Adjustable closing apparatus for excavated trench sections of deep partition walls

Abstract: A method for providing deep partition walls in the ground, wherein, by means of a drill head (3), pits (8) are drilled, spaced apart, to the desired depth, whereafter the ground panel (11), located between the two pits (8), is excavated by means of a deep-wall cutter (10) comprising at the two sides thereof guide elements (12), guided by the walls of the pits (8) during excavation of the ground panel (11). In this manner, successive ground panels can interconnect perfectly to yield a sealing wall, continuous at all points, consisting of a hardenable mass to be provided in the excavated trench.

Description: For providing deep partition walls in the ground several methods are known. According to NL-A-87.02430 such method comprises: excavating a first well by means of an excavator; excavating a second well by means of the excavator, which second well is shifted relative to the first pit over a distance approximately corresponding to the greatest length dimension of the excavator; excavating, by means of the excavator, the ground panel, located between the first and the second well; and filling up the thus formed panel space with a hardenable mass. The excavator used consists of a deep-wall cutter, with which a first well or pit of rectangular section is excavated and subsequently, laterally shifted relative thereto, a second pit of rectangular section is excavated, shifted laterally relative to the first pit. Subsequently, the intermediate ground panel is excavated by means of the deep-wall cutter. In order to obtain a continuous wall, it is of the utmost importance that the panel space thus provided connects to the pits excavated on both sides thereof. Consequently, when the ground panel located between two pits is excavated, there must be an overlap in the principal direction of the wall, and, also, the deviation in a direction perpendicular to the wall to be excavated can only be slight. For measuring this deviation in a direction perpendicular to the wall to be excavated, inclinometers are used as described in above-mentioned NL-A-87.02430. The precision of these inclinometers is insufficient to guarantee that the adjoining panels are in sufficient abutment in a direction perpendicular to the plane of the wall. In order to obtain a sufficient abutment, each wall panel must be of a thicker design than is necessary. There is a relation between the necessary thickness of the wall and the accuracy with which the position of the wall can be measured at a great depth. From JP-A-59-130.290 a method is known in which these drawbacks have been overcome and, consequently, a deep wall can be made whose adjoining panels exhibit only a very small deviation relative to each other in a direction perpendicular to the wall to be provided in the ground. According to this method the first and the second well are excavated with an excavator of circular section, designed as a drill head, where after the ground panel located between the first and the second well is excavated with a second excavator, laterally fitted with tubular guide elements, which, during excavation, are guided by the walls of the first and the second well. By excavating the around panel by means of an excavator which, during excavation, is guided by the first and the second well, provided in the ground earlier, it is ensured that even at a great depth, the panel space thus provided perfectly connects to these two wells excavated earlier. For that purpose, it is of course necessary that the first and the second pit are excavated in the ground truly vertically and this can be effected with drilling equipment which is known per se. For excavating the next ground panel, the first well of that next panel must be free of the hardenable mass provided in the preceding panel. For that purpose, prior to filling the preceding panel space with a hardenable mass, the second well is separated from the adjacent ground panel by means of a support tube, securable in this second well as is known form DE-A-1.484.545, where after the newly excavated panel space and the first well are filled with a hardenable mass. In this manner, the second well of the preceding panel is kept clear for receiving the tubular guide element of the excavator during excavation of the adjacent ground panel. If this support tube is to provide good sealing properties, the friction during insertion of the tube in and removal thereof from the second well is considerable, limiting the depth of a well in which such support tube is to be placed. A solution for this problem is proposed in DE-B-1.634.323, from which an adjustable closing apparatus is known, comprising two arc-shaped elements, which are mutually connected by means of a ladderlike spread mechanism. This closing apparatus can be inserted in the second well in a fold-in position and subsequently brought into a tube-like closing or sealing position by means of the spread-mechanism. The object of the invention is to provide an adjustable closing apparatus of the above described type which is more easily insertable in and removable from a second well of an excavated trench section. According to the invention this object is achieved in that the adjustable closing apparatus comprises a support tube, having a diameter which is smaller than the diameter of the second well said support tube being provided on at least one side with an inflatable body, which extends over at least one-fourth of the tube circumference and which is inflatable by means of liquid or air. Such a support tube can be easily inserted in the second well after excavation of a first ground panel, the inflatable body being directed towards the next ground panel tube excavated. By filling the inflatable body with liquid or air, the opposite side of the tube is pressed in a closing or sealing position against the first ground panel space to be closed. This space is then filled up with a hardenable mass, and after hardening of that mass the liquid or air is removed form the inflatable body, which enables the support tube to be easily removed. The next ground panel can now be excavated, while a guide element of the excavator can be received in the well from which the support tube has been removed. Embodiments of a support tube according to invention will now be further explained with reference to the accompanying drawings. In these drawings: Fig. 1 is an outline showing the connection problems of successive panel spaces; Fig. 2 shows the method and apparatus for excavating or drilling the first and the second pit of a ground panel; Fig. 3 shows the method and apparatus for excavating a ground panel located between two wells; Fig. 4 shows the filling of the first panel space with a hardenable mass, in the presence of a support tube in the second pit of that panel space; Fig. 5 shows the excavation of the second ground panel; Fig. 6 shows a first embodiment of a support tube; and Fig. 7 shows a second embodiment of this support tube. Fig. 1 shows a first panel space A in full lines and a next panel space B in broken lines. The depth L of such a wall is for instance 100 m below the ground level O. The thickness D of the panel space is for instance 1 m, while at a depth of 100 m the overlap d of the two panel spaces must be at least 50 cm in order to obtain an abutting wall that is impervious to water. In that case, the deviation angle α must not be more than 0.3° and this extremely slight deviation is not measurable by the measuring equipment presently available. Consequently, in order to obtain an overlap of at least 50 cm all the same, the thickness D of the wall panel, and hence the allowable deviation angle α, will have to be increased. Fig. 2 shows the situation where two wells 8 have been drilled, spaced apart a distance 9, while a third well 8 is being drilled by means of a drill apparatus 1. The wells 8 already drilled are filled with a support liquid 4, such as for instance bentonite. The drill apparatus 1 comprises a Kelly-rod, known per se, whose lower end mounts a drill head 3. The Kelly-rod is suspended from a hoist disc 5, suspended from the drill apparatus 1 by means of a cable 6. The drill head 3 has a weight of about 35 tons, while via the cable 6 a vertical lifting power of about 10-15 tons is exerted on the drill head 3, so that this drill head 3 is suspended with a weight of about 20-25 tons from the drill apparatus 1 in the manner of a plumb. The soil loosened up by the drill head 3 is discharged upwards in a conventional manner, together with the support liquid 4 present in the hole that has already been drilled. In a separator 7, the support liquid 4 is separated from the mass of soil transported upwards, whereafter the support liquid 4 can be supplied again to the well to be excavated. In this manner, truly vertical holes of a depth of more than 100 m can be provided in the ground. Fig. 3 shows how the ground panel 11, located between two successive wells 8, is excavated by means of a deep-wall cutter 10. The deep-wall cutter or a similar excavating apparatus such as for instance a grip, is provided with tubular guide elements 12 at the sides thereof, which guide elements have such a diameter that they are movable with some play 14 in a well 8. The guide elements 12 project from the excavator 10 on opposite sides in the direction of excavation, while the projecting parts 13 of the guide elements 12 preferably have a conical shape so that they can be moved probingly within the wells 8. The projecting parts 13 are weighted, so that the deep-wall cutter 10 is pulled into the ground. One of the guide tubes 12 is connected to the excavator 10 by means of a parallelogram construction 16, so that lateral play can be taken up. By means of springs 17, the guide tube 12, connected to the excavator 10 via the parallelogram construction 16, is held against the rubber blocks 18, arranged on the excavator, so that both a positive and a negative play can be taken up. The excavator 10 is suspended from a drill apparatus 1 by means of a cable. It is not necessary to push the excavator 10 into the ground by means of a tube arranged on the trailing end thereof. Mounted on the excavator 10 are pumps 19 for discharging the support liquid blended with the mass of soil, which is fed to a separator 7. The wells 8 accommodating guide tubes 12 have been excavated to a somewhat greater depth than the desired depth of the partition wall to be provided in the ground, in order to accommodate the projecting parts 13 of the guide tubes 12 at the moment when the deep-wall cutter 10 has reached the desired depth. As shown in Fig. 3b, the diameter of the wells 8 is greater than the thickness 15 of the ground panel 11, the thickness 15 corresponding, of course, to the width of the excavator 10. Because the excavator 10 is guided by the guide tubes 12 as the ground panel 11 is being excavated, a perfect alignment of the panel space 11 with the wells 8, present on both sides thereof, is automatically realized. The maximum deviation is determined by the play 14 between the outer wall of a guide tube 12 and the wall of a well 8. After excavation of the ground panel 11 in the manner discussed above, a support tube 20 is arranged in the second well 8, as shown in Fig. 4. This support tube 20 serves to keep open the second well 8 while the hole consisting of the first well 8 and-the panel space 11 connecting thereto is filled with a hardenable mass 22. As a hardenable mass, for instance a concrete mixture can be used, optionally further provided with a reinforcement. The support liquid 4, present in the panel during excavation, is displaced by the hardenable mass 22 or pumped off. The support tube 20 (see Fig. 6) consists of a metal tube, comprising an inflatable body 21 over at least one-fourth of its circumference, which inflatable body, together with the wall of the support tube 20, constitutes an expandable chamber, which can be filled with air or a liquid under pressure. The support tube 20 is fixed in a well such that the inflatable body 21 abuts against the successive ground panel 11. Consequently, the support tube 20 is secured against the inner wall of the well 8. After the hardenable mass 22 has at least partially hardened, the support tube 20 is removed from the well 8 after the air or liquid used for expanding the inflatable body 21, is removed by suction. Subsequently, as is shown in Fig. 5, the adjacent ground panel 11 is excavated in the same manner as shown in Fig. 3. The successive panel space thus provided perfectly connects to the preceding panel space, as described hereinabove. Consequently, this means that the thickness of the panel space need not be greater than the necessary thickness d, as shown in Fig. 1. As a result, a considerable saving in material can be achieved. Further, an important advantage is that the total length of the excavator in the direction of the partition wall can be utilized, because an overlap in lateral direction, as shown in Fig. 4 of NL-A-87.02430, is no longer needed. Fig. 7, finally, shows a second embodiment of the support tube 20. Arranged on one side of the support tube 20 is an inflatable body 21, while on the side opposite this inflatable body there are arranged outwardly projecting support strips 24, between which a sealing strip 23 can be accommodated so as to be axially slidable. When the support tube 20 is removed from a well 8, this sealing strip 23 can be left in the hardenable mass 22 of the preceding panel space and subsequently be incorporated into the hardenable mass 22, to be provided in the next panel space.

Claims: Adjustable tube-like closing apparatus for excavated trench sections, for use in a method of providing deep partition walls in the ground, such method comprising the steps of excavating a first well (8) of circular section, excavating a second well (8) of circular section, which second well is shifted relative to the first well over a distance (9) approximately corresponding to the greatest length dimension of the excavator, to be used for excavating the ground panel (11) located between the first and second well (8), said excavator being laterally fitted with tubular guide elements (12), which during excavation are guided by the walls of the first and second well (8), separating the second well (8) from the adjacent trench section, consisting of the first well (8) and the adjacent ground panel space (11) by means of a tube-like closing or sealing apparatus (20), which can be inserted and fixed in the second well (8), and filling up the adjacent trench section (8, 11) with a hardenable mass (22). said adjustable tube-like closing apparatus comprising a support tube (20), having a diameter which is smaller than the diameter of the second well (8), said support tube (20) being provided on at least one side with an inflatable body (21) which extends over at least one fourth of the tube circumference and which is inflatable by means of liquid or air. Tube-like closing apparatus according to claim 1, characterized in that the support tube (20), on the side opposite the inflatable body (21), is provided with outwardly projecting support strips (24) for accommodating therein a sealing strip (23) so as to be axially slidable.

Inventors: VERSTRAETEN ALEXANDER JULIEN, VERSTRAETEN, ALEXANDER JULIEN
Applicants: VERSTRAETEN BEHEERSMIJ BV, BEHEERSMAATSCHAPPIJ VERSTRAETEN B.V.
Application year: 1993
Main classification: E02D5
IPC codes: E02D5