each well.
• a second coconut and cocopalm grinding area 150 meters from the resort was utilized to supply the four shallow wells close to the resort building.
• These wells were also joined with a piping system run in a trench.
• a manual well selection system for each well type could supply pump pressure to any given well while sealing the three others.
• a 20 MPa high pressure jet pump was used with a rotatable pressure pipe to score the lithified reef stone at the base of each 20 m well in a 360° arc to a radius of 50 cm to initiate the aperture.
• the jet pipe with the nozzle removed was then temporarily placed with a removable pressure packer at the base of the hole to protect the well piping from high pressure.
• the base of the well was pressurized with the jet pump using a pressure relief at a maximum pressure of 3 MPa.
• the lithified reef stone began to crack as the pressure was slowly elevated and as the crack opened the aperture formed at the base of each well.
• the jet pump hardware and packer were removed.
• the slurry piping was rinsed after each injection cycle for both wells.
• the approximately one hectare, 30 x 300 m rectangular space beneath the roadway was selected for elevation.
• the starting elevation of the highway was 0.3 m with a uniform level grade.
• the geotechnical profile of the area includes a relatively uniform dredged fill to a depth of 5 meters over a sandy consolidated bay mud profile that extended to 30 meters, followed by a cemented mudstone layer to a depth of 50 meters Based on this information, elevation apertures at a depth of 30 meters were selected to intersect with the mudstone interface.
• the fill strategy would require relatively frequent injections of high uplift thickness.
• a grid of 30 wells on four lines spaced 10 meters apart on a 5 meter staggered grid was selected.
• a total of 120 wells would be required.
• the close spacing of the wells was necessary to ensure that by pressurizing the wells the roadway could be lifted as a slab to avoid local bending that might fail the paving surface.
• the well layout along the roadway and example slurry injection bulk flow sequence are shown in Figure 8 .
• the first pipe manifolded the odd numbered wells on the southern shoulder vertical wells.
• the third pipe manifolded the odd numbered inclined wells under the southern lane.
• the sixth pipe manifolded the even numbered inclined wells under the northern lane.
• the seventh pipe manifolded the odd vertical wells on the northern shoulder.
• the eighth pipe manifolded the even vertical wells on the northern shoulder.
• a progressive cavity pump was installed on each of the eight lines that could run in either forward direction or reverse direction.
• Each well had a separately actuated pneumatic valve.
• These wells were also joined with a piping system run in a trench.
• a sophisticated automatic well selection system could supply pump pressure to any given well while sealing all the others wells along that particular manifold line. All solids were supplied from either a Northeast or Southeast slurry forming station.
• the fir bark had few binding problems in the piping and so the less saturated float product worked quite well despite incomplete saturation with water.
• the system operated using baywater.
• the dilute slurry pump drove the centrifugal floats concentrator and the hydrocyclone.
• the roadway elevation project provided a degree of base isolation to the highway which reduced the transmission of seismic energy to the highway.
• the increased vapor bubbles created by the slow decomposition of the fir bark migrated upward through the shallow dredge fill profile which was most vulnerable to liquefaction as well as upward through the sandy bay mud.
• the presence of these bubbles reduced the tendency for soil pore pressure to rise with seismic activity and so reduced the likelihood of liquefaction of the soil.
• a mechanism for providing variable back-pressure to the subterranean aperture is provided.
• a hydrocyclone style separator or other similar centrifugal solids separation device on the flow of liquid exiting the underground space may be utilized.
• a hydrocyclone style separator will provide a variable back-pressure that increases with liquid flow rate.
• the diameter of the hydrocyclonic separator and its inlet and outlet sizes may be altered to adjust the amount of pressure required to drive a given flow through the unit. In this way, a level of back-pressure may be used that is adequate to maintain the size of the subterranean aperture.
• the formula for the requisite volume of flow that is delivered to the subterranean aperture includes make-up water.
• This make-up water may be utilized to account for a volume of fluid that may be lost from the subterranean aperture to the surrounding soil structure.
• the volume of the aperture must increase and at the end of an injection process, the aperture's volume will decline as the additional liquid added escapes.
• the deposited solids are compressed by the mass of the overburden of soil above. While solids are being added to the aperture, the added solids will displace liquid that was added to increase the size of the aperture.
• a centrifugal separation device such as a hydrocyclone accelerates deposition of coarse solids including sand and coarse lignocellulosic materials.
• Bentonite clay thickeners are shear-thinning and thus their apparent viscosity declines when they pass through a high shear environment inside a hydrocyclone.
• a hydrocyclone may be used to alert operators that one of several conditions will require adjustment: the deposition fluid viscosity may require reduction to expedite lignocellulosic settling rates, the size or degree of water saturation of the incoming prepared lignocellulosic materials may require increase, or alternatively additional exit wells locations might be simultaneously used so as to increase the areal fraction of the aperture through which liquid passes. Increasing the number of exit wells used increases the apparent area of the aperture and thus increases residence time for settling of particles.
• An additional alternative to reduce the population of coarse lignocellulosic particles in the exiting flow is to reduce the total fluid entry and exit flow rates.
• the location of the active aperture determines the area where solids deposition underground will occur.
• the balance of forces in the subsoil space determines the location where the aperture will form or persist. These forces are partially determined by the initial stress state of the soil. In one arrangement, these forces may be adjusted by altering the stress state of the soil.
• a crack can form when the forces that are normal to the dimension of the crack holding the soil together reach zero at the edge as the crack propagates.
• Aperture geometry may be actively altered by a system that changes the force magnitude or direction with time in different locations.
• the viscous fluid can optionally contain some combination of nearly 50% by mass fine mineral material whether from recycle of fluid exiting the aperture or from addition of up to 12% bentonite clay.
• the fluid may also contain from 40-1000 ppm anionic polyacrylate, 0.1-2% cellulose pulp subjected to lignin removal operation, or polysaccharide gums at a concentration of 0-1% for example guar or xanthan gum.
• the use of any of these viscosifying materials solely or in combination can achieve the goal of enabling the injected material to act as a fluid jack to increase the local height of the aperture to accommodate lignocellulosic solid particles wherein more than 50% by mass of the material does not pass a 5 mm square opening screen.
• weights placed in specific locations on the top layer of soil affect aperture shape.
• weights can be placed around an injection in a ring pattern. The force exerted on top of the soil from these weights increases the pressure necessary to inject material through the volume of soil lying under the ring pattern at the injection depth. This can create an aperture with a higher vertical to horizontal displacement ratio due to the injected material aligning in a vertical column due to the resistance generated by the external pressure created by the weights.
• a vertically oriented anchoring device such as a shaft, tube, cable or other similar structure may pass through the upper portion of the soil profile and be anchored in the ground beneath the plane of an existing, proposed or possible aperture zone. Applying a tensile force to the vertical oriented anchoring device creates a compressive load downward on the space where the aperture zone might be and provides a closing force on this space.
• the vertical distance between the points of application of the lower and upper reaction forces determines the areal extent in the horizontal plane of the soil zone influenced by the applied load as is understood by the science of Soil Mechanics.
• Anchoring devices of various types both above and below the zone to be under compression may be used including soil nails, augers and anchoring plates that pivot to anchor into soil when tension is applied.
• Figure 9B depicts an alternative technique employing a cable as the tensile member creating the compressive force.
• the cable may be inside tubing to avoid contamination of the cable and pulleys with soil.
• a single cable may pass down to pulleys underground or a stub cable or chain connected to the subterranean anchor may rise to the surface where a surface mounted tensioning arrangement may attach to it.
• the surface mounted device for applying tension to the vertically rising stub cable or chain is thus protected from contamination by soil.
• a cable has the capacity to apply tension to a number of such soil anchors at once using a single cable winch as an actuator. They can also be placed with precision similar to the weight method described earlier.
• a sequence of anchoring systems like cables or screws for applying force have the advantage of "sewing" the ground together as there is an upward force applied from the anchoring auger and a downward force from the superterranean tightening mechanism.
• a single 3,000 kg cable winch can create 6,000 kg compressive force on each anchored cable because there would be 3,000 kg on each of two cables passing to the subterranean anchor. If the same cable passed through 20 cable anchors in a line stretching over a 100 m, it would create 1,176 kN force or the equivalent of parking 5 fully loaded 24 metric ton trucks in a line at the push of a button. Other varieties of techniques could be used to compress screw type or hydraulic soil force application systems automatically.
• a 1,1176 kN force applied along a 100 m line, arc, or circle will likely stop an aperture from opening and also close one along the line that is already open. This enables careful shaping of elevated spaces and the dynamic flow of solids within a filled or filling aperture.
• two small augers can be driven in the ground on either side in a horizontal plane of an anchoring plate with a threaded rod above it. Connecting these and then tightening a bolt downward against the anchoring plate causes a downward force on the plate. This increases the pressure on the volume of soil underneath the plate which force is translated to an upward tension on the two horizontally adjacent augers in the soil.
• This particular method does not involve perforating the soil directly in the area where the downward force is applied but instead perforating the soil some distance to either side horizontally of the compressive force application.
• Figure 10 (A) illustrates in more detail a compressive soil anchor and 10(B) shows a soil anchor with a slurry injection discharge at the upper end of the auger anchor that enables rotation to clear plugs which may form when injecting biomass materials.
• the placement of the subterranean discharge port normal to the axis of the anchoring device assists in reduction of plugging and enables higher fluid velocity in a selected direction.
• the addition of a liquid pressure jet operating at 7-38 MPa assists in pushing the injected slurry forward if applied such that the jet impinges on the fluid after the solids have begun moving outward from the axis of the well and into the aperture.
• the jet may be used to clear plugged material and assist cleaning along with the rotating normally oriented discharge port mentioned earlier.
• a second soil anchor such as an auger which can be placed a precise distance above a lower anchor enables application of compressive and tensile forces to alter the tendency of apertures to either open or close.
• Tensile forces encourage opening and compressive forces encourage closing or reduce the tendency to open.
• an area of subsoil can be in compression and moments later after adjustments are made to the mechanism, it may be in tension or the level of compression may be dramatically reduced relative to surrounding soil.
• Dynamic aperture shaping is thus enabled as well as direct movement of aperture fluids from one area to another area without pumping fluid in or out of the aperture at the surface.
• Removal of fluid is accomplished while maintaining back-pressure to support the aperture height.
• This can be done using a reversible pump such as a progressive cavity or a peristaltic pump whose rate is adjusted to maintain adequate back pressure or by a hydrocyclone device which increases back-pressure intrinsically as flow rate increase.
• An additional way for this to occur is to discharge fluid from within the aperture out of exits whose altitude above the ground may periodically be adjusted but which will intrinsically provide back pressure to the exiting fluid flow based on that discharge altitude.
• a reversible pump such as a progressive cavity or a peristaltic pump whose rate is adjusted to maintain adequate back pressure or by a hydrocyclone device which increases back-pressure intrinsically as flow rate increase.
• An additional way for this to occur is to discharge fluid from within the aperture out of exits whose altitude above the ground may periodically be adjusted but which will intrinsically provide back pressure to the exiting fluid flow based on that discharge altitude.
• Each of the methods just described for metering exit flow enables passage of solid
• movement to or from the aperture fluid may be transferred around the aperture by sequential compression of areas of the aperture. This is conceptually similar to squeezing a tube of toothpaste to move the toothpaste around inside the tube. Without surface fluid, movement to or from the aperture fluid may be transferred around the aperture by sequential compression of areas of the aperture. This is conceptually similar to squeezing a tube of toothpaste to move the toothpaste around inside the tube.
• FIG. 12 The use of anchoring mechanisms to induce fluid flow is illustrated in Figure 12 .
• an aperture is bounded on two sides by compressive anchors that restrict flow but still allow some light flow to the right.
• Column 2 illustrates the impact of a third bounding side which narrows and strengthens flow downward.
• the anchors on the three bounding sides preclude the fluid flow in these three direction and constrain the aperture as depicted in column 2.
• column 3 the external flow to the aperture is stopped and a sweeping closure movement is induced by applying compression at first one and then sequentially a second location moving downward. This drives liquid flow from within the aperture space and may help to both drain and level the intra-aperture solids toward the unbounded lower edge.
• Column 1 would have a longer solid settling time than column 2 because a larger area of the aperture is experiencing flow.
• the higher rate in column 2 might, for example, lead to an unacceptably high proportion of the dense solids exiting the aperture without deposition.
• the solids may move with the induced flow. If the solids have settled, the supernatant fluid may move in this way so as to ease its removal or recycling to transport more solids to the aperture.
• Removal of supernatant fluid from the aperture enables its recovery and reuse. This recovery is accomplished by direct addition to the injection pump sump. The recovery of valuable viscosifying agents such as guar gum, sodium bentonite and cellulose pulp is also accomplished in this way.
• the complete leak-off of extra fluid from the subterranean aperture will require about 1 week. Thus it is best to first measure the elevation achieved by injection at least one week after injection is ceased. The minimum elevation achieved with solids 50% of which do not pass a 5 mm square screen opening will be about twice the median 5mm size or about 10 mm.

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• 2022
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