Patent Publication Number: US-8523493-B2

Title: Modified storage pod and feeding system for binder utilized for in-situ pilings and method of utilizing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     U.S. Provisional Application No. 61/203,084 was filed on Dec. 17, 2008, for which these inventors claim domestic priority. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is generally related to the field of pilings utilized for the support of above grade structures, and specifically to the creation of in-situ pilings by the disposition of binding material, or binder, within a borehole by a tool assembly. Together with a portion of the soil whose volume it replaces, and water which is either added or already present in the borehole, the binder forms an in-situ piling which is used as an alternative to conventional pilings. The finely powdered binder is typically transported to the tool assembly from a bulk storage container or pod by blowing air into the pod and the delivery lines. However, one factor which can adversely impact the integrity of an in-situ piling is pockets or void spots resulting from air entrained within the binder. It is desirable to deliver the binder to the borehole with a minimal volume of air. 
     SUMMARY OF THE INVENTION 
     The present apparatus and method approach the problems associated with excessive air in the binder by reducing the amount of air introduced into the binder for fluidization for transport. This air is introduced, by necessity, as a transport mechanism for conveying the binder from its supply pod, through surface hoses, and through the boring-mixing type tool into the subsurface. 
     The disclosed apparatus provides an improved mechanism which assists in controlling the uniformity and predictability of the structural properties of in-situ pilings. The disclosed apparatus may be used as a replacement for known feeder systems for binder materials utilized in fabricating in-situ pilings. The known feeder systems typically comprise a cell wheel and feeder box located at the bottom of the storage pod. The pod is pressurized, and binder is delivered to the transport hose by the rotation of the cell wheel. This type of feeder system, for the reasons explained further below, can result in excessive air being entrained within the binder. 
     The disclosed apparatus reduces the amount of air introduced into the binder as required for transporting the binder to the tool  10 , thereby decreasing problems which are associated with the presence of excessive air in the fabrication of in-situ pilings. The disclosed apparatus also reduces the maintenance required on the feed mechanisms of containers used for supplying materials utilized in fabricating the in-situ piling. The present invention replaces the binder feeder system currently being utilized with a binder storage pod having a fluidization chamber which, as described below, receives injected air at a slightly higher pressure than the pressure within most of the pod. An actuated valve is located beneath the fluidization chamber. It should be noted that the term “storage pod”, as utilized herein, refers to various storage vessels and tanks which are utilized for delivering and/or storing binder and/or other powdered components utilized in the construction of in-situ pilings. Such storage pods may include devices which are mobile and transported either under integral mechanisms, or which are trailer and/or skid mounted. 
     An embodiment of the storage pod comprises an upper chamber which receives air at a first pressure through a first air inlet. The storage pod further comprises a fluidization chamber disposed beneath the upper chamber where the fluidization chamber receives air through a second pressure by a second air inlet means, the second pressure exceeding the first pressure. An adjustable valve is disposed below the fluidization chamber, where the valves has an inlet end and a discharge end, wherein binder from the fluidization chamber enters the valve through the inlet end and is discharged through the discharge end. The discharge end of the valve is connected to the feeder hose which delivers binder to the tool placed in the borehole. A valve actuator is connected to the adjustable valve which provides for controlled operation of the valve. The valve actuator may be controlled by a digital processor or other device which determines the theoretically required volume of binder at a particular time, based upon various input, such that a controlled binder flow rate may be realized by the controlled throttling of the valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS AND FIGURES 
         FIG. 1  schematically shows equipment which may be utilized in constructing in-situ pilings. 
         FIG. 2  schematically shows an embodiment of a storage pod according to the disclosed invention. 
         FIG. 3  shows an exterior view of an embodiment of a portion of the binder feeder system according to the disclosed invention. 
         FIG. 4  shows a cross-sectional view of the binder feeder system shown in  FIG. 3 . 
         FIG. 5  shows an exploded view of the portion of the binder feeder system shown in  FIGS. 3-4 . 
         FIG. 6  shows an exploded view of an alternative embodiment of the apparatus shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Background of In-Situ Pilings 
     Underlying supports for above-grade structures are often referred to as “piles” or “pilings”. Such structures may also be referred to as “supports”. The terms piles, pilings, and supports will, for purposes of this disclosure, be regarded as synonymous. The term “piling” in its general sense is a structure that gives a known vertical response to a load exerted directly on top of it. The familiar construction of a beach-side pier relies on this property. The pier structure is simply built so as to be tied to the top of the pilings and is supported at its underside by the pilings. 
     A support of the type pertinent to the present invention is formed in-situ below grade and utilizes as part of its composition the soil whose volume it replaces. The structure of an in-situ piling contrasts with conventional supports, which are generally lengths of tree trunk grown and prepared, or cast concrete shapes manufactured elsewhere or on-site from foreign material. Conventional pilings and supports preferably are driven or otherwise placed in direct contact with bedrock or other supporting structures. If the bedrock or other structure is too deep to achieve direct contact, then reliance for support is placed on the “skin friction” between the piling and the surrounding soil. 
     The inherent advantage of the continuity of an in-situ piling with its surrounding soil is evident. Its equivalent of skin friction is a merger of the surrounding soil with the enhanced material of the in-situ piling. This continuity with the surrounding soil forms a very substantial difference with conventional supports, which is advantageous whether or not the in-situ piling reaches bedrock or other supporting structures or relies on the engagement (for convenience sometimes referred to as skin friction) of the in-situ piling with its surroundings. In fact, the in-situ piling does not have a skin in the same sense as a conventional piling has. 
     In-situ pilings may be fabricated where the only required materials for delivery to the installation site are water and binder (often cement or lime or both). A boring-mixing tool  10 , as schematically shown in  FIG. 1 , is also brought to the site, which is used to dig into the ground  12  forming a borehole  14 . As the borehole is drilled or, alternatively, withdrawn from the borehole, the boring-mixing tool mixes water, or other suitable liquids, and binder into the existing earth material. The intended result is a sub-grade column on which an above-grade structure may rest, existing in the earth without requiring off-site manufacture of the piling or the need to drive the piling into place. 
     Several methodologies have been proposed for fabrication of in-situ pilings in the manner described above. Perhaps the oldest is often called the “dry method”, in which a tool  10  bores into the ground  12  and while so doing adds a binder to the borehole cuttings, where the binder reacts with water already existing in the soil, with it to form a cementitious column. The shortcomings of the dry method are evident. There may not be enough water present for the purpose. Still, the dry process has been widely used, and still is in use to this day. 
     Another process, commonly called the “wet method”, has also been widely used. In this method the binder is provided as a slurry of water and binder, which is injected into the ground  12  while the tool  10  bores into it. There are considerable disadvantages in this system including wastage of binder, variability of the properties of the piling from depth to depth, and clean-up costs, which can be very large. 
     There have been previous efforts to overcome the disadvantages of the wet and dry methods. One is familiarly called the “modified dry method” in which the soil is preconditioned with water as the tool  10  moves down, and binder is added on the way up. This is the subject of U.S. Pat. No. 5,967,700 issued Oct. 19, 1999, title “LIME/CEMENT COLUMNAR STABILIZATION OF SOILS” to Gunther, an inventor herein. Another previous effort is European patent No. 0411 560 BI granted May 4, 1994 to Trevi S. P. A. which describes an effort to produce an in-situ piling with only sufficient water provided for “humidification”. 
     The current practice for injecting the dry binder into the subsurface region is by entraining it in a pressurized stream of air, i.e., “fluidizing” the binder, which typically occurs when the dry binder is transferred via hose  16  from a storage pod  18  to the bore tool  10 . Unavoidably this practice means injecting very substantial volumes of air into the subsurface structure along with the binder. There, unless it can escape, the air can form pockets in the piling which reduce the strength of the column itself. As discussed in Gunther&#39;s U.S. Pat. No. 7,341,405, which is incorporated herein in its entirety by this reference, the presence of air adds to the volume of the mix, and a large heaving of surrounding soil will be formed. The &#39;405 patent disclosed a means of providing an environment in which the air would readily percolate out by providing sufficient fluidly (or fluidization) of the mixture through utilizing excess water for fluidization. Alternatively, as disclosed herein, reduction of the entrained air can reduce the volume of air placed in the in-situ piling. 
     Background to the Known Feeder System and its Disadvantages 
     Powered (or granular) binder is supplied at the site in bulk transport  20  and held for discharge from the storage pod  18 . The amount of binder being dispensed is not detected from a flow-sensing device, but rather from the continuous weighing of the storage pod  18  with its contents. The reason for this measurement method is that flow sensing devices are speedily destroyed by the abrasive binder. The diminishing weight of the storage pod  18  and its contents has been found to be a sufficient measure of the dispensed binder. 
     The binder is conveyed from the tank or storage pod  18  through a hose  16  extending from the storage pod  18  to the top of a tower  22 , and then down to the tool  10 , under propulsion of a pressurized air stream. The air enters the bore along with the dry binder. There is typically at least a 40 foot flow path from the tank to the tool. Under the existing known apparatus and method, the binder is fed into the air stream at a rate determined by a feed mechanism such as a cell wheel (also referred to as a star wheel) located at the bottom of the storage pod  18 . 
     The known feed system employed for dispersion of binder from the storage pod  18  into the feeder hose  16  utilizes a cell wheel, which is set below the v-shaped bottom of the pod, where fluidization of the binder, to the extent it occurs, takes place. The cell wheel is rotatably fastened to the bottom of the storage pod  18 . The cell wheel has a plurality of pockets or sections in radial arrangement about the wheel. Typically, eight pockets are utilized in the cell wheel. The cell wheel is employed to control the amount of binder injected into the soil. The amount of binder injected can be controlled by altering the speed (rpm) of the cell wheel. 
     In the known practice for creating in-situ pilings, binder is fed into the cell wheel from the overlying volume of the storage pod  18 . As the cell wheel rotates, the binder drops into a “box” or compartment underlying the cell wheel. An air stream is introduced into the box to “fluidize” the binder which has been dropped into the box. The pressure of this air stream is generally the same as the pressure applied to the overlying storage pod  18 , such that there is no appreciable pressure differential between the tank pressure and the pressure in the feeder box beneath the cell wheel, aside from the pressure exerted by the height of the overlying binder. The fluidized binder leaves the box through a feeder hose, typically 2 inch diameter, for delivery to the tool  10  located at the subsurface. 
     Ideally, the rate of feed of the cell wheel is proportional to its rate of rotation. This rotation rate may be under the control of a program which responds to the depth and the known amount of binder desired at that depth based upon the known data. It is desirable to achieve control over the flow rate of the binder because of the impact of binder volume to the properties of the in-situ column, and also to utilize binder in a cost-effective manner. However, with the known feed apparatus, it is difficult to maintain effective control over the binder flow rate. The cell wheel system is only effective at steady state flow rates, with little flexibility for adjustment. If a relatively small flow rate is desired, the cell wheel rotation is slowed. However, a slowly rotating cell wheel allows the introduction of a large volume of air, without binder, into the feeder box and feeder hose, and thus into the piling column, resulting in the problems discussed above. Moreover, because the binder is highly abrasive, the cell wheel is subjected to constant internal wear which abrades the components of the cell wheel and increases the tolerances between the cell wheel and its housing, resulting in a further loss of control of the binder flow rate, and a larger volume of binder to be injected. Alternatively, if a large binder flow rate is desired, a rapidly spinning cell wheel is almost in the way of itself, such that the pockets of the cell wheel cannot be emptied fast enough. 
     In addition to the problems identified above with the present binder feeder system, the cell wheel system results in a pulsing injection of binder, particularly at lower rotational speeds of the wheel. The pulsing occurs when non-fluidized binder from the cell wheel is “dumped” into the feeder box and impacted by the airstream flowing through the box. In other words, the content of the feeder hose down stream from the feeder may alternatively consist of a low amount of binder followed by a large amount of binder. This pulsing is very undesirable because it interferes with achieving the desired column for the in-situ piling, which often requires being able to control the binder flow rate. 
     Description of the Present Invention 
     Referring now to  FIGS. 2-6 , the presently disclosed invention comprises a binder storage pod  100  which comprises a feeder system  102  which replaces the cell wheel-feeder box discussed above.  FIG. 2  schematically shows the relation of the storage pod  100  and the general components of the feeder system  102 . Storage pod  100  comprises material fill pipes  104 , which are utilized to fill the storage pod with binder or comparable material. The substantial portion of storage pod  100 , referred to as the upper chamber, indicated as Zone  1 , receives air and maintained in a pressurized state by applying air pressure at a first air inlet  106 . The storage pod further comprises a lower section called the fluidization chamber  108 , which is to be distinguished from the v-shaped bottom of the pod. The fluidization chamber  108  comprises its own air inlet, which is referred to herein as the second air inlet  110  to distinguish it from the first air inlet  106 . Disposed below the fluidization chamber  108  is an actuated valve  112 . This lower portion of the storage pod  100  may be referred to a Zone  2 , and during operation portions of it will have a higher pressure than in Zone  1  because of localized air injection as discussed below. 
     The actuated valve  112  may be adjusted over a range of openings extending from a first position where the valve opening only allows the passage of a small volume of binder, up to, and including, a fully open position which allows binder flow rates several time larger than the flow rates achievable with the cell wheel. Actuated valve  112  is used in combination with one or more small diameter (e.g., ¼″) air injection inlets located in close proximity to the valve, such as second air inlet  110 . The small diameter air injection inlets are utilized for injection of air into the fluidization chamber  108  immediately adjacent to the actuated valve  112 . Air is injected into second air inlet  110  when the actuated valve  112  is opened. An additional air inlet, referred to third air inlet  114 , may be connected directly to the body of actuated valve  112  such that air may be injected directly into the throat of the valve when it is opened. The injection pressure for one, or all, of the air injection inlets  110 ,  114 , is slightly higher, such an additional 10 percent, than the pressure of the air injected into the tank by first air inlet  106 . First air inlet  106  is sized to provide a substantially larger volume of air than injection inlets  110 ,  114 . For example, if air inlets  110 ,  114  are ¼″ in diameter, first air inlet  106  may range from 1¼″ to 2″ in diameter. The actuated valve  112  comprises an actuator  116  which may be hydraulic, pneumatic or electric and may be controlled by a computer or programmable controller utilized for determining the required amount of binder for a particular location in the in-situ column as described in the &#39;405 patent. 
     In essence, the disclosed feeder system creates two pressure zones within the storage pod  100 . The first zone, Zone  1 , extends upwardly in the storage pod  100  from approximately first air inlet  106  and comprises a substantial portion of the storage pod, and is approximately maintained at a first pressure P 1 . The second zone, Zone  2 , is located generally around the fluidization chamber  108  is slightly elevated (for example by 10 percent above the first pressure), by the incoming air stream from one or both of the small diameter air injection inlets,  110 ,  114 , which will typically be a significantly smaller diameter than air injection inlet  106 . The incoming air stream through air injection inlets  110 ,  114  is regulated and maintained at a sufficiently small volume such that the overall tank pressure P 1  does not equalize to the higher pressure P 2  of the second zone. The outlet of actuated valve  112  is connected to feeder line  118 . Feeder line  118  receives air at the first pressure P 1  from air line  120  when actuated valve  112  is opened such that a small pressure differential exists between the second zone and the feeder line. This differential assists in a flow of fluidized binder through the actuated valve  112  when the valve is opened. For example, the first zone, and the pressure to the feeder line P 1 , may be maintained at approximately 5 atmospheres of pressure, while the pressure in the second zone P 2  may approach 5.5 atmospheres, resulting in a 0.5 atmosphere differential between the fluidization chamber  108  and the feeder line  118 . The air injection through the small diameter injection inlets  110 ,  114  allows for complete fluidization of the binder immediately before the binder is discharged into the feeder line  118  for delivery to hose  16  for transport to bore tool  10 . It is to be appreciated that because of the changing level of binder in the storage pod  100 , which will impose its own pressure based upon the height of the binder within the pod, and the lack of a physical barrier between Zone  1  and Zone  2 , there is not a definitive boundary between the two Zones, but rather a transition between the higher pressure around the fluidization chamber and lower pressure in the upper chamber of the storage pod  100 . 
       FIG. 3  depicts an embodiment of the fluidization chamber  108  and actuated valve  112 . As shown in  FIG. 3 , a spacer  122  may be utilized to attach the feeder system  102  to the bottom of the storage pod  100 . As shown in  FIG. 3 , the fluidization chamber  108  may be configured in a bowl shape on the outside, and may contain a cone-shaped internal configuration as shown in  FIG. 5 . The fluidization chamber  108  may comprise a first flange member  124  which mates to either spacer  122  or directly to the bottom of storage pod  100 . Fluidization chamber  108  may further comprise a second flange  126  member for connecting the fluidization chamber to actuated valve  112 . A funneled conduit is disposed between the first flange member  124  and the second flange member  126 , the funneled conduit comprising the throat opening to the inlet of the actuated valve  112   
     As shown further in  FIG. 3 , second air inlet  110  may comprise a nipple which screws directly into a threaded port in the fluidization chamber  108 . Likewise, third air inlet  114  may comprise a nipple which threads into the body of actuated valve  112 .  FIG. 3  also shows the edges of a first cloth membrane  128  which may be disposed between the first flange member  124  of fluidization chamber  108  and either spacer  122  or the overlying storage pod  100 .  FIG. 3  shows the protruding edges of second cloth membrane  130  which is disposed between the second flange member  126  and the actuated valve  112 .  FIG. 3  also shows exit port plate  132  which makes up to the discharge side of actuated valve  112 . A connector  134  leads to feeder line  118 , as shown in  FIG. 2 . 
       FIG. 4  shows a sectional view of the assembly depicted in  FIG. 3 . As shown in  FIG. 4 , first cloth member  128  acts to disperse the air injected from second air inlet  110 , thus assisting in the fluidization of binder which enters the fluidization chamber  108  from the upper chamber of storage pod  100 . First cloth member  128  lines the inside cone of fluidization chamber  108 . Fluidization chamber  108  may further comprise a screen member  136  which conforms to the shape of the inside cone of the fluidization chamber  108 , and overlies first cloth member  128 , as shown in  FIGS. 4 and 5 . Alternatively, first cloth member  128  may overlay screen member  136 . As shown in  FIG. 5 , first cloth member  128  comprises an opening  138  which aligns with the opening at the bottom of the fluidization chamber  108 . The edges of the opening  138  may be retained by the corresponding edges in the opening of screen member  136 . Thus air which is injected through second air inlet  110  is dispersed by both the screen member  136  and the first cloth member  128 . 
       FIG. 4  also shows how a ported bushing  140  is disposed within the throat of actuated valve  112 . As further shown in  FIG. 4 , second cloth member  130  is placed between fluidization chamber  108  and actuated valve  112 . Second cloth member acts to disperse the air injected from third air inlet  114 . As shown in  FIG. 5 , an entry port  142  in the housing of actuated valve  112  allows air to be injected into the throat of the valve. This air is first dispersed by second cloth member  130 , before entering the ports of ported bushing  140 . As shown in  FIG. 4 , the edges of second cloth member  130  extend downwardly into the throat of actuated valve  112 , and may form a pocket as around the bushing as shown in  FIG. 5 , forming a permeable membrane between the throat of the valve and third air inlet  114 . Thus, additional air is dispersed in the throat of actuated valve  112  to maintain the fluidized nature of the binder as it is dispersed from the storage pod  100  into the feeder line  118 . It should be noted that the air injected into third air inlet  114  may be at the same pressure as that injected into second air inlet  110 , or may be injected at a lower pressure, including that of the injection pressure of first air inlet  106 . 
     The configuration of the first cloth member  128  and the second cloth member  130  creates a localized zone of higher pressure than is present in the substantial remainder of the storage pod  100 , thereby creating a pressure differential between the fluidization chamber  108  and the feeder line  118  when actuated valve  112  is opened, because the feeder line is maintained at the same pressure as the pressure in most of the storage pod  100 . This pressure differential enhances the fluidizing of the binder contained within the fluidization chamber  108 , and reduces or eliminates the problems associated with the existing feeder systems discussed above. 
       FIG. 6  shows an alternative embodiment for a fluidization chamber  208 . In this embodiment, air from second air inlet  110  enters into the fluidization chamber  208  through a goose neck conduit member  210 . The first cloth member  128  and the second cloth member  130  are assembled in a similar fashion as with the embodiment shown in  FIG. 5 . The apparatus described above suggests a method for delivering fluidized binder from a storage pod to a borehole for creation of an in-situ piling. The method comprises the steps of first injecting air into the upper chamber of the storage pod  100  at a first pressure P 1 . This injection causes a substantial volume of the storage pod to have this first pressure, referred to as Zone  1 . The storage pod  100  also comprises a fluidization chamber  108  below the upper chamber, where the fluidization chamber has an upper end connected to the upper chamber and a lower end. Air is injected into the fluidization chamber  108 , at intervals, at a second pressure P 2  which is higher than the first pressure P 1 . A valve  112  is connected to the lower end of the fluidization chamber  108 . This valve  112  is opened at the same intervals that air is injected into the fluidization chamber  108  at the second pressure P 2 . The valve  112  comprises an inlet and an outlet, where the inlet is connected to the fluidization chamber  108  and the outlet is connected to a feeder line  118 , where the feeder line is maintained at the first pressure P 1  and the feeder line is connected to a hose  16  for transport to a bore tool  10 . A first cloth member  128  may be disposed between the upper chamber of the storage pod  100 , which cloth member acts to disperse the air injected from second air inlet  110 . Air may also be injected into the throat of the actuated valve  112  through third air inlet  114  at the same time air is injected into the fluidization chamber  108 . The air injected into third air inlet  114  may either be at first pressure P 1 , second pressure P 2 , or some pressure between the first pressure and the second pressure. 
     While the above is a description of various embodiments of the present invention, further modifications may be employed without departing from the spirit and scope of the present invention. Thus the scope of the invention should not be limited according to these factors, but according to the following appended claims.