US3250075A - Method of retaining wall construction and anchoring - Google Patents

Description

May 10, 1966 s.':-:. WEBB ETAL METHOD OF RETAINING WALL CONSTRUCTION AND ANCHORING 5 Sheets-Sheet 1 Filed Sept. 26, 1963 /x i Mw w a 6 5 M M N O W T N NE on w H m W 7 66 A Mw/M WM.

May 10, 1966 s. E. WEBB ETAL 3,250,075

METHOD OF RETAINING WALL CONSTRUCTION AND ANCHORING Filed Sept. 26, 1965 5 Sheets-Sheet 2 ATTORNEYS METHOD OF RETAINING WALL CONSTRUCTION AND ANCHORING May 10, 1966 s. E. WEBB ETAL 5 Sheets-Sheet 3 Filed Sept. 26, 1963 F/rs, 5,4.

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METHOD OF RETAINING WALL CONSTRUCTION AND ANCHORING Filed Sept. 26, 1963 5 Sheets-Sheet 4 I 51 PZA/VE ATTORNEYS May 10, 1966 s. E WEBB ETAL METHOD OF RETAINING WALL CONSTRUCTION AND ANCHORING Filed Sept. 26, 1965 5 Sheets-Sheet 5 vbrll),

5M WON map E 05 W W 2 m m w n r f? 4 ya u m United States Patent 3,250,075 METHOD OF RETAINING WALL CONSTRUCTION AND ANCHORING Spencer E. Webb, Los Angeles, and Joseph H. Lipow,

Inglewood, Calif.

Filed Sept. 26, 1963, Ser. No. 311,897 1 Claim. (Cl. 61-39) This invention relates to a system. for producing a ground-mounted tension anchor and systems for constructing retaining walls with tension anchors.

Retaining walls may be classified in two broad categories; first, the type installed against cut banks of ground .to retain the cut bank from falling into the excavated portion, and second, the type where the wall is constructed and the area behind and uphill from the wall is filled to produce, for example, a large level plot than could otherwise be obtained. Each of these types of walls conventionally employ a footing of substantial'size for supporting the weight of the wall and a cantilever portion for resisting the overturning moment of force produced by the retained ground. When the height of the retaining wall is relatively limited the conventional means for construction are generally adequate and no unusual procedures need to be used that would incur unusual construction or material costs.

However, for relatively high Walls of the first type, i.e., cut bank retaining walls, it is generally necessary either to slope the bank or to use shoring for restraining the cut ibank during continued excavation and before the wall is erected. This shoring is in itself expensive and also interferes with the continued excavation and final wall construction. Further, an extremely high cut bank retaining wall must be of such extreme size proportions, for example, the-wall thickness at the base, that the cost of materials for such a wall often is prohibitive.

With relative high retaining walls of the second type, i.e., back filled retaining walls, it is conventional to use tiebacks for assisting in supporting the wall to thereby obviate the necessity of the wall being of the extreme size proportions mentioned above. These tie-backs, also commonly known as dead men, are usually comprised of a post or the like anchored in a ground a substantial distance behind the retaining wall and a cable or the like extending between the post and the wall. Since there may be a series of these tie-backs horizontally spaced along the wall and each generally positioned above the orginial ground level, the tie-backs substantially interfere with the operations of back filling with earth and properly compacting the backfill. Good construction practice and many building codes require that the fill earth be placedin lay- -ers of-limited depth and compacted between layers and,

have also been used on cut bank type retaining walls by digging trenches back from the wall, setting an anchor member, running a cable in the trench from the wall to the anchor member, and then filling and compacting the trench.

It is an object of this invention to provide a novel systern for producing a ground anchored tension member and employing such. tension member in novel systems of retaining wall construction. I

Another object of this invention is to provide an inexpensive and consistently efiective method and apparatus forming an anchor in the ground to which tension may be applied.

A further object of this invention is to provide novel systems for constructing relatively high retaining walls in multiple stages wherein novel type anchors are employed but do not interfere with or require back filling and com- Patented May 10, 1966 pacting and the need for shoring excavated walls is usually eliminated.

Still another object of this invention is to provide a novel system for anchoring temporary shoring to an excavation wall for minimizing the obstructions formed by shoring and assisting in construction of the final wall.

Other and more detailed objects and advantages of this invention will appear from the following description and the accompanying drawings.

In the drawings:

FIGURE 1 is a perspective view with portions broken away and shown in section of a tool for creating the cavities in the ground that are employed in the systems of this invention.

FIGURE 2 is a sectional elevation view of the anchor system of this invention although the view is not neces' sarily oriented in the most common angular position with respect to a vertical plane.

FIGURE 3 is a sectional elevation view similar to FIG- URE 2 illustrating a modified form of the anchor arrangernent of this invention.

FIGURES 4A, 4B and 4C are diagrammatic elevation views of the progressive steps of our system for constructing a cut bank type retaining wall.

FIGURES 5A, 5B and 5C are diagrammatic elevation views of the progressive steps of our system for constructing a bank fill type retaining wall. FIGURE 5D illustrates a modified form of this type of retaining wall.

FIGURES 6A, 6B and 6C are diagrammatic elevation views of the progressive steps of our modified form of system for constructing a cut bank type retaining wall,

FIGURES 7A, 7B, 7C, 7D and 7E are diagrammatic elevation views of the progressive steps of our system for shoring the walls of an excavation and constructing a retaining wall for the excavation.

Referring now more particularly to FIGURE 2, the tension anchor assembly, generally designated 10, of this invention is constructed by boring a hole 11 in the ground in the desired direction and to the proper depth and then creating an enlarged cavity 12 at the desired location in the hole 11 which is generally at the bottom. A tension member such as a rod 13. of the proper length and having an enlarged assembly, generally designated 14, mounted on the lower end thereof is then lowered into the hole 11. Fluid concrete 15, or any other suitable fluid material that hardens to a mass having substantial compressive strength, is then introduced into the'hole 11 in a sufficient quantity to fill cavity 12 and at least a portion of hole 11. After the concrete 15 has hardened and is thereby secured to the rod 13, an upward tension force may be applied to rod 13 causing the mass of concrete within cavity 12 to compress the portion 16 of the ground above the cavity thereby transmitting the load to the surrounding ground.

The depth of hole 11 and thus the distance between cavity 12 and the surface of the ground will vary for the particular use that is to be made of the anchor assembly 10 and the condition and type of soil encountered. It has been found that if the cavity 12 is relatively near the surface then an applied tension load will cause a cone of earth to be sheared from the surrounding ground and lifted thereby resulting in the anchor assembly failing to sustain any further tension load. While the actual shape of such cone of earth will be irregular, in general it will be a cone having an axis aligned with the tension rod 13 with the angle between the tension rod 13 and the conical surface substantially equal to the shear angle of the soil. The tension required to produce this type of failure is approximately equal to the weight of the volume of earth within the cone plus the shear forces. However, it is specifically contemplated by this invention 'that the cavity 12 of the anchor assembly 10 be at a depth greater than that which would result in failure by lifting 'Of the anchor is achieved far exceeds that which may be applied when failure occurs in the form of the lifting of a cone of earth. By way of illustration it has been found that in most soil conditions a depth of about 15 feet is the minimum preferred depth. Also by way of example and not limitation, a tension anchor assembly was constructed wherein the bore 11 was of five-inch diameter and 16 feet deep, the cavity 12 was of 19-inch diameter, and sand and three-eigh ts inch pea-gravel were used in the concrete. This anchor assembly was able to withstand a continuously applied tension load of 50 tons for 24 hours and a tension load of 75 tons applied for a short duration before the load test was discontinued.

The enlarged assembly .14 may be of any convenient form capable of adequatelytransmitting the load between the concrete mass and the rod. For example, it has been found adequate to employ three flange plates 17 spaced from each other by heavy ribs 18 with the lowermost plate 17 engaging a nut 19 on the tension rod13. A spacer 20 may be used to properly position the assembly 14 from the bottom of the'hole. The wall 21 or the like that is to be secured to the ground by the anchor member may be provided with a sleeve 22 through which rod 13 passes and an appropriate plate 23 is used to transmit the force from the tension adjusting nut 24 to the wall.

In the modified form of tension anchor assembly 10a illustrated in FIGURE 3, a plurality of cavities 12a, 12b and 120 are provided at different depths for increasing the tension that may be applied on the rod 13a. This modification is particularly useful where extreme tension forces on the rod 13a may be anticipated or the soil conditions are such as to be easily compressible. The use of a plurality of cavities results in distributing the tension load applied to the rod 130: over a plurality of areas and strata of ground. FIGURE 3 also illustrates a modified form of enlarged assembly 14a which may be employed wherein arm members 17a are hinged to the rod and spring biased to extend outwardly into the adjacent cavity for adequately transferring the load from the surrounding concrete a to the rod 13a. FIGURE 3 also illustrates completely filling the hole 11a with concrete to the surface which While not structurally necessary is preferred for preventing caving in of the walls of the hole or water filling the hole to weaken the compressive strength of the earth above the cavity.

Referring in detail to FIGURE 1, a cavity tool, generally designated 30, is illustrated for creating the heretofore described cavity 12. The'physical construction of tool 30 forms no part of this invention and is illustrated and described merely for purposes of disclosing one mannet in which the cavity 12 may be created. It will readily appear to those skilled in the art that other devices may be used instead of tool 30 for properly creating cavity 12 without departing from this invention. Tool 30 includes a mandrel 31 adapted to be attached to an appropriate drill string for lowering into the hole 11. Mandrel 31 has a central bore 32 and a flange 33. A lower mandrel 34 has an upwardly extending tube 35 for closely surrounding the downward extension of mandrel 31 and a key 36 joins mandrel 31 and tube 35 for permitting relative axial movement therebetween and preventing relative rotation. Lower mandrel 34 is also provided with a central bore 37 communicating with laterally extending ports 38. A thrust bearing 39 is connected to the top portion of mandrel 34 and the upper flange is rotatable relative to the mandrel. A plurality of blades 41 extend longitudinally between and are pivotally connected toflanges 33 and 40. In their normal position blades 41 are bowed slightly outwardly. Each blade 41 is provided with an appropriate cutting edge 42. The tool is lowered into the hole 11 and with mandrel 34 engaging the bottom of the hole the tool is rotated by means of mandrel 31 which is connected to the drill string. A downward force is applied to the drill string, and therefore to mandrel 31, during rotation thereby forcing the blades 41 to bow outwardly and engage the wall of the hole. The preferred operation is to draw a suction on the drill string during rotation whereby the cuttings by blades 41 are drawn through ports 38 between the blades and upwardly through bores 37 and 32 and the drill string. Continued rotation and application of downward force causes the tool 30 to ream the cavity 12 to the desired dimensions. The tool 30 is then removed and tension anchor assembly 10 installed as heretofore described. In this manner the desired shape of cavity 12 is created wherein the cavity is essentially concentric with the hole 11 and of the proper overall diameter to achieve the desired characteristics of the tension anchor.

. plane 53 is at a particular angle to the horizontal and may be calculated :by soil engineers or required by the appropriate building and construction codes. In the construction system of this invention a first stage of ground 54 is excavated at the top of where the retaining wall will be located and only to a vertical depth which is practical and perimissable for avoiding complex shoring of the wall 55 of the excavation. Tension anchor assemblies 10, diagrammatically illustrated in these figures, are then installed at the upper and lower limits of this first excavation in the manner heretofore described. These tension anchor assemblies 10 are positioned at a substantial angle to the verticle and extend to a depth beyond the designed slip plane 53. The tension anchor assemblies 10 are spaced horizontally along the excavation at appropriate intervals for producing the desired retention forces. A retaining wall segment 56 of a height equal to the wall 55 of the excavation is then installed. The wall 56 is secured to the tension anchor assemblies 10 and the appropriate tension is applied to hold the wall in place. Wall 56 may be of any convenient type such as but not limited to prestressed concrete, precast concrete, cast-in-place concrete, masonry block, steel panels and the like. A second stage of earth 57 is then excavated immediately in front of wall 56 to the desired depth as heretofore described. Tension anchor assemblies 10 are then installed at horizontally spaced locations along the lower end of the excavated wall 58 and a retaining wall 59 is installed in the same manner heretofore described. The top of wall 59 is connected to the base of wall 56 by an appropriate structural member 60 for transmitting the outward load on the top of wall 59 to the tension anchor assemblies 10 extending from the base of wall 56. Structural members 60 may be of any convenient form and may even include an impervious apron to prevent water from seeping down behind wall 59 from the area in front of wall 56. This procedure of excavating in stages, installing tension anchor assemblies 10 at base of each excavation, installing retaining Wall segments 61, 62, etc., and connecting the wall segments with structural members 60 is repeated until the desired new grade level 52 is reached. An appropriate footing 63 may be provided at the base of the lowermost retaining wall.

segment to prevent undesirable erosion and to support the vertical load developed by the wall segments and anchor assemblies. For clarity of illustration the retaining walls 56, 59, 61 and 62 have been illustrated as being laterally spaced a substantial distance whereas in actual practice such spacing may be reduced to the minimum necessary to adequately support the previously installed retaining wall segment during excavation therebelow.

The retaining wall system of FIGURES 5A, 5B and 5C is for retaining a bank of fill earth in an area 70 above the original ground line 71 to create a new grade level 72. Without a retaining wall, generally located by phantom line 73, the area 70 could only be filled to the design slip plane 74 and a large area of the new grade level '72 would be lost. As is conventional the original ground line 71 is benched as shown by phantom lines 75 for obtaining an optimum backfill and compaction. A wall segment 76, of any of the convenient types heretofore described with respect to wall segment 56, is constructed to a limited height. If the wall segment 76 and subsequent wall segments are to be of a preformed type rather than formed in place it is preferred that vertical columns, coinciding with phantom line 73 be set in concrete footings 77 before wall 76 is installed. The columns are longitudinally spaced at appropriate intervals for supporting the wall segments and of a total height equal to the proposed total wall height. A plurality of tension anchor assemblies 10 are installed at the base of wall segment 76 and extend at a substantial angle to the vertical into the area :behind the retaining wall. Where the heretofore-described columns are employed the tension anchor assemblies 10 are preferably located at each column and connected thereto. The wall segments are then placed behind the columns. A first stage of earth 78 is then filled in and compacted behind wall segment 76 and to the height of wall segment 76. Wall segment 76 is preferably of a height and adequate strength for permitting this backfill and compaction procedure without overturning the wall segment and without requiring bracing of or tie-backs to the top portion of this wall segment. Further, the wall segment need not be of sufiicient strength independent of further anchoring to resist the overturning moment caused by the retained ground when the wall is finished to its complete height as would be required with conventional construction methods. Referring specifically to FIGURE 53, a second series of horizontally spaced tension anchor assemblies 10 are then installed from the top of wall segment 76 and through the already compacted ground 78. A second wall segment 79 of relatively the same height and structural characteristics as wall segment 76 is then installed on top of and connected to wall segment 76. The second stage of earth 80 is then backfilled and compacted. This procedure of installing tension anchor assemblies 10 at the top of the last-placed wall segment, installing retaining wall segments 81, 82, etc;, and backfilling and compacting ground areas 83, 84, etc. is repeated until the desired new grade 72 is reached. In this manner the area behind the retaining wall that is being 'backfilled and compacted is completely unobstructed by tie-backs or the like and therefore backfilling and compaction may be readily and efiiciently completed. Each Wall segment is tied back both top and bottom by tension anchor assemblies 10 for supporting the loads of subsequent backfilling and compaction of higher levels and for retaining the earth after the entire retaining wall and backfill has been completed. Thus, each wall segment may have the structural characteristics heretofore mentioned. I i 7 FIGURE 5D illustrates a modified form of the'backfill type retaining wall system illustrated and described with respect to FIGURES 5A, 5B and 5C. In this system of FIGURE 5D it is again preferred, although not essential, that a plurality of horizontally spaced columns 90 be set in concrete 91 at the location of the base of the Wall. A first wall segment 92, again of-any type and of limited height,-is then installed behind the columns. A tension anchor assembly 10 may be installed at each column 90 at the base of wall segment 92. The first stage of backfill and compaction to the top of wall segment 92 is completed and then a second series of tension anchor assemblies 10 may be installed along the top of that wall segment. A second series of columns 93 are then set in concrete 94 in the filled and compacted ground. A second wall segment 95 is then installed behind columns 93 and tension anchor assemblies 10 are installed from the top of wall segment 90. This series of procedures is continued until the desired new grade 96 is reached. A structural member 97 may be employed between the top of each wall segment and the bottom of the next higher wall segment similar in purpose and construction to the heretofore-described structural member 60, and therefore it is obvious that the anchor assemblies 10 may be installed at the base of each successive wall segment rather than at the top of each preceding wall segment. The successive wall segments have been illustrated as being spaced a relatively substantial distance for clarity of illustration, whereas in actual practice there generally will be a greater proportional difference between the height of a wall segment and its distance from each-adjacent wall segment.

Referring more particularly to FIGURES 6A, 6B and 6C, a modified form of retaining Wall system for retaining a cut bank is illustrated and in contrast to the system of FIGURES 4A, 4B and 40 the completed wall will be substantially vertical. A first stage excavation of ground 101 is made leaving an exposed wall 102 of a height having all of the characteristics of the heretofore described wall 55. Tension anchor assemblies 10 are installed at the top and the base of exposed wall 102 and preferably extend in a more horizontal direction than any of the heretofore-described tension anchor assemblies 10. The tension anchor assemblies 10 also preferably extend a depth beyond the design slip plane 103 drawn from a location that will be the base of the completed retaining wall. A wall segment 104 of any convenient type such as those described with respect to wall segment 56 is then installed against wall 102. Means are provided for supporting some of the downward vertical load on wall segment 104 and these means may include a cantilever beam 105 connected at one end to the wall segment 104,.supported intermediate its ends by means 106, and connected at its other end to the ground such as by a vertically extending tension anchor assembly 10. The top and bottom of wall segment 104 are secured to the tension anchor assemblies 10. A second stage excavation of ground 107 is then made to the desired depth and extends beneath wall segment 104. Another series of horizontally spaced tension anchor assemblies 10 are installed at the base of this excavation and a second wall segment 108 is installed below wall segment 104. In FIGURE 6B wall segment 108 is specifically illustrated as a preformed type wall which is moved into place, although it is to be understood that a cast-in-place type wall may be employed. It is preferred that means 109 be provided at the top and bottom of each preformed type wall segment for interlocking and connecting such wall segment with previously and subsequently installed wall segments. This procedure of excavating in stages, installing tension anchor assemblies 10 at the base of each excavation, and installing a Wall segment 110, 111, etc. is repeated until the desired new grade level 112 is reached. An appropriate footing 113 may be provided at the base of the lowermost retaining wall segment to prevent undesirable erosion and to assist in supporting the entire wall in the vertical direction. The cantilever means attached to Wall segment 104 may then be removed. It may be seen that it is preferred to place tension anchor assemblies 10 at an angle more closely approaching the horizontal so that there is no excessive downward force on the attached wall segment. In fact, under many conditions, it may be possible to develop a sufiicient frictional force between the wall segment and the excavated wall to adequately support the wall segment while subsequently excavating therebelow thereby eliminating the necessity for any vertical support means such as the desired cantilever beam 105.

Referring now to FIGURES 7A, 7B, 7C, 7D and 7E,

a system is illustrated for shoring the walls of an excavation during the excavation and using the shoring means for completing a vertical retaining wall that may also be a structural wall such as in the basement of a building. A plurality of longitudinally spaced soldier beams '120 are installed along the desired line of the excavation and to a depth beyond the desired finished grade 121 of the excavation. The beams 120 may be driven into the ground or placed in drilled holes. A first stage of ground 122 is excavated including the area between the soldier beams 120 and to a small depth 123 behind the soldier beams. The depth of the excavation of ground 122 should be such that good workmanlike practice and building codes do not require shoring of the exposed wall 124. Appropriate lagging 125 is then installed behind and extends between the soldier beams 120. Lagging 125 may be of any convenient type depending for example on whether or not waterproofing of the final wall is required and in the drawings lagging 125 is illustrated as corrugated sheet steel. A tension anchor assembly is then installed at the base of excavation 122 and secured to the soldier beam 120. A second stage of excavation of ground 126 is then made to the heretofore-described desired depth. A second segment of lagging 127 is installed and a second series of tension anchor assemblies 10 are installed at the base of the excavation of ground 126. This procedure of excavating to a limited depth in stages, installing lagging, and installing tension anchor assemblies is repeated till the desired finished grade 121 is reached. Thus, the entire excavation has been made without any shoring being positioned in the area of excavation to obstruct the excavation. Referring specifically to FIGURE 7D, appropriate bolts 128 may be installed on the soldier beams 120 for securing a form 129 at a location spaced from the lagging 125, 127, etc. A concrete wall 130 may then be cast in place between the form 129 and the lagging and surrounding the soldier beams 120. A footing 131 may also be provided around. the base of the soldier beams and the wall 130.

Having fully described out invention, it is to be understood that we do not Wish to be limited to the details herein set forth or to the details illustrated in the drawings since it will readily appear to those skilled .in the art that numerous modifications and combinations may be made Without departing from our invention which is of the full scope of the appended claim.

We claim:

In a method of constructing a relatively high Wall for retaining filled ground, the steps of: boring a hole in the ground at the desired base of the wall at a substantial angle to the vertical in a direction beneath the ground to be retained -by the Wall, enlarging the diameter of a portion of the hole at a substantial depth, securing a tension member in the hole by filling the enlarged diameter portion of the hole with a hard setting material, erecting a wall segment of a height capable of retaining earth filled therebehind to such height and equal to only a portion of the total wall height, securing said Wall segment to said tension member and applying tension to said member to securely locate said Wall segment, placing fill earth behind the wall and compacting the earth to the level of the top of the Wall segment, installing another tension member at the top of said Wall segment by boring a hole in the filled ground at a substantial angle to the vertical and enlarging the diameter of a portion of the hole at a substantial depth and securing such tension member in the hole by filling enlarged diameter portion with a hard setting materiaL, securing the top of said Wall segment to the latter said tension member and applying tension to the latter said member to securely locate said wall segment; and successively erecting additional wall segments at successive different vertical elevations to a desired total Wall height, back-filling and compacting earth behind each successive w'all segment, installing a tension member from the top of the previously installed Wall segment subsequent to such back-filling and compacting and before erecting the next successive wall segment therea-bove, and securing the base of each said successive wall segment to the top of next \previously erected wall segment and tension member prior to erecting the next wall segment.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Construction Methods (pubL) of November 1962, pp. 116, 117, and 118.

German Application to Bauer, DAS 1,104,905, 1961.

CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

JACOB SHAPIRO, Assistant Examiner.

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