FR2666361A1 - Method for pushing back a ground water table - Google Patents

Abstract

Installation for pushing back a ground water table, capable of being opened and closed at will and with total and immediate sealing at the end of work, characterised in that it is composed, in combination, of: - a cylindrical element intended to be inserted into the spoils of the work in question and reinforced by a cross-shaped support in order to receive a pump on its support; - a pump support stopper of frustoconical overall appearance, exhibiting a peripheral groove in which a sealing gasket is housed; - and a hollow retention piece, of frustoconical overall appearance, with the same opening as the said pump support, and exhibiting in its internal face towards its upper part a curved groove intended to receive the said sealing gasket and, at its lower part, a shoulder in order to fit onto the upper rim of the said cylindrical element and, on its external face, hooping improving its adherence to the concrete.

Description

 The present invention relates to a method for lowering a groundwater table and to an installation for implementing this method.

 We know that the term "drawdown of the water table" designates the operation which consists in lowering the level of a water table by appropriate pumping, in order to put out of water land intended to receive civil engineering works. , such as building foundations and the like.

 The installation which is the subject of the invention has the advantageous characteristic of being able to open and close at will, and it also presents the advantage of perfect and immediate sealing at the end of the work.

This installation consists of three elements cooperating together, namely:
- A tubular housing intended to be introduced into the embankment in order to receive the pump thereon on its support;
- A pump support shutter, in the shape of a truncated cone, fitted with a seal, and intended to work against back pressure;
- And a hollow retaining part also of frustoconical shape, fitting at its base around the tubular housing and having towards its upper part a groove with which cooperates said seal, this part being intended to be embedded in the raft and closed by a concrete plug to work also in back pressure.

 This installation is used in the process according to the invention by introducing the tubular housing into the sump, then the pump on its support, and by placing the retaining part over it, then by pumping, then pouring the raft around the retaining part and finally by reassembling the pump support so as to create a seal between the seal and its housing and by pouring over the concrete plug.

The invention will now be described in more detail with reference to the attached drawing in which:
FIG. 1 is a vertical section of the installation in place at the time of its implementation,
Figures 2, 3 and 4 are top views respectively of the tubular housing, the pump support and the retaining part.

 And Figure 5 is a section similar to Figure 1, at the end of the implementation of the method.

 In this drawing, the general reference 1 designates a metallic cylindrical element reinforced by a support 4 in the form of a cross, intended to receive the pump support. This element is shown placed in the embankment R at the desired level.

We have also designated by the general reference 2 a part made of metal or PVC, of frustoconical shape, intended on the one hand to support the pump P, on its upper face and on the other hand to play the role of shutter. To this end in a
peripheral groove of this part is housed a rubber flange 5 intended to
serve as a seal with the retainer.

The upper and lower parts of this part 2 are reinforced and connected by vertical cross-shaped reinforcements 6 also serving to support the weight of the pump P. A locking system 7 in the form of a ring is provided for lifting the part. , or keep it from falling when it isn’t working yet
in back pressure.

 Finally, the general reference 3 designates a retaining part of general appearance which is also frustoconical, with the same opening as part 2.

 On its inner face, this part 3 has, on the one hand a curved groove or groove 8 intended to receive the seal 5 of the part 2 when the latter is in the high position (FIG. 5), and on the other hand a shoulder 9 intended to come to fit on the upper edge of the part 1. The groove 8 is slightly flattened so as to crush the seal 5 and ensure sealing.

 On its outer face, this part 3 has raised hoops 10 intended to improve the adhesion between the part and the concrete of the raft.

The method according to the invention, using this installation comprises the following steps:
In a first step, the tubular housing I is introduced into the embankment R up to the desired level, and the shutter 2 is placed there on the support 4.

 The pump is then lowered onto its support, and the tablecloth is folded down.

 After temporary removal of the pump, the retaining part 3 is then placed, and after replacing the pump, the part 3 is prescored by a concrete ring 11, the thickness of which takes at least two circles 10.

 The slab 12 is then poured over the previous assembly, reserving, above the sump, the location 13 for the subsequent pouring of a concrete plug reinforced with bars, wait 4.

 In the next step, the pump is reassembled and extracted, and the part 2 is reassembled by means, for example, of a cable passed through the loop 7, and the hydraulic pressure is allowed to rise to locate any leaks.

 The entire pump and its support are lowered to treat said leaks.

 The part 2 is brought back definitively, and a concrete slab 15 is poured, in order to block said part 2 which, with the joint 5 constitutes the plug, under pressure, for retaining the sheet in re-formation.

It must be considered that the density of part 2 is necessarily greater than that of water. According to a subsidiary feature of the invention, this part being
made of hollow metal or plastic, it can have a hole at the top to fill it with water and closed by a threaded plug. which, added to its own weight, gives it the necessary weight.

 Of course, many details fall within the scope of the invention. Thus the leveling of the parts 2 and 3 makes it possible to ensure the correct positioning of the part 2 in the part 3. Similarly, the sharp angles will preferably be rounded to be less brittle and, at the top of part 3, ensure a better seal before pouring the concrete.

 Note that the height of the cylindrical housing 1 will be defined so as to pump below the lowest level of the raft.

Claims (3)

 its support - of a generally frustoconical-looking pump support shutter, having a peripheral groove in which a seal is housed; - And a hollow retaining part, of general frustoconical shape with the same opening as said pump support, and having in its internal face towards its upper part a curved groove intended to receive said seal and at its lower part a shoulder for fitting onto the upper edge of said cylindrical element and on its external face, hoops improving its adhesion to concrete.  - a cylindrical element intended to be introduced into the embankment of the structure under consideration, and reinforced by a cross-shaped support to receive a pump on  characterized in that it is composed, in combination:  1. Installation for the drawdown of a water table, capable of being opened and closed at will and of total and immediate tightness at the end of the work, 2. Installation according to claim 1, characterized in that the pump support is hollow and reinforced by at least one cross-shaped reinforcement to receive the pump and comprising a ring for raising and retaining said support. 3. Method for the drawdown of a water table by means of the installation according to claims 1 and 2, characterized in that it consists of the following succession of steps:  - In a first step, the cylindrical element is introduced into the embankment up to the level allowing the pumping of the sheet below the lowest level of the raft; ;  - in a second step, the pump is lowered onto its support ensuring tight sealing in said cylindrical element and the pumping of the sheet is carried out,  - in a third step, the retaining part is placed above the sump, and it is sealed, reserving the location for a retaining plug,  - In a fourth step, a leakage check is made by letting the hydraulic pressure rise, after raising the pump support to the position where its seal is in place in the groove of the retaining part; optionally the pump is lowered to treat said leaks;  - Finally, in a fifth step, the pump support is permanently reassembled and blocked in place by pouring the concrete retaining plug into the space reserved for this purpose.