US1836083A

US1836083A - Method of forming piling

Info

Publication number: US1836083A
Application number: US360135A
Authority: US
Inventors: Anthony P Miller
Original assignee: Individual
Current assignee: Individual
Priority date: 1929-05-03
Filing date: 1929-05-03
Publication date: 1931-12-15
Anticipated expiration: 1948-12-15

Description

Dec. 15, 1931. A. P. MILLER METHOD OF FORMING FILING Filed May 5, 1929 INVENTOR Azzifiany 1 1ml BY I ATTORN EY and caving action.

Patented Dec. 15, 1931 ANTHONY r. MILLER, 0F 'ILEASANTVILLE, NEwJJnRsEY METHOD 01 FORMING FILING Application filed ma 3, 1929 Serial Mateo A35.

The present invention is concerned with a method of installing mushroom piling, and while capable of a Widerange of utility is particularly concerned with the installation of such piling in fine water-bearing sand, such, for instance, as beach sand.

It is well recognized that fine sand, particularly water-bearing sand, presents'peculiar problems insofar as excavation work of any kind is concerned. If the'sand is saturated with water it will run and drift freely and it is difficult to work in such sand without -using some method of enclosure to prevent the sand from filling the excavation.

Attempts have been made to overcome these difliculties and to devise methods of installing concrete mushroom piling inwater bearing sand without the use of sheathing and by the expedient of lowering the water level in the sand to the line of the pro posed piling excavation, then digging down to the water level and continuing to'dig until the'wet sand at the bottom of the hole forms a mushroom by its natural running Such a method, disclosed in the prior patent to Ferry & Miller,

No. 1,593,445, dated July 20th, 1926, has' proven unreliable in practice." 4

One of the principal difficulties of the method is the fact that when a well-point system is used to lower the water level over a predetermined area in which it is proposed to install a series of pilings, the water level in the sand is never horizontal. That is to say, the capillary action of the fine sand results in the creation of a. water level which gradually slopes from the wellpo'ints towards the center of the area to be dried; This condition of a sloping water level in the sand results in the formation of anextremely lop-sided mushroom since the excavation Will tend to unduly cave at the side nearest the higher water level point and will fail to cave at the sidenearer the lower water level point.

A contributory factor here is the Water flow toward the well points, which. even assuming a nearly horizontal water level will wash sand from one side ofthe' mushroom toward the other, thereby causing caving at one side and filling in at the other a resultant tendency toward lop-sidedness! Even assuming therefore that all mush room pilings of a set could be simultaneous- 1y sunk and installed while the water level remains stationary, all of these pilings would have lop-sided mushrooms impairingnot only their ability'to rsis'tzcompres sion but their ability to'serve' as anchorages for 'a superimposed building structure;

With such an eccentrically-loaded footing the slightest settlement in the base' would cause a bending moment in thepill'ar or fracture the pillar adjacent the mushroom or cause it to shear off at the mushroom. The eccentricity of the mushroom would' be diflicult todetect even though the engineers maintained a careful inspection onjthejo'b and the. fracture of several pilings in one footing would ofcourse create a veryserious and dangerous condition. p a Asa practical matter the water level can never be maintained at exactly the point'de sired. The well points'are always working and tending'to' lower thewater level, Whereas the'pilings are installed successively and-not simultaneously. The result is that the bot tom of one mushroom piling will'be at one level and the bottom of the next one will be ata level considerably below it, due not only to the sloping =water level,;-but-to the con tinuously lowering waterlevel' in the sand. The result of this condition-isthatlarge mar gins ofsafety must be'figured in construct-j ing pilings. The liner shells whichare used '85 for the pillarmolding shafts of the piling excavationsarenever of the' right length; A superimposed structure will be better sup-' ported at certain pointsthan itwi-ll atothers. The cost of construction and the materials for any given installation can never be accurately calculated in advance. a I i The pressure at the base'of the piles distributes itself downwardly through the soil; at an angle of approximately 60 (inbeach sand). The piles when used for foundation footings are placedclose together. In conse quence the pressure through-the soil from the higher piles would be transmitted tothe mushroom of certain' o f the lower'pilesyin- I of the patented method is the fact that by such method concrete is poured into the saturated sand at the bottom of the mold in order to form the completed piling. When this heavy material is poured into place the sand at the bottom of the mold splashes and runs, some of the concrete sinks into the sand, the carefully prepared mushroom bottom of the mold is broken down, additional sand shales or cavesin on the concrete and the final result is a lop-sided mushroom of non-homogeneous formation, and 'consistmg simply of a plurality of loosely separated concrete fragments having no coherence and little structural strength.

- Another disadvantage of the prior meth- Qds has been the fact that neither the size nor the shape of the mushrooms have been uniform and even the most careful practice of prior methods has f-ailed to insure any real uniformity in mushroom sizes and shapes, much less in length of pillars or in load sustaining ability.

- accordance with the present method 1 overcome all of the above noted difficulties in that 1 render the depth of the piling excavations independent of the water level in the sand, produce symmetrical mushroom enlargements at the bottom cfthe excavations, install a series of pilings of equal depth and strlrctural strength and produce a hom'ogeneousconcrete mushroom anchorage at the bottom of the piling.

' In carrying out the method I reduce the water level inthe sand to a point below the depth of the proposedpiling excavation and maintain it below such depth in the entire area where piling is to be installed. The vertical boreo'f the piling excavation is then drilled to any desired depth which may be accurately determined by prior engineering calculations. a v

Having drilled the vertical bore I insert a'metalline-r or shell, this shell being preferably of a novel construction which permits it to be readily slipped up and down, in the bo r'e until it reaches exactly the proper positi-on. Shells-of standard size may be used inasmuch as the exact bore length is always known-in advance before excavation is startedand in no manner dep'ende'nton or controlled by variations in the water level in the sand. c :lnorder to form the mushroom enlargement I partially fill the bore with water up, to a definite and predetermined level, I then introduce an agitating tool and agitate the otherwise inner body of water which is slow 1y draining through the sand toward the artificially produced lower water level. The

water agitation whether it be in-the nature of a vertical wave action or a swirling motlon or a comblnation of both Wlll tend to scour away or erode the sand walls of the unlined lower portion 0f the bore, thereby radially enlarging the upper portion of the unlined lower end of the bore and gradually filling up the bottom thereof with the sand displaced "and washed down by the scouring.

With each stroke or revolution as it may be of the agitating means that lateral portion of the'fsand wall of the'bore which is in contactwith the water will be radially enlarged. Similarly at each stroke or revolution the level of the body of water will be lowered due first to the progressively increasing bore diameter and second to the water drainage through the sand.

Agitation is preferably stopped while :a

certain amount of water still remains in the bottom of the hole, this water acting as it drains outthrough the sand to leave a symv metrically rounded bottom for the mushroom enlargement which has been produced by the scouringor eroding action. The sand which is washed away toformthe enlargement fills in at the bottom of the shaft so that the bottom of the final mushroom mold will be considerably above the bottom of the original shaft excavation. V L a A feature whichcontributes to symmetry and accurate size determination isthe fact that no excavating ope-rationsare performed except'the initial drilling of thesh-aft or bore.

Uniformity .cf' size is -assured by the simple expedient of accuratelydetermining (1) the depth of the bore (2) the amount of water poured inand (3) the duration of agitation. Obviously no great skill is required for accurate determination of these controlling factors. p 1 I Having produced the mold for the pilii'ig, powdered concrete is gently sprayed or sifted into the mold so that the sand mold walls will not shale off or break down. This concrete, taking up the moisture from the walls of the mushroom mold, rapidly hardens and forms a homogeneous concrete mass unmixed withsand. Where the mold; is not sufficiently wet at its bottom to moisten the concrete, supplementary moistening- -agents may be intr'oduced through the bore. it

Having thus formed the mushroom the piling is completed by pouring concrete into the shell to form the pillar, the substantially hardened mushroom base thereby integrally uniting the pillar and mushroominone sub-3 stantiallyhomogeneous structure. The. shell lining of the bore of courseprevents admixwell waterlowering apparatus such as is disclosed in my copendin 'application, Serial No.- 224,206, filed October 5th, 1927, to be used, and the water level lowered over a wide area by a single pump, as opposed to conventional methods in which numerous well points, hose lines and other complex apparatus encumber the field of operation and seriously interfere with the expeditious carrylng out of the work. This application is a continuation in par of my copending application, Serial No.-

320,813, filed Nov. 21, 1928.

The invention may be more fully under-' stood from the following description in connection with accompanying drawing which is a diagrammatic broken vertical sectional view showing a pair of deep well pumps in position to lower the water level throughout a considerable area and showing from left to right three successive stages or steps in the fabrication of a piling.

In the drawing the normal water level in the sand is shown by the dot-and-dash line wm. The first step of the method is to lower this water level to a point which int-he area of operations is below the proposed bottom of the piling excavations, the

' new lowered water level being shown at yand sloping somewhat due to the capillary action of the fine sand. 7

I may use ordinary suction well points for this purpose but I prefer to use deep Well pumps such as those illustrated. Each of these pumps includes a casing 11 having a screen 12 and the drill point 13 at its lower end. Rotary force pump 14 disposed within the casing 11 is connected by an operating shaft 15 to a motor 16 mounted on top of the casing 11 and the water forced upwardly by the pump is carried off to discharge by the pipe 17. In practice a single pump of this nature, if sunk deeply enough will serve to reduce the water level over a large area, but I have shown two of the pumps in operation in the drawings.

The drawings show from left to right three successive stages in the construction of the piling, these y The drawing shows from left to right three successive stages in the construction of the piling, these stages being for'the convenience of description lettered A, B and C.

Having lowered the water level I sink a Vertical bore, or shaft 18 in sand preferably; using an ordinary auger 10 toform the excavation. The next step is to insert'therelatively light gauge metal shell'19 into the bore to apoint where the top of this shell is substantially at the surface level of the sand.

This shell is preferably provided.- witha" slightly flaring entering mouth 20 which scales and trims the walls of the bore 18, shaving some of the sand off of the walls. and causing it to fall intothe' bottom'of the'excavation. The purpose of this flare is to permit the ready adjustment of theshell in the bore to exactlythe proper height and to prevent the shell from'becoming so firmly frictionally held. in the sand bore that itcannot be moved either up or down. When the shell is onceproperlyadjusted sand is sifted into the annular space between-shell body and shaft wall, so that the shell is firmly held in position.

After emplacing the shell or liner thenext step is to enlarge the, bottom of the shaft or bore 18 to form a sandmold for'the' mushroom, bulb, or pedestal portionof the piling. Numerous expedients may be resorted to in this connection, but I preferably employ a special enlarging process of my owninven tion. This process consists generally ofp'ar tially filling the bore with water and then agitating the otherwise inert body of-water to erode or wash away the sand at the lower end of the bore. As an incident of suchagi tation the bottom of the bore becomes par,- tially filled with the sand which has been eroded from the bore walls immediately below the metal shell 7 and the bottom of the final mold is well above the bottom of the original shaft 18. r

Preferably enough water is poured to "fill thebore up to approximately thelower end of the shell, the water being poured from bucket 22 or in any other suitable manner. That portion of the drawing indicated 'gen-' erally at Adepicts the partially completed mold after the shaft has been sunk, the liner emplaced, and the water poured in to the desired level. As suggested above numerous modesof water agitation might be'employed. Preferably, however, the agitation is mechanically accomplished, one convenient meth od being simply to introduce the auger 10 and vertically reciprocate it by hand. This action sets up a wave motionin' the body of water which so far as I have been able to-determine is somewhat complex. It includes a vertical water flow along the walls of the bore andat the same time somewhat of'a swirling action due to the effect of the spiral auger blade. In that portion of the drawing designated at B I have shown the water agitation method in progress and have also shown'on a much exaggerated scale in dotted lines a rather crude diagramof' the changing shape of the mold after each reciprocation of the auger.

' What apparently happens is thatthe water scours away a thin annular film of sand from the wall of the bore at each reciprocationof the auger and this sand deposits in the bottom of the bore. Each succeeding wave act-ion takes effect on a wall section of decreased length. This is due to the fact that the water level isconstantly lowered asthe bore is enlarged and the bottom-=of the hole is con:-

stantly rising as the sand which has been washed away flows into the bottom of the hole. Lowering 'ofthe water level is further expedited by the seepage of the water into i 1} the sand down to the artificial water level,

After this agitation has been carried onto the desired extent the auger is preferably withdrawn leaving. some Water still in the bottom of the hole.

This water causes the sand bottom of the mold to assume a curvature in accordance with the well known running angle of saturated san The upper general conical portion of the mold has walls I sloping at the well .knowncaving angle of sand and these sloping walls will either run directly in the bottom of the mold ormay be connected to the bottom of the mold by a general vertical wall portion (not shown) .in accordance with the extent to which agitation offthe water has taken place (note varying mold shapes shown in dotted lines at B, n

i Myexperiments todate lead me' to theconclusion that the particular method of agitating the otherwise inert body of water is subject'to considerable variation without materially changing the efficacy of the method. In other words while :a reciprocating screw auger gives a combined up and down and swirling motionto the water I believe that any other .instrumentality for giving either this combined action or" giving either the swirling or the up-anddown motion indei pendently would serve the purpose. As typical of other instrumentalities that mightbe used l may mention conventional motor driven or manually operated rotary or re oiprocatory agitators of various-types.

There is shown at C the complete mold after the waterhas drained out of it and prior to the introduction of the concrete or cementitious piling material.

At this time unless the sand in the bottom i of the mushroom isgiven time to dry, it will homogeneous, bulbous pedestal structure 24 conforming to the shape of the mushroom sand mold. This structurehaving substantially hardened, the piling is completed by latter is completely hardened, the pillar and mushroom will be integrally welded together i-ntovone substantiallyhomogeneous strong mass.

It will of-course be apparent that in many instances it is not necessary tocompletely fill the mushroom mold with the :cementitious dry mix. Where the mold is comparatively dry and hard, as it may sometimes be in fairly coarse sand, concrete pouring maybe safely resorted to. On the other hand, where sand is line, so that the water which has been used in forming the mushroom does not flow off quickly or freely, the dry mix may be used to absorb the water and then the wet concrete immediately poured in upon it, making the base partly a dry mix and partly a wet mix. In other words, the exact nature of the sand in which the work is being carried out will be the determining factor in the extent to which the dry mix must be used. It is more or less optional whether the pillar is poured while the concrete of the base is'still green or after it is partially hardened. By using the former method, however, the weight of the concrete in the pillar tends to compact the concrete in the base and force it tightly against the mushroom mold.

What Iclaim is 1. A method of forming a mold for a mushroom piling in water bearing sand which includes the stepsof artificially lowering the water-level in the sand below the proposed bottom of the ilin excavation sinkin a straight shaft which terminates above the lowered artificial water level filling the shaft- 7 with water to a'height at least equal to the top "of the proposed mushroom and agitating the otherwise inert body of water while the latteris draining through the sand to effect erosion of sand. from the walls of the mold and deposition of such sand in the bottom of the mold. a s

2. A method of field-fabricating concrete pedestal pilings in water bearing sand whichincludes the steps of sinking a straight shaft the bottom of which is above the water level in the sand at the time the shaft issunk, :partially filling the bottom of the shaft with water to a levelat least as high "as the top of the proposed mushroom and while the water is seeping out of the shaft through the sand agitating the otherwise substantially inert body of water to scour away part of the wall of the shaft, said scouring being accompanied by the depositing of the eroded sand in the bottom of the shaft whereby the bottom of the shaft is raised and an enlargement of the shaft is formed then filling the sand mold thus formed with concrete. 7

3. A method of forming a mold for mushroom piling in beach sand which includes the steps of artificially lowering the water level in the sand below the proposed bottom of the piling excavation, sinking a straight shaft which terminates above the artificially lowered water level, filling the shaft with'water to at least the height of the top of the proposed mushroom and so agitating the otherwise inert body of water while the latter is seeping through the sand as to set up a vertical wave motion along the walls of the shaft, causing erosion of the sand from the walls of the shaft and deposition of the eroded sand in the bottom of the shaft.

4:. A method of forming a mold for mushroom piling in beach sand which includes the steps of artificially lowering the water level in the sand below the proposed bottom of the piling excavation, sinking a straight shaft which terminates above the artificially lowered water level, filling the shaft with water to at least the height of the top of the proposed mushroom and so agitating the otherwise inert body of water while the latter is seeping through the sand that a swirling impetus is imparted to the water to effect erosion of the sand from the lower portion of the shaft Walls and the forming of an enlargement at the bottom of the shaft.

5. A method of forming a mold for mushroom piling in beach sand which includes the steps of artificially lowering the water level in the sand below the proposed bottom of the piling excavation, sinking a straight shaft which terminates above the artificially low,- ered water level, filling the shaft with water to at least the height of the top of the proposed mushroom and so agitating the otherwise inert body of water while the latter is seeping through the sand as to effect a compound swirling and vertical wave motion causing erosion of sand from the walls of the mold and deposition of eroded sand in the bottom of the mold.

6. A method of forming a mold for a mushroom piling in water bearing sand which includes the steps of sinking a straight shaft the bottom of which is above the water level in the sand at the time the shaft is sunk and below the proposed bottom of the mushroom mold, lining the upper portion of the shaft with a metal shell, filling the shaft with water to a level at least as high as the top of the proposed mushroom and while the water is seeping out of the shaft through the sand,

agitating the otherwise substantially inert body of water to scour away the unlined part of the wall of the shaft, said scouring bein accompanied by a deposition of eroded san in the bottom of the shaft whereby the bottom of the shaft is raised as an enlargement of the shaft is formed.

7 A method as set forth in claim 6 and wherein the liner shell is of thin gauge material inserted without driving and without the use of a core and is provided with a flaring entering end to shave and trim the walls of the mold and facilitate forcing in of the shell to the desired extent and in which the annular space around the shell produced by cutting away of sand as an incidentvof inserting the shell is refilled with sand to frictionally hold the shell in place and prevent it from slipping into the subsequently formed mushroom mold.

Signed at Atlantic City in the county of Atlantic and State of New Jersey this 1st day of May A. D. 1929.

ANTHONY PAUL MILLER.