EP0372535B1 - Process for establishing a measuring point for ground water, and device for carrying out this process - Google Patents

Abstract

In the process, a pipe (2), which bears a filter pipe (3) at its lower end, is installed in a bore hole (1) in the ground. Above the filter pipe (3), an intermediate piece (18) with closable radial openings is inserted into the pipe, into which piece a joining piece can be introduced until it rests against a stop, which joining piece closes the bore hole of the intermediate piece and connects the openings to a cementing linkage (19) which can be installed in the pipe (2). After the installation of the pipe (2), firstly the annular space (5) under the intermediate piece (18) is filled with filter material. Subsequently, the cementing linkage (19) and the joining piece (21) are inserted and a liquid sealing material, which hardens after introduction, is pumped through the openings into the annular space (5) above the layer of filter material. <IMAGE>

Description

The invention relates to a method for building a groundwater measuring point, in which a pipeline with a water inlet opening at its lower end is installed in a borehole in the ground and in which the annular space between the pipeline un the borehole wall in the region of the water inlet opening with filter material and for sealing water-bearing layers is filled with essentially water-impermeable material, an intermediate piece with closable, radial openings being inserted into the pipeline above the water inlet opening, after the installation of the pipeline and the filling of the filter material layer, a cementing rod is inserted into the pipeline and connected to the openings in the intermediate piece and a liquid sealing compound which solidifies after insertion is pumped into the annular space above the filter material layer by the cementing rod and the openings.

Groundwater measuring points, also called level wells or groundwater observation wells, are required in the catchment area of water extraction systems in order to be able to carry out a quality control of the groundwater before the groundwater enters the extraction well. To produce such groundwater measuring points, the depth of which can be more than 1000 m, bores of 180 mm in diameter are often drilled according to the prior art, into which a pipeline composed of plastic pipes with an outer diameter of 75 mm is subsequently installed. The annulus between the bore wall and the pipeline is in front all in the area of the filter pipe located at the lower end of the pipeline, but also mainly filled with gravel, whereby clay barriers are installed between individual gravel beds in order to separate the water-bearing floors found when the well was sunk and to prevent mixing or unwanted contamination of the groundwater prevent. The clay material to form the sound barriers is also poured into the bore as a bed. In DE-PS 30 12 709 such an expansion is shown using the example of a multiple level of comparatively shallow depth. A disadvantage of this known procedure is that the filling of the annular space requires a considerable amount of time, particularly in the case of groundwater measuring points of greater depth, since very long pauses after the introduction of the different materials are required in order to be able to monitor the correct fit of the individual fillings by means of soldering. With deeper bores there is also often the problem that the backfilling gets stuck in the upper region of the bore and can only be brought into the intended position with great difficulty and with considerable expenditure of time. If the clay barriers are leaking due to inadequate backfilling or if they are not in the right place, there can be external inflows that render the groundwater measuring point unusable.

EP-A-0 177 623 discloses a method of the type mentioned at the outset for the construction of water extraction wells, in which cement milk is used as the subsequently solidifying material to fill the annular space between the pipeline and the wall of the borehole. For the expansion of a groundwater measuring point, the use of cement milk as so-called jacket cementation is not suitable because of the particularly high tightness requirements there and because of the exclusively used plastic pipes.

It is an object of the invention to provide a method of the type mentioned at the outset which enables the annular space between the bore wall and the pipeline to be reliably filled, separating the individual floors of the bore.

According to the invention, this object is achieved in that the sealing compound to be introduced into the annular space consists of a pumpable suspension of clay powder, cement and water and contains approximately four parts clay powder and approximately one part cement. The density of the suspension is preferably adjusted to 1.29 to 1.32 g / cm 3.

The sealing compound according to the invention penetrates completely into all areas of the annular space to be filled and, after it has solidified, ensures a complete seal with respect to the individual floors in all separating layers of the drilled profile. Subsequent subsidence is avoided, as no voids remain empty.

In order to avoid penetration of the suspension into the filter material layer, it can be provided in a further embodiment of the method according to the invention that the filter material is covered with a layer of clay before the suspension is introduced.

The invention further relates to a device for performing the specified method, consisting of a tubular intermediate piece which can be installed in the pipeline and which can be closed with radial openings which is the same or smaller in inside diameter than the inside diameter of the pipe and which is in the bore below the openings protruding stop has an insert that can be inserted into the intermediate piece and which is in contact with the stop by the Pipe can be inserted into the intermediate piece and closes the bore of the intermediate piece and consists of a cementing rod that can be connected to the connecting piece and can be installed in the pipeline, the outlet opening of which can be connected to the openings through a channel in the connecting piece.

Such a device is known from EP-A-0 177 623. In the known device for connecting the cementing rod to the openings in the intermediate piece, a pressure transmission device is provided, which contains a pressure introduction tube and two closure members, each consisting of an inner, elastic tube, the end regions of which are provided on both sides by means of a fastening clamp and a support ring and a toothed ring are attached. The pressure introduction pipe is surrounded by an intermediate pipe which is open at the bottom and to which the elastic pipes are fastened. The elastic pipes are connected to the pressure introduction pipe via pipe sockets and can be pressurized via this. This embodiment of the known device is very complex and not suitable for small diameters.

From US-A-1,912,578 a device for carrying out a cementing process is known which has a tubular intermediate piece which can be installed in the pipeline and which can be closed with radial openings and which has a stop projecting into its bore below the openings. A sleeve is inserted into the intermediate piece, which contains a check valve, the housing body of which consists of an easily destructible material, for example cement or aluminum. For cementing, the sleeve is closed with a cementation plug and, by a pressure built up in the pipeline, pushed until it touches the stop, thereby opening the radial openings in the intermediate piece. The cement suspension is then poured in directly through the expansion piping. As a result, after the cementation has ended, a cement plug remains in the casing, which must be drilled out, including the cement plug and the valve housing. This known device is not suitable for small pipe diameters, such as are provided for groundwater measuring points, and for the use of plastic pipes.

It is further known from DE-B-1 284 915 to mount valves for cementing a multi-zone borehole in a tubing string inserted into the borehole, which valves can be opened with the aid of an actuating tool which is attached to a cementing rod. A foot tube is attached to the cementing rod under the tool. When cementing, the open end of the foot tube is positioned at the opening of the valves without, however, making a tight connection between the foot tube and the valve openings.

The invention has for its object to provide a simple device with which the annular space between the built-in pipe and the bore wall can be filled with the pumpable and then solidifying sealant without the risk of damage to the pipe and at the lower end of the Pipeline arranged filter pipes for water entry exists.

According to the invention, this object is achieved in that the connection piece has sealing rings above and below the openings, which bear against the bore of the intermediate piece in a pressure-tight manner, that the connection piece consists of a sleeve which can be closed at the lower end and has radial openings in the orientation opposite the openings in the intermediate piece and has a longitudinal groove into which the stop of the Intermediate piece engages and that in the bottom of the connecting piece a check valve blocking the sump is arranged, which is connected to the channel in the connecting piece.

The cementing device according to the invention has the advantage that after filling the annular space and expanding the cementing rod with the connecting piece, the interior of the pipeline is freely accessible up to the area of the water inlet opening and can be used on site with the devices for conveying before water samples or for examining the groundwater can be. The device according to the invention is easy to use. The check valve in the bottom of the sleeve allows the liquid in the pipeline to pass through the connector when the cementing rod is installed. This prevents the connection piece from displacing the liquid in the manner of a plunger piston and thus generating a buoyancy which complicates the lowering of the cementing rod.

To close the radial openings in the intermediate piece, according to a further proposal of the invention, flaps can be provided which rest on the outer surface of the intermediate piece and are held in a radially movable manner by leaf springs.

Figur 1

das Profil einer Grundwassermeßstelle mit einer Verfüllung des Ringraums nach dem Stand der Technik,

Figur 2

das Profil der Grundwassermeßstelle gemäß Figur 1 mit einer Verfüllung des Ringraums nach dem erfindungsgemäßen Verfahren,

Figur 3

einen Längsschnitt durch eine Vorrichtung zum Bau einer Grundwassermeßstelle nach dem erfindungsgemäßen Verfahren.

The method and the device according to the invention are explained in more detail below with reference to exemplary embodiments shown in the drawing. Show it

Figure 1

the profile of a groundwater measuring point with a filling of the annular space according to the prior art,

Figure 2

the profile of the groundwater measuring point according to Figure 1 with a filling of the annular space according to the inventive method,

Figure 3

a longitudinal section through a device for building a groundwater measuring point according to the inventive method.

Figure 1 shows the profile of a groundwater measuring point, which was expanded in the usual way belonging to the prior art. A pipe made of plastic pipes was inserted into a bore 1 drilled to a depth of -210 m with a diameter of 220 mm in the range from 0 to -50 m and a diameter of 175 mm in the range from -50 to - 210 m 2 installed, which has at its lower end in the range from -198 to -206 m a filter tube 3 and then a sump tube 4. The sump tube 4 ends at a depth of -208 m and is closed there. The nominal diameter of pipeline 2 is from 0 to -40 m 115 mm and below 65 mm. The annular space 5 between the pipeline 2 and the wall of the bore 1 is filled with various filling materials. In the lowest section 6, which extends from the bottom of the bore 2 to a depth of -195 m, there is a gravel fill of grain size 1-2, through which the groundwater reaches the filter tube 3. Section 7 above is filled to a depth of -161 m with filling gravel of grain size 2 - 8. In order to separate sections 6, 7 from floors above, section 8 is designed as a sound seal. A fill follows in section 9 from filling gravel and alternating clay seals in sections 10 - 13 and in between fillings of filling gravel in sections 14 - 17. The described filling of the annular space 5 between the pipeline 2 and the wall of the bore 1 results from the manufacture of the Drilling determined the type and location of the pierced layers and the need to close the pierced barrier layers by installing clay seals in order to prevent water from different floors from mixing and the associated contamination of the groundwater.

The introduction of the individual sound barriers when filling the hole is very difficult and time-consuming, since the correct position of the individual fillings has to be monitored again and again by means of soldering. If the sound barriers are leaking or if they are not in the right place due to the gravel settling, the groundwater measuring point is unusable for accurate monitoring of the groundwater.

These disadvantages are avoided by the method illustrated in FIG. The method is explained using the example already shown in FIG. 1. After this, a tubular intermediate piece 18 is inserted into the pipeline 2 a few meters above the filter tube 3, the wall of which has radial openings. A cementing rod 19 inserted through the pipeline is connected to the openings in the intermediate piece 18 and is connected to a pump 20 for days. Now, for pouring the filter section into the lower section 6, filter gravel of grain size 1-2 is introduced from outside into the bore 1 to almost below the intermediate piece 18. If the discharge of filter gravel inadvertently increases beyond the intermediate piece 18, the excess amount can be conveyed to the surface again by connecting the cementing rod to a rinsing pump.

When the gravel fill has the correct height, a liquid, pumpable sealing compound is pumped into the annular space 5 with the aid of the pump 20 via the cementing rod 19 and the openings in the intermediate piece 18 until the annular space in the area of the floors 7-17 is completely filled. Afterwards, an amount of water corresponding to their intake volume is pumped in to clean the pump and the cementing rod.

The sealing compound is mixed in a mixing plant, whereby a pumpable suspension is made from powdered clay, cement and water, which becomes solid after application by setting the cement with little or no increase in volume.

The cementing rod can be removed immediately after the sealing compound has been pumped in, if the openings in the intermediate piece can be closed by special means. If this is not the case, or if the closure proves to be leaking, the cementing rod must remain installed until the sealing compound has solidified. After removing the cement rod, the passage through the intermediate piece is free. The intermediate piece forms a closed part of the pipeline, since the openings through the sealing compound and gfs. the additional funds are tightly closed. The groundwater measuring point can now be pumped free and put into operation in the usual way.

FIG. 3 shows an embodiment of the intermediate piece 18 and a connecting piece 21 adapted to it, which is located at the lower end of the cementing rod 19. The intermediate piece 18 consists of a cylindrical tube 22, which has at its two ends an external thread 23 for screwing on a threaded sleeve for connecting the intermediate piece 18 to the upper and lower branches of the pipeline 2. The tube 22 has in its wall two mutually opposite openings 24 which have the shape of an elongated hole. In the area of the openings 24 are on the The outer surface of the tube 22 has flat contact surfaces 25 on which plate-shaped flaps 26 lie tightly, which completely cover the openings 24. The flaps 26 are held by leaf springs 27 and pressed against the contact surfaces 25. The leaf springs 27 are screwed to the outside of the tube 22 with the interposition of a lining piece 28. In the bore 29 of the tube 22 there are two opposing stop knobs 30 below the openings 24. The stop knobs 30 are fastened in the wall of the tube 22 and protrude from the bore 29.

The connector 21 consists of a tube 31 which has an internal taper thread 32 at its upper end, into which the lower end of the cementing rod 19 can be screwed. In its central region, the tube 31 has a shoulder with a smaller outside diameter, onto which two sealing rings 33 and a sleeve 34 arranged between the sealing rings are pushed. The sealing rings 33 and the sleeve 34 are held in their position by a head piece 35 which is screwed onto the lower end of the tube 31. A sealing ring 36 is also arranged between the head piece 35 and the tube 31. The head piece 35 has a bore 37 which can be closed by a valve ball 39 arranged in the lower end 38 of the tube 31. A collar 40 in the bore of the tube 31 prevents the valve ball 39 from being flushed up through the tube 31.

The connector 21 can be inserted into the bore 29 as shown. The position of the connector 21 is determined by two grooves 41 in the head 35, in which the stop knobs 30 engage. In this way, the connector 21 is fixed in its axial position and in its angular position in the intermediate piece 18. In this position, the two sealing rings 33 are located above and below the openings 24 and the openings 24 are opposite openings 42 of the same size, which are formed in the tube 31 and in the sleeve 34. In this way, through the connector 21 a pressure-tight connection between the bore of the cement rod 19 and the openings 24 is created. The sealing compound conveyed by the cementing rod 19 cannot therefore penetrate into the bore 19 of the intermediate piece 18 and the pipeline connected to it.

The connector 21 can already be used for days in the construction of a groundwater measuring point in the intermediate piece 18 and installed together with this with the pipeline 2 in the bore 1. Here, the valve ball 39 enables the liquid present in the bore to penetrate into the interior of the pipeline 2 in order to avoid increased buoyancy. If the pipeline 2 is installed, the cementing rod 19 is retracted and screwed to the internal taper thread 32 of the connecting piece 21. Here, the stop knobs 30 secure the connector 21 against rotation. When the sealant is pumped in, the valve ball 39 closes the bore 37, while the flaps 26 are lifted outward from the contact surfaces 25 by the delivery pressure, so that the sealant can reach the annular space 5 unhindered. When the filling of the annular space 5 has ended, the flaps 26 are pressed by the leaf springs 27 against the contact surfaces 25 again, as a result of which the openings 24 are closed. The cementing rod 19 can now be pulled out together with the connecting piece 21 from the intermediate piece 18 and the pipeline 2. After removal of the cementing rod 19 and the connecting piece 21, the free passage in the pipeline 2 up to the sump tube 4 is given.

Claims (5)

1. A method for constructing a groundwater monitoring site, in which a tubular conduit (2) having a water inlet opening (3) at its lower end is installed in a borehole (1) in the ground, and in which the annular chamber (5) formed between the tubular conduit (2) and the wall of the borehole in the area of the water inlet opening (3) is packed with filter material and, for sealing off water-bearing strata, with a material essentially impermeable to water, with an intermediate section (18) having closable radial apertures (24) being inserted in the tubular conduit (2) above the water inlet opening (3), with a grouting gear (19, 21) being introduced into the tubular conduit following installation of the tubular conduit (2) and following packing of the filter material layer (6) and being connected to the apertures (24) in the intermediate section (18), with a fluid sealing compound solidifying following its application being pumped through the grouting gear (19) and through the apertures (24) into the annular chamber (5) above the filter material layer (6), characterized in that the sealing compound is a pumpable suspension of powdered clay, cement and water and contains about four parts of powdered clay and about one part of cement.
2. The method as claimed in claim 1, characterized in that the density of the sealing compound is at least 1.3 g/cm³.
3. The method as claimed in any one of the preceding claims, characterized in that the filter material is covered with a layer of clay prior to the application of the sealing compound.
4. A device for implementing the method as claimed in any one of the preceding claims, with a tubular intermediate section (18) adapted to be installed into the tubular conduit (2) and having closable radial apertures (24), said intermediate section having an inside diameter equal to or smaller than the inside diameter of the tubular conduit (2) and including below said apertures (24) a stop means (30) extending into the interior of its bore (29), with a connection member (21) insertable into the intermediate section (18) and adapted to be introduced through the tubular conduit (2) into the intermediate section (18) until its abutting engagement with the stop means (30), closing the bore (29) of the intermediate section (18), and with a grouting gear (19) connectible with the connection member (21) and adapted to be installed into the tubular conduit (2), the grouting gear exit opening being connectible with the apertures (24) through a channel (42) in the connection member (21), characterized in that the connection member (21) includes above and below the apertures (24, 42) sealing rings (33) which are in pressure-tight engagement with the bore (29) of the intermediate section (18), that the connection member (21) is comprised of a sleeve (31) closable at the lower end (39) and having radial apertures located in an orientation opposite the apertures (24) in the intermediate section (18), and that it includes a longitudinal groove (41) for engagement with the stop means of the intermediate section (18), said stop means being configured as a knob (30), and that a check valve (37, 39) inhibiting flow in the direction of the mud fluid and communicating with the channel (42) is arranged in the bottom (38) of the connection member (21).
5. The device as claimed in claim 4, characterized in that the radial apertures (24) in the intermediate section (18) are closable by flap structures (26) resting on the outer surface of the intermediate section (18) and being held in a radially movable relationship by means of leaf springs (27).

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