US3507121A

US3507121A - Tie rod anchoring method and apparatus

Info

Publication number: US3507121A
Application number: US731685A
Authority: US
Inventors: Carl-Olof Oskar Morfeldt
Original assignee: Atlas Copco AB; Sandvik AB
Current assignee: Santrade Ltd; Atlas Copco AB
Priority date: 1964-11-11
Filing date: 1968-05-20
Publication date: 1970-04-21
Anticipated expiration: 1987-04-21
Also published as: NL139791B; DE1297044B; AT275419B; FI44359B; NO121388B; SE318830B; CH459074A; GB1129113A; NL6514655A; BE672171A

Description

April 21; 1970' CARL-O LOF' 'QQMORFELD 3,

TIE ROD ,ANCHORING METHOD AND APPARATUS 7 Original Filed Nov. 1, 1965 I v s Sheets-Sheet 1 I NVEN 70R CarL- Dim Qskar MorfeLdt ATTURNEYS April 0 b. |v'|oRFE:LD1f 3,507,121

I TI nonin'cnonme Mmflob AND APPARATUS- Original Filed Nov; 1955 s Sheets-Shet INVEN TOR Carl- Olaf Os/uir NorFe cH:

ATTORNEYS A ril 21 1970'. "CAL OLOFd,MOIFELDT 3,507,12

3 ROD ANCHORING METHOD AND APPARATUS v Original Filed QvQi. 1965 s Sheets-Sheet s INVENTOR CwrL- 0101 Oskar Morfeldi:

"11% JW 2; RM

ATTORNEYS United States Patent 3,507,121 TiE ROD ANCHORING METHOD AND APPARATUS Carl-Olaf Oslkar Morfeidt, Lidingo, Sweden, assignor of one-half to Sandvikens .Iernverks Aktiebolag, Sandviken, Sweden, a corporation of Sweden, and one-half to Atlas Copco Aktiebolaget, Nacka, Sweden, a corporation of Sweden Continuation of application Ser. No. 505,877, Nov. 1, 1965. This application May 20, 1968, Ser. No. 731,685 'Claims priority, application Sweden, Nov. 11, 1964, 13,549/64 Int. Cl. E02d 5/74 US. C]. 6139 1 Claim ABSTRACT OF THE DISCLOSURE According to the present invention, anchoring of a structural part in the ground is effected with the use of a hollow tie rod which at one end thereof is provided with an anchoring head which can (where the same is required) penetrate rock as Well as loose earth. The tie rod is forced--anchoring head firstinto the ground, being extended as desired by the addition of lengths of hollow tie rod to the initial rod, until the anchoring head has reached a desired anchoring locus; then, a fluid grouting composition is passed into and through the tie rod and through the anchoring head into the area surrounding the anchoring head and fore part of the tie rod. Once the grouting has hardened it adheres to the head and the adjacent part of the tie rod, thereby anchoring the rod in the ground. Finally, the rear end of the tie rod is connected to the structural part to be anchored.

This application is a continuation of application 505,- 877, filed Nov. 1, 1965 now abandoned.

The present invention pertains to a method for anchoring tie rods in the ground for supporting and stabilizing objects as permanent and provisional building structures for instance retaining walls for housing foundations and wharves, coiferdams, suspension bridges, antenna masts, etc. The invention also pertains to a tie rod for performing the method and an anchored construction made in accordance with the method. I

If for instance a levelled site is excavated in the ground and the boundaries thereof are supported by a retaining wall of sheet piles, it provides certain problems to support the wall againts the earth pressure acting from the surrounding ground. These problems are especially difficult in townareas when excavating sites for house foundations, tunnels etc. in the midst of surrounding buildings, which have to be protected against sagging and collapsing. A common method is to support the retaining wall at the inside by means of struts, but this implies the obvious inconvenience that the struts occupy a part of the site. Another alternative is to use long sheet piles and drive them into the ground sufficiently deeply below the bottom of the excavation in order to obtain stability against the earth pressure. This requires, however, very long sheet piles and cannot be done if there is rock ground under the earth material situated at a too high level. Therefore the sheeting is often anchored by means of tie rods directly outwardly from the excavated site. The tie rods can be anchored in earth material either by means of anchor piles or anchor blocks or slabs, but this is expensive and does often not provide a sufficiently strong support. When the rock level is high this kind'of anchoring is often difficult or even impossible to employ. An efficient anchoring is obtained by attaching the tie rods in rock ground below the earth, but with previous 3,507,121 Patented Apr. 21, 1970 methods this requires excavation of the earth layers in order to lay the rock bare or alternatively insertion of a tube casing through the earth down to the rock.

The invention provides a solution to the previous problems by a new method for anchoring by means of tubular tie rods which are driven into the ground to a suitable length and depth for anchoring, after which a grouting mix is supplied under pressure along the internal cavity of the tube to the anchored end and is injected into the surrounding ground. After hardening of the grouting mix the hardened body forms an anchor on the rod. In order to render it possible to drive the rod to sufficient length the rod should comprise a number of shorter rod parts, which are interconnected, suitably by threaded connections as for instance coupling sleeves. Furthermore the tie rod should at its protrusion end have an anchor head which is adapted to penetrate through stony material and into rock ground.

Further details of the invention appear from the following specification and the appended drawings which illustrate:

FIG. 1, a section of a sheet piling anchored in rock ground by means of a tie rod according to the invention.

FIG. 2, a section on a somewhat smaller scale of a sheet piling anchored in earth ground by means of a tie rod according to the invention.

FIGS. 3-8 show details of the tie rod according to the invention.

FIG. 1 shows a sheet piling 10 with

earth layers

11 and 12 on 'both sides. The layer 11 has a higher level than the layer 12 and exerts an earth pressure on the sheeting. Below the earth layers there is rock ground 13. Earth material on rock ground as shown in the figure is often called overburden.

For supporting the sheeting against the earth pressure a tie rod 20 is driven in obliquely downwardly at an inclination of for instance 3550 to the horizontal plane through the soil layer 11 into the rock ground. The tie rod is tubular and is composed of shorter tube parts 21, which are externally threaded at their ends and jointed by means of internally threaded coupling sleeves 22. At the lower end of the rod an anchor head 23 is attached which has cutting edges, in order that the tie rod can be drilled through the overburden layer 11 and possible stones and a distance into the rock ground.

The upper end of the rod comprises a rod element 25- forming a connection adapter for connection to the waling 27 of the sheeting. A nut 26 screwed onto the adapter 25 rests on the waling 27 and transmits the force from the sheeting 10 to the tie rod 20.

FIG. 3 shows a tubular rod part 21 for the tubular rod 20. The rod part 21 has external threads 30 at each end and an internal cavity 31 extending along the whole rod part. The internal diameter should be sufliciently great to let through a sufiicient flow of grouting mix and is usually l020 mm., often 12-18 mm. The outer diameter is chosen so large that the wall thickness of the tube is sufiicient for obtaining the necessary mechanical strength for resisting as well the percussion stresses when the rod is driven into the ground as the tension from the anchored sheeting. The wall thickness can be for instance 320 mm, preferably 515 mm. The outer diameter is suitably l.5-3.0 of the internal diameter.

The tubular rod part 21 has suitably a cylindrical external surface in order to facilitate the rotation thereof when it is driven through earth material or other overburden material but it is also possible to use a rod having a polygonal outer cross section. The length of the rod parts can be 24 meters or preferably 2.5-3.5 meters. This length can be equal for most of the rod parts in a tie rod, but in order to adapt the position of the upper end of the rod correctly in relation to the waling, it is convenient to have a set of rod parts of varying lengths for connection at the upper end.

FIG. 4 shows a coupling sleeve 22 having an internal thread 32 matching the external threads30' on the rod parts. The tie rod is formed by coupling together the rod parts by means of the extension sleeves, so that the end surfaces of the rod parts abut, the cavities 31 forming a continuous cavity along the whole tie rod. Instead of using separate coupling sleeves the rod parts can be externally threaded at one end, the other end being widened and threaded internally with a thread matching the external thread.

FIG. shows a shank adapter 33 for connecting the tie rod to a percussion drilling machine, one end 34 being threaded for connection to a coupling sleeve, the other end being adapted for connection to a rock drill or rod driving machine. A hole 36 through the wall of the adapter is connected to an internal longitudinal cavity 37, so that a flushing medium as water, which is usually necessary for drilling in rock, can be supplied by means of a flushing head along the internal cavity to the fore end of the rod. In the same way a grouting mix can be supplied when the drilling is finished.

FIG. 6 shows the connection adapter 25, which has one end 38 threaded for connection to a coupling sleeve, the other end being threaded with a thread 39 suitable for the connection of an anchoring element like the nut 26 in FIG. 1. The thread 39 should have a sufficient length to permit tightening of the nut and a relatively small pitch so that the nut can be tightened against the pressure acting on the anchored sheeting. This means that the thread 39 usually has a greater length and a smaller pitch than the thread 38, the pitch of the latter usually being comparatively large. The portion 40 of the connection adapter between the threads can suitably be polygonal as illustrated in the figure, so that the adapter can be held with a wrench when tightening the nut 26.

When driving in the tie rod the shank adapted 33 is screwed into the uppermost extension sleeve 22a (FIG. 1). The grouting can be performed through the shank adapter or some other adapter by means which are obvious for the person skilled in the art and therefore not illustrated. For attaching the tie rod to the anchored construction the shank adapter is removed and substituted by the connection adapter 25.

FIG. 7 illustrates the anchor head 23, which at its rear part is threaded and screwed onto the foremost tube part 21 in the rod and at its fore part has cutting edges 70 on hard metal inserts brazed to the head. The inserts may have relatively small dimensions, because the rod has to penetrate an often easily penetrable layer of earth material plus possibly a number of stones and, in case of rock ground anchoring, also a short distance into the rock ground. The diameter of the cutting edge portion should be greater than the diameter of the parts of the rod behind the anchoring head and preferably also'greater than the diameter of the coupling sleeves.

The rear surface 71 of the anchoring head and the laterally projecting portions 72 behind the cutting edges provide a firm grip between the tie rod and the grouted material. The firmness of connection is increased by the adhesion between the mantle surface of the rod and the grouted material, and the connection is further strengthened if the grouted material extends so far rearwardly along the tie rod that one or more of the coupling sleeves become embedded therein.

For supply of flushing medium when the rod is driven in and also for supply of grouting mix the internal cavity of the rod terminates at openings 73 in the anchoring head. Such openings should preferably be placed only at or in the vicinity of the penetration end of the rod and not further back, because rearwardly situated openings would cause too great losses of flushing or grouting medium. The openings 73 may be placed laterally on the flushing head, in order to prevent earth material from being forced into them, and they can for this purpose be more or less rearwardly directed. It is, however, possible to have also one or more forwardly directed openings, for instance in the front surface of the anchoring head. The openings should be sufliciently large to let through a sufiicient flow of grouting mix, and it is often suitable that the total area of the openings is equal to or even greater than the area of the channel in the rod.

FIG. 8 shows a flushing head 75 for connection to the shank adapter 33, illustrated in FIG. 5. The flushing head has on its inside gaskets which tighten the connection on both'sides of the hole 36 in FIG. 5. The flushing head can be used as well for supply of flushing medium as for the grouting.

When anchoring a construction with tie rods according to FIG. 1 the tie rods are suitably driven in before excavation of the ground down to the level marked 12. Along a sheet piling of the illustrated kind there are of course several tie rods, the spacing distance between them being determined in dependance of the height of the sheeting and other factors according to conventional calculations.

When the tie rods are driven in by means of a percussion drilling machine, the rod is provided with a shank adapter as the one above described for connection to the drilling machine. The rod consists of shorter parts 21, which implies the important advantage that the rod can be driven in to a great length at the same time as the length of the rod can be adjusted to a varying level of the rock ground. It is thus possible to anchor the rods in rock ground even if the rock is situated at a deep level below the ground. The rod is driven into the rock to a sufficient anchoring depth, which depends upon the quality of the rock. In general a suitable anchoring length is 1-5 meters, preferably 2-4 meters. When anchoring a retaining wall in rock ground as illustrated in FIG. 1 the tie rod should usually be inclined about 45.

When the desired penetration is achieved, grouting mix is supplied at the rear of the rod and pressed along the internal channel to the anchoring head and through the opening or openings in the latter. The mix fills the drilled hole 28 in the rock, and in case the rock is cracked the mix fills also the cracks and strengthens the rock. When the mix has hardened it anchors the rod 20 in the rock. When the mix has obtained suflicient hardness, the shankadapter 33 is removed and replaced by the connection adapter 25. The nut 26 is screwed along the connection adapter to contact with the waling. Thereafter the ground can be excavated down to the level 12.

The method according to the invention can be employed also for anchoring in earth material without underlying rock as illustrated in FIG. 2. A sheet piling Wall 50 is subjected to pressure from the earth mass 51. The sheet piles are driven in to below the level-of the ground layers 52 on the opposite side of the sheeting. For supporting the sheting, tie rods 53 are driven in obliquely downwardly through the earth material 51. In the same way as described in connection with FIG. 1 this can be done before excavating the ground to the level 52. Grouting mix is supplied through the tubular rod and injected into the ground, so that the lower part of the rod is surrounded by a mass 54 of earth material mixed with grouting mix. The mass 54 adheres to the rod and forms after hardening a ballast anchor on the rod. The other end of the rod is connected to a waling 55 on the sheet piling. The spacing between the tie rods and the inclination of the rods are determined by conventional calculation based upon the height of the sheeting, the properties of the soil, etc. A tie rod with a small inclination angle to the horizontal plane is more effective than a steeper inclined rod, because the tension therein provides a greater horizontal component for supporting the sheeting, but on the other hand the ballast anchor 54 cannot be too close to the surface of the ground, because then it will become too weakly anchored. When anchoring a sheet piling in earth material as shown in FIG. 2 the tie rods connected to the upper part of the sheeting are suitably inclined downwardly by an angle of 30. In order to stabilize the lower part of the sheeting extra tie rods 60 can be driven in along the lower part of the sheeting and in the same Way provided with ballast anchors 61 and connected to the sheeting at walings 62. Such extra support is useful when the lower level 52 has to be excavated to a depth close to the lower end of the sheeting, the passive earth pressure from the earth layer 52 being so small that it is insufficient for stabilizing the lower end of the sheeting against the active earth pressure from the opposite side. The lower tie rods can be inclined by a small angle than the upper ones and may be horizontal.

When anchoring other kinds of constructions the inclination of the tie rods can be other than now mentioned. For-anchoring foundation slabs, caissons and similar the tie rods can be directed vertically downwards. In other cases it would be possible to use more or less upwardly directed tie rods as for anchoring the roof of a tunnel in earth material.

As grouting mix is used preferably cement slurry with or without sand. The setting and hardening properties of the cement should be chosen with regard to the circumstances in each case. If for instance there is a risk that the cement is washed away by water in the ground, then a rapidly setting cement should be used. By setting of concrete is meant the beginning of the hardening and by hardening is meant the subsequent period during which the concrete obtains its final strength. As above mentioned the internal diameter of the tie rod and the openings of the anchoring head should be sufliciently large to let through a sufficient flow of the mix, so that the grouting is performed before the setting of the mix begins. Instead of concrete other grouting mixes can be used which have the property of hardening from fluid to solid state after a certain period of time, for instance lime slurry or plastic.

During the grouting the mix should be spread along the tie rod in order to obtain adhesion between the grouted mass and the rod. At the same time it is desirable to spread the grouting mix as far as possible in the lateral direction, so that the anchoring surface perpendicularly to the rod becomes as large as possible. The spreading in the longitudinal direction can be improved by pulling the rod back and forth in the longitudinal direction during the grouting. Another way of increasing the longitudinal spreading is to use grouting mix instead of Water as a flushing medium during the final stage when the rod is driven in.

The length of the tie rod for anchoring in earth ma terial depends on several factors as the properties of the earth, the inclination of the rod and the level of the grouted zone in relation to the ground level. Usually the suitable tiev rod length is l030 meters, often -20 meters. The length of the grouted zone may be 3-5 meters. As above said a necessary condition for driving in the tie rod to a great depth is that the rod is composed of shorter rod parts which can be added to the rear end of the rod successively as the driving in proceeds by aid of for instance a percussion drilling machine. A tie rod in one piece cannot be driven in to the depth which can be achieved by the rod according to the invention.

The material in the rod should endure a high constant tensile stress and at the same time permit the driving in by a drilling machine or in some other way. A suitable material is in the first place steel of an analysis and heat treatment which gives the desired properties. It is poss ble to use carbon steel, but in order to increase the tensile strength it has been found suitable to employ a low-alloyed steel containing manganese. The tensile strength can be further increased by tough hardening the steel. If the tie rod is to be used under long time corroding conditions it can be made of a corrosion resistant material.

As appears from the foregoing the method according to the invention provides essential advantages when anchoring such objects as foundations of buildings, sheet pilings and similar in ground, which at least adjacent the anchored object consists of earth layers. The invention provides possibilities for anchoring objects in rock ground which is covered by earth without preceding removal of the earth or insertion of a protective casing through the earth. As the tie rod consists of interconnected shorter portions it can be driven in to a great depth, so anchoring can be performed in rock ground even if the rock is covered by an earth overburden of relatively great thickness. Furthermore the length of the rods can be adapted to the level of the rock by using a suitable number of rod parts. Cracked rock can be strengthened by injecting so much grouting mix that not only the hole formed by the tie rod in the rock but also the cracks in the rock around the hole are filled with grouting mix. The described anchoring in rock can of course also be adapted for anchoring in large stones.

The property of the tie rod according to the invention that it permits driving in to great lengths and depths can be used for anchoring also in ground consisting exclusively of earth material as above described. This means a great saving of work when anchoring for instance a wharf wall. Such anchoring has earlier often been done by excavating earth for the tie rods and anchor slabs at the ends of the rods. After mounting the rods and the anchor slabs the excavated earth has been brought back to its original place. The invention makes such excavation unnecessary, as the rods are driven into the ground and the anchor is cast directly by grouting of the earth material. By aid of the invention it is also possible to perform anchoring in earth layers of such thickness that the rock cannot be reached, the anchoring being simple to perform in comparison with previously known methods, at the same time as the anchoring can be easily adapted to tension loads of different sizes and can be used also for great tension loads.

A special advantage of the invention is that it permits anchoring in places where no anchoring has been possible with previous methods, as for instance at the lower end of a sheet piling, at a sheet piling in an earth tunnel or at other kinds of Work, where the tie rod is anchored at a zone far below the level of the ground.

In the foregoing is described how the invention is used for anchoring either in rock covered by earth or in earth material only. The invention can be modified for anchoring in ground situated under water as the bottom of rivers and lakes. For this purpose the tie rod is driven through the Water into the bottom and grouting is performed. This kind of anchoring is actual especially in connection with water buildings as colferdams, caissons and bridge pillars, and makes it possible to anchor said constructions rapidly and effectively in the bottom without diverting the water.

In general the invention makes it possible to anchor a tie rod at an anchoring zone which is separated from the anchored object by intermediate layers of any kind, and the anchoring can be made without previous removal of the said intermediate layers by excavating, insertion of tube casings, draining by aid of colferdams and similar.

I claim:

1. Method of anchoring in the ground a part of a building structure by means of a single-walled imperforate hollow tie rod an initial section of which supports at its fore end a hollow anchor head with wear-resistant inserts and openings for discharge of fluids and being driveablefore end firstinto loose earth and into rock, which comprises driving the initial section of tie rod into the ground --anchor head first; adding a similar section of imperforate hollow tie rod to the initial section by the aid of coupler means; as the rod is being driven into the ground supplying a flushing medium to the rear end of the rod and forcing the same through the rod into the anchor r .c 7 1 head to issue only through openings in the anchor head; continuing to drive the tie rod into the ground and adding additional similar imperforate sections until the anchor head is located at a desired anchoring locus in the ground whilst a part of the tie rod to the rear of said anchor head is in a loose earth environment in which it would be unfeasible to secure a tie rod, the driving being performed in such a way that if the rod meets rock after penetrating loose strata it is driven a distance into the rock for subsequent fastening in the rock by grouting but if the rod continues to meet only loose strata it is driven to a suflicient anchoring depth; passing a fluid grouting composition into and through the tie rod and into the anchor. head to issue only through openings in the anchor head into the area surrounding the anchor head and adjacent portion of the tie rod where said composition hardens to and bonds the particles of said area together to provide an anchor on the tie rod; and finally connecting the rear end of the tie rod to the building structure part to be anchored.

. A 7 8 7 References Cited UNITED STATES PATENTS 10/ 1965 Whittington 61--53.68 1/1966 White 61-39 4/1966 Ratliff 6139 1/1968 Turzillo 61-39 3/1968 Lagerstrom 52155 FOREIGN PATENTS 4/ 1964 Canada. 3/ 1964 Switzerland.

HENRY C. SUTHERLAND, Primary Examiner 15 J. L. RIDGILL, J 11., Primary Examiner US. :1. X.R.