DE19525590A1 - Building-trench formation method below water-table - removes earth along inside of one wall and forms anchroing points below table for later tightening from water-displacing box - Google Patents

Abstract

The trench is formed where the water table is high and cannot be lowered, using walls and a non-buoyant bottom forming a seal. After removing earth along the inside of one wall, anchoring points (A) are formed from the surface and several metres below the water table. These are later tightened from a water-displacing box (10) bearing against the wall at its open side. Slit-trench walls can be used as the trench walls, the anchoring points and the direction of the anchor bolts being determined by a guide tube for the drill, the tube being fixed to the wall.

Description

Our invention relates to a method for producing an excavation pit in areas with high groundwater levels, where an additional Lowering is not permitted.

The normal case for creating a construction pit in one Area would be a construction method that is at least limited in time Groundwater lowering. In the case of groundwater management with the well the groundwater level in the excavation pit and the drained groundwater drained off. The water table among the surrounding properties is also affected, since the groundwater level changes depending on the shape of a lowering funnel Permeability of the subsoil, permeability of the groundwater horizons, lowering depth and duration of lowering up to several kilos meters distance.

In some cities there are very high requirements regarding the Influencing the groundwater level so that it is not even possible Lich is to sink the groundwater 2 to 3 m for a construction measure ken. In addition, injection soles, the construction pits below with a kind Lock the lid, not always approved, since it is partially with the Introducing chemicals work and because of the buoyancy safety very deep excavation walls are required. The injection sole is about the same depth below the ground due to the safety against buoyancy Arrange the pit of the pit like the groundwater above the building plot sole stands. In the event that the client or the approval do not hear such an injection sole as a waterproof sole cover  or does not allow such deep sealing walls, the sole of the construction must pit to be concreted with underwater concrete.

Our invention is concerned with the manufacture of an excavation pit the conditions that no groundwater, even in the short term, abge may be lowered and that a sole made of underwater concrete len is. So far, in such a case, the pit could be enclosed The excavation pit wall only above the groundwater table be anchored. This resulted in large ones for the pit walls Spans between the underwater concrete floor as a lower support the top of the pit and the anchor attachment points camp. The pit wall must therefore have a much higher bending rate absorbing elements and deformations than when the anchor is set lower sentence points. The bending moments increase more than quadratically Distance between the anchor points, therefore there are construction pit walls to be designed much stronger with a wider span. The price for the pit walls, which often only meet temporary requirements must rise accordingly.

Our invention eliminates the drawbacks of large deflections the pit walls by a manufacturing process that the installation of Anchoring below the restrictive conditions mentioned below of the groundwater level. Because of the exponential increase the bending moments and the deflections is what is provided here Procedure especially for deep construction pits, which are marked by an Un water concrete base and above secured by only one anchor layer who can, which must also be above the water level, advantageous.

The implementation of our method according to the invention can be explained with reference to FIGS. 1 to 4.

Fig. 1 pit with anchoring according to the prior art

Fig. 2 pit with trench

Fig. 3 tensioning the anchor in the protection of a concrete box

Fig. 4 removal of the excavation pit

Fig. 1 shows a section through an excavation pit. From the surface ( 1 ), the bounding excavation walls ( 2 ) are introduced into the construction ground. The groundwater level ( 4 ) is very close to the surface. The construction pit should be excavated up to level ( 3 ). According to the prior art, the anchor ( 5 '') with the grout ( 6 '') would be set in the area above the groundwater. The anchors can be tensioned conventionally above the groundwater level. After that, the earth would be excavated, and the construction remains filled with groundwater. The bottom would be made of underwater concrete and the water would be pumped out. The construction pit wall would have to absorb the entire earth pressure between points A '' and B.

FIG. 2 shows the procedure in our invention. First, the construction pit wall is created. Depending on the requirements, diaphragm walls or sheet piling are used. Then a trench is dug along the wall of the excavation pit, which is then blown open to the inside of the excavation pit. The base width of the trench must be a few meters. The anchors are then introduced from the surface ( 1 ) of the construction pit. The anchor device ( 7 ) is at the original level of the earth's surface or on a level just above the groundwater level. The drilling direction for the anchor device can be specified via a pipe guide of the drill pipe. This allows the anchors to be placed at the correct angle below the water table. If necessary, fix the pipe guide to the construction pit wall ( 2 ). If the pit is a diaphragm wall, recesses can be provided in the previously determined position. If necessary, a diver can uncover the openings after the trench has been made and insert the drill pipe: For a sheet pile wall, an opening must be made under water; after the drill pipe has been inserted at the correct starting point A, the anchor is manufactured using conventional methods. An injection anchor is shown by way of example in FIG. 2. The anchor rod or the prestressing steel bundle on the anchor head must have a greater tolerance in this type of manufacture, so that there is no problem that the steel protrudes too short from the excavation pits and cannot be correctly grasped during the later tensioning process.

Fig. 3 shows the tensioning process of the set anchor in the groundwater. A concrete box ( 10 ), which can be lowered due to its high weight in the ground water, is pivoted and lowered into the trench filled with water via a lifting device ( 8 ). The concrete box is open at one end and at the top. Along the edge of the open box side there is a sealing element ( 11 ).

The seal can be inflated or operated via a hydraulic system be. The box is in the position you need to tension the anchor has provided, the seal is activated and the interior of Emptied water. The horizontal pressure of what is outside sers presses the box against the sealing wall and you get a good one Tightness. An exemplary size of the box would be a depth of 2 to 4 m, a width of 2 to 3 m and an open long side of 2 up to 6 m.

All work for tensioning the anchors can then be carried out in the box. The anchor point A and the later support point of the excavation wall with this method, the underwater concrete base B is essential closer together. The pit wall can thus be considerable be dimensioned more favorably.

The further procedure is outlined in FIG. 4. After the "underwater anchors" have been set and tensioned, the soil in the construction pit is excavated. The underwater concrete ( 12 ) is placed on the excavation base. The concrete base must be designed to be buoyancy-proof. Either a heavyweight sole is installed or the sole is anchored down. You can then pump off the groundwater.

Another embodiment of our invention uses instead of Concrete box, a box made of steel, which may be ballasted must be sword.

Reference list

1 surface
2 excavation wall
3 construction pit sole
4 groundwater table
5 anchors
6 compression body
7 anchor device
8 hoist
9 suspension
10 boxes
11 seal
12 underwater concrete sole

Claims (7)

1. A method for producing a construction pit in areas with low, high groundwater levels using construction pit walls and a buoyancy-proof underwater concrete sole as a bottom-side construction pit seal, characterized in that the soil is removed along the construction pit wall within the construction pit and anchoring members with an anchor point of several meters below the groundwater level are produced from the surface, with the later tensioning process being carried out by a water-displacing box, which lies on the sealing wall with its open side. 2. A method for producing a construction pit according to claim 1 ge is characterized by the fact that diaphragm walls serve as the pit walls be prepared and the starting point and the direction of the approach kers can be determined via a pipe guide of the drill. 3. A method of manufacturing a construction pit according to claim 2 ge indicates that the pipe guide of the drill on the diaphragm wall is fixed. 4. A method for producing an excavation pit according to claim 1, ge is characterized by the fact that steel sheet pile walls are used as excavation pit walls be used in the anchorage point of the underwater Openings are separated into which the drill pipe is inserted becomes. 5. A method for producing an excavation pit according to one of the claims che 1 to 4, characterized in that the water-displacing Box is made of concrete and a umlau on its open side fende seal has.   6. A method for producing an excavation pit according to one of the claims che 1 to 4, characterized in that the water-displacing Box made of steel and a umlau on its open side fende seal has. 7. A method for producing an excavation pit according to claim 5 and 6 characterized in that an elastic seal as a seal is hose that is pneumatically or hydraulically driven.