Hydraulic and earth engineering – Earth treatment or control – Chemical
Reexamination Certificate
1998-07-23
2001-07-10
Bagnell, David (Department: 3673)
Hydraulic and earth engineering
Earth treatment or control
Chemical
Reexamination Certificate
active
06257803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention, in general relates to a system and method for injecting chemical grout and, more particularly, to grout injection devices that accept three grout components simultaneously.
The use of chemical grout injection devices are, in general, known. They typically disclose methods and apparatus useful for injecting either a pre-mixed grout, such as cement, or for injecting two grout components simultaneously so as to create a chemical reaction that produces grout in-situ. Chemical grouts that require the mixing of two components are referred to as “binary” grouts.
Chemical “additives” are sometimes used with binary grouts to modify some characteristic of the resultant grout, for example the time it takes for the grout to set or cure. If the additive hastens the time required to set, it is commonly known as an “accelerator”. Usually, the additive is included as a mixture in solution with one of the two principle component parts before they are combined (and reacted together).
When grout is being injected into an area in which a pervasive flow of water exists, such as is found under or around water dams or through cracks in the dam structures, the water will be flowing at great volume and under great pressure. If the grout being used under such or similar circumstances were of a slow set (cure) time, the pervasive flow would simply carry the grout away as soon as it is injected, never being able to stop the flow or to seal the crack.
For a greater understanding of this problem and of certain prior solutions, U.S. Pat. No. 5,342,149 to McCabe et al, that issued Aug. 30, 1994, is useful and is herein incorporated as a reference.
An especially fast setting grout is required under such conditions. In particular, the binary grout components must be reacted so as to form an especially fast setting grout which is used to form an immediate barrier that can obstruct the pervasive flow. Accelerators are likely required to hasten setting time of even the fastest curing binary grouts.
Although the terminology is not elegant, a “glob” of especially fast setting grout must be formed as it is injected into a crack or crevice or fissure (each term is used interchangeably herein) in order to stop the flow. The grout must set-up and adhere to the surrounding structures before the pervasive flow can carry it away.
The necessity to inject an especially fast setting grout to seal a pervasive flow creates two inherent problems. A very fast setting grout, by definition, sets up quickly. Once set, it can no longer flow. As the cited McCabe prior patent reference addresses, it is not possible to react a very fast setting grout at the surface and then pipe it to a location to be grouted because it would “set” in the pipe and cease to flow. Therefore, it must be reacted in-situ. That is the purpose of having an injector. The first problem, then, is the need to react a fast setting grout in very close proximity to the crack or crevice to be filled with grout.
If a crack or crevice that is sealed is, in fact, sealed using only an especially fast setting grout, the crack or crevice will not be entirely filled by the grout. This is a second problem that is encountered when using an especially fast setting grout.
The tendency of the especially fast setting grout to form a “glob” does not stop once the pervasive flow is stopped but rather continues as more grout is injected into the crevice. Therefore, minute crevices are not adequately filled by the fast setting grout and voids can occur in even larger areas that are to be filled. Indeed, a series of adjoining “globs” can be formed that may provide a poor fill pattern.
Test core samples that may be drilled and extracted after to determine the quality of the grouting operation may contain excessive voids, possibly not satisfying predetermined specifications, and possibly even causing penalties to be incurred by the grouting contractor.
Indeed, the various “globs” may not completely stop the flow. A lesser volume of fluid (typically water) may find various paths around the “globs” and may continue to flow. This is worse than it seems. The mere fact that any flow might continue means that erosion will occur which, in time, can only exacerbate the problem.
The ideal solution is to vary the setting time of the resultant (reacted) grout during actual grouting operations. This has not been accomplished in the past because there has been no way to inject an additive, for example to hasten the set time to initially seal a pervasive flow and then gradually reduce or even eliminate the amount of additive that is being combined with the binary grout components as they are reacted.
Prior art has required that the fast setting grout be injected to seal the pervasive flow and then to either continue to seal the opening with the fast setting grout as best as can be accomplished or, alternatively, to stop the grouting process, readjust the grout mix by eliminating the additive from one of the two grout components (before they are reacted), and then to restart the grouting process anew.
To restart the process with a different grout “mix” results in a lack of continuity and a break in the integrity of the grout seal as the first “fast setting” grout will have set and created an interface (surface) against which the next round of grout must make contact. This can result in a path that can encourage additional or future leaks to occur as, for example, the water from a water dam eventually migrates under pressure to take advantage of the dissimilar grout interface. If the grouting process is continued with the fast setting grout, voids, as was described above, can form.
A monolithic pour (i.e., a continuous pour) is desirable to prevent a grout interface from being formed, yet no known way has heretofore been developed to do this that can actually vary the grout formulation and thereby vary the fill characteristics during the process of reacting and injecting grout, referred to herein as either injection or during the “pour”.
One ideal solution, if it were possible, would be to allow varying the amount of additives that are used so as to initially provide a grout mix with an especially fast setting time to initially seal the crack enough to stop the pervasive flow, and to then vary the amount of additives “on the fly” so as to provide a grout mix with a slower setting time, but with better fill characteristics. If no cessation of grouting occurred, a monolithic pour having optimum fill characteristics would result.
As mentioned briefly above, prior types of two component grout injectors require that the desired additive be first mixed together with one of the two binary components. When a long hole is included, a great deal of pipe intermediate the surface and the old injector will be filled with the additive mixed together with one of the grout components. If the process is stopped and later restarted without the use of the additive, a great deal of wasted “mix” containing the additive results in one of the pipes as well as the need to reclaim the components during extraction of the injector. The risk of spillage at the surface also arises as is discussed in greater detail hereinafter.
A second ideal solution, if it were also possible, would be to vary the grout formulation (i.e., the type of grout provided by a manufacturer) that is being injected (used) without stopping the grout injection process.
For example, various types of binary urethane chemical grouts, aside from the additives that may be used with them, when reacted produce grouts that have different characteristics as is well known among those having ordinary skill in this art. Some grouts set more quickly than others (without the use of accelerators) because the setting time is an attribute of the particular formulation of grout that is being sold under any of various trade names. These various kinds of chemical grouts are available from the various manufacturers, again as is well known in the arts.
Some of these off-the-shelf grouts will adhere bett
McCabe Howard Wendell
McCabe William Ernest
Bagnell David
Lagman Frederick L.
Rinne, Jr. Risto A
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