Patent Publication Number: US-5158398-A

Title: Method and apparatus for an excavation support system for trenches

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is directed to a method and apparatus for an excavation support system and, more particularly, to a method and apparatus for supporting the walls of an excavation to prevent a cave-in of the walls defining the excavation. 
     2. Description of the Prior Art 
     According to the prior art, a first portion of the trench was dug to a first depth and a trench box or support was assembled in or placed in such first portion. The trench was then dug to its full depth, making the trench approximately twice the depth of the first portion. 
     To support this additional trench depth, the U.S. Pat. No. 3,212,270 to Benintend issued Oct. 19, 1965 shows the use of plates 12 which slide downwardly along guides made up of flanges such as 20, 22 and 23 affixed to and within the walls of safety cage 11. Because only a single plate 12 can be accommodated by each set of flanges, the trench depth is limited to approximately twice the height of safety cage 11. 
     In U.S. Pat. No. 4,059,964 issued Nov. 29, 1977 to Pavese, there is shown a sheeting installation frame 71 which installed in the pit to a first depth. Sections 72 are then installed into support frame 71 and hammered downwardly through the undug soil beneath the support. Finally, the remainder of the pit is dug between the extended sections 72 (see FIGS. 9, 10 and 11). The marginal edges of sections 72 overlap so that a complete pit wall is created. Since frame 71 only provides for a single set of sections 72, the depth of the final pit is approximately equal to twice the height of support frame 71. 
     In Japanese Printed Publication 56-77422, after frame 2 is positioned in the trench mouth and shored up as with supports 3, panels 7 are made to engage channels created by guides 6 and slide downwardly behind the frame 2. Once panels 7 are in place, the remainder of the trench can be dug. Since the guides 6 can only handle one set of panels 7, the trench depth is limited to about twice the height of frame 2 (see FIGS. 6 and 7). 
     The prior art does not show how a trench can be supported, which trench has a depth a number of times the height of the trench box or shield. The present invention is directed to meet these needs. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus for supporting the walls of a deep trench a number of times the depth of the trench box or trench shield used to support the trench walls at the trench entrance adjacent the surface of the excavation. A trench is dug to a first depth and the walls about the trench are supported by a trench box or shield. A series of soldier piles are sunk into the ground in front of the trench box or shield and guided into proper position by a series of guides on the front panel of the trench box or shield. The soldier piles can be as long as desired, and are selected to exceed the pit depth so that the ends will engage the soil below the pit floor. 
     The soldier piles can have a generally I-beam configuration to handle single plates between adjacent piles or the soldier pile channels can be subdivided into multiple channels to handle three plates in face-to-face relationship. Each channel has a stop at a fixed depth. Thus, the plate in the channel closest to the trench box or shield is positioned first, then the next one is moved to a lower depth as the trench is dug deeper, and finally the plate remote from the trench box or shield is set in place as the trench excavation is completed. It is an object of this invention to provide an improved method and apparatus to support an excavation. 
     It is another object of this invention to provide an improved method and apparatus to support an excavation using soldier piles. 
     It is still another object of this invention to provide an improved method and apparatus to support an excavation using soldier piles and plates movable within the channels of said soldier piles. 
     It is yet another object of this invention to provide an improved method and apparatus to support an excavation using soldier piles having a plurality of channels and a plurality of plates, one for each channel and extendable in staggered relationship below a trench box or shield whereby an excavation of a depth a number of times greater than the height of the trench box or shield can be supported and shored. 
     Other objects and features of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings which disclose, by way of example, the principles of the invention and the best modes which have been presently contemplated for carrying them out. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings in which similar elements are given similar reference characters: 
     FIG. 1 is a side elevational view of a trench first stage with trench box side walls and temporary struts installed. 
     FIG. 2 is a top plan view of the excavation of FIG. 1 with the trench box completed by the addition of end walls or panels. 
     FIG. 3 is a side elevational view, in section, of a temporary strut of the type shown in FIG. 1. 
     FIG. 4 is a front perspective view of a side wall or side panel used as a trench box or trench shield. 
     FIG. 5 is a fragmentary top plan view of a joint member used to join two side wall sections or side panels. 
     FIG. 6 is a fragmentary top plan view of the joint used to assemble an end panel to a side wall or panel and to accommodate reinforcement plates. 
     FIG. 7 is a side view of an alternative form of side wall or side panel used as a trench box or trench shield. 
     FIG. 8 is a side view of yet another form of side wall or side panel used as a trench box or trench shield. 
     FIG. 9 is a side view of an excavation according to the present method and apparatus showing the trench box and soldier piles with temporary struts in place and the side panels removed so that the inner details are visible. 
     FIG. 10 is a fragmentary top plan view, partially in section, showing one form of soldier pile and a channel of the side panel. 
     FIG. 11 is a side view of an excavation according to the present method and apparatus showing the trench box and soldier piles in place with the reinforcement plates set and the temporary struts placed and the side panels removed so that the inner details are visible. 
     FIG. 12 is a fragmentary top plan view, partially in section, of a multi-channel soldier plate and a channel of the side panel. 
     FIG. 13 is a front elevational view of one wall of the excavation of FIG. 11. 
     FIG. 14 is a top plan view of the excavation of FIG. 11. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to FIGS. 1 to 8, the method and apparatus used to construct and reinforce the preliminary portion of the trench excavation 20 is shown. Typically this type of trench is dug with a width of about 13 feet, a height of eight feet with a low portion H 2  of five feet and an outwardly tapered lead section of a height H 1  of three feet. The trench is about 43 feet in length as shown by L in FIG. 2. Once dug, the side walls of the trench 20 are supported to prevent a cave-in of the soil by side panels 22 and end panels 24, and the side panels are shored up by temporary struts 26. The side panels 22 and end panels 24 are prefabricated structures which can be inserted and removed and re-used at other excavation sites. 
     The side panels can be fabricated as of reinforced concrete as shown in FIG. 4 . Panel 28 has a reinforcement structure of steel beams (not shown) to which are attached lifting eyes 30 and a channel structure including shoulders 32, 34 to receive the soldier piles as set forth below. Two side panels 28 can be joined by the joint 36 shown in FIG. 5 which serves to hold the two side panels 28 in alignment. The side panels 22 can also be fabricated of steel plates joined together. As shown in FIG. 7, a front steel plate 40 of side panel 38 is joined to a rear steel plate 42 by means of the square spacer tubes 44 formed adjacent the top of plates 40, 42 and near the bottom of these plates. A terminal wall 46 prevents the soil from entering side panel 38 when it is placed. A suitable tool jaw or a chain through upper tube 44 permits the side panel 38 to be placed as desired. 
     For some applications, it is desirable that the preliminary portion of the trench be deeper than five feet and in the range of ten feet or even where the trench box or shield must provide greater strength, the side panel 38 of FIG. 7 can be modified to side panel 48 of FIG. 8 which includes the strengthening rib 50 or could, if desired, include additional spacer tubes 44. 
     The temporary struts 54 as shown in FIG. 3 are closed steel boxes whose length L 1  is generally eight inches, height H 3  is six and three quarters inches and has a thickness of five-eighths of an inch and an overall length of approximately eleven feet. These struts are generally placed at thirty inch intervals along the side panels. Alternatively, the struts could be suitably sized timbers. 
     To hold end panel 24 assembled to side panels 22 (only one of which is shown in FIG. 6), a U-shaped bracket 56 is employed. U-shaped bracket 56 has two upstanding arms 58, 60 which may be extensions of the reinforcement structure of side panel 28 of FIG. 4 or added to front plate 40 of side panels 38 and 48 of FIGS. 7 and 8, respectively. Welded to arm 58 is a further bracket 62 welded by joining portion 64 to arm 58. Portion 64, together with portion 66, form a channel to receive a reinforcement plate (not shown) for side panel 22, while portion 66 with portion 68 receive a reinforcement plate for end panel 24 (not shown). A final fillet or plate 70 is attached between side panel 22 and arm 60 to further support bracket 56. 
     Once the trench box or trench shield (made up of side panels such as 28, 38 or 48, end panels such as 24) is in place, the temporary struts 54 are removed and the remainder of the excavation 20 completed as shown in FIG. 14. The remainder may be in the range of 12 feet to 32 feet, giving a total excavation depth of 20 feet to 40 feet. For shallow excavations, the excavation may be completed once the trench box or trench shield is in place. For deeper excavations, the excavation is done in stages as will be set forth below. 
     Now the soldier piles 80 are driven into the excavation 20 floor so to extend approximately two to five feet below the excavation bottom to anchor the soldier piles 80 as shown in FIG. 9. Included on the front face of soldier piles 80 are a series of Y-shaped brackets 82, better seen on FIG. 13, which support a series of temporary struts 84 to hold the positions of the soldier piles 80. The soldier piles 80 may be in the form of I-beams or two T-sections joined to form an I-beam of the desired dimensions. As shown in FIG. 10, side panel 28 has two L-shaped shoulders 32, 34 which create therebetween a channel to receive soldier pile 80, and thus assure that the position of the soldier piles 80 are directly adjacent the faces of side panels 28. 
     Soldier pile 80 is made up of two T-shaped sections 86, 88 joined along their free legs, as by welding, so that the distance between the respective T-bars can be controlled to receive only one set of reinforcement plates. If the soldier piles are to be used with the deeper excavations and multiple reinforcement plate pairs are to be employed, then a full I-beam 90 is used as in FIG. 12. Flange 92 is set in the channel made up of shoulders 32, 34 on side plate 28, and flange 94 is spaced therefrom. Channel wall members 98 are then welded along arm 96 joining flanges 92, 94 at suitable distances to establish three separate channels for pairs of reinforcement plates as will be discussed below. It should be noted that the support bracket 56 and further bracket 62 of FIG. 6 have a total length equal to the soldier piles 80, and that bracket 56 and the channels created by arm portions 64, 66 and arm 58 and portion 68 are also divided into three channels each to handle three sets of reinforcement plates. 
     Although the discussion has been in terms of side panels 22, 28, 38 and 48, it should be understood that the form of end panels 24 can be the same as the side panels 28, 38 and 48 except that their length is shorter. The end panels 24 will also have channels formed of shoulders such as 32, 34 and will receive soldier piles as well. The reinforcement plates for the end panels will be moved in a combination of the soldier pile channels and the end brackets as is true of the reinforcement plates for the end plates of the side panels 22. 
     Now the reinforcement plates 100 are added to reinforce the walls of the excavation below the trench box or trench shield side walls 22. The plates 100 will rest on the floor of the excavation 20 or may be driven below such floor. 
     As the excavation 20 becomes deeper, it is not possible to shore up the excavation walls with a single level of reinforcement plates 100, because the plates become too large and too heavy to move. Instead, multiple levels of reinforcement plates 100 are used and the pit is dug to its maximum depth in stages. Turning now to FIGS. 11 and 13, there is shown the arrangement of three levels of reinforcement plates 100 to shore up the walls of an excavation having a total depth of forty feet. The trench box or trench shield is fabricated in the preliminary portion of the excavation employing side walls 22, and the soldier piles 90, as shown in FIG. 12, are sunk into the excavation 20 floor as above-described. A series of struts 84 are placed in the brackets 82 on the face of soldier piles 90 to fix the positions of such soldier piles 90. A first level of reinforcement plates 100 is positioned in the channel C 1  closest to the walls of excavation 20 and moved downwardly until it comes to rest against stop 102 in channel C 1  which prevents further downward movement of plate 100 and fixes its position with respect to the side wall 22 and the side wall of the excavation 20. The excavation 20 is now dug deeper by approximately the height of a reinforcement plate. 
     Next, a further reinforcement plate 100 is placed in each of the channels C 2  and moved downwardly until they come to rest against a stop 104 in channel C 2 . The second plate 100 takes a position such that it overlaps the end of plate 100 in channel C 1 , so there are no gaps through which the wall could penetrate. Again, the excavation is made deeper by approximately the same amount as before. Finally, a third level of plates is lowered in channel C 3  until the plates 100 strike the excavation 20 bottom preventing further downward movement If desired, the plates can be driven below the excavation floor. The plates 100 in channel C 3  are furthest from the excavation 20 walls and overlap the bottom of plates 100 in channel C 2  to prevent undesired gaps. 
     Excavations of more than 20 feet but less than 40 feet could use two levels of reinforcement plates 100, or smaller plates 100 could be used for the shorter holes even though three levels of plates 100 are employed. 
     While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiments, it will be understood that various omissions and substitutions and changes of the form and details of the devices illustrated and in their operation may be made by those skilled in the art without departure from the spirit of the invention.