Method and device for mixing earth in situ for the formation of underground walls or diaphragms

Abstract

In a device, which is suspended from cables or other flexible or articulated structures, for the mixing in situ of earth for the formation of underground walls or diaphragms presenting in its lower part disaggregating means (1) for the disaggregation of the earth, above the disaggregating means are positioned correcting means (5, 13) for the direction of the excavation being able to rotate around substantially vertical axes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the attached drawings in which:

FIGS. 1 and 2 illustrate respectively in frontal and lateral view the excavation device according to the present invention in a first form of embodiment and mounted on a first kind of machine with a rigid antenna;

FIGS. 3 and 4 illustrate respectively in frontal and lateral view the excavation device according to the present invention still in a first form of embodiment and mounted on a second kind of machine with a swinging boom;

FIGS. 5 and 6 illustrate respectively in frontal and lateral view the excavation device according to the present invention in a second form of embodiment and mounted on a member with cables;

FIGS. 7, 8 and 9 illustrate respectively in frontal view (FIG. 7) and lateral view in two different operating positions (FIGS. 8 and 9) the excavation device according to the present invention in a third form of embodiment and still mounted on a member with cables;

FIGS. 10 and 11 illustrate respectively in frontal and lateral view the excavation device according to the present invention in a further form of embodiment and mounted on a machine with a rigid rod.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The excavation device presents disaggregating means which are traditionally made up of a double pair of toothed drums 1 which are independent or mechanically coupled and are motorised with at least a motor element (mounted on the axis of the drums) The motorised part is overlapped by a sealed chamber with an access trapdoor 2 for mounting and maintenance and control circuits.

By means of pipes, which are not illustrated, it may be supplied with the aggregating fluid and/or fluidising liquid at high pressure via nozzles, which are also not illustrated, used to disaggregate any eventual clods of earth which might be found between the toothed drums.

During the phase of advancement into the earth the pair of drums rotate towards the inside where they tend to accumulate shredded earth due to the effect of the action of the teeth and the fluid which is pumped at high pressure (20-40 MPa). A mixing area 3 is created in this zone where nozzles of the type which have previously been described pump aggregating fluid and fluidising liquid derived from the same feed.

According to the present invention, correcting means for the direction of the excavation made up of milling means or motorised mixers are arranged above the body 4 which holds the drums 1.

During the functioning of these correcting means the drums are made to rotate in an opposite direction and that is towards the outside in such a way as to exert a downward pressure which stabilises the fluid and is useful for improving the homogeneous nature of the treatment and tends to move the earth which is present in the mixing chamber 3 downwards. During this action, the drums continue to be aided by the liquid which is fed under pressure by means of the above-mentioned nozzles. As the earth moves downwards it tends to free the chamber between the two drums which will tend to be filled again by the earth from above which has been previously mixed and further kept in motion by the said motorised correcting means.

According to a first form of embodiment, with the aim of correcting the direction of the excavation, upper milling members 5 are used with the aim of correcting the direction of the excavation, having rotation axes which are substantially vertical (see FIGS. 1, 2, 3 and 4).

Each milling member 5 can swing around its own hinge which hinges it to the excavation device and rotate around its own longitudinal axis.

The reaction of the torque which is applied to these in order to keep the earth in motion also acts on the excavation device in its entirety. Thus if both the milling members 5 rotate in the same direction, the excavation device tends to rotate in the opposite twisting direction.

If instead the milling members 5 are made to rotate in an opposite direction, the torque is cancelled out, but not the force of friction on the surrounding material. For reasons of symmetry the residual force has a direction which is perpendicular to the plane of the diaphragm, precisely in the main direction. Inverting the direction of rotation of the milling members also inverts the direction of the correcting force.

The device, in the configuration of the machine which is shown in FIGS. 1 and 2, ends in its upper part with a rod or antenna 6 which is substantially as long as the depth of the excavation to be reached and which will contain feed pipes or cables of the device and be guided by a guide tower 7 which will prevent any undesirable rotation. The height of such a tower constitutes a limit to the depth which may be reached.

In an alternative form of embodiment, which is shown in FIGS. 3 and 4, the rod 6 is replaced with a cable system 8 in order to increase the depth which may be reached. Furthermore an external guide system 9 is used suspended from the machine (crane) with a hollow prismatic section and an inner guided element 10 with an equally prismatic section.

The two guide elements are engaged with the device on the outside and during the first few metres of drilling. The device is rendered independent at greater depths and is guided along the walls of the excavation.

FIGS. 5 and 6 show a further form of embodiment in which the excavation device is supported by a cable system 11, but above all there are two overlapping pairs of milling members 5 instead of a single pair. In this case the force of friction and the torque of the milling group are considerably increased which means that the results obtained are optimised.

Again with the intention of improving the function of the milling group it may also be made up of several pairs arranged at a distance from each other along a structure 12 which supports them as illustrated in FIGS. 7, 8 and 9.

The structure 12 is of a flattened and elongated shape in such a way as to maintain a distance between the various corrective forces and to be substantially far from the walls of the excavation.

Again with the aim of correcting the direction of excavation in the direction away from the plane of the panel and in the torsional direction of the panel, the correcting means, rather than the milling members 5 arranged in one, two or more pairs as described above, may be mixing members for the mixed earth, preferably arranged in its upper part and having a substantially vertical rotation axes.

These mixing members are also shown in FIGS. 10 and 11 and are made up of appendices 13 which extend laterally from vertical rods 14. The rods 14 are positioned laterally and parallel to the antenna 15 and rotate around their own longitudinal axis controlled by motors 16 which are positioned above.

The appendices 13 are of a variable number and length according to necessity and their ends act on the surrounding earth during the rotation of the rods 14 which support them when they are rotated by the motors 16.

The reaction of the torsional torque, which is applied to the lateral ends or mixing members 13 in order to maintain the earth in motion, also acts on the excavation device. Thus, if the mixing members 13 rotate in the same direction, the excavation device tends to rotate twisting in the opposite direction.

If instead the mixing members are made to rotate in the opposite direction, the torque is eliminated, but not the friction force on the surrounding material. For reasons of symmetry the residual force travels in a direction which is perpendicular to the plane of the diaphragm, precisely in the main direction. Inverting the direction of rotation of the mixing members 13 also inverts the direction of the correcting force.

In order to produce a feed without correcting force the mixing members are not made to rotate or are intermittetly activated in one direction and then in the opposite direction.

Alternatively two pairs of such members may be installed and kept in continuous opposite pair rotation.

The upper mixing members fulfil two further advantageous aims.

One of these is to keep the fluidised earth in motion in the area above the excavation device. This motion slows down the phenomenon of the hardening of the aggregating fluid thus consenting the introduction of such a fluid during the drilling phase, extending the mixing time to the total return time and thus improving the quality of the mixing operation. On the other hand, the extraction time decreases because it is not conditioned by the control of the dosage of the aggregating fluid.

As the aggregating fluid is introduced in the excavation phase, it also functions as a fluidising liquid, thus avoiding the need for the introduction of water during the first phase. This alternative has the effect of drastically reducing the total amount of fluid which has to be introduced into the excavation, and consequently decreases the amount of waste fluid which generally overflows throughout the whole process and which results in problems relating to the disposal of special waste and an increase in costs.

The other advantage is that in the case of emergencies (cave-ins, temporary breakdowns which result in the hardening of the mixture) the mixing members may be used to re-open a return route through the mixed material, thus permitting the retrieval of the equipment.

The upper mixing members may be produced in orientating fashion. This would extend their field of action in terms of mixing, as well as in terms of extraction from the excavation in the case of an emergency. The control of the direction may also improve the correcting effect which has been described above.

Claims

1. An excavation device, which is suspended from cables or other flexible or articulated structures, for the mixing in situ of earth for the formation of underground walls or diaphragms comprising in its lower part disaggregating means for the disaggregation of the earth wherein above the disaggregating means are positioned correction means for the direction of the excavation capable of rotating around substantially vertical axes.

2. Device according to claim 1, wherein the correction means for the direction of the excavation are milling members which rotate around their own axis and swing around the hinge which hinges them to a body of the excavation device.

3. Device according to claim 2 comprising two of the milling members which are arranged diametrically opposite each other on the body of the excavation device.

4. Device according to claim 2 comprising two pairs of the milling members, the members of each pair being arranged diametrically opposite each other on the body of the excavation device.

5. Device according to claim 2 comprising a plurality of pairs of the milling members, spaced along the upper structure of the body of the excavation device, the members of each pair being arranged diametrically opposite each other on the body of the excavation device.

6. Device according to claim 2, wherein each member of each pair of milling members can rotate in the same or in the opposite direction in relation to the other member of the same pair.

7. Device according to claim 5 wherein the support structure of the milling members comprises a flattened and elongated shape.

8. Device according to claim 1 wherein the correcting means for the direction of the excavation are mixing means which rotate around substantially vertical axes.

9. Device according to claim 8 wherein the mixing members are comprise appendices which extend laterally from vertical rods, which are positioned laterally and parallel to the antenna of the machine; the rods rotate around their own longitudinal axis controlled by motors which are positioned above.

10. Excavation and mixing method carried out by correction means of the direction of the excavation according to claim 1, wherein the direction of drilling is corrected respectively: in rotation, if all the correcting mean rotate in the same direction, contrary to the correction;in the normal direction on the plane of the excavation, if the rotation direction of the correcting means is opposite pair rotation.

11. Method according to claim 10 wherein the aggregating fluid is introduced during the excavation and also functions, temporarily, as a fluidising agent.