AU2005297473B2

AU2005297473B2 - Method for embedding rock anchors

Info

Publication number: AU2005297473B2
Application number: AU2005297473A
Authority: AU
Inventors: Archibald Richter
Original assignee: Minova International Ltd
Current assignee: Minova International Ltd
Priority date: 2004-10-21
Filing date: 2005-10-21
Publication date: 2011-05-12
Anticipated expiration: 2025-10-21
Also published as: RU2007118695A; CN101048574B; AU2005297473A1; PL1805395T3; DE502005010239D1; WO2006042530A1; DE102005050929B4; DE102005050929A1; ZA200702994B; RU2376474C2; CA2584378A1; EP1805395A1; ATE480695T1; US20070264088A1; CN101048574A; EP1805395B1; CA2584378C

Abstract

A hardening mass is comprised of a mixture of hardenable plastic and hardening plastic supplied to an inner channel (8) of a drill rod (1) over a preset transport time. The plastics and the mixing ratio of the plastics are selected such that the transport time corresponds to a hardening time and the hardened mixture fills the flow path between the mixing point and output of a drilled hole of a rock.

Description

Method for embedding rock anchors The invention relates to a method for embedding rock anchors. 5 A prior method for embedding rock anchors is taught in DE 102 34 255 Al. In this method a drilling/injection anchor, in the form of a drill rod having a central internal passage, is driven into the rock to be consolidated. Flushing with liquid is simultaneously carried out, whereby the drilled hole is LO widened. Upon attainment of a predetermined drilling depth injection of a viscous cement mixture takes place through the internal passage of the drill rod, which cement mixture fills the drilled hole and hardens to form a concrete core in which the drill rod remains. 15 This method is intended in particular for soft and sandy rock. In harder rock, as is encountered in particular during headway timbering in underground mining or when tunnelling, curable plastics materials are primarily used instead of concrete. 20 These curable plastics materials are introduced into the drilled hole through a lance after the hole has been drilled and the drill rod withdrawn; the lance is then immediately withdrawn from the hole and a rock anchor driven into the drilled hole, which rock anchor is then bonded by the curable 25 plastics material to the surrounding rock in a secure and load carrying manner. The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the 30 purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present 2 invention as it existed before the priority date of each claim of this application. Throughout the description and claims of this specification, 5 the word "comprise" and variations of the word, such as "comprising" and "comprises", is not intended to exclude other additives, components, integers or steps. It is a preferred object of the invention to provide a method 10 whereby, in a continuous work process, an anchor rod, which may also be the drill rod, is embedded as a rock anchor by filling the drilled hole with a curable plastics material, it being ensured, firstly, that the drilled hole is filled with the plastics material over its entire length and, secondly, that 15 despite the usual overhead working no significant quantities of plastics material escape from the drilled hole. According to the present invention there is provided a method for embedding a rock anchor, whereby an anchor rod having an 20 internal passage is inserted in a drilled hole, through which internal passage a free-flowing, self-curing composition is forced, comprising filling the finished drilled hole with the composition such that the composition cures in the drilled hole with the anchor rod remaining in the drilled hole to form a 25 rock anchor, wherein the method comprises the steps of: e drilling the drilled hole; e selecting a hardenable plastics material, a hardening plastics material and their mixing ratio such that a self-curing composition formed from the hardenable 30 plastics material and the hardening plastics material in the defined mixing ratio has a curing time H; e feeding the hardenable plastics material and the hardening plastics material to the internal passage of the anchor rod for a predetermined feed time F; 35 and 3 e mixing the plastic materials at a mixing point located shortly before or in the internal passage to form the self-curing composition; wherein the feed time F and the curing time H are 5 coordinated to one another such that the feed time substantially corresponds to the curing time and leads to substantially complete filling with the self-curing composition of the flow path between the mixing point and the outlet of the drilled hole. 10 In this solution, account is taken of the fact that curable plastics materials yield in a short curing time significantly greater hardness or viscosity than a cement injection. On the other hand, it is avoided that the curable plastics material 15 causes contamination of the drilling machine or the environment, or that relatively large quantities of the plastics material are expended in an uneconomic manner. To produce such hardening, a radical polymerisation of curable 20 components such as unsaturated polyester resins, vinyl esters, epoxy acrylates and silicate resins is used - for example, by admixing peroxides in a volume ratio of 1:1 to 10:1. Suitable curable and hardening plastics are described, for 25 example, in DE 103 15 610 B4, DE 101 24 466 Cl and DE 102 18 718 Cl. A major advantage of the invention is that it permits substantially automatic filling of the drilled hole, the latter being filled substantially completely from the tip of the drill rod or rock anchor to the mouth of the drilled hole, and the 30 drill rod or rock anchor being completely encased with the hardened plastics material. An essential safety requirement of mining and tunnelling is thereby fulfilled. One of the essential criteria of the invention is that the feed 35 time F and the curing time H are coordinated with one another.

4 The curing time H of the plastics material is determined by the selection of the hardenable plastics material and of the hardening plastics material and optionally of further components, and by the mixing ratio of the components, but also 5 by the temperature of the environment, of the quantitatively major components and of the rock. The feed time F is defined as the time required for complete filling of the flow path of the curable mixture. That is to say LO that the hardening of the curable plastics material takes place only after mixing of the hardenable and hardening plastics. The flow path is therefore the distance between the mixing point and the mouth (outlet) of the drilled hole. If the mixing of the two components is effected by a static mixer, the mixing L5 point is located at this static mixer. In that case the flow path includes the further internal passage as far as its outlet to the external circumference of the drill, and therefore, generally, as far as the drill tip. The flow path further includes the drilled hole surrounding the anchor rod. The feed 20 time is therefore so calculated that, while taking account of the characteristic curve of the feed rate of the pumps, in particular the pressure-dependence of said characteristic curve, it is sufficient for the volume of the internal passage and the volume of the drilled hole surrounding the anchor rod 25 to be filled. The invention may be implemented by first drilling a hole with a conventional drill rod and then immediately withdrawing the drill rod from the hole and inserting instead a tubular anchor 30 rod (= rock anchor) having an internal passage. In addition to the other advantages, this method has the advantage that the drill tip to be used for hard rock, which is expensive, can be used multiple times. However, it is also possible to drill the hole with a drill rod equipped with an internal passage, which 35 is configured at the same time as a suitable anchor rod. This 5 drill rod remains in the drilled hole and is used after drilling as a rock anchor according to the invention. The disadvantage of single use is compensated by the operational advantage that time-consuming work steps are dispensed with. 5 In the context of this application the use of the drill rod as a rock anchor is described in particular; however, the invention also applies to a method whereby, as described, a subsequently inserted anchor rod having an internal passage is LO used instead of the drill rod, the method being usable identically in both cases. Preferably, the method further comprises the step of flushing the internal passage and the drilled hole with air during 15 and/or after the drilling, and in any case prior to the introduction of the curable mixture. This ensures that the curable mixture does not form any cavities in the drilled hole and comes into intimate contact with the wall of the drill rod and the wall of the drilled hole. This measure can be used 20 additionally to the flushing of the drilled hole with water usual in the drilling operation, and has the advantage that water residues are blown out of the drilled hole and dried. It should be pointed out that the drill rod may be provided at 25 its tip with a bore-crown, the cutting teeth of which describe a drilled hole diameter which is greater than the external diameter of the drill rod. The curing of the hardenable plastics component involves an 30 increase in viscosity above the viscous and pasty range. A viscosity of the hardenable component of at least 100 000 Pa x sec is aimed at, so that the bond between the plastics composition and the drilled hole and the drill rod is so secure that the drill rod cannot be pulled from the drilled hole or 35 rotated therein under the usual operating loads associated with 6 the drilling operation and the injection of the plastics composition. This makes it possible to detach the drill chuck, in which the drill rod is clamped for the purpose of drilling, and/or the injection head (adapter for connecting the plastics 5 feed pipes to the internal passage of the anchor rod/drill rod), from the drill rod without the aid of a holding device or gripping wrench for retaining the drill rod - for example, by rotating the drill chuck in the reverse direction These advantages are obtained by the preferred features of the 10 invention that the viscosity of the curable mixture in the curing time is at least 100 000 Pa x sec and that the curable mixture hardens sufficiently during the curing time that the torque of the drill rod in the drilled hole is greater than the torque required to detach the drill rod from the drill chuck 15 retaining the same. In an advantageous development, the step of making the curable composition comprises admixing a substance or synthetic material which causes pre-crosslinking of the components, with 20 an increase in viscosity to more than 500 pa X sec, within the curing time, to the curable mixture or to one of its components; and wherein the plastics materials comprises the substance or synthetic material which causes pre-crosslinking of the components. The plastics materials, after being brought 25 together and mixed, become crosslinked in a very rapid chemical reaction to form what is here called a pasty mass. This is brought about by admixing suitable substances, such as amines. In accordance with one embodiment, the inlet of the internal 30 passage of the drill rod may be blocked by a non-return valve which is open in the filling direction. Handling is thus simplified and operating safety increased in that, after the components have been brought together and mixed and before the start of the chemical reaction leading to hardening, an 35 increased viscosity (greater than 500 X Pa sec, preferably 7 greater than 1000 Pa sec) is attained. This pre-reaction is brought about by admixing to one of the components small quantities of substances having suitable thixotropic properties, for example, from the group of amines. 5 Through this initially slight but very rapid increase in viscosity before the start of the curing finally intended (thixotropic effect), it is achieved that the curable mixture of plastics materials does not flow out of the drilled hole, 10 thus failing to permit the pressure increase which is required to fill the entire drilled hole and all the cavities completely and without gaps. The preferred step of blocking the inlet of the internal 15 passage of the drill rod by a non-return valve which is open in the filling direction serves to shorten the duration of the drilling and injection process. This prevents plastics composition not yet completely cured from running, dripping or flowing from the internal passage of the drill rod after its 20 detachment from the drill chuck or after detachment of the plastics feed conduit. In calculating the feed time and coordinating same with the curing time, the characteristic curve of the feed rate of the pumps by which the hardenable component and the hardening component are fed to the internal 25 passage of the drill rod must be taken into consideration. Ideally, pumps having a delivery rate per time unit, which is not dependent on counterpressure, are sought. For this reason piston pumps, in particular radial piston pumps, are especially 30 suitable. These are especially advantageous because a temperature increase of the plastics materials, which could cause a change in the characteristic curve of curing and in particular a shortening of the curing time, is avoided.

8 To prevent liquid shocks and the consequent bursting of conduits, it is/should be provided in the development of the method that the pumps can start with a delay. A reduction in pump speed to avoid pressure spikes is also advantageous 5 shortly before the end of the feed time. Alternatively, pumps having a pressure-dependent characteristic curve of feed rate may be used to convey the hardenable plastics material and/or the hardening plastics material. Such 10 pumps - for example, gear pumps - have the advantage of simple construction. Moreover, the pressure-dependent characteristic curve of pump feed rate has the advantage that pressure spikes are avoided. On the other hand, in the event of internal run back of surplus feed quantities, pressure-dependence causes 15 heating; the characteristic curve of curing, and in particular the curing time, must therefore be suitably adapted. In the preferred feature that the feed time for the filling volume V to be filled downstream of the mixing point conforms 20 to the equation (taking account of the characteristic curve of the feed rate of the hardenable and hardening plastics materials): H V=KxJ(q +q )dt (I) , where 0 V = filling volume of internal passage downstream of 25 mixing point plus filling volume of drilled hole qA = feed quantity per time unit of hardenable plastics material qH = feed quantity per time unit of hardening plastics material 30 dt = time increment H = curing time K = constant taking account of location-independent factors, in particular temperature and constitution of 9 rock, the feed of hardenable and/or hardening plastics material is switched off if the feed pressure exceeds a predefined limit value. In this case, however, a run-down programme of the drive motors of the pumps may be switched 5 on, whereby the speed of the pumps is reduced to zero continuously or in steps. Damage to the feed system and possible contamination by one of the plastics components are thereby avoided. 10 However, if in this case the pressure rise can be traced to curing of the plastics material before complete filling of the drilled hole, a new drilling must be carried out and in some cases the drill rod may be lost. However, in this case incorrect coordination of filling time and curing time has 15 occurred. If filling time and curing time are precisely coordinated, the pressure-dependent switch-off occurs as precisely as possible at or shortly before the time when the plastics material emerges from the mouth of the drilled hole. 20 It is also possible, however, to predefine the feed time F manually or by an adjustable clock. The aim is to achieve a curing time, and therefore a filling time, of less than one minute. 25 The coordination of filling time and curing time may be carried out by tests, although the characteristic curve of the pump feed rate and the filling volume V of the internal passage and of the drilled holes surrounding the drill rod should be taken at least roughly into account. The algorithm to be applied in 30 coordinating filling time and curing time is defined by equation (I) above.

9a In fully exploiting the advantages of an embodiment of the invention, namely the rapid and secure embedding of a rock anchor in a drilled hole, the preferred feature that the 5 feeding step comprises feeding the plastics through an injection head: * which is permanently connected via conduits to feed pumps of the plastics material carried on a transport vehicle; 10 e which is guided movably between a rest position and an operating position on the transport vehicle, and * which in the operating position is connectable in a pressure-sealed manner via a connecting piece to the end of the anchor rod projecting from the drilled hole has 15 special importance. The preferred feature that the feeding step comprises feeding the plastics through the said injection head ensures the safe connection of the plastics feed conduits to the internal passage of the anchor rod/drill rod and avoids unnecessary assembly and 20 adjustment operations serving this purpose. To achieve this, use is made of an injection head - also called an adapter in this application - which serves firstly as the plastics conduit and secondly as a tool for connecting the internal passage of the anchor rod to the plastics pumps. 25 The preferred feature that the injection head has a stop valve for closing and opening each conduit located in each of the conduits of the plastics materials within the injection head wherein both stop valves can be opened and/or closed only 30 synchronously in normal operation serves the purpose of avoiding untimely mixing of the components, especially before 9b they have reached the intended mixing point and the static mixer, and therefore of preventing premature curing of the plastics materials and contamination of the conduit systems by hardening plastics materials. 5 The preferred feature that the conduits formed in the injection head and connected to hoses on the feed side open, on the side facing towards the connecting piece (connection side of the connecting piece), into a smooth surface serves a similar 10 purpose and at the same time ensures effective cleaning of parts of the feed system where plastics deposits cause malfunction. An embodiment of the invention is described below with 15 reference to the drawings, in which: Fig. 1 shows schematically a drill rod with drill chuck and feed adapters (injection head); 20 Figs. 1A & 3A show schematically a static mixer, mixer housing and non-return valve; Fig. 2 is a feed rate graph; 25 Figs. 3 and 4 show schematically a drill rod with drill chuck and feed adapters (injection head); and Fig 4A shows schematically opposed half shells having recesses. 30 It is illustrated in the Figures that a drill rod remains in the hole that has been drilled therewith and is immediately 9c retained and embedded in the drilled hole as an anchor rod/rock anchor. The drilling process is therefore also described in relation to the Figures. However, if the drill rod is withdrawn from the drilled hole after the production thereof, and is 5 replaced by an anchor rod as the rock anchor, the production of the drilled hole no longer falls within the scope of this invention; otherwise, however, the whole of the exposition describing the inventive method for filling the internal passage of the anchor rod and the drilled hole with a hardening 10 plastics mixture (curable mixture), is applicable. The following description applies to all the Figures unless deviations are expressly pointed out in relation to individual Figures.

10 The drill rod 1 having a bore-crown 2 is driven into a rock 19 of solid stone by the drill chuck 3. For this purpose the drill chuck 3 is driven in the feed direction 4 and in the rotational direction 5. 5 The drill rod consists of a plurality of parts, in this case two, which can be joined together to yield a predefined length by being screwed into a nut 6. For this purpose the drill rods are provided on their external 10 circumference with a screw thread which fits into a corresponding thread of the union nut 6. This thread also serves the purpose of enabling a good connection between the drill rod 1 and the plastics material to be injected into the drilled hole. 15 The bore-crown 2 is fitted with teeth 7. These teeth 7 define a drilled hole cross-section having a diameter Di. The diameter Di is greater than the external diameter DA of the drill rod 1 and therefore also greater than the 20 internal diameter of the thread Dr. The volume of the drill rod can be calculated with sufficient accuracy from the mean diameter D 2 = (DA + D 1 )/2. Passing through the centre of the drill rods 1, or of the partial sections of the drill rod, is an internal passage 8 which opens in the 25 bore-crown 2 into a collecting chamber 9 and outlet passages 10. The internal passage can be supplied, through the drill chuck 3 via suitable adapters, first with water or air as flushing means and then, preferably also via the drill chuck but also via another suitable connecting piece 30 which is illustrated, for example, in Fig. 4, with a hardenable plastics composition and a hardening plastics material.

11 Only the parts of the device intended to be supplied with plastics material are shown schematically here. These are the injection head/adapter 11, which can be placed on the end face of the connecting piece, here the drill chuck, and 5 which includes internal passages 12 and 13. The internal passage 12 is connected via the hose 27 and the feed pump 14 to a reservoir 15 for a hardenable plastics composition. The internal passage 13 is significantly smaller in diameter than the internal passage 12; its 10 cross-sectional area is approximately 1/10 the cross sectional area of the internal passage 12. The internal passage 13 is connected via the hose 25 and a feed pump 16 to a reservoir 17 for the hardening plastics composition. Because the hardenable plastics composition and the 15 hardening plastics composition are mixed in a ratio of 10:1 or less (as low as 1:1; see above), the feed pump 16 is designed correspondingly smaller. The internal passages are brought together within the connecting piece/drill chuck 3 in a collecting chamber 18 which communicates 20 directly with the internal passage 8 of the drill rod. In Fig. 1 it is shown that the first segment of the drill rod includes a static mixer 20 at the inlet of its internal passage 8. Such a mixer may also be located at the 25 beginning of each segment. If the static mixer is in the form of an insertable component, it is sufficient if such a static mixer 20 is inserted in the internal passage 8 of the last drill rod 1 to be installed. The detail illustration shows an insert component 21 in which a non 30 return valve/ball valve 22 is integrated, in addition to the static mixer 20. The insert component 21 may, for example, be screwed via a thread into the internal 12 passage 8 of the last drill rod to be installed before drilling. The method is operated as follows: 5 To drive the drill rod 1 into the rock, only one drill rod element is first placed in the drill chuck. The drill chuck is set in rotation in the direction 5. At the same time a feed force 4 (not represented) is exerted on the drill rod. 10 A drilled hole having the diameter Di of the bore-crown or of the cutting teeth 7 on the bore-crown is thereby produced. When the drilled hole has attained the length of the first segment of the drill rod, the union nut 6 is screwed on to the free end and a further segment of the 15 drill rod 1 is screwed into the union nut 6, being fed (in a manner not shown) through the drill chuck from behind. As this happens the drilled hole may be flushed (in a manner not shown) with water which is supplied through the internal passage of the drill rod. 20 When the intended depth of the drilled hole has been attained (e.g. approximately 2 m to 2.50 m) the drilling process is ended. The collecting chamber 18 of the drilled hole is now charged with air (in a manner not shown) 25 through the internal passage 8 of the drill rod, the drillings being thereby flushed from the drilled hole and the drilled hole being cleaned and dried. The drilled hole is then charged with a hardenable plastics 30 material which has been previously mixed with a hardening plastics material. The volume to be filled is, firstly, the internal passage 8 from the mixer 20 onwards and, secondly, the drilled hole, i.e.: 13 Vges = VI + VBohrloch - VBohrstange = pi/4 (LB X (D 1 2 - D22) + L, x Di2) Charging is effected by the pumps 14 and 16. These are, for 5 example, radial piston pumps which can provide a pressure independent feed quantity per time unit. However, they may also be gear pumps, since, given the high viscosities of the plastics materials to be conveyed, inadmissible losses are not to be expected, so that the delivery law can be 10 determined with sufficient accuracy. The feed rate is now so defined by suitable pre-setting and speeds of the drive motors 24 and 26 of the pumps that, taking account of the characteristic curve of pump feed 15 rate and the delivery law, the quantity of hardenable plastics material and hardening plastics material to be charged is conveyed in precisely the feed time which corresponds to the curing time. The curing time of the plastics material can be determined, on the one hand, by 20 the selection of the plastics components and, on the other, by the mixing ratio and the temperature. The temperature may be assumed to be, for example, 30 0 C. The hardness to be adopted by the plastics material in the curing time is determined by practical considerations. In particular, the 25 plastics material should not emerge freely from the mouth of the drilled hole, but should appear at the mouth of the drilled hole at most as a pasty mass. Moreover, it is advantageous for the speed of the whole drilling and charging operation if the plastics material at the mouth of 30 the drilled hole has cured sufficiently for the drill chuck to be detached from the drill rod without the need to hold the drill rod with special auxiliary means, or to prevent it from falling out of the drilled hole. A viscosity of 14 100 000 Pa sec may be sufficient, but preferably is exceeded. Through suitable admixtures, pre-crosslinking of the plastics mixture introduced may occur, with an increase in viscosity (see above: more than 500 Pa sec), even before 5 the curing reaction itself begins or takes effect. It is desirable to detach the drill chuck as quickly as possible from the drill rod, at a time when the plastics mixture last introduced has not reached the end of its 10 curing time. For this reason the non-return valve 22 is provided upstream of the static mixer, opening in the charging direction and preventing the plastics mixture introduced from flowing out of the internal passage in the opposite direction. 15 After detachment of the drill chuck from the drill rod, the connecting piece/drill chuck may be flushed with one of the plastics components or with water. The corresponding apparatus is not illustrated. 20 Fig. 2 shows schematically a feed rate graph of the plastics components conveyed, that is, in particular the hardenable plastics component and hardening plastics component and, optionally, the further admixed substances. 25 The curve of the feed quantity per time unit over time is shown, and above it the corresponding pressure curve in the collecting chamber 18 or at another point. The feed rate depends, on the one hand, on the speed curve of the drive motors of the pumps. In addition, with some types of pump, 30 account must be taken of the pressure-dependence of the feed rate. A constant characteristic curve of feed rate, such as that of radial piston pumps, would be ideal. In any 15 case, the aim is that the pumps start running with a progressive action, in order to avoid pressure shocks. The method according to the invention can therefore also be 5 carried out if the hardenable and hardening plastics materials are conveyed during the feed time F at a variable feed rate according to a predetermined curve of feed quantity per time unit, in particular with a delayed and increasing feed rate at the start of the feed time, or if 10 the hardenable and hardening plastics materials are conveyed during the feed time F at a feed quantity per time unit which is pressure-dependent according to a predetermined law. In any case, the following applies: 15 If, after attainment of the maximum set speed, the feed quantity per time unit decreases as pressure increases which happens, firstly, because the flow path of the plastics mixture is lengthening and, secondly, because viscosity is increasing - the total feed time is so 20 calculated that the charging quantity within this feed time (represented in the graph by the hatched area below the feed rate curve) corresponds, as described above, to the volume of the internal passage and the drilled hole, and that this feed time corresponds to the curing time. It is 25 thereby achieved that the plastics mixture arriving at the mouth of the drilled hole has become sufficiently viscous to block said mouth and to encase the drill anchor so securely that it withstands the torque applied during detachment of the drill chuck, and that it does not fall 30 out of the drilled hole through its own dead weight. Given this precondition, it is possible to operate the control device 28 manually or by pre-setting an operating 16 time for the pump motors. However, control may also be provided via the pressure sensor 23, by means of which the pumps are switched off or (as illustrated) a run-down switching occurs when the pressure upstream of the mixing 5 device (for example, in the collecting chamber) exceeds a preset limit value G to be determined by experimentation. Fig. 3 differs from the above in that: 10 Upon completion of the drilled hole, the drill chuck is removed. The connection of the anchor rod/drill rod 1 to the injection head/adapter 11 is effected by a connecting piece 3. The latter consists (as shown in the detail illustration of Fig. 4) of two half-shells 31, 32, each of 15 which has a semicircular recess 33, 34 along its length. These recesses complement one another in the closed state of the half-shells in the direction of the arrows to form a circular-cylindrical internal passage having varying diameters. The diameters are so designed that in the closed 20 state (as shown in Fig. 4) the internal passage fixes the connecting piece in a form-fitting manner to the injection head 11 on one side and to the anchor rod/drill rod 1 on the other. The injection head therefore has a widened portion 35 which fits into a correspondingly widened 25 diameter of the internal passage 33, 34. To retain the anchor rod/drill rod 1, the internal passage has a coarse internal thread which corresponds to the external thread of the anchor rod/drill rod 1. 30 It is shown in Fig. 3 that the space 18 between the end of the injection head 11 and the end of the anchor rod/drill rod 1 is bridged and radially sealed by means of an annular 17 seal 30. Here, too, the static mixer is located at the beginning of the anchor rod/drill rod 1. In the embodiment according to Fig. 4, by contrast, the 5 static mixer is located in the connecting piece 3 formed by the half-shells 31, 32. To achieve this, the mixing elements 20 are located here, too, in an insert component/mixer housing 21 configured as a circular cylindrical tube. This tube has at its beginning an 10 outwardly widened portion 36 which, in the closed state of the half-shells 31, 32 in the direction of the arrows, is enclosed form-fittingly by a corresponding recess in the internal passage of the half-shells 31, 32 and is fixed both axially and radially. In addition, the internal 15 passage of the half-shells 31, 32 fits snugly around the tube of the mixer housing. This is especially important because the mixer housing 21 is preferably made of plastics material and is only made 20 sufficiently pressure-resistant by its close abutment to the walls of the half-shells firmly pressed together. Furthermore, it is especially important that the mixer housing is also supported form-fittingly in the axial direction at its outlet end, in order to prevent a mixer 25 housing made of plastics material from splitting or rupturing axially. This axial fixing is effected in the example illustrated by abutment of the mixer housing against the end face of the anchor rod/drill rod 1 facing towards it, which anchor rod/drill rod 1 is in turn fixed 30 in the half-shells of the connecting piece. The non-return valve illustrated and described with reference to Figs. 1 and 3 is not shown in this case, but would also be used here with corresponding advantage.

18 Upon expiry of the filling time and completion of the charging of the drilled hole, the half-shells are moved apart (against the arrow direction), so that the anchor 5 rod/drill rod and the injection head are released. As this happens the static mixer which, as described, is in the form of a modular unit, may also be ejected, because it is still filled with the hardening plastics mixture. If necessary the injection head and/or the connecting piece 3 10 are cleaned and a new modular unit is then inserted as the mixer before said components are clamped to another anchor rod/drill rod and charging thereof commences. In the method according to Fig. 4 an extended form of 15 control is also used. The apparatus for charging a drilled hole is switched on and off by the switch 29, which synchronously activates the two stop valves 38 and 39 in the internal passages 12, 13 of the injection head 11, to allow through-flow or to effect pressure-proof blockage. 20 At the start of charging the two pumps 24, 26 are set in operation by means of the control unit 28. When pressure has built up in the supply conduits 25, 26, the stop valves 38, 39 are synchronously opened by means of the switch 29, so that the mixing and charging process begins 25 immediately with both components present. Upon expiry of the operating time/curing time, as described previously, the switch 29 again activates the stop valves 38, 39, causing synchronous and abrupt closing of the stop valves 38, 39. It is thereby ensured that after blocking at 30 the outlet face 37, i.e. the end face oriented towards the mixer 20, none of the components can now emerge and cause contamination thereof. It is additionally provided, however, that after opening of the half-shells 31, 32, the 19 outlet face is cleaned with a pressurised water jet. At any rate, the outlet face 37 is configured flat and without projections or recesses, so that it can be easily and effectively cleaned. 5 When the stop valves have been switched to block the flow, the two pumps build up a higher pressure in the conduits 25, 27. This pressure is detected by pressure sensors 23 in each of the conduits and is supplied to the control unit 28 10 via the lines 40, 41. The maximum limit pressure to which are each of the respective conduits may be subjected is stored in the control device. If either of these limit pressures is reached, the control device switches off the pump drive concerned, preferably both pump drives/ 15 motors 24, 26. The embodiment according to Fig. 4 additionally includes the special feature of the method, that the two plastics components, or their feed lines 12, 13, are brought 20 together at a Y- or T-junction in the injection head, at a point located shortly before, or optimally in, the outlet face 37. Precisely the last-mentioned case facilitates keeping clean, or cleaning, of the outlet face.

20 List of reference signs 1 Drill rod, anchor rod 1 2 Bore crown 2 5 3 Drill chuck 3, connecting piece 4 Feed direction 4 5 Direction of rotation 5 6 Nut 6, union nut 6 7 Teeth 7, drilling teeth 7 10 8 Internal passage, central passage 8 9 Collecting chamber 9 10 Outlet passages 10 11 Adapter 11, injection head 12 Internal passage 12 15 13 Internal passage 13 14 Feed pump 14 15 Reservoir 15 for a hardenable plastics composition 16 Feed pump 16 17 Reservoir 17 for the hardening plastics composition 20 18 Collecting passage 18, intermediate space 19 Rock 19 20 Static mixer 20, mixing elements 21 Insert component 21 mixer housing 22 Non-return valve/ball valve 22 25 23 Pressure sensor 23 24 Motor 24, pump drive 25 Hose 25, conduit 26 Motor 26, pump drive 27 Hose 27, conduit 30 28 Control device 28, control unit 29 ON/OFF switch, switch 29 30 Sealing ring, seal 31 Half-shell 31 21 32 Half-shell 32 33 Recess 33 34 Recess 34 35 Widened portion 35 5 36 Widened portion 36 37 End face, outlet face 37 38 Stop valve 38, solenoid 39 Stop valve 39, solenoid 40 Line 40 10 41 Line 41 Drilled hole cross-section with diameter Di External diameter DA of drill rod 1 Internal diameter Di of thread 15 Mean diameter D2 = (DA + Di)/2

Claims

1. Method for embedding a rock anchor, whereby an anchor rod 5 having an internal passage is inserted in a drilled hole, through which internal passage a free-flowing, self-curing composition is forced, comprising filling the finished drilled hole with the composition such that the composition cures in the drilled hole with the anchor rod 10 remaining in the drilled hole to form a rock anchor, wherein the method comprises the steps of: e drilling the drilled hole; e selecting a hardenable plastics material, a hardening plastics material and their mixing ratio such that a 15 self-curing composition formed from the hardenable plastics material and the hardening plastics material in the defined mixing ratio has a curing time H; e feeding the hardenable plastics material and the hardening plastics material to the internal passage 20 of the anchor rod for a predetermined feed time F; and * mixing the plastic materials at a mixing point located shortly before or in the internal passage to form the self-curing composition; 25 wherein the feed time F and the curing time H are coordinated to one another such that the feed time substantially corresponds to the curing time and leads to substantially complete filling with the self-curing composition of the flow path between the mixing point and 30 the outlet of the drilled hole.

2. Method according to claim 1, comprising the step of flushing the internal passage and the drilled hole with 23 air during and/or after the drilling step, and in any case prior to the introduction of the plastic materials.

3. Method according to claim 1 or 2, comprising the step of 5 arranging a mixer in the internal passage.

4. Method according to claim 3, wherein the mixer is a static mixer arranged upstream of the internal passage. 10

5. Method according to any one of the preceding claims, wherein the viscosity of the self-curing composition in the curing time is at least 100 000 Pa sec.

6. Method according to any one of the preceding claims, 15 wherein the drilling step comprises: * drilling the drilled hole with a drill rod having an internal passage and a drill chuck retaining the drill rod in the drilled hole such that the drill rod is used as the anchor rod; 20 wherein the self-curing composition hardens sufficiently during the filling time that the torque of the drill rod in the drilled hole is greater than the torque required to detach the drill rod from the drill chuck retaining same. 25

7. Method according to any one of the preceding claims, wherein the step of making the self-curing composition comprises the step of admixing a substance or synthetic material which causes pre-crosslinking of the components, with an increase in viscosity to more than 500 Pa sec, 30 within the curing time, to the self-curing composition or to one of its components; and wherein the plastics materials comprises the substance or synthetic material which causes pre-crosslinking of the components. 24

8. Method according to any one of the preceding claims, comprising the step of blocking the inlet of the internal passage of the drill rod by a non-return valve which is open in the filling direction. 5

9. Method according to any one of the preceding claims, comprising the step of conveying the hardenable and the hardening plastics materials at a pressure-independent feed quantity per time unit during the feed time F. 10

10. Method according to any one of the preceding claims, comprising the step of switching off or otherwise terminating the feeding of plastics materials if a predefined limit pressure is exceeded. 15

11. Method according to anyone of the preceding claims, wherein, taking account of the characteristic curve of the feed rate of the hardenable and hardening plastics materials, and where a filling volume V is the filling 20 volume of the internal passage downstream of the mixing point plus a filling volume of the drilled hole, the feed time F for the filling volume V conforms to the equation: H V=KxJ(q+qH)dt , where 0 25 qA= feed quantity per time unit of hardenable plastics material qH = feed quantity per time unit of hardening plastics material 30 dt = time increment H = curing time 25 K = constant taking account of location-independent factors, in particular temperature and constitution of rock. 5

12. Method according to any one of the preceding claims, which further includes the step of providing a transport vehicle and an injection head wherein the transport vehicle carries feed pumps of the plastic materials which feed 10 pumps are permanently connected to the injection head by conduits and wherein the feeding step comprises feeding the plastic materials through the injection head: - which injection head is guided movably between a rest position and an operating position on the 15 transport vehicle, and - which injection head is in the operating position connectable in a pressure-sealed manner via a connecting piece to the end of the anchor rod projecting from the drilled hole. 20

13. Method according to claim 12, wherein; - a stop valve for closing and opening each conduit is located in each of the conduits of the plastic materials within the injection head; and 25 both stop valves can be opened and/or closed only synchronously in normal operation.

14. Method according to claim 12 or claim 13, wherein the conduits formed in the injection head and connected to 30 hoses on the feed side open, on the side facing towards the connecting piece (connection side of the connecting piece), into a smooth, surface. 26

15. Method according to any one of claims 12 to 14, wherein the connecting piece consists of two half-shells which are movable relative to one another perpendicularly to the flow direction of the plastics materials conducted in the 5 interior thereof and which in the assembled state enclose in a pressure-sealed manner, or otherwise connect, the injection head on one side and the end of the anchor rod projecting from the drilled hole on the other. 10

16. Method according to claim 12, wherein the conduits of the plastics materials are conducted separately from one another in the injection head and in that the plastics materials are brought together in the connecting piece. 15

17. Method according to claim 16, wherein a static mixer is arranged in the internal passage of the anchor rod.

18. Method according to claim 16, wherein a static mixer is arranged in the connecting piece. 20

19. Method according to claim 18, wherein the static mixer has a tubular configuration with mixing elements arranged in its mixing tube and wherein the half-shells of the connecting piece form in the assembled state a guide 25 passage fitting snugly around the mixing tube, in which guide passage the mixing tube is fixed at both ends for support against the inlet pressure of the plastics materials entering the mixer. 30

20. Method according to claim 7 wherein the increase in viscosity is no more than 1000 Pa sec.

21. Method according to claim 7 wherein the increase in viscosity is at the start of the curing time. 27

22. Method according to claim 13 wherein the drive motors of the pumps can each be switched off by means of a pressure sensor located in its respective feed conduit upon attainment 5 of a predefined maximum pressure.

23. Method according to claim 1 wherein the anchor rod is held in the drilled hole at the end of the curing time H by the cured resin without the use of an auxiliary means. 10

24. Method for embedding an anchor rod inserted in a hole drilled into a rock in a hardened composition of plastics material, the rod having an internal passage through which the composition is fed to the hole wherein the method comprises 15 steps of: " selecting a hardenable plastics material and a hardening plastics material; e feeding under pressure the hardenable plastics material and the hardening plastics material during a preselected feeding 20 time separately to the mouth of said passage in a preselected mixing ratio, " said feeding time being preselected such, that feeding leads to substantially complete filling with the curable composition of the flow path between the mixing point and 25 the outlet of the drilled hole; e selecting any or all of the hardenable plastics material, the hardening plastics material and the mixing ratio such that the curing time substantially corresponds to the feed time; and 30 o mixing the hardenable plastics material and the hardening plastics material while being fed to said internal passage.

25. The method of claim 24 wherein the step of selecting any or all of the hardenable plastics material, the hardening 28 plastics material and the mixing ratio is effected such that at the end of the feed time the composition at the mouth of the drilled hole has cured such, that the rod is held in the bore (without the need of any auxiliary means). 5

26. The method of claim 24 wherein selecting any or all of the hardenable plastics material, the hardening plastics material and the mixing ratio is effected such at expiry of the feed time the composition at the mouth of the drilled hole has cured 10 such, that the viscosity of the hardened composition is at least 100 000 Pa sec.

27. The method of claim 24, wherein the inserting step comprises the steps of: 15 e inserting a drill rod in a drill chuck for retaining same, e drilling a hole in the rock by means of said drill rod having an internal passage, and after completion of the hole * leaving the rod therein to serve as the anchor rod. 20

28. The method of claim 24 wherein the step of selecting any or all of the hardenable plastics material, the hardening plastics material and the mixing ratio is effected such at expiry of the feed time the composition has cured such, that 25 the torque of the drill rod in the drilled hole is greater than the torque required to detach the drill rod from the drill chuck retaining same.

29. The method of any one of claims 24 to 28 wherein the 30 mixing step comprises mixing the hardenable plastics material and the hardening plastics material while being fed to said internal passage at a mixing point located shortly before the internal passage. 29

30. The method of any one of claims 24 to 28 wherein the mixing step comprises mixing the hardenable plastics material and the hardening plastics material while being fed to said internal passage at a mixing point located in the internal 5 passage.

31. The method of claim 24 in which the feeding step comprises feeding at a pressure-independent feed quantity per time unit. 10

32. Method for embedding a rock anchor substantially as hereinbefore described with reference to the accompanying drawings.