US2488074A

US2488074A - Means and method for grouting drilled-in caissons

Info

Publication number: US2488074A
Application number: US46304A
Authority: US
Inventors: Joseph H Thornley
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-08-26
Filing date: 1948-08-26
Publication date: 1949-11-15
Anticipated expiration: 1966-11-15

Description

JNVENTOR J. H. THORNLEY MEANS AND METHOD FOR GROUTING DRILLED-IN CAISSONS Filed Aug. 2G, 1948 Nov. l5, 1949 Patented Nov. 15, 1949 UNITED STATES PATENT OFFICE MEANS AND METHOD FR GROUTIN G DRILLED-IN CAISSON S Joseph H. Thornley, Great Neck, N. Y.

Application August 26, 1948, Serial No. .46,304

(Cl. (i1-50.)

9 Claims. 1

The present invention relates to that step in the installation of drilled-in caissons which has to do with the making of a tight joint between the caisson pipe and the rim of the rock socket, and also if necessary making the rock socket fluid tight. The general structure and mode of installation of a drilled-in caisson is disclosed in my Patent No. 1,822,550.

In installing a drilled-in caisson, the shell, which is preferably a piece of pipe of from 18 to 36 inches in diameter, and of from 1/2 to inch Wall thickness, is driven down into the ground by means of a steam hammer. o f the Vpipe has a shoe of tempered tool steel or other high strength steel .reinforcing the same to provide a suitable cutting edge, and to provide a seat on the rock.

Usually the shell is driven to rock before it is cleaned out. However, if driving resistance becomes too great due to hard layers or to boulders, the shell `may be cleaned out from time to time previous to reaching bedrock. The contents of the shell may be removed by jetting, spudding, sand pumping, flowing with air jets and coring. This depends upon the type of material encountered. When hard layers are encountered, a drill bit Aof somewhat less diameter than the inside of the shell is worked up and down in the casing, and the material loosened is jetted or bailed out of the casing. Boulders are removed by drilling, or may be broken up by a churn drill and the pieces removed by a plunger bucket.

After the caisson shell has been driven to rock, and the material inside excavated, the rock socket-is drilled. This may be done by meansof standard well-drilling equipment using a string of tools of appropriate weight. Drilling of the rock socket is alternated with hailing, and therock fragments may be collected for study, so that a record of the nature of the rock ymay be made. The caisson shell is then re-driven into the `socket to obtain a seal between the cutting shoe and the rock.

In those instances where there is impervious soil or disintegrated rock overlying the harder rock, the shoe drives into this material and may make a perfect water seal at once. However, in other cases, the shoe strikes hard rock at the very first, and in this case it is necessary to drill out a shallow socket in the hard rock and then drive the shoe into the socket. This reaming out operation is sometimes quite dimcult, and if the rock is friable, it is apt ,to chip and Yleave The lower endV There are also instances in which the rock,V

itself carries water-bearing seams which may extend diagonally across the socket of the caisson, and so make it d iicult to exclude water. The rock socket generally will `be cut or drilled into solid rock, but .if any fissures or water-bearing seams are encountered, they .may jbe closed by the ivresent:method` Y In order to get a perfect drilled-in caisson, all that is actually necessary is to exclude the sand from the socket, so that the grout, when placed under water, will displace the Water and make a good bond with the surface of the rock socket. The exclusion of sand from the socket where the joint is not completely tight can usually be done effectively -and simply by carrying a considerable head of water in the caisson pipe. The water head -inside the pipe is preferably substantially in excess of the pressure of the ground water outside the pipe. There is then a tendency for a flow of water to pass from the inside to the outside of the pipe and very little tendency for .sand or any foreign matter to enter. The quality and sufciency of the rock itself is fully demonstrated by the record of the drilling, which may provide an inch-by-inch record of rock conditions 4as the socket is drilled out.

However, occasionally an engineer may have the idea that it is necessary to go down into the rock socket and personally inspect, by visual observation, the sufficiency of the rock for the load. Where this is to be done, it is necessary to shut out practically all water, as well as sand or other vforeign material from the socket, so that the -same may be de-watered for inspection pur- DOSCS To provide sucha tight and de-watered socket, the installer aims to ream out the socket and drive the shoe into it to a sufficient degree to cut olf the inow of water. But, for reasons above noted, this is not always possible, and where it is not possible, grouting is resorted to.

Heretofore, in grouting the joint between the caisson pipe and the rock socket or the rock socket itself the following procedure vhas been employed:

Through the open yupper end of the caisson pipe, one or two cubic yards of a cement and sand grout is deposited in the socket through the water by means of abottom dump bucket. This charge of grout should extend two or three feet up into the caisson pipe. Thena .grout head is set into the top of the pipe. It contains a .gasket whichvv 3 can be tightened against the side walls to make a fiuid tight joint with the inside surface of the caisson pipe. The head carries a small tell-tale pipe extending down t a pre-determined level below the head. Starting with the caisson pipe sealed and full of water, air from a supply under about 125 pounds pressure is introduced into the pipe, and it forces the water in the pipe down against the grout and lowers the top level of the water in the caisson by air displacement. By means of a cock on the tell-tale pipe, it is possible to determine when the level of the water has been forced below the end of the tell-tale tube, thereby indicating the desired volumetric displacement of grout through any openings in the socket or between the rim of the socket and the pipe. As the operation proceeds in the normal fashion, increase in the air pressure is transmitted through the water column to the grout, and the grout is forced out through the openings in the socket or in the joint between the socket and the pipe to a position where, when it sets, it will cut off the infiow of water or other foreign material. When the desired displacement of grout has occurred, then it is necessary to drop the internal pressure to a point where no substantial flow occurs either way, and with the apparatus in this condition, the grout is permitted to set, thus providing the desired seal of the openings between the inside and the outside of the socket.

One of the chief disadvantages of the aforesaid method which my present invention obviates is'the necessity for drilling out the unused grout on the inside of the pipe and socket. Also a practical difficulty is that where air pressure is employed, it is generally not feasible to use a pressure of more than 125 pounds per square inch, available from standard compressors. Obviously, compressors for a higher pressure may be employed, but there is a limit to the pressure which may be employed where air under pressure is used for forcing out the grout. First, in the case of accidental blowout of the head, there is great danger of damage to equipment and personnel. Also, in the event that the frictional hold of the soil on the caisson pipe should be exceeded, the pipe might be lifted in an uncontrollable manner. The present -invention does not require compressed air as a motive force. Only hydraulic pressure is used.

Furthermore, since all of the grout must be deposited at once, and this must be enough to meet all possible requirements, it is customary to introduce more than it is expected will be needed. The result isthat the remaining grout must all be drilled out after setting and this is time consuming and expensive. If the grout is fairly stiff, the pressure is sometimes not sufficient to deposit an adequate quantity outside of the socket, with the result that when the drilling-out operation is performed, the small hold which the remaining gr-out on the outside has is not enough to give a satisfactory seal. My present invention avoids these objections.

A .further objection to the known practice is that considerable work must be done after the grout has been deposited in the bottom of the bore, and before pressure can be applied to force it into the rock or around the shoe. Where the apertures are small, the grout may move out very slowly. Under these conditions, the initial set may begin before the grout has reached the proper location, and the operation will beun- 4 satisfactory. This may be avoided by the present invention.

A further difliculty of the known method resides iii` the inability to wash out the openings or leaks in the socket immediately before the grout is introduced. In the known method, even though the head be put in place and sealed, and air introduced under pressure to Wash out the leaks and openings in the bore, this head must be removed in order to permit introducing the grout and in that interval the return flow of water and sand, or other foreign material, may occur and defeat the washing out process. The present invention avoids this difficulty.

The object of the present invention is to provide an improvement in the method of and means for grouting a drilled-in caisson, which will largely avoid the above difficulties and objections and expedite the overall operation of grouting and of iinishing the caisson.

According to the present invention equipment is provided for sealing the top of the caisson pipe water; then the grout may be deposited, and byy the prevailing hydraulic pressure forced out through. the openings. If the first charge of grout fiows out too freely, a stiffer charge may be placed, or more grout may be deposited by the operation of the pump and the conduit. Then when the desired amount of grout has been displaced through the openings to the outside, the remaining grout in the socket and foot of the caisson pipe may be exhausted or evacuated by displacing the same with water out through the grouting conduit which has a suitable valved T-connection permitting either the inflow of grout from the grouting pump when it is desired to introduce the grout or the outow of grout when it is desired to remove the remainder of the same from the socket. This displacement ofv the grout out tlnough the conduit is done without dropping the internal pres-sure, so that the grout which is deposited in and outside the openings will not be disturbed while the excess grout is being removed. The socket maythen stand under hydraulic pressuresubstantially equal to the ground water pressure whereby the deposited grout is permitted to set and thus seal all the openings without requiring drilling out of the unused partsY of the charge of grout.

The apparatus employed is relatively simple, requiring only the sealing head for the upper end of the pipe, a water connection to a suitable water pump, a grout pump and grouting conduit which extends through a packing gland in the head, and is extensible by longitudinal shifting and by the addition or substraction of threaded sections. This conduit has a T-connection, one leg Vof which leadsto thegrout pump under the control of a valve, andthe other leg of which leadsto waste through another control valve.v

ing the equipmentV of my invention and prac-` ticing the method of the same, I shall describe, in connection with the accompanying drawings, a specific embodiment of the invention.

In the drawings:

Figure 1 is a vertical section, more or less diagrammatic, of a caisson to be grouted, and the equipment required to perform the grouting operations;

Figure 2 is an enlarged vertical section of the grouting head with the uid connections omitted;

Figure 3 is a bottom plan view of the piston or closure member for the upper end of the caisson pipe, showing the connections for the water pipe and the grout conduit therethrough; and

Figure 4 is a side elevational view on a larger scale than Figure 1, showing the preferred construction of the lower end of the grout conduit.

In Figure 1 the caisson pipe I has been driven to bedrock 2, cleared of the enclosed soil and a short socket, say six inches in depth, has been reamed out below the cutting shoe 3, which is carried on the lower end of the pipe I. The caisson pipe has been driven down into the socket, as indicated at 4, and the rock socket 5 has been drilled down a distance, for example, l2 inches below the end of the pipe I. An attempt has been made to dewater the bore of the pipe and the socket, and the result has been an inow of water and ne sand at the opening 1 between the shoe and the rock upon which it is seated. The opening at 1 need not be as large as shown in the drawing to admit ne sand and Water to an intolerable extent, but for the sake of illustration the opening 1 is here shown as fairly large.

In order to be able to dewater the socket 5, so that the same may be Visually inspected, the opening 1 must be closed off, and this is now to be accomplished by grouting. The caisson pipe is kept lled with water and the sand bailed out to clean out the socket. The upper end 8 of the caisson pipe 1 which extends above the ground line 9, is then closed 01T by a so-called grouting head Il! which, in general, comprises a sealing member and means for holding it in place in the open bore of the pipe. Y

The upper end of the pipe I may be provided with a perforated reenforcing ring I2 Welded thereto, or it may consist merely of the pipe cut oi square with four equally spaced openings I5 for receiving the cross bars I3 and I4. The four equally spaced openings I5, which may be formed in the upper end of the pipe wall, or which may be formed in the reenforcing ring I2, as the case may be, are large enough to receive the cross bars I3 and I4. The cross bar I3 is provided with a notch in the center, in which the straight across bar I4 is disposed. The cross bar I3 is preferably made up of two short pieces I6-I6 separated the necessary distance to receive the cross bar I4, and these two short pieces I6-I6 are welded to a bridge piece I8, whereby the bottom faces of the cross bars I3 and I4 lie in the same plane. Obviously, the cross bars, which are for the purpose of resisting displacement of the sealing piston I8 by their strength in shear, may be constructed in any other suitable manner. Alternatively, other means for holding the closure in the bore of the pipe I may be employed. In the preferred form shown, the cross bar I3 is rst put in place, and then the cross bar I4 is shoved in place through its registering openings and the notch in the cross bar I3. The piston I8 is preferably a unitary casting of cylindrical form, open at the bottom and closed at its upper end by the plate or head I9. It may be made 4up 1.6i' wrought parts welded together. Internal cross' webs 20 reenforce the head I9 and the skirt of the piston. The piston ts fairly closely in the pipe I, but the nuid tight seal is perfected by means of a gasket ring 22 of resilient material,

such as rubber, neoprene, or other suitable yielding material. This gasket 22 is disposed between the tapered shoulder 24 at the margin of the head I8 and an overlying plate or ring 23, which in turn. abuts against the pins or cross bars I3, I4. A circle of studs (not shown) may extend between the head I9 of the piston I8 and the ring or plate 23 for compressing the packing ring 22, but this service of compressing the packing ring 22 may be performed by the internal pressure with only sufficient connection between the plate or ring 23 and the piston I8 to'hold the parts together.

The plate 23 which is shown in Figure 2 has openings therethrough at opposite sides of the rcentenas indicated in the dotted lines at 25, 26 for the clearing of the grout conduit 21 and water pipe 28, respectively. The central part of the plate 23 may optionallybe cut out to leave only a ring. The water pipe 28 has an extension 29 down to a point below the piston, but close to the upper end of the caisson pipe for delivering water under pressure from the connection 30 leading to a suitable water pump through the control valve 32. A bleed valve 3| connected to the water line 28 optionally may be provided for permitting the escape of fluid from inside the caisson pipe I when that is desired. A pressure gauge 33 is connected to the water pipe 28, so that it always indicates the pressure on the inside of the caisson when the head is secured in place.

The water pump which supplies the connection 30 is preferably a road pump capable of delivering around or 200 gal-lons of water per minute at a maximum pressure of 500 pounds per square inch. The grout conduit 21, which extends through the head, is preferably constructed of a one-inch or one and one-half inch hush joint drilling tube made up in suitable sections, so that its lower end may be extended down to the bottom of and contact with the floor of the rock socket 5. After it is brought against the Vfloor of the rock socket, it is then raised a few inches and clamped in place, preferably by means of the packing gland 34 indicated in dotted lines in Figure 3. A rather harsh packing material is used in the gland 34 for gripping the conduit 21 tightly against displacement by internal pressure. By releasing or tightening the bolts on the gland the conduit may be released or gripped to permit it to be moved or held stationary as desired.

The lower end of the conduit 21 is closed but.

trolled by the shutoff valve 31-which is normallyV closed, and which is opened only when the unused grout deposited in the bottom of the bore is to be discharged. The other leg or branch indicated at 39 extends through a control valve 4Q to a connection 42 from a grout pump. This pump is preferably capable of delivering up to 5' cubic feet per minute against a head of 250 pounds, or 2 cubic feet per minute against a head of 500 pounds, Provision is made to supply the 201.11? ,pump With-.grout 0f the proper consistency,

which may be relatively thin or'relatlvely stiff as the occasion demands.

The operation of the system is as follows: When it is found that an opening such as that shown at 1 requires to be closed off, or that the socket intersects a crack in the rock which admits ground water, or otherwise there is some opening admitting sand or water from the outside into the inside of the bore of the caisson at or below the lower end of the pipe: I, grouting may be resorted to. 'Ihereupon the pipe I is iilled with water and the sand bailed out. The grouting head I is put in place in the upper end of the caisson pipe I. The piston I8 with its gasket 22 and clamping plate or ring 23 is introduced into the bore of the pipe I and the gasket put under suflicient initial compression to insure that the internal pressure on the piston head Will complete a tight seal `by expanding the gasket 22. The cross bars I 3 and I4 having been put in place, and the conduit 21 lowered to the iloor of the rock socket 5 and then raised a short distance and clamped in place, as indicated in Figure 1, the Valve 32 from the water pump will be opened admitting water under pressure, rst at a relatively slow rate to bring the pressure up to a value which Will be great enough to overcome the pressure of ground water on the outside of the opening 1. By suitable control of the valve 32 and observation of the gauge 33, the operator may judge of the rate of outflow through the opening 1 or other opening to be sealed, and having washed out the opening 1 by outflow of waterl to the desired degree, he starts the operation of the grout pump, opening the control valve 40 and keeping the discharge valve 31 closed. Thereby grout from the grout pump is delivered through the connection 42, branch 39 and grouting conduit 21 down to the bottom of the socket, while the pressure in the socket is held at a value not lower than the pressure of the ground water outside. displace water and any other fluid material on the inside of the opening 1 towards the outside, and thus the internal pressure may be maintained wholly or partly by the grout pump while depositing grout into the socket 5 and possibly a foot or so up in the lower end of the pipe I. If the grout is too fluid to show the desired resistance to outflow, a thicker or stiffer grout mixture may be discharged through the conduit 21 until it is observed that as the grout is discharged, the pressure on the gauge 33 rises. the openings in the rock arebeing blocked since the resistance to outilow of the grout is evidently becoming greater.

there is no longer any escape passage for the water except by expelling the grout through the openings in the rock. When the pressure has risen to the desired extent or the predetermined v volume of grout has been expelled, grout pumping is discontinued, and the pressure in the caisson reduced to about that of the outside water head. This is accomplished by opening the water valve and releasing a small amount of water until the gauge pressure drops back to normal. As long as this normal pressure is maintained, there will be no tendency for the water outside the pipe to force the grout back into the pipe. If during this operation, it is desired that more or a stiffer grout mixture should be utilized, this may readily be done by manipulating the pumps and valves to stop further inilow of water from- The introduction of the grout tends toV ThisV indicates that As grout continues to be pumped in the pressure will continue to rise, since4 the water pump and to admit the grout from the grout pump. When suflicient grout has been forced out through the opening, as may be judged by the operator through the action of the gauge 33 and his manipulation of the valves and pumps, it is then desirable to remove the excess of grout in the bore 0f the caisson, and this is done by opening the exhaust or discharge valve 31 in the branch 38, the Valve 40 from the grout pump being at this time closed. By introducing water from the water pump by opening the valve 32, the descending flow in the column of water forces the grout out through the openings 35 in the lower end of the conduit 21, the flow through the conduit 21 then being in the reverse direction, namely, upwardly and out through the discharge connection 38 to waste. So long as the pressure inside the caisson is at all times maintained above normal" outside water pressure this operation of exhausting the surplus grout in the casing will have no tendency to cause inow of deposited grout into the caisson.

In performing the operations above described, care is exercised at all times not to employ an internal pressure which will be great enough to force the entire caisson pipe upwardly in the soil. For this purpose a very careful observation of the level is maintained, as it is desired that the pipe, which, for example, may be 30 inches diameter, will not move upwardly so much as elf of an inch.

Since the signiiicant operations all occur at the foot of the caisson pipe to which the operator has no direct access for determining what is going on, he must observe certain relations of pressure and flow, so as to get the displacements of the various fluid or semi-fluid materials in the directions and at the times desired. The pressure gauge is an important indicator taken in conjunction with-other parts of the system. The pressure relations will be more clearly brought out as follows: Initially, before the grouting head is put in place, the caisson pipe is lled with water, and a full head of water is maintained in the casing, so as to limit the inflow of sand, and While the caisson pipe is Open, the sand is bailed out until the socket is reasonably clean. The grout headv and its connected pipes will then be placed in position. The packing gland 34 is released. The grout conduit is inserted, and sections screwed together until the lower end of the conduit 21 rests on the bottom of the socket. It is then raised up about four inches, and the packing gland is tightened down to hold the grouting,

conduit in place. The valves 31 and 39 in the grouting conduit branches will be closed oi and the valve 32 in the water line opened and the water pump started. As soon as the casing is full of water, the water pressure will rise sharply, and here care must be taken that a pressure which will displace the pipe I upwardly must not be allowed to build up. If the water pump is operated slowly, a critical rock water pressure may be noted from the action of the pressure gauge 33. At this pressure, the water will be forced out through the openings in the rock or below the shoe, and this outward or reverse ilow Should be continued for from ve to ten minutes.

rock socket. As soon as the grout begins to flow into the cracks or through the sand through which the water has been escaping, the gauge pressure will go up, since the grout is less freeowing than the water. If the pressure mounts rapidly the water inlet valve will be used to check the inow of the water, and the water will ultimately be shut oi entirely whenthe inow of the grout is suflicient to maintain or steadily increase the pressure.

If after pumping in a couple of yards of grout Vthe pressure still drops sharply when the inflow of grout is checked, then a drier less plastic grout will be introduced. This stiiler grout may even contain some line sand. The grout pump may be stopped for a short time to allow the stiffening of the grout which has been forced around the shoe or into the sand and then started again and the pressure studied. If the pressure runs up, it may be concluded that the grout is eiective. When the grout pressure has run up as far as it is l considered safe, with due consideration for the possible lifting of the pipe, the grout pump is shut down and the grout line valve to the pump closed. The water pump is then started, and the grout Waste valve 3l opened. Water pressure which is maintained below the pressure required to place the grout but never below the natural ground water pressure, then forces the grout in the grout conduit 2'I and in the bottom of the bore back up through the grout conduit and out through the grout waste connection 38. The grout conduit may be raised or lowered to exhaust all the grout in the rock socket and up in the' lower end of the pipe I.. When clear water begins to ow out from the grout waste line, it is evidence that all removable surplus grout has been discharged. Throughout this process of lremoving the excess grout, the pressure in the bore of the caisson has been maintained on the deposited grout in the rock passage by maintaining the Water pressure.

This is accomplished by manipulating the grout exhaust and water inlet valves having reference to the reading of the gauge 33.

An optional variation of the procedure to seal off a caisson which is persistently leaking around the shoe is as follows: The procedure up to the deposit of the grout as recited above is to be followed and sucient grout under low water pressure to bring the grout to a level a couple of feet above the cutting shoe is deposited. Then the water inlet valve 32 is closed and the grout pressure increased to a point above the critical external friction value of the 30-inch pipe in the ground. The shoe 3 will be raised from its seat 4 in the rock, and the grout under pressure will flow out freely around it. When this has been permitted to the desired extent, the grout pressure is dropped, and the shoe 3 reseated by driving the casing pipe I down by means of a steam hammer and a suitable fitting. Normally there will be enough air trapped in the top of the caisson pipe I, so that this redriving may be accomplished without danger of bursting the pipe I, which might occur if the pipe is filled with inelastic fluid throughout.

It is to be observed that the sealing piston of the grout head is utilized to constitute the pipe i a closed chamber, so that an artificial head may be brought upon the fluid in the bore of the caisson. Theoretically, the pipe I might be extended up to the point where a genuine water head would perform the service just as well as the artificial head produced by the pump displacement. That is to say, the method is not strictly dependent upon using the grout head, but the 10 grout head is the preferred equipment for use in performing the method of my invention. 1 I do not intend to be limited to the details of equipment and the'sequence of steps above described, except as they are made essential in the ,appended claims.

I claim: 1. Grouting means for rock socketed caissons comprising a closure member for sealing off the head of the caisson pipe against escape of pressure, a water supply connection extending through said closure member for introducing water at the upper end of the caisson, control means for regulating the input of water through said connection, a grout conduit passing through said closure member and being held in sealed relation thereto, said grout conduit being extensible to the foot of the caisson, a valved connection from a source of grout supply under pressure to said grout conduit to permit grout to be discharged under pressure into the lower end of said caisson, and a valved connection from the grout conduit to waste to permit grout to be evacuated from the lower end of the caisson by displacement with water.

2. Grouting means for grouting a rock socketed caisson employing a caisson pipe extending to a rock socket, comprising in combination a grouting head for sealing the upper end of the caisson pipe, a water pipe having valved connection with a source of water under pressure extending through said head to the upper end of the caisson, a grout conduit passing through said head and being adapted to extend to the lower end of the caisson pipe, a releasable sealing means for sealing the grout conduit to the head, a controllable connection from a source of grout under pressure to said grout conduit, and a controllable connection from the grout conduit to waste to permit the displacement of grout from the lower end of the caisson through said grout pipe, and releasable means for holding the grouting head upon theA upper end of said caisson pipe.

3. Method of grouting an opening at or below the joint between the lower end of a caisson pipe and a rock socket which comprises covering the opening with water inside the caisson, increasing the water pressure on said opening above the pressure of ground water outside whereby the now of water tends to be out through the opening, displacing the water over said opening with a charge of grout, displacing a part of the grout out through the opening to make the desired grout seal, then while holding the fluid pressure at approximately the pressure of ground water, displacing the grout upwardly out of the caisson pipe, and then allowing the grout outside the pipe and rock socket to set and thereby form a grout seal of the opening.

4. Method of grouting an opening at or below the joint between the lower end of a caisson pipe and a rock socket to which it is to be sealed which comprises closing oi the upper end of the casing, charging the closed casing with water under pressure greater on the inside of the opening than the pressure of ground water outside the opening, extending a conduit to the bottom of the pipe and discharging a charge of grout at the lower end of the caisson pipe to a level above the opening, displacing some of the grout through the opening by pressure, and displacing the remainder of the grout out through the conduit while holding the pressure on the inside of the opening at a value not less than that of the ground Water outside the opening.

5. Method of grouting a rock socketed caisson to produce tightness thereof, which comprises establishing water pressure in the rock socket at a Value not less than the pressure of the ground water outside, displacing the water in the rock socket and in the lower end of the caisson pipe with a charge of grout while maintaining in said socket and in said lower end of the pipe a pressure equal to or greater than the pressure of the ground water, increasing the internal pressure and raising the caisson pipe to permit discharge of grout under the end thereof to the outside by said pressure, redriving the caisson pipe to reduce or prevent the outflow of grout, and maintaining internal pressure approximately equal to the outside pressure to allow the deposited grout to set.

6. Method of grouting a rock socketed caisson to produce tightness thereof, which comprises establishing water pressure in the rock socket at a value not less than the pressure of the ground Water outside, displacing the Water in the rock socket and in the lower end of the caisson pipe with a charge of grout while maintaining a pressure equal to or above the pressure of the ground water, raising the caisson pipe to permit discharge of grout under the end thereof to the outside by said pressure, redriving the caisson pipe to reduce or prevent the outflow of grout, then while said water pressure in the socket is maintained displacing the excess grout upwardly and out of the caisson pipe, and maintaining internal pressure approximately equal to the outside pressure to allow the deposited grout to set.

7. Method of grouting a rock socket and its joint with a caisson pipe which comprises charging the pipe and socket with water under sufflcient pressure to prevent inilow of ground water through the openings to be grouted, and while maintaining said pressure depositing a charge of fluid grout inside the foot of the caisson pipe, displacing some of the grout out through the openings to be grouted, and removing the excess 12 grout While it is still uid from the inside of the rock socket and allowing the outwardly displaced grout to set while maintaining the inside of the socket under hydraulic pressure substantially equal to the pressure of ground Water outside the socket.

8. Method of grouting a leaky rock socket of a rock socketed caisson to exclude the iniiow of extraneous material which comprises lling the caisson with water, sealing the upper end of the caisson, increasing the water pressure to a value suilcient to prevent the inflow of extraneous material and to force Water out through the leaks to be grouted, extending a grouting pipe down through the caisson pipe to the rock socket, forcing grout through said grouting pipe to deposit a charge of grout in the socket and in the lower end of the caisson pipe while maintaining the iluid pressure in the caisson pipe high enough to create outward flow, forcing grout out through the leaks to be sealed until suilcient has been deposited on the outside of the joint to provide an adequate seal When the grout sets, then stopping the inow of grout and displacing grout out through said grouting pipe by Water forced in at the top of the caisson pipe While holding the pressure inside the joint at not less than the pressure outside the same and allowing the grout outside the joint to set to seal the joint.

9. Grouting means for rock soeketed caissons comprising a head for closing the upper end of the caisson pipe, a grouting conduit extensible to the lower end of the caisson pipe and open at its lower end, said conduit extending through the head and having a, valved grout supply connection and a valved discharge connection, said head having a valved water supply connection for supplying water under controlled pressure into the upper end of the caisson pipe.

JOSEPH H. THORNLEYe No references cited.