Method of and arrangement for setting anchors in loose rock ranging from cohesion-poor to non-cohesion rocks

During setting of anchors in loose rocks ranging from cohesion-poor to non-cohesion rocks, an anchor including a drilling rod and a drilling crown is used, in which the drilling rod is provided with a central axial opening and with radial opening in the region to the drilling crown to supply a mortar suspension or the like through the central axial opening during the drilling process.

BACKGROUND OF THE INVENTION 
Setting of anchors in rocks ranging from friable or cohesion-poor rocks to 
non-cohesion rocks for stabilizing of walls requires special steps for 
obtaining a stable position of the anchor. During the formation of a bore 
hole in such rocks, the problems arise in that the walls must be 
stabilized for preventing their collapse after withdrawal of a drilling 
rod. It is known to drill in these cases with casings and to compress the 
bore holes with cement mortar with simultaneous withdrawal of the tube. In 
this method the injected cement mortar also penetrates into the immediate 
surrounding area of the bore hole. The hardened bore hole filling is then 
again drilled and an anchor is inserted in the thusly produced opening and 
fixed with cement mortar. With this procedure it is possible to set the 
anchors in the above mentioned types of rock; however, this can be done 
with a relatively high time consumption and costs. 
Rock anchors are also known which are simultaneously used as drilling rods 
and therefore include a tubular base body provided with a drilling crown 
at its front end. The above mentioned base body is profiled for producing 
a binding action with a mortar casing and has a plurality of openings in 
its peripheral region. During the drilling the rinsing medium, for example 
water, is supplied through the drilling crown and the above mentioned 
openings. Then after the end of the drilling, a mortar suspension is 
supplied into the produced bore hole. Under the above mentioned 
conditions, the sufficient penetration of the cement mortar in the rock 
surrounding the bore hole is not achieved in many cases, and thereby an 
insufficient adhesion of the anchor is produced. 
A similar problem arises in many cases during production of pile 
foundations composed of individual piles provided with anchors. When for 
example an alternating sequence of cohesion-poor or non-cohesion layers on 
the one hand, and relatively solid layers on the other hand occurs along a 
path corresponding to the length of the pile, special steps must be taken 
to insure that the pile over its entire length has an average 
cross-section sufficient for the static carrying capacity of the 
respective pile foundation. In this case it is impossible to produce an 
opening which subsequently is filled with concrete, since the 
cross-section of the opening in the region of the soil layer is always 
provided with narrowings and the availability of the average cross-section 
over the whole length of the pile cannot be guaranteed in addition to the 
above mentioned narrowings. 
In the latter mentioned case there is of course the possibility of an 
encased drilling, to insure the required uniform cross-section, especially 
maintaining an average cross-section. 
The above mentioned known processes are either very labor and cost 
intensive and require therefore an expensive machinery, or can be used 
only to a limited extent with respect to the coherence of the respective 
rocks. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a method 
of and an arrangement for setting anchors in rocks of the above mentioned 
general type which avoid the disadvantages of the prior art. 
More particularly, it is an object of the present invention to provide a 
method of and an arrangement for setting anchors which insure a reliable 
and stable positioning of anchors with substantially standardized 
available tools or structural elements in the above mentioned complicated 
conditions pertaining to partially cohesion-poor or non-cohesion rocks. 
In keeping with these objects and with others which will become apparent 
hereinafter, one feature of the present invention resides, briefly stated, 
in a method in accordance with which during the drilling a mortar 
suspension or the like is supplied through the central opening of the 
drilling rod provided with radial openings in the region close to the 
drilling crown. 
In accordance with the invention, a known injection drilling anchor can be 
used which, however, is provided at its front region close to the drilling 
crown with outlet openings through which as well as through the central 
rinsing opening a mortar suspension or a similar medium can be supplied 
during the drilling. Directly during the drilling process and in 
particular synchronously with advancement of the drilling, the rock 
surrounding the bore hole is compressed with a mortar suspension so that 
respective steps for stabilization of a bore hole wall are dispensed with. 
Since during this procedure smaller particles released during drilling are 
washed away by the mortar suspension, a high volume mixture including 
coarser released particles and mortar suspension is formed in the 
surrounding area of the drilling rod. In this manner a relatively deep 
penetration of the rock surrounding the bore hole and thereby a reliable 
securing or fixing of the anchor is obtained. A further advantage is 
achieved in the gap-free and therefore reliable encasing of the rock 
anchor with a mortar suspension. Thereby a reliable corrosion protection 
is obtained in the alkaline atmosphere produced in the immediate 
surrounding area of the anchor. 
A further advantage of the method, both for setting of rock anchors and 
forming ground piles for foundations is a one-stage process, since in the 
same working process a quasi drilling and pre-cementing is performed. 
Therefore a preliminary making a hole is dispensed with. 
In accordance with a further feature of the present invention, the process 
is performed so that relatively fine portions of the loosened material are 
washed away and relatively coarse portions of the loosened material are 
rinsed with the mortar suspension and bound with the latter during 
hardening. The outer diameter of the casing produced from the mortar and 
surrounding the anchor is controlled at a predetermined supply pressure of 
the mortar suspension by varying of the speed of drilling. Since the above 
mentioned washing out effect at a predetermined supply pressure of the 
mortar suspension is laterally expanded due to the low mechanical 
stability of the rock surrounding the opening, the radial dimensions of 
the mortar encasing of the anchor can be easily controlled by the drilling 
speed and thereby the drilling advancement. This opens simple 
possibilities for adjusting to different types of rock. 
A further feature of the present invention is the arrangement for anchoring 
which includes the above mentioned anchor with a drilling rod and a 
drilling crown, wherein the drilling rod has a central axial opening and 
radial openings for simultaneously supplying the mortar suspension through 
the central opening during drilling. At the end of the drilling rod facing 
away of the drilling crown, the drilling rod is provided with an adaptor 
which is used for rotary drive and for supply of the mortar suspension. 
In accordance with a further feature of the present invention, the adaptor 
has a bush for receiving an end of the drilling rod and transporting a 
torque, and a stationary housing for supplying a mortar suspension. The 
bush can have openings in the region of the housing and abutment means for 
the drilling rod inside. The housing can form a ring chamber surrounding 
the bush and fixed between immovable and detachable abutment members. With 
this feature the adaptor has an especially simple and advantageous design. 
It is composed of a few basic elements which are easily accessible for 
maintenance and inspection. 
The drilling crown can have a tubular projection, a freely rotatable 
tearing tool, and a support for the tearing tool which can include side 
webs. Such a drilling crown is advantageous for erecting off ground piles 
in soils with an alternating sequence of cohesion-poor and solid layers. 
Since the side webs which laterally extend from the projection form a 
support for the freely rotatable tearing tool, there is a possibility to 
select the radial dimensions of this arrangement so that an opening formed 
in the ground has an average cross-section over its entire length, in 
which the tearing tool is effective and in which in each case a 
penetration of released material and mortar suspension is insured. For 
static computations a definite concrete cross-section can be taken into 
consideration whose radial dimensions are practically determined by the 
respective radial dimensions of the side webs in connection with the 
tearing tools mounted on them. Thereby in these relatively difficult 
cases, a single working step can be used both for producing the opening 
and for compressing the mortar to form a reinforced ground pile over a 
definite depth and, corresponding to the radial dimensions of the drilling 
crown, having definite radial dimensions, said dimensions--as seen over 
the whole length of the pile --do not fall below the dimensions of an 
average cross-section corresponding roughly to the radial dimensions of 
the drilling crown. 
In accordance with a further feature of the present invention, side webs 
can be arranged in a plane extending through the axis of the projection. 
The side webs can be straight and have a square or a rectangular 
cross-section. They can be helically wound in the rotary direction of the 
drilling rod, for example about their longitudinal axes. They can extend 
from the drilling crown rearwardly at an angle relative to the axis of the 
projection in an arrow-like shape. 
When the side webs are formed in accordance with these features, they are 
also suitable as a transporting element for displacing the forwardly 
released material to the rear side of the drilling crown. When the side 
webs are helically wound in the rotary direction of the drilling drive of 
the drilling rod and in some cases surround their longitudinal axes, the 
movement of the side webs in the mixture composed of the mortar suspension 
and the released material leads to a transporting action in direction 
toward the rear end of the drilling crown. The arrow-shaped extension of 
the side webs from the front side of the drilling crown facilitates the 
penetration during the rotary drilling. It should be emphasized that both 
a rotary and impact drilling can be performed as well. 
In accordance with a further feature of the present invention, the drilling 
crown has a plurality of outlet openings for the mortar suspension 
supplied through the drilling rod. The exact location of these outlet 
openings is arbitrary. They serve particularly for escaping of the mortar 
in such a region in which during the rotary drilling the tearing tool 
rotatable opposite to the drilling drive is efficient. The tearing tool 
performs the functions of the mixing elements for making a mixture of 
released coarse-grain material with mortar suspension. Under the action of 
the rotatable tearing tool, a substantially homogenous mixture of mortar 
suspension and released material is produced in the region of the drilling 
crown. It is displaced by the displacing action of the side webs in 
connection with the tearing tool towards the rear side of the drilling 
crown. 
The tearing tools can be arranged so that their axes are perpendicular to 
the side webs, and they can be provided with uniformly distributed cutting 
members. The cutting members or edges can be composed of a hard metal and 
dimensioned so that their effective region is confined inside the mixture 
to be mixed. 
The tearing tools can be arranged so that they cover at most 50% of the 
surface of the bore hole produced during drilling. Therefore, despite the 
rotatable drilling crown a sufficient flow cross-section is available in a 
region of flow of the released material toward the rear side of the 
drilling crown. 
The lateral extension of the side webs can have a radius corresponding to 
such a radius which permit a penetration of the mortar suspension during 
setting a rock anchor or erecting a ground pile. The projection can be 
provided with an outer thread for screwing with a drilling rod, and the 
outer thread can be formed preferably as a round thread or other threads. 
The novel features which are considered as characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A drilling rod in accordance with the present invention is identified as a 
whole with reference numeral 1. It is used simultaneously as an anchor, 
and more particularly both as a rock anchor for stabilization of the walls 
of the hollow spaces and also for piles serving for ground solidification. 
The drilling rod 1 is formed as a hollow cylindrical main body which is 
provided over its entire length with a thread-shaped formation in the 
shape of a round thread. Advantageously it is produced by a cold 
deformation, for example in cylinders or rollers. 
The drilling rod 1 carries at its end a drilling crown 2 which is provided 
in a known manner with a central rinsing opening 3 extending coaxially to 
the drilling rod 1 or its central axial opening 4. 
The drilling crown is formed as a plate-shaped, for example square main 
body, extending transversely to the axis of the drilling rod 1 and 
provided at its peripheral sides with cylindrical depressions 5. The 
depressions 5 have such sizes that their deepest points are in contact 
with an outer circle describing the outer thread. At its end facing toward 
the sole of the bore hole, the drilling crown carries prism-shaped 
projections 6 which have a star-shaped arrangement and serve as cutting 
edges. The projections 6 extend in direction toward the corners of the 
square main body. The projections 6 are formed around the lateral limiting 
edges of the above mentioned main body and end at a small distance from 
the points at which the drilling rod 1 is arranged. In this construction 
the projections 6 or the cutting edges are effective not only at the end 
side but also in the peripheral region. At the side of the bore hole sole 
the projection 6 ends in the central region of the main body in inclined 
surfaces 7 which are inclined in direction toward a mouth of the rinsing 
opening 3. In its axial direction, or in other words in direction of the 
arrow 8, the drilling crown 2 has as short size as possible. The 
connection between the drilling crown 2 and the drilling rod 1 is 
preferably formed releasable. 
Since the drilling crown 2 is formed as short as possible in the direction 
of the arrow 8, the rock material released during the operation of the 
drilling rod in the end side region of the drilling head can be 
transported over a shortest path and also with minimum possible flow 
resistance to the side region of the drilling crown which faces away of 
the bore hole sole. Since the drilling crown 2 is releasbly mounted on the 
drilling rod 1, an exchange of the drilling crown for adjusting the 
drilling rod to different crown or rock properties or drill hole diameters 
is possible. 
The drilling rod in its region adjacent to the drilling crown 2, or in 
other words extending from the drilling crown over a length of for example 
0.5 m, is provided with openings 9. The central opening 4 of the drilling 
rod 1 communicates with the outside through these openings. 
One or several extension portions are connected with the drilling rod 1 by 
not shown coupling parts. They correspond to the drilling rod 1 in their 
sizes and their other characteristics, however, are not provided with the 
openings 9. 
The drilling rod 1 itself or the drilling rod extended in the above 
described manner is provided with an adaptor part 10 at its end facing 
away from the drilling crown 2. The adaptor part 10 is schematically shown 
in FIG. 3. It has a connecting portion 11 connected to a not shown conduit 
for anchoring mortar or a mortar suspension. A not shown coupling part for 
connecting a conventional drilling drive for drilling and/or impacting 
operation is provided at the point 12. 
The adaptor part 10 as shown in FIG. 3 has a bush 13 with an inner thread 
corresponding to the outer thread of the drilling rod 1. The bush 13, as 
shown in the point 14, is inwardly closed and is again provided with an 
inner thread at 12. This inner thread forms a coupling member for a not 
shown drilling drive. An abutment body 15 is fixedly mounted on the outer 
surface of the bush 13, and its function will be explained hereinbelow. 
The bush 13 is surrounded by a stationary housing 16 which carries a 
connecting member 11 and which is provided with an inner annular chamber 
17. The chamber 17 communicates in a not shown manner with the connecting 
member 11, so that the mortar suspension can be supplied through the 
connecting part 11 in direction of the arrow 18 into the annular chamber 
17. A cylindrical recess 19 is formed in the outer surface of the bush 13 
radially directly opposite to the annular chamber 17. The recess 19 is 
provided with a plurality of radial openings 20. 
An impacting member 21 is screwed in the bush 13. In the shown embodiment 
it is formed as a relatively short tubular cylinder provided with an outer 
thread. It is inserted to the location 14 at which the inner chamber of 
the bush is closed. The impacting member 14 is provided with a plurality 
of radial openings 22, which are in alignment with the openings 20. 
Therefore, the annular chamber 17 and the inner chamber of the abutment 
member 21 communicate with one another for supplying the mortar 
suspension. The impacting member 21 insures that during screwing of the 
end of a drilling rod into the bush 13, the screwing-in depth of the 
drilling rod is limited and the drilling rod does not cover the openings 
20. The housing part 16 which surrounds the bush 13 with a small play is 
held in its position abutting with a small play against the abutment body 
15, by means of a further abutment body 23 which is axially movable 
relative to the bush 13. The abutment body 23 is arrested on the bush 13 
by a plurality of clamping screws 24. In operation of the adaptor part 10, 
the housing 16 is immovably held between the abutment bodies 15 and 23 
which are rotatable together with the bush. 
The arrangement described in FIGS. 1-3 is used for setting rock anchors in 
friable rocks which range between rocks with low coherence to rocks with 
no coherence at all. In such situations during drilling instead of 
conventional rinsing means, a mortar suspension or cement dispersion is 
used, which is supplied through the connecting member 11 under pressure. 
During the drilling advance the mortar suspension flows both from the 
rinsing opening 3 of the drilling crown 2 and from the openings 9 of the 
drilling rod 1. A relatively fine grain material produced during the 
drilling process is washed away, while to the contrary the relatively 
coarse material remains in the bore hole and forms directly a mixture with 
the mortar suspension so as to harden at a later time, together with the 
latter. The mortar suspension required for producing a bond between the 
anchor on the one hand and the surrounding rock on the other hand, is 
introduced into the bore hole during the drilling process. Thereby not 
only the stabilization of the bore hole obtained directly during drilling, 
but also relatively large-space penetration of mortar suspension in the 
rock surrounding the bore hole is achieved. The last mentioned effect is 
further improved by the washing away of relatively fine-grain material. In 
the finally finished bore hole, the anchor is surrounded by a 
concrete-like casing which is composed of a mixture of mortar suspension 
and relatively coarse rock particles. Due to the large-volume penetration 
of the mortar suspension into the surrounding rock, a stabilization of the 
rock and a reliable mounting of the anchor is produced. 
FIGS. 4-6 show a drilling crown 2 which is designed for a predetermined 
application. This is the case in which an alternating sequence of layers 
of friable or non-coherent rock and relatively solid supporting layers are 
arranged in direction of the depth of a bore hole. The characteristic 
feature of this layer sequence is that in the region of the friable layers 
a collapse of the walls of the bore hole must be taken into consideration, 
while this does not occur in the region of the solid layers. For 
eliminating the disadvantages connected with the expected non-uniform 
cross-section of the bond system including the anchor and the surrounding 
mortar layer, a drilling head 2 described hereinbelow is proposed. 
The drilling head 2 includes a tubular projection 25 which is provided 
outside with a relatively coarse thread, preferably a round thread. It has 
side webs 26 mounted on its front part facing toward the sole of the bore 
hole. The mounting can be performed in any manner, for example by welding 
with the outer wall of the projection 25. 
The above mentioned side webs 26 extend in the shown embodiment 
substantially in a plane which includes the axis 27 of the projection 25. 
They extend from the projection 25 rearwardly in the shape of an arrow, or 
in other words, directed from the sole of the bore hole. In accordance 
with FIG. 4, they form an angle of approximately 45.degree. with the axis 
27 and can have for example a square cross-section as well as a 
rectangular cross-section. 
The projection 25 is formed screwed by its thread with the drilling rod 1 
formed in accordance with the embodiment of FIGS. 1-3. In the mounted 
condition of the drilling head 2, the axis 27 is coaxial to the central 
axial opening 4 of the drilling rod 1 in FIG. 1. The opening 28 of the 
projection 25, which forms the extension of the opening 4, ends in a 
portion 29 at its end facing toward the sole of the bore hole. The portion 
29 has a conical end tip and is provided with a rinsing or outlet opening 
30 at its end. The opening 30 is coaxial to the axis 27. The projection 25 
is provided with further lateral outlet openings 30' which communicate 
with the opening 28. 
Tearing tools formed a rotational bodies are identified with reference 
numeral 31. They extend perpendicularly to the side webs 26 and are freely 
rotatable around axes 32 lying in their plane. The tearing rools 31 are 
arranged on the side webs 26 at their sides facing toward the sole of the 
bore hole. The rotary support of the tearing tools 31 on the side webs 26 
can be obtained in any desirable manner as long as the strength required 
for the drilling operation is ensured. 
Each tearing tool 31 includes a rotation-symmetrical ring member 33 with a 
plurality of cutting members 34 arranged at its peripheral outer side. The 
cutting members 34 are preferably uniformly distributed over the periphery 
of the ring member 33. The cutting members 34 in the shown embodiment have 
a parallelepiped shape with projecting cutting edges 35 at their front 
side, or in other words, at their side facing toward the sole of the bore 
hole. It is to be understood that the remaining edges of the cutting body 
34 also operate as cutting edges. The above described both tearing tools 
31 are formed as identical elements with respect to one another. 
The system composed of the side webs 26 and the tearing tools 31 has such 
dimensions that, as considered in an axial projection of FIG. 6, it 
occupies at most 50% of the surface with the radius 36, within which the 
tearing tools 31 provide a drilling or loosening action. As a result, 
during the drilling advance a sufficient cross-section in the region of 
the rotatable drilling head is available for transporting the torn, 
comminuted or loosened material to the rear side of the drilling head 2, 
or in other words to the side opposite to the sole of the bore hole. 
A cutting member 37 extends on each tearing tool 31 over its ring member 32 
at its side facing toward the sole of the bore hole. The cutting member 37 
has an angular prismatic shape. It further contributes to the cutting, 
tearing and loosening action during the drilling advancement. 
The utilization of the drilling head 2 of FIGS. 4-6 is substantially 
similar to the utilization of the above described drilling head. During 
producing of a bore hole, preferably with operation of an exclusively 
rotatable drilling head, a mortar suspension is directly supplied into the 
drilling rod, flows through the axial opening 4 into the opening 28 of the 
drilling head, and finally exits through the outlet openings 30, 30'. Due 
to the drilling process, the friable rock is loosened, fine or finest 
components are washed away, while the coarse components are mixed with the 
discharging mortar suspension to finally harden with the latter. The 
tearing tools which rotate during the rotary drilling opposite to the 
rotary direction of the drilling rod act for tearing the rock during the 
drilling advance, and also partially comminute the loosened coarse 
particles, especially a mixture of the loosened particles with the mortar 
suspension discharged through the openings 30, 30'. The tearing tools 
thereby simultaneously perform the function of mixing organs, so that 
during the drilling advancement a mixture of mortar suspension and coarse 
rock particles is formed behind the drilling crown 2, and the zone of the 
rock loosened by the drilling process or the bore hole remains constantly 
filled and no hollow spaces are formed. In the final condition, the anchor 
formed by the system of the drilling rod and drilling crow is bound on its 
whole length in the mortar impregnated with rock particles. In 
correspondence with the consistency of the surrounding rock as well as the 
introducing pressure of the mortar suspension, more or less deep 
penetration of the mortar suspension and the surrounding rock is achieved. 
The region of the rock or ground penetrated by the discharging mortar, 
which after hardening around the anchor forms a concreted, stabilized 
zone, has however an average cross-section which is independent from the 
layer sequence of the ground and is determined by the radius 36. 
The latter means that, for example with the use of the process with 
reinforced pile foundations, the average cross-section of the pile is 
determined by the radius 36 depending on the construction of the drilling 
crown. This further means that with the given difficult conditions with 
alternating sequence of layers with different consistency, a ground pile 
can be set whose average cross-section is variable by structural 
dimensions of the above mentioned radius 36 in wide limits. The necessity 
of using a casing drilling is dispensed with, and a single working step is 
utilized for introducing the anchor into the ground or soil in a drilling 
manner and for compression of the mortar during drilling. 
The above described drilling crown can be modified in various forms. In 
particular, any tearing tools rotatable about their axes can be used to 
perform simultaneously certain mixing action for the mixture of rock 
particles and mortar suspension. Moreover, the side webs 26 can be wound 
in a helical manner as seen in direction of the arrow VI, and also with 
respect to their longitudinal axes and their cross-section can have such a 
profile that a transporting action of the rock loosened by the tearing 
tools can be performed in direction of the sole of the bore hole. 
It is possible to use more than two tearing tools 31, as long as a 
sufficient space for displacing the material loosened in the region of the 
bore hole sole is retained in the section torn by the radius 36. Also, 
instead of two side webs 26, more side webs can be provided as long as the 
above mentioned requirements are satisfied. useful application in other 
types of constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
method of and an arrangement for setting anchors in loose rocks ranging 
from rocks with poor cohesion to rocks with no cohesion, it is not 
intended to be limited to the details shown, since various modifications 
and structural changes may be made without departing in any way from the 
spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.