Abstract:
A method for measuring parameters of plastic ground (2), includes forming aole (3) in the ground (2) and placing a pipe (7) in this hole (3) to collect groundwater in various places. The pipe (7) is equipped with several closed chambers (8) which are closed off on the outside of the pipe (7) by filters (9), and through which conduits (10) extend. The conduits (10) are connected separately onto the chambers (8). Measurements are carried out after the plastic ground (2) has been pressed against the filters (9) through settling.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns a method for measuring parameters of plastic ground, according to which method a hole is made in the ground and a pipe is provided in this hole to collect groundwater in various places. 
     2. Discussin of the Prior Art 
     In a number of cases, it is required to measure the interstitial water in , for example, clay layers that are being considered to store waste in and to take samples of this water. This measuring must be done in various places in the ground. 
     Providing a separate borehole in every place to be measured and collecting water from these places via pipes which are provided in the boreholes is time-consuming and harms the environment to a large extent. 
     Hence, it has already been tried to measure the parameters of the ground in various places with one borehole and one pipe. 
     According to a known method, a borehole is drilled which is considerably larger than the pipe which is provided in it afterwards, whereby zones of the ground around the pipe are sealed by what are generally called packers, i.e. for example inflatable rings. 
     According to other known methods, fill material is provided around the pipe. 
     The application of packers or fill material is not only time consuming, but the methods do not allow for reliable measurements or restrict the possible measurements. 
     SUMMARY OF THE INVENTION 
     The invention aims to remedy these disadvantages and to provide a method for measuring parameters of plastic ground which allow for a large number of measurements in a simple manner in different places in the ground without the use of packers or fill material. 
     This aim is reached according to the invention in that a pipe is used which is provided with several closed chambers which are closed off on the outside of the pipe by means of filters, and in which conduits extend which are connected separately onto the chambers, and in that measurements are carried out after the plastic ground has been pressed against the filters by means of settling. 
     The invention also concerns a device which is particularly suitable for applying the above-mentioned method and which has a simple construction, but which allows for multiple and precise measurements. 
     Also, the invention concerns a device for measuring parameters of plastic ground, which contains a pipe, characterized in that the pipe has a number of closed chambers which are closed off on the outside of the pipe by means of filters, and conduits which are connected separately onto the chambers and extend through the pipe. 
     The conduits can be connected to a measuring laboratory which is situated, for example, beneath the ground. 
     According to a special embodiment of the invention, the chambers and thus also the filters are ring-shaped. 
     Other particularities and advantages of the invention will become clear from the following description of a method and device for measuring parameters of plastic ground according to the invention. This description is given as an example only and does not limit the invention in any way. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a section of plastic ground with a borehole in which is provided a device according to the invention; 
     FIG. 2 shows a section according to line II--II in FIG. 1; 
     FIG. 3 shows the detail which is represented in FIG. 2 with F3 to a larger scale; 
     FIG. 4 shows the detail which is represented in FIG. 2 with F4 to a larger scale. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a gallery 1 which was dug in plastic ground, namely clay ground 2, and into which opens a borehole 3. 
     At the end of the gallery 1 is formed an underground measuring laboratory 4. The gallery 1 is coated with a metal inner wall 5 and closed off on the side of the borehole 3 by means of a concrete wall 6. 
     The device for measuring the hydraulic pressure of the groundwater around the borehole 3 and for taking samples of this groundwater mainly includes a pipe 7 over which are spread a number of closed chambers 8 which are closed off on the outside by means of filters 9 and which are connected onto measuring equipment 11 via conduits 10 which include among other things manometers, and which is erected in the laboratory 4. 
     The pipe 7 is round and long, with a length of, for example, ten meters, and made of stainless steel. It includes of a number of pipe segments 12 with possibly varying lengths, which are connected to one another with connecting elements 13 or filter elements 14. 
     The connecting elements 13 each constitute of a short piece of pipe which is provided with a flange 15 on the outside and over which the pipe segments 12 to be connected are slid with one end. This end is welded to the flange 15. 
     The filter elements 14 include two pipe parts 16 and 17 and the ring-shaped filter 9. The pipe part 17 has a narrowed end which sticks in the pipe part 16 and is welded onto this part. Both pipe parts 16 and 17 have a flange 18 on their outside. A pipe segment 12 is slid over the pipe parts 16 and 17 up against the flange 18 and welded onto this pipe part. 
     The filter 9 is made of a rigid, porous material such as sintered stainless or ceramic material. It surrounds the pipe parts 16 and 17 between the two flanges 18 and is welded or glued onto these flanges. Opposite the filter 9, the pipe part 17 has a smaller diameter over a certain distance, so that an above-mentioned chamber 8 is formed between the filter 9 and the outside of the pipe parts 16 and 17. 
     In this chamber 8 opens a duct 19 which extends through the wall of the pipe part 16 and is connected onto a conduit 20 of stainless steel which is welded onto it and extends through the pipe 7 into the laboratory 4. The duct 19 and the conduit 20 together form the above-mentioned conduit 10 which connects the chamber 8 to the measuring equipment 11, erected in the laboratory 4, so that the hydraulic pressure in the chamber 8 can be measured. The conduit 20 can be removed from the measuring equipment 11, so that a sample can be taken via the conduit 20 of the water which filters through the filter 9 in the chamber 8. 
     The end of the pipe 7 is sealed by means of an end part 21. 
     Before the measuring, the borehole 3 is drilled in the ground 2 from the gallery 1. 
     The pipe 7 is provided in the borehole 3 immediately after the drilling, that has a diameter which is slightly bigger than the largest diameter of the pipe 7, i.e. the diameter of the ring-shaped filters 9. As the clay ground 2 settles, it will press rapidly, i.e. within a few hours, against the pipe 7 and thus also against the filters 9. 
     The flow rate which flows in the chambers 8 depends on the filters 9, so that these are selected as a function of the application. Thanks to these filters 9 and the direct contact of the ground 2 with these filters 9, precise measurements can be obtained in various places along the borehole 3, despite possible different hydraulic fields. 
     Since each of the chambers 8 is separately connected to the measuring equipment 11 and to, among other things, a manometer by means of conduit 10, the hydraulic pressure can be simultaneously measured in different places in the borehole 3. At the same time, other parameters can be measured such as the pressure gradient and the flow. 
     By disconnecting the pipes 20 from the measuring equipment 11, samples can be taken of the water in different places in the ground 2 via the conduits 10. These places are known since the distance between the chambers 8 and thus their location on the pipe 7 is known. On the basis of the samples, the conductance, the gas solubility, etc. can be measured. 
     Thanks to this device, the in-situ migration with sorbing and non-sorbing radionuclides, for example tritiated water, can be measured, in particular in clay layers that are being considered to store nuclear or toxic waste. Via conduit 10 and the chamber 8 with filter 9 connected onto it, such radionuclides can be injected in the ground 2. On the basis of measurements of the amount of nuclides in the water which is collected via other conduits 10 from other chambers 8, whose distance to the first-mentioned chamber 8 is precisely known, it is possible to check how and at what rate water migrates in the ground. 
     The invention is by no means limited to the above-described embodiment; on the contrary, within the scope of the patent application, many changes can be made to the described embodiment. 
     Thus, the pipe 7 can also be made of synthetic material instead of stainless steel. In this case, the welded joints can possibly be replaced by glued joints.