US3690388A - Installation of sand drains - Google Patents

Abstract

Methods and equipment for installing sand drains in water bearing earth; and an open ended tubular shell is lowered into the earth while allowing the water bearing earth to freely enter into the interior of the shell; a close fitting auger is used to remove the water bearing earth from the shell and then the shell is filled with sand and subsequently withdrawn from the earth thus leaving the sand to provide the desired sand drain.

Description

[ 51 Sept. 12,1972

United States Patent Hilton et al.

....l98/213 X 4/l96l Goodrich........... .198/213 11/1969 ....6l/63 [541 INSTALLATION OF SAND DRAINS 292,550 1/1884 Fairly................

2 981 403 [72] Inventors: Joseph Lawrence Hilton Oakland,

NIL; G an Incline 3,478,524 .m...

Village, Nev.; Lewis Fred Cavin,

Primary Examiner-Jacob Shapiro San Lorenzo, Calif.

[73] Assignee: Raymond lntemational lnc.,

Attorney-Ward, McElhannon, Brooks & Fitzpatrick, Joseph M. Fitzpatrick, Charles B. Cannon, Carrol G.

New

York, NY.

July 20, 1970 [21] Appl. No.: 63,968

[22] Filed:

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m mmmm wm efl mem num fmw mw Wr.um M m Mm .mkfly m I e] m m e w m 0 w ueu 1 m m m m .mhmfi mmm m um o.moue l t fifd 1 dm lm emm m m n m l m i wm w 93 m m mm .n em m mm Mwkmsbmamd 1 32 3 33 64 l 12 2 nunwn RB 67 i8 85 B ,139 97 5 2 ll 1 .d 1 3% m m UE U l l l n /6 m n" nLm m m [11 e m u U w mm 6.0 .7 A u 2 1 l P Han c t r wE3 m m a a 6 Y. my MUN m A M m m "h "r m R D m n 99 m mww L f o m d 5 3. mm U .mm 35 m m m mm l 37 U 5.5 r 2 2 PATENTED SE? 12 I972 SHEET 1 OF 2 INSTALLATION OF SAND DRAINS This invention relates to methods and equipment for installing sand drains and, more particularly, to methods and equipment for installing nondisplacement sand drains.

While the several aspects of the present invention are subject to a wide range of applications, they are especially suited for use in the installation of sand drains in water bearing earth comprised of a relatively firm surface earth and a softer-underearth, and will be particularly described in that connection.

Sand drains are regions of high water permeability placed artificially in the earth and connected to a region of minimum fluid pressure such as the atmosphere. Essentially, sand drains function to permit relatively rapid water pressure release from locations in the earth where excess water pressures have developed due to'construction operations. Excess water pressures in the ground can be built up as a result of the placement of heavy structures or earth fills on the ground, or the driving of pilings into the ground. Because of high excess water pressures, the stability of such structures in earth fills may be poor. Furthermore, such structures and earth fills will incur settlements with time as the excess water pressure is gradually dissipated at a rate de- I close to these water pressure concentrations it is possible to obtain dissipation of the water pressure effects within a very short time so that a stable condition may be achieved before further construction is undertaken.

Generally, sand drains are constructed by forming a vertical hole in the earth and filling the hole with sand or other moisture permeable material. Actually, it is the hole itself, which is open to the ground surface, that achieves the moisture equalization effects. The sand or other moisture permeable substance, however, is needed to maintain and to structurally reinforce the vertical hole while at the same time allowing relatively free flow of water to the surface.

The formation of the vertical hole and the placement of sand or other moisture permeable material in silty earths pose especially difficult problems. These earths are typically comprised of a relatively firm surface earth sometimes formed from earth fills, and a softer silty or muddy underearth, the relatively firm surface earth extending, for example, l20 feet below the ground surface and the muddy underearth extending 7-80 feet below the ground surface. Experience has shown that generally known hole forming methods are ineffective in these mentioned water bearing earths. The commonly utilized method of predrilling a hole to the required depth and filling same with sand or other moisture permeable material has been found unworkable since lower muddy earth is squeezed into the drilled hole and closes it off before the sand or other material can be properly positioned therein. The use of known pre-excavator methods have also been found unworkable. The latter methods commonly use an outer open ended shell which encloses and houses an open ended inner shell. Usually, the outer shell and the enclosed inner shell are lowered by known driving methods to the required depth while allowing the water bearing earth to freely enter up into the interior of the inner shell. The inner shell containing the water bearing earth is then extracted from the outer shell by air pressure, leaving the outer shell in the ground. The outer shellis then filled with sand and thereafter is also withdrawn from the earth, thus leaving the sand to provide the desired sand drain. ln driving the inner and outer shells, however, the relatively firm surface earth forms a plug in the inner shell thus causing, in a well known manner, some detrimental lateral displacement of the earth surrounding the hole. In addition, in extracting the inner shell from the outer shell, a vacuum is created beneath the lower end of the inner shell, thus pulling the water bearing earth into the hole defined by A the outer shell.

The present invention overcomes the abovedescribed difficulties and permits the installation of effective and reliable sand drains with minimum effort and without substantial soil displacement.

According to one aspect of the present invention, a sand drain is constructed by lowering into the water bearing earth an open ended shell while allowing the water bearing earth to enter freely up into the interior of the shell through the shells lower end. The earth, which has entered into the shell through the lower end, is then removed, while maintaining the shell in the ground. Thereafter, sand is introduced into the interior of the shell, and then the shell is withdrawn from the ground, leaving the sand'to provide the desired sand drain.

As hereinafter described in detail, the present invention may be carried out by lowering an open ended tubular shell defined by joined upper and lower sections into the water bearing earth to a depth substantially corresponding to the length of the lower section, while allowing the water bearing earth to enter freely up into the lower section through its lower end. The upper section of the shell is then removed from the lower section, the latter remaining positioned in the earth. A close fitting auger is then placed within the lower section and utilized to remove from the lower section the earth which is inside. The auger is then removed from the lower section, and the upper section of the shell repositioned and joined to the lower section. Thereafter, sand is introduced into the shell via the upper section and the shell, including both the upper and lower sections, is withdrawn from the earth, while leaving the sand in the earth to provide the desired sand drain.

In accordance with another aspect of the present invention, air is provided beneath the lower end of the auger during its removal from the shell so as to prevent the undesirable buildup of a vacuum which could cause the surrounding water bearing earth to be drawn into the hole defined by the shell. in addition, the upper and lower sections of the shell are constructed to be joined together by a substantially air-tight seal. This construction enables the pressurization of the shell when withdrawing same from the earth, thus positioning the sand in the hole while the shell is being removed.

According to a further aspect of the present invention, there is provided novel sand drain formation equipment comprising a shell which serves to form the sand drain hole, as well as an auger which serves to remove the water bearing earth from the shell. The shell is comprised of hollow cylindrical tubing having first and second sections. The mentioned first and second sections are constructed to be mechanically joined together. The firstsection is of a length equal to substantially the depth of the sand drain to be installed,

and has open upper and lower ends; the second section has a closed upper end and has sand input means defined therein. The auger may be comprised of a stem portion and helical flights positioned about the stem portion. ln addition, the flights of the auger are provided with flexible'edges for making sealing engagement with the interior surface of the shell.

, Therehas thus been outlined rather broadly the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the. artmay be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure isbased may readily be utilized as a basis for the designing'of other structures for carrying out the several purposes of the invention. It is important, therefore, that thevclaims be regarded as including such equivalent constructions as do not depart from the spirit and scope of the invention. I

Speciflcembodiments of the invention have been chosen for purposes of illustration and description, and

are shown inthe accompanying drawings forming a part of the specification wherein:

FIGS.-:l-7 are side elevational views, mostly in section, showing in sequence, the several steps undertaken in the installation of a sand-drain according to the present invention;

FIG. 8 is an enlarged elevational view, taken in section, of an auger constructed in accordance with the presentinvention and used in the sequence of steps illustr ated in FIG 1-, '--7; I

FIG. 9 is a side evationalview, taken in section, of a {shell construct accordance with the present invention and also sed n the sequence of steps illustrated in FIG. 1;and, I

' FIG. l0is a .l0ofFlG.9.

In FIGS. l--j7, -'the re is shown a mass of saturated water bearing e a'rkthf-l-8which, in the usualsituation, may extend dowrito a considerable depth below the surface, for le from 60 to 80 feet, before reaching afi e320 of solid earth or rock. As also somewhat sch iany shown in FIG. 1, the water ay ,corjtipris'e a relatively firm surface r brmuddy underearth 24, the relafta'gmentary view taken along line 10- surface.

In accordan shown in FIG the relatively x underearth 24, The'j working hole 26 may be provided by any knownfimeth'iod, such as drilling with an auger, jetting etc. As will become more apparent hereafter, the provision'of the working hole 26 prevents the buildup of a plug"? ithin hollow equipment subsequently placed in the earth.'- P I As shown inFIG Z an open ended tubular shell 28 having joined upper and lower sections 30 and 32 respectively, is lowered into the water bearing earth 18 through the working hole 26 to a depthsubstantially corresponding to the length of the lower section 32. The structural details of the shell 28 will be more fully described hereinafter. As those skilled in the art will appreciate, the shell 28 may be lowered by any known means, such as by a vibrator or driving hammer (not shown). During the lowering operation, the softer underearth 24 freely enters up intothe interior of the shell 28 through the open bottom end of the shell's lower section 32. After the shell 28 has been positioned as described above, the upper section 30 isthen removed to provide free access and working room on the ground about the lower section 32.

As shown in FIG. 3, the underearth 24 which has entered up into the shell 28 through the lower end of lower section 32 is then removed. To this end, a close fitting auger 34 is placed within the lower section 32 and passed therethrough to removethe water bearing earth. As shown in FIG. 8, the auger 34 may be comprised of a stem portion 36 having an internal channel 38 and helical flights 40. The internal channel 38 extends through the stem portion 36 and opens out through an aperture 42 (FIG. 1) in the tip of the auger 34. In addition, a strip of belting 44 (FIG. 8) is secured on the edges of the flights 40 of the auger 34 by suitable fastening means, such as a plate 46. It;will be appreciated that the auger 34 is thus provided with flexible edges which make sealing engagement with the lower portion 32 of the shell 28 (FIG. 3), and which facilitate inthe removal of the underearth 24 within. As schematically shown by the arrows 48 in FIG. 3, compressed air is supplied from an external source (not shown) and is introduced at ground level through the internal channel 38 of the auger 34, and applied beneath the lower tip of the auger 34. The application of this air within the lower -section 32 of the shell prevents the buildup of a vacuurrrwhen the'auger 34 is removed, and thus'prevents th pulling of surrounding water bearing earth into the hole defined by the shell.

Depending on the consistency of the water bearing earth which has entered up into the-lower section 32, it may be necessary to make a plurality of passes with-the auger 34 in order to completely remove the water bearing earth. FIG. 4 shows the lower section 32 of a shell having the water bearing earthfjcompletely removed therefrom. Y y i 't a After the water bearing earthwhich had entered 'up into the lower section 32 of the shell has been removed, the upper section 30 is repositioned and secured to the lower section 32 as sho'wninFlG. SJAt' this point, sand 50 is introduced into the shell 28fvia the upper section 30 to substantially fill at least the lower section 32. As shown, the sand '50 is poured from a sand skip 52 into the shell 28 through a sand input S4formed near the upper end of the upper section 30..As shown in FIG. '1, the sand input 54 is provided with an air-tight door 56 mounted on a pivot 58,

Thereafter, as shown in FIG. 6, the door 54 is closed and pressurized air is admitted to the interior of the shell28 via an air connection 60 also located near the top of the shell 28. The applied pressurized air facilitates the removal of the shell 28 while at the same time properly positioning the sand inthe thus formed hole. Simultaneously, the shell 28 is withdrawn from the water bearing earth 18 while leaving the sand 50 to provide a completed sand drain. The thus completed sand drain is shown in FIG. 7.

Referring now to FIGS. 9 and 10, there is shown in greater detail the shell 28 used in connection with the installation of sand drains in accordance with the present invention. As aforesaid, the shell 28 is comprised of upper and lower sections 30 and 32, respectively, mechanically joined together; the lower section 32 being of a length substantially equal to the depth of the sand drain to be installed and having an open outer end (not shown). The lower section 32 also has a flange or collar 62 which forms a seat for the upper section 30. A tenon 64, having an outer diameter slightly smaller than the internal diameter of the lower section 32, is provided on the upper section 30 in order to engage and extend into the lower section 32. As shown in FIG. 10, pulling hooks 66 are provided on the upper section 32 in order to provide suitable means for pulling the shell 28 from the ground. Lifting hooks 68 are also provided-on the upper section 30 by means of pad eyes" 70 or the like. The hooks 68 extend down to and are secured by latches 72 provided beneath the flange 62 of the lower section 32. The lifting hooks 68 function to transmit to the lower section 32 the pulling forces applied to the pulling hooks 66 on the upper section 30.

In order to make the shell 28 substantially air-tight and thus increase the effectiveness of the pressurized air applied through the air connection 60, an O ring 74 or similar seal is provided between the tenon 64 and the lower section 32. In order to secure and hold the 0 ring 74 in position during the removal and repositioning of the upper section 30 to the lower section 32, two spaced apart metal bands 76 may be integrally formed on the outside of the tenon 64.

Also as shown in FIGS. 9 and 10, the lower section 32 of the shell 28 is provided with two male members 78, located opposite each other 180 about the periphery of the lower section 32. The upper section 30 of the shell 28 is also provided with slots shaped in complement to the male members 78, and arranged on the upper section 30 so as to engage the male members 78. The cooperation of the male and female members 78 and 80, respectively, prevents relative rotation between the upper section 30 and the lower section 32 and functions as guide means for carrying out quick hook up between the upper and lower sections.

Thus, it will be seen from the above that in accordance with the present invention there are provided methods and equipment for installing sand drains without causing substantial adjacent earth displacement, and which permit the installation of effective and reliable sand drains.

Having thus described the invention with particular reference to the preferred forms thereof, it will be obvious to those skilled in the art to which the invention pertains, after understanding the invention, that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the claims appended hereto.

What is claimed and desired to be secured by Letters Patent is:

1. A method for forming a hole in the earth, said meth d om risin the ste s of insertin an 0 en ended tu ulai' shefi down in to the earth s o that ihe earth surrounded by the shell enters up inside it and thereafter causing an auger to bore down into the shell and removing the auger longitudinally from the shell while wiping the inner surfaces of the shell with flexible elements secured to the flights of the auger.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3'G9O'388 Dated September 1 2J 1972 Inventor(s) Hllton: t al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Abstract line 2, delete the word "and";

Column 1., line 51, for "7" read --70--;

Signed and sealed this 20th day of March 1973.

(SEAL) Attest:

EDWARD M FLETCHER JR ROBERT GOTTSCHALK Attest1ng Officer Commissioner of Patents ORV. O-1050 (10-69) USCOMM-DC SO375-PE9 v.5. GOVERNMENT PR2

Claims (1)

1. A method for forming a hole in the earth, said method comprising the steps of inserting an open ended tubular shell down into the earth so that the earth surrounded by the shell enters up inside it and thereafter causing an auger to bore down into the shell and removing the auger longitudinally from the shell while wiping the inner surfaces of the shell with flexible elements secured to the flights of the auger.

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