US2875584A - Method for making structural foundations - Google Patents

Description

March 3, 1959 TuRzlLLo METHOD FoR MAKING STRUCTURAL FouNDATToNs Filed Aug. l2, 1955 INVENTOR. LEE TURZILLO A ORNEY IUnited ,States Patent O METHOD FOR MAKING STRUCTURAL FOUNDATIONS Lee Turzllo, Akron, Ohio, assignor to Intrusion-Prepakt, Incorporated, Cleveland, Ohio `Application August 12, 1955, Serial No. 528,074

6 Claims. ('Cl. 61--50) This invention pertains to the art of structural foundations or the like and more particularly to pier and abutment foundations and the method of constructing same.

The invention is particularly applicable to piers for bridges over water and will be described with particular reference thereto, although it will be appreciated that the invention has broader applications.

t t In the art of constructing such piers, it is desirable to have the lower end of the pier resting upon a massive and structurally sound body such as the bedrock which p acts to resist the downward force exerted by the struc-l `ture being supported without settling or shifting.

In some localities, there exist relatively thick sub-surface layers of stones, large rocks and boulders over the bedrock which make it practically impossible to extend the pier members to the bedrock or obtain a structurally sound body, as a base support for the pier. Such stones, p

`rocks and boulders do not have in and of themselves suicient strength to support large weights and they are `particularly subject to settling and shifting.

Heretofore, where such subsurface layer of stones and boulders existed, it has been necessary to either break up, remove, or drill a suiiciently large opening or passage `through the stones and boulders so that the pier members could pass through the layer to the bedrock itself. This is a very time-consuming and expensive op` plurality of large hollow structural members downwardly `through the earth to the upper surface of the sub-surface layer` of stones, rocks, or boulders, drilling a hole of a relatively small diameter and smaller than `that of the hollow member into such layer for a short distance and through one or more of the rocks and the spaces therebetween, flowing water under pressure into this hole to washout any silt, muck or other fines from the hole and any adjacent spaces between the rocks, to leave the spaces and hole iilled with water, pumping a owable grout or cement to the bottom of such hole to displace `the Water with the grout or cement, allowing the grout or cement to harden, drilling a new small diameter hole through the hardened mass of grout and rock to a space Atherebelow and through additional rocks, stones or boulders and the spaces therebetween, repeating the washing, grouting and drilling operation as many times as is ,necessary going deeper each time until bedrock is reached or until a consolidation of the layer of the rocks has been effected of a mass suciently large to actas a :Mutable footing for the hollow members. The result ice isV a solid mass of hardened grout and boulders at the lower end of the hollow member which, of itself, sustains the load of the member or transmits this load directly to the bedrock. Obviously the grouting may be stopped short of the bedrock, if desired, assuming that the mass of rocks consolidated is sufficient to carry the required load.

The hollow member may be filled with rocks and .then a grout pumped into the base, or a grout alone may be employed to till the hollow member.

If a plurality of hollow members has been employed, usually it is desirable to. drill through each member and then do the grouting simultaneously. The result in some instances will be, if the members are sufficiently close together, a solid grouted area integral from one member to the next.

The principal object of the invention is the provision of a new and improved method of providing a structural foundation where a sub-surface layer of stones and large boulders exists usually over the bedrock which enables a firm foundation to be constructed rapidly and at a relatively low cost.

Still another object of the invention is the provision of a new and improved method of providing a foundation which renders it unnecessary to break up or remove stones and large boulders which might be overlying the bedrock.

Still another object of the invention is the provision of a new and improved method of providing a firm rigid structural mass extending from the lower end of vertical support members to bedrock, where a sub-surface layer of stones and boulders overlie the bedrock.

The invention may take physical form in a number of different steps and combinations of steps, preferred embodiments of which will be described in. this specification and illustrated in the accompanying drawing which is a part hereof and wherein:

Figure 1 is a fragmentaryY cross-sectional view of the earths surface showing schematically the typical layers to be encountered down to the bedrock, and also showing `a fragmentary portion of a pier in position and illus trating a step of the present invention.

Figure 2 is a fragmentary View somewhat enlarged, similar to Figure 1, showing a further step in accordance with the invention.

Figure 3 is a View similar to Figure 2 but showing a still further step.

Figure 4 is a cross-sectional view somewhat similar to Figure 1 and showing a pier and foundation constructed in accordance with the present invention.

Referring now to the drawings wherein the showings are for the purposes of illustrating the invention only and not for the purposes of limiting same, Figure 1, as indicated, shows a typical cross-sectional view of the earth to which the present invention pertains. Thus such earth comprises a lower layer of solid bedrock 10, immediately thereover a layer of stones, rocks and/or large boulders 11, a layer of silt, mud or shale indicated generally at 13, and over this a layer 14 of water.

The various layers 11, 13 and 14, may have any vertical thickness as may be found at the particular site where the foundation is to be constructed. The present invention has nothing to do with such thickness nor with the specific materials from which the various layers are made up but deals solely with the provision of a solid foundation where a layer of rocks, stones and/or boulders 11 exist below the earth wherein'the expense and difficulty of forming a passage through the layer for vertical supporting members is high.

The layer of stones, boulders and rocks 11, hereinafter referred4 to generally as rocks, may consist of rocks of any and all sizes arranged in random fashion, with,

gewest spaces 12 between the individual rocks which are gen-V erally filled with a silt, mud or shale.

The pier for which the foundation is to be constructed consists, in the embodiment shown, of a large concrete box A resting on theA upper surface of thev layer 13 and extending upwardly to above the upper surface of the layer of water 14.

Thev box A may take any known or desired shape or configuration but in the* embodiment shown it has a large diameter vertical passage 24 defined by a metallic tube 25.

In carrying out the invention, the box A is located at the desired job site. Thereafter an elongated hollow conduit 30 is telescoped downwardly through the passage 2'4 and is forced downwardly through the layer 13 until the lower end of the conduit 30 cornes to rest on the upper surface of the boulder layer 11.

The conduit 30 preferably has a diameter, when the operations to be described are completed, having the load carrying strength and sideward stability later to be required of it. Dimensions of from 30 to 60 inches or more are not uncommon. The dimensions of the conduit 30 and the sidewall thickness may be as desired or as is required for the particular load to be carried, and as these dimensions form no partof the present invention, they will not be described further herein.

The outer conduit 30 may or may not be a supporting member in and of itself. In the event it is not a sup* porting member, it may be removed when the operations to be described are completed. Basically, however, the conduit 30 forms the outer covering of a leg or stanchion from` the box A to the upper surface of the layer 11.

The conduit 30 may be forced downwardly through thelayer 13 by any conventional known means such as water jetting,` hammering, or the like. It may also be made up of any number Iof sections placed end to end. Regardless of the way it is forced downwardly,` it eventually comes to rest on the upper surface of the layer of stones and boulders 11, in which case further eiorts using conventional means will not serve to force the conduit further downwardly.

The interior 31 of the conduit 30 may be cleaned of the mud or silt by any conventional or known means, although in some instances this step may be omitted. Alternatively, the lower end of the conduit 30 may have been closed during the forcing of it downwardly through the layer 13 and may not require cleaning of any mud or silt. In the event, however, that the lower end was left open, it is preferably cleaned. Preferably the in* terior 31 is lled with water at all times, the elect of such water being to resist any inward pressure on the conduit 30 and preventing its collapse.

In the embodiment of the invention shown, a vertical beam 33 of a length to reach from the upper surface of the rocks 11 to a point within the hole 24 is passed downwardly through the conduit 30 until the lower end comes to rest on the rocks 11. The beam 33 may be of any desired construction but is shown in the drawings as being of an H shape. In some instances the beam 33 may be eliminated, its primary purpose being to give lateral stability to the ultimate leg or stanchion.

It will further be apparent that to provide a passage Vfor the conduit 30 through the rocks 11 would be an expensive and time-consuming proposition. Heretofore it been necessary to remove or break up this overburden so that the conduit 30 and the beam 33, or both, could extend through the layer 11 and rest on the upper surface of the bedrock 10.

In accordance with the present invention, this is not necessary. Thus a tube 35 of a diameter substantially smaller than the diameter of the conduit 30 is then passed downwardly through the opening 24 and the opening 31 parallel to the bearn 33 to a point such that it comes to rest on the upper surface of the rocks 11. The length of this tube 35 is preferably such that it will reach4 to; a

point above the upper surface of the box A and above the earths surface prevailing at that point.

The purpose of the tube 35 is primarily that of a guide for the insertion of various tools, pipes or hoses downwardly through the conduit 30 to the stones and boulders 11, and as an exit or waste tube for the silt, sand and mud to be washed from the spaces between the boulders 11 as will appear. As such, the tube 35 and the beamV 33 could be combined, if desired.

It will be appreciated that any number of conduits 30 may be passed downwardly from the box A as well as beams 33. At this point in the construction, it will be obvious that the pier has little supporting strength primarily because the overburden layer 11 is not a firm foundation for the weights to be imposed upon the beams 33 and the conduit 30.

A drill, not shown but of conventional construction, is passed downwardly through the tube 35 and a hole (indicated by dotted lines 37 of Figure 1) is drilled downwardly a short distance through the rock layer 11. The drill may be of any desired size, smaller of course than the inner diameter of the tube 35, but a diameter of 4 to 6 inches for the drill has been found satisfactory in practice. The drill, depending on what it encounters, either forces the stones aside, if they are small, or forms a hole through one or more of the rocks and through the spaces 12 therebetween which, as above indicated, are lled with mud, silt, or sand. The vertical depth of the drilled hole may be less than one foot or to any convenient depth, but usually not over ten feet.

When the hole 37 has been drilled to a suitable depth, the drill is removed and a wash pipe 36 isl inserted through the tube 35 and into the hole 37 as far as it will go. The pipe 36 preferably has a substantially smaller diameter than the tube 35 and a diameter substantially smaller than that of the drill. The purpose of this dif'- ference in diameters is to enable the pipe 36 to pass easily into the hole 37 and to leave space between the inner surfaces of the hole 37 and tube 35 and the outer surfaces of the pipe 36, through which the mud, silt and sand may be washed upwardly to the top of the tube 35.

In accordance with the invention, water under high pressure is then forced or flowed through the wash pipe 36 to ilush the mud, sand and silt out of the spaces between the stones and boulders, the mud, sand and silt, as it is washed out, being carried upwardly through the space between the tube 35 and the pipe 36 to the top of the tube 35 where it is discharged with the water and disposed of. The water may be recovered, if desired, and again pumped downwardly through the pipe 36. Normally, the wash pipe 36 will work its way downwardly through the drilled hole 37 as the silt, sand and mud are washed out of the drilled hole and also out of the spaces 12.

This washing operation is continued until there is some assurance that all of the mud, silt and sand that can `be washed out of the spaces 12 has been washed out. This will generally be indicated by the appearance of clear water flowing out of the top of the pipe 35.

As indicated, the pipe 36 is forced or jetted to the bottom of the hole 37 during this washing operation.

As soon as it appears that all the mud, silt and sand i have been washed out of the spaces 12, a cement grout is forced downwardly through the pipe 36 under pressure to the base of the hole 37 and into the water lled spaces l2 between the rocks. This grout is heavier than water and physically displaces it which then flows upwardly through the tube 35 and out of the top.

A sucient amount of grout is pumped into the spaces 12 to insure that all of the water in the spaces has been displaced therefrom. Preferably an additional amount of grout is forced through the pipe 36 until the lowerend of the tube 35 is filled, e. g., l0 feet is lilled. Thereafter the pipe 36 is withdrawn to a point above the lower end of the tube 35 and water is again pumped therethrough to wash the grout out of the pipe 36 and out of the lower end of the tube 35 to approximately its lower end. Such grout is obviously washed out of the top of the tube 35 as was the mud, sand and silt.

At the completion of this grouting operation, it may be reasonably expected that a grouted area as defined by the lines 40 of Figure 2 will exist. The grout in the area 40 is then allowed to solidify.

The grout, in accordance with the invention, s of the type which will pump readily over relatively long distances, will flow through relatively narrow spaces without appreciable settling, will harden under water, and will not shrink when it hardens.

Ordinarily such a grout will consist of Portland cement, a pozzolanic ily ash having a relatively low carbon content, and other additives such as described in U. S. Patents No. 2,588,248, 2,434,301, 2,434,302, all assigned to the assignee of this application. Any of these grouting compositions,` either singly or in combination, have been found to fulfill the requirements of the present invention, and particularly al grout which, when it hardens, will not shrink. lf the grout should shrink as it hardens, it will pull away from lthe boulders leaving water filled spaces between the grout and the boulders and result ina poor foundation. On the other hand, with a grout which does not shrink but, in fact, expands a slight amount, a firm bond between the hardened grout and the boulders results.

t The drill is then reinserted in the tube 35 and a hole 42 is drilled through the now solidified grout in the area 40 to an unsolidied area below the area 40. This hole is shown generally by the dotted lines 42 of Figure 2.

` Upon the completion of the drilling of this hole 42, the drill is removed and a wash pipe 36 is again inserted in the tube 35 down to the bottom of the hole 42. High pressure water is again forced into this wash pipe 36 to remove silt, muck or sand from between the spaces between the rocks 11. Upon the completion of this washing, a grout as above described is forced under pressure into the water iilled spaces between the rocks 11. The area which may reasonably be expected to be grouted is indicated by the numeral 46 of Figure 3.

The grout in the area 46 is then allowed to harden and if the grouted area 46 is not sufficiently large and/ or does not reach to the bedrock 10, the drill is again inserted in the tube 35 and a hole 48 is drilled through the solidied grouted area 40 and 46 down to the ungrouted area below the grouted area 46. The same washing and grouting procedure is again repeated.

These operations are continued until the grouting material has reached and is in contact with the bedrock 10, or until there exists a sufficiently massive grouted area below the end of the conduit 30 and beam 33.

This may be determined by drilling core samples or by virtue of knowing the depth of the bedrock from the surface of the water and the depth of the final grouting operation.

Following any of the grouting operations above described, or before the first grouting operation, gravel or other rocks may be poured into the conduit 30 so as to completely fill the conduit 30 and the tube 25. This gravel may be packed or otherwise tamped in position, or the force of gravity may be allowed to position it. Thereafter a grouting material as above described is pumped downwardly through the tube 35 and allowed to work its way upwardly through the aggregate in the pipe 30. lf desired, the pipe 35 may be gradually withdrawn so that its end is always below the upper surface of the grout. As the grout rises in the tube 30, it displaces the water thereover. Alternatively the tube 35 may be withdrawn leaving the pipe 36 extending to the base of the conduit. The grout vis then pumped through the pipe 36. Figure 6 shows a grouted area 47 to bedrock and conduit 30 grouted as at 50 to the top of the box A.

Using the present invention,'it has been possible/to obtain what is in effect a monolithic concrete structure extending from or adjacent to the bedrock 10 to the top of the box A reinforced with steel beams from the box A to the upper layer of the solidified stones and boulder overburden 11.

It will further be appreciated that if a plurality of conduits 30 are used and are sufficiently close together, it will be possible to obtain a monolithic concrete structure thro-ughout all of the boulder overburden underlying the box A so that in effect each pipe 30 and each beam 33 will be resting upon the same solid mass of hardened grout and boulders. 4

In effect, a base will be provided for each pier having a maximum load bearing characteristic generally equal to that of the bedrock itself.

The invention has been described with particular reference to preferred steps to carry out the invention. Obviously modifications `and alterations will occur to others upon a reading and understanding of this specification, such modifications and alterations differing substantially from the specific steps described, and it is my intention to include all of such modifications and alterations insofar as they come within the scope of the appended claims.

Having thus described my invention, I claim:

l. A method of providing a firm foundation for a pier or the like where a relatively thick layer of large rocks and line material overlay the bedrock, and over that a layer of mud or silt, comprising the steps of forcing a conduit through the mud or silt to the upper layer of the rocks, placing a smaller diameter guide tube in such conduit to extend to the upper surface of the rocks and line material, inserting a drill through such pipe and drilling a hole through the rocks and fine material for a definite distance, inserting a still smaller diameter wash pipe through such guide tube and into the drilled hole, owing water under pressure through such pipe to wash the tine material from between the rocks out through the space between the pipe and tube and thereby form spaces between the rocks, forcing a tiowable grout through such pipe to displace the water now in the spaces between the rocks, allowing such grout to harden, drilling through the hardened grout and rocks to an area therebelow, insertinga wash pipe in the guide tube to force water under pressure into said area to wash fine material therefrom to form spaces between the rocks, filling the washed out spaces with a owable grout, allowing the grout to harden, and .repeating such operation until a grouted area exists below the lower end of the conduit sufcient to support the loads to be carried thereby.

2. The combination of claim l wherein the conduit is then filled with aggregate and a tiowable grout is pumped to the bottom of the conduit and allowed to work its way upwardly through such aggregate to provide a solid monolithic structure from the upper end of the conduit to the bedrock.

3. The combination of claim l where the entire area .below the conduit to the bedrock is Washed and grouted.

4. A method of providing a firm foundation for a column where water, mud, silt and large rocks overlie the bedrock, comprising the steps of sinking a conduit through the water and silt to the upper surface of the rocks, positioning a supporting beam in such conduit also to rest on the upper surface of the rocks, positioning a guide tube in the conduit to rest on the upper surface of the rocks, filling the conduit with aggregate, pumping a flowable grout to the lower end of the conduit allowing such grout to work upwardly through the aggregate to displace the water in the conduit, inserting a drill in the tube and drilling a hole into the layer of mud, silt, and rocks, forcing water under pressure into such hole to wash mud and silt from between the rocks to form spaces between the rocks, forcing a flowable grout into such spaces to displace ther water', allowingl the grout to harden,` drilling a` hol'evthroughr the hardened grout to an area in the mud, silt and rocks therebelow, forcing water under pressure to lwash the mud and sil-t from between the rocks to form spacesV therebetween, forcing a grout into such water illed spaces, and repeating such operation until a solid monolithic structure exists from the upper end of the conduit tothe bedrock. f

5. A methodof providing a subsurface foundation for piers orthe likefwherein a strata of large rocks with earth lilling the spaces therebetween overlays the bed-rock comprising. the` stepsf of sinkingl a hollow conduit through the earth to the upper surface of said strata, drilling a hole of.less dia-meter than said conduitl partially through said strata, washing the earthV from said spaces between the rocks by water under pressure, and while the water still remains in saidspaces, forcing a purnpable grouting materialA of. a; type which hardens under water and does not shrink upon hardening, into said drilled hole to displace said water andl to llr said spaces with said grouting material, allowing the grouting materialv to harden thereafter extendingy saidrstmentioned hole further into said strata and: beyond the: lowermost point of said hardened grout, washing the earth from the spaces between said rock below said hardened grout by water under pressure and while the waterstillremains in said spaces pumping said groutingv material intov said spaces and repeating such operationsv until a continuous grouted area comprised of a mixture of; rock and hardened grout in the spaces therebetweenxexist between thebed-rock and the lower end ofv said. conduit.

6. methodsoftproviding: a foundation below the surface of. the earth wherein a strata oflarge rocks overlays the bed-rock, the spaces between'the rocks being fil-led by they earth comprising Vthe stepsy ofA sinking a largediameter tube through the earth to the upper surface of said strata, drilling a hole into the strata of rocks for a distance less than the vertical height-"of sa-idlstrata,-forcing water under pressure into such hole to wash thel earth out of such spaces andy while said water is inl saidspaces, forcingl a owable grout capable of hardening under water into the hole to displace the water inthe washed outspaces and replace it with said grout,4 allowing the grout to harden,

lthen drilling aV continuation of said hole through such hardened grout to a point below the hardened grout and a further partial distance into said rocks, again forcing water into such hole to wash out the earth from said spaces, and while said water remains in said spaces, forcing said flowable grout `into saidl spaces to displace the water and replace it with said grout,y allowingy the grout toy hardenvand repeating such sequence of operations until acontinuous layer of rock and hardened grout exist from the bed-rock tothe lowerk surface of the conduit, filling the conduitwith anaggregate and pumping a llowable grout-into the bottom of lsuch conduit and allowing. the grout to work upwardlythrough the aggregate to displace the water inthe tube with a'hardenable grout.

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