Pipe supporting dam assembly for pipeline construction and method

A pipe supporting dam assembly and method for pipeline construction employing a planar dam sheet with a collar and a flexible sleeve for receiving and supporting the pipe, and clamping means to seal the collar to the outside of the pipe to prevent fill material in the trench being washed away by groundwater along the outside surface of the pipe, particularly in the case of sloping pipeline construction.

BACKGROUND OF THE INVENTION 
The present invention relates to pipe supporting dam assemblies and methods 
for pipeline constructions, being particularly useful for preventing the 
flow of groundwater from following the path along the outside of the 
sloping pipe and washing away bedding of backfill material in the pipeline 
trench which can cause structural collapse or the consequent build-up of 
fines of the backfill that can cause heaving of the upper pavement 
surface, or silt pollution at the point of pipe-to-surface penetration. 
In such pipeline construction for sewer and drainage systems and the like, 
PVC or other pipe conduits are installed in the earth in a trench and 
covered with stone bedding and then the backfill material to give a solid 
and compact base to the pipe installation. In order to have bedding 
material that will compact, material that has a very low plasticity (which 
allows water to transmit through it freely) has to be used. For example, 
bedding material used for PVC pipe is generally washed stone which has 
high compactibility and it also has voids that allow water to move through 
it freely. Especially in a soil fill that has a high plasticity content or 
index, groundwater seeks the easiest route through the stone, seeking its 
own level, and will follow the slope of the pipe along the outside surface 
thereof. When this happens, the bedding and other material on top of the 
pipe, which normally contains fines, generally sand, is subject to water 
picking up these fines in the bedding or other material packed around the 
pipe and carrying them along either the bottom of the trench or along the 
outside surface of the pipe, frequently developing a build-up that can 
cause a structural fill collapse in the road. 
Prior to the present invention, there have been two principal technologies 
for trying to mitigate against such water flow effects. One has been to 
pour concrete around the pipe, but this creates an undue stress on the 
pipe, especially with ground movement; and, in addition, the concrete does 
not seal to the PVC pipe so the water can still flow along the outside 
surface of the pipe. Another technique has been to create an earth or a 
clay dam, where the clay is actually imported to the site and packed 
around the pipe; but this also leaves much to be desired since its 
effectiveness depends upon correct installation and because clay has a 
high plasticity index which results in the development of voids, with the 
clay, moreover, not actually sealing to the pipe but allowing the 
groundwater to flow along the outside of the pipe. 
BRIEF SUMMARY OF THE INVENTION 
An object of the present invention, therefore, is to provide a new and 
improved pipe supporting dam assembly and method that are not subject to 
such disadvantages and that, to the contrary, support the pipe along the 
trench, effectively preventing groundwater from traveling therealong and 
thus obviating the possibility of road collapse. 
Another object is to provide a novel pipe supporting dam assembly for 
pipeline construction that is easy to install and has both long-lasting 
water sealing and dam features. 
Other and further objects will be explained hereinafter and are more 
particularly pointed out in the appended claims. 
In summary, however, from one of its broader viewpoints, the invention 
embraces a pipe supporting dam assembly for earth trench pipeline 
construction to prevent fines in bedding and other material filled into 
the trench from being carried away by groundwater along the outside 
surface of the buried pipe, the assembly having, in combination, a planar 
dam sheet having a circular opening from which a collar extends for 
receiving the pipe, and a flexible connector sleeve disposed over the 
collar and the adjacent portion of the pipe received therethrough to 
connect the same and support the pipe, and clamping means for sealing the 
sleeve to the collar and the pipe to stop the flow of groundwater and 
fines carried thereby at the dam sheet and to prevent passage along the 
outside surface of the pipe. Preferred and best mode embodiment and 
details are hereinafter presented.

DETAILED DESCRIPTION OF THE INVENTION 
Refering to FIG. 1 of the drawing, a section of pipe 2, such as a PVC or 
other sewer or drainage pipe or the like, is shown assembled with a planar 
dam sheet 1 formed with a central or other interior preferably circular 
aperture or opening 1' from which a reentrant collar 5 extends, shown 
rearwardly or to the left in FIG. 1. In accordance with the invention the 
dam sheet 1 is to be filled transversely across a trench T, FIGS. 4 and 5, 
with the side edges contacting and preferably embedded within the side 
walls of the trench, and the bottom edge inserted in the bottom of the 
trench. By fabricating the dam sheet 1 of relatively flexible or resilient 
non-rotting, corrosion-resistant and light-weight plastic material, such 
as ABS (acrylonitrile- butadiene- styrene or the like), it may be 
transversely flexed and snap-fitted into the trench side walls as shown in 
FIG. 5. Except for the aperture or opening 1', the dam sheet will be 
impervious to groundwater flow along the interior of the trench T. 
The pipe 2 is shown received through the opening 1' and collar 5 and is 
supported by a resilient sleeve connector 3, as of rubber, that is fitted 
at one end (right, in FIG. 1.) over the collar 5 and at its extension or 
other end (left, in FIG. 1) fits over the adjacent portion of the pipe 2 
received through the collar 5. The resilient nature of the sleeve 3, with, 
if required, a tapered cross-section depending upon the relative diameters 
of the inner surface of the collar 5 and the smaller outer diameter of the 
pipe 2, enables a tight fit which, when clamped, as by metal band strips 4 
tightened over the sleeve 3 at the regions of its overlap of the collar 5 
and the pipe 2, FIG. 1, effects an excellent support suspension of the 
pipe(horizontally through the dam sheet or at an incline or slope, as 
desired) and seals against groundwater with accompanying fill fines and 
the like passing along the outer surface of the pipe across the dam sheet 
1. 
While, as before stated, it is desirable that the dam sheet 1 be light 
weight and flexible for the purposes of the above-desired trench 
installation, structural reinforcement can be provided without sacrificing 
lateral flexibility by forming diagonal ribs 6, and to strengthen the 
intergral collar 5 and accommodate for torque forces resulting from the 
pipe suspension, one or more coaxial circular ribs 7, FIG. 1, may 
similarly be provided, also deformed out of the plane of the dam sheet 1. 
An important point of assembling the pipe 2 with the dam sheet is that the 
collar 5 does not touch the pipe, as is shown in FIGS. 2,3 and 4. The 
diameter of the collar, as before stated, is larger than that of the pipe. 
It is the flexible connector 3 that aligns or supports the pipe in 
position through, but not touching, the walls of the collar 5 or aperture 
1'. This suspension, moreover, eliminates any material stress on the pipe 
2, as well. The rubber or other resilient sleeve connector 3 has enough 
resilience to absorb shock and produce a cushioning effect between the 
pipe and the dam sheet, while it effects the previously desired seal 
across the dam sheet. 
Further modifications of the invention herein described will occur to those 
skilled in this art and all such modifications are deemed to be within the 
spirit and scope of the invention as defined in the appended claims.