Патент USA US2115009код для вставки
April 26, 1938. R E_ DQNCAS'TER 2,115,009 BACKFILL FOR RETAINING WALLS Filed Aug. 22, 1956 F15 A I 1171 57;: \ .PZ/I’CELL anaasizr Patented Apr. 26, 1938 , r A 2,115,009 v0 UNITED stars 2,115,009 i 1..) > ‘ BACKFILL FOR RETAINING ‘WALLS Purcell Eli Doncaster, Fort‘ William, Ontario, 'Ganada 7 Application August 22, 2 Claims. This invention relates to back?lls for retaining walls and like engineering structures. There is almost no ?eld of engineering in which there is less uniformity and less accurate knowledge of basic factors than in retaining structures. Structures, which on the basis of accepted theory of pressure and resistance should have failed, have proved stable, and others built strictly in accordance with accepted practice and 10 apparently with liberal factors of safety have failed. ‘There are few, if any engineering structures in which factors of safety and liberal allowance for contingencies are used as generously as in retain 15 ing structures, and yet in general the amount of materials used in and the costs of the construc tion of these structures appear unnecessarily large in comparison to what is considered ade quate in other engineering structures. One of the main difficulties is that, under present prac 20 tice, there is no control whatever of the pressure exerted by the ?ll or backing materials on the re taining structure, and it is this di?iculty which it is the object of the present invention to remedy. According to the invention the back?ll is made 25 up partly of the usual ?lling or backing material and partly of relatively light hollow members placed between the retaining structure and the plane of rupture of the ?ll material. As these 30 hollow members have a much lower weight per unit of volume than the ordinary ?lling material, they not only allow the point at which the maxi mum pressure of the ?ll is exerted on the retain ing structure to be controlled, but they cause a reduction in the total outward pressure exerted. This permits the structure to be made smaller or of lighter materials than would otherwise be pos sible, and may permit the use of a different type of structure than would otherwise be possible, 40 such as steel sheet piling instead of gravity walls or wooden sheet piling instead of steel. In addi tion, where piling is used in soft foundation soil, it permits shorter piles to be used. The hollow members also present the advantage of reducing 45 the passive resistance required of the earth at the toe of the structure, which is of importance in the case of relatively soft or unresistant foundations. Finally, by reducing the amount of ?ll materials as to whose actions and pressures there is so 50 little clear knowledge, they reduce the factor of 5 ’ 1936, Serial No. 91,459 (01. 61—39) exert an outward pressure against the retaining structure. The invention will be more fully understood by reference to the attached drawing, in which: Figure l is a perspective view of a back?ll em bodying the invention. Figures 2, 3, 4 and 5 are views of various means for retaining the hollow members in position in the back?ll. In the drawing a retaining structure is indi 10 cated at l and the back?ll at 2. The back?ll is shown as being made up‘ partly of the usual back ?lling material whose plane of rupture is indi cated at 3 and whose plane of repose is indicated at 4. Between the plane of rupture 3 and the 15 inner surface of the wall I are placed one or more relatively light hollow members 5 which may be either tubular, as shown, or of any other cross section and may be made of any material which. is strong enough so that the members will not 20 collapse under the pressure exerted on them. As examples of suitable materials may be mentioned; plain or corrugated light steel pipe, such for in stance as used for culverts; concrete pipe; or‘ wood stave pipe, creosote treated or not accord 25 ing to water conditions. These light hollow members not only reduce the total outward pressure exerted on the retain ing structure but make it possible to lower the point of maximum pressure on the latter. Grav ity walls as illustrated are always made heaviest and their cross section is greatest near their base, and in the case of sheet piling, in connection with which the invention has perhaps its most im portant application, this lowering permits a re duction in the size of the tie rod and tie rod an chorages, which are expensive units. The lower ing of the point of maximum pressure is most marked in the cases where the hollow members rest on a stringer supported on piles, since the 40 members and the piles directly support a con siderable portion of the ?ll directly above the members. The hollow members may in certain cases be provided with holes in their lower are. This may 45 be useful in the case of quay walls and the like wherethere is water on one side which rises and falls, since the holes will allow the members to ?ll when the water rises and-empty easily when it falls, so that extraneous water pressures are 50 uncertainty in connection with the structure. The hollow members may be left free in the back?ll or held in any desired position by special avoided. Moreover, if the water table is high, the members will act to carry off- the water to means, in which case they have some effect in ?ll when the latter is open ended. reducing the tendency of the rest of the back?ll to weep holes in the structure or on the ends of the ‘ In Figure 1 the members are shown as being 55 2 2,115,009 free in the backfill and this is the way in which they may usually be arranged. However, in some cases, such as when the ?ll is in a plastic condi tion when placed, it may be necessary or desirable to ?x the members in position in the ?ll in such a way as to prevent its subsequent movement. Var ious ways in which this might be done are illus trated in Figures 2 to 5. When the members are so retained in position they tend somewhat to re duce the outward pressure exerted on the retain ing structure by the rest of the back?ll. In Figure 2 a hollow member is shown as being supported on piles and held against out ward movement by means of a tie member 6 ?xed to a suitable anchorage 7. In Figure 3 a member is supported on a cradle bent'8 and in Figure 4 on a different cradle bent 9, more completely restrict ing its movement. In Figure 5 a member is shown as being held against outward movement by piles driven into the back?ll between it and the wall and having their upper ends supported by tie members It] ?xed to a suitable anchor age “. ' » It will be understood that althoughrin Figures 5 2 to 5 only one hollow member has been shown a plurality of such members might be used.v ' I claim:--- 7 g ' 1. Retaining wall construction comprising a re 10 taining structure, a back?ll therefor, and light hollow members in said back?ll between the plane of rupture thereof and said retaining structure. 2. Retaining wall construction as de?ned in ' claim 1,.in which the hollow members are metal 15 pipes. PURCELL ELI DONCASTER.