A method and plant for consolidating soil by injecting liquid in the soil

Description

[0001] The present invention relates to a plant for consolidating soils through injection into the subsurface of suitable materials in liquid form, such as, for example, liquid mortar.

[0002] Methods and plants have been long known for consolidating soils through injection of liquids.

[0003] Italian patent No. 1 083 340 discloses a plant which comprises a preferably self-propelled structure intended to be located at the surface, which carries a drill in the form of a rotating rod consisting of more sections which are screwed one following the other, and means to cause the same to rotate and penetrate the soil to the desired depth. The rod consists of several sections, which are gradually added to the rod as it descends into the soil. The first rod section comprises mill-shaped means adapted to bore the hole into the soil in which the rod is caused to penetrate in a gradual manner. The rod, or more precisely the various sections thereof, comprises at least two concentric tubes that are suitable to generate a gap around a central duct. Both the central tube and the gap directly communicate with the outside, limited to the first rod section.

[0004] Consolidating liquid is fed through the central duct, at a pressure ranging between 150 and 400 kg/cm², while pressurised air is fed through the gap at a pressure ranging between 5 and 10 kg/cm².

[0005] After the desired depth has been reached, the rod is withdrawn while being rotated, and the liquid and air injection is started. Thereby a sort of solid column is created which has a substantially circular, but irregular, section, since the penetration distance of the liquid from the rod axis depends upon the characteristics of the soil in which it is inserted, which characteristics are quite variable. In crumbly soils, the penetration distance is clearly higher than in more compact soils.

[0006] The rotation is imparted to the rod by a hydraulic motor, and the rod is outputted from a rotating head that is supported by a saddle vertically moving along an injection tower. The axial movement is imparted to the saddle by means well known to those skilled in the art, the description of which is omitted.

[0007] Through the known plants, waterproofing, inter alia, or strengthening walls are built, which are obtained by creating a series of adjacent and partially interpenetrating columns. This operative mode finds a major limitation in the fact that, in order to create a continuous wall, a large number of columns requires to be created.

[0008] JP 02 0270015 A discloses a plant as defined in the preamble of claim 1. Similar plants are known from JP 03 005517 A, JP 09 049225 A and JP 11 050443 A.

[0009] The object of the present invention is to overcome the aforementioned drawback by providing a simple, inexpensive, and reliable solution.

[0010] Said object is achieved, according to the invention, by a plant as defined in claim 1.

[0011] The advantages and constructive and functional features of the invention will be clearly understood from the detailed description below, which illustrates, with the drawings in the annexed tables, one preferred embodiment thereof, which is given by way of non-limiting example.

Fig. 1

shows the schematic side view of an injection unit.

Fig. 2

schematically shows the top portion of the vertical drilling tower, with the hydraulic layout of the invention.

Fig. 3

shows section III-III of Fig. 2.

Fig. 4

shows, in cross section, the end portion of the drilling and injection rod, and the adjacent rod section.

Fig. 5

shows the cross section of a column built according to the invention.

[0012] In the figures, a self-propelled means 1 is seen which is provided with a drilling tower 2, on which a saddle 3 slides, which is connected to the tower 2 by a cylinder-hydraulic piston assembly 4. The saddle 3 supports a rotatable head 5 which is fastened to the saddle by means of two brackets 31 which hold a central flange 57 of the head 5.

[0013] The head 5 is connected to a hydraulic motor 6, also supported by the saddle 3, which causes it to rotate through the hydraulic fluid fed by a pump 7. The head 5 comprises an outer tube 56 bearing a co-axial tube 51 therein, which is adapted to define a gap 52.

[0014] The gap 52 and the tube 51 are communicated, through a known rotating joint 50, respectively with a feeding duct 510 of consolidating liquid and a pressurized air feeding duct 520. The head 5 is shaped as the drilling rod 55 sections being connected thereto.

[0015] Secured to the drilling rod 55 through a bush 54 are two in use horizontal surfaces 53, also called wings, which are individually shaped in the form of a circular sector. Said wings 53 face a proximity sensor 8 supported by the brackets 31. The sensor 8 is intended to perform the functions which will be defined below.

[0016] The hydraulic motor 6 is fed through pressurized fluid from the pump 7 by means of a three-way switching valve 71 which intercepts two different ducts 72, 73 for the feeding and return of fluid to the motor 6.

[0017] The valve 71 is manually driven by the operator in three operative positions. In the first position, illustrated in Fig. 2, the motor 6 is connected to the pump 7 via the first duct 72, and to the exhaust pipe via the second duct 73. In the second position, the pump 7 is directly connected to the exhaust pipe. In the third position, the motor 6 is connected to the pump 7 via the second duct 73, and to the exhaust pipe via the first duct 72.

[0018] Thereby, the pressurized fluid can be induced to flow through the motor 6 in opposite directions, with corresponding opposite directions of rotation of the drilling rod 55.

[0019] From the first duct 72 an auxiliary branch of the exhaust pipe 74 branches off, along which a shut-off valve 75 and a flow adjusting device 76 are located in series. The valve 75 is driven in a usual manner by the pulse emitted by the proximity sensor 8 which through a common control circuit 81 causes it to snap from the closed (in Figure) to the open position. The adjusting device 76 schematically comprises a throttling valve and a by-pass branch of the same throttling valve, which is, in turn, intercepted by a check valve. Said adjusting device 76 is manually calibrated and driven, so as to establish the pressurized fluid flow rate which flows within the exhaust pipe branch 74 when the shut-off valve 75 is opened.

[0020] With reference to Fig. 4, the lower part of the drilling rod is seen to comprise a centrally hollow mill 550 the cavity of which communicates with a chamber 551 via a valve 552. The valve 552 communicates, in turn, with the central duct 553 defined within a bush 554. The central duct 553 communicates with the outside through two nozzles 555 which pass through the outer tube 556, while between the bush 554 and outer tube 556 a gap is defined from which two nozzles 557 start, also leading to the outside. The outer duct 556 and the bush 554 are screwed on two different concentric diameters of a joint 558 which is centrally hollow and axially passed through by a series of ducts 559 which open in the gap between bush 554 and outer duct 556. The top end of the joint 558 has a threaded hold which screws on the central tube 51 of the next rod section, while the outer tube 56 of the next rod sealingly couples within a cylindrical seat of the joint 558 located outside the hold.

[0021] Thereby, the gap 52 between outer tube 56 and inner tube 51 of the next rod section is in communication with the gap between bush 554 and duct 556, while the tube 51 is in communication with the central duct of the bush 554.

[0022] The aforementioned configuration of central tube 51 and outer tube 56 and joint 558 is repeated in all the sections of the drilling rod 55 and in the header 5 lower part.

[0023] The operation of the above described device is as follows. After the machine has been positioned in the desired site, the first rod section is introduced into the soil. The first rod section has a diameter of 105 mm and a length ranging between 800 and 1500 mm, while the next sections have equal diameter and a length ranging between 1000 and 3000 mm.

[0024] The rod is rotated according to a preset direction of rotation at 60 rpm with the simultaneous feeding of drilling liquid, usually water, at a flow rate of 90 lit/min and a pressure of 30 bars. Simultaneously, 3000 lit/min of air are fed under 8 bar pressure. In this condition, the switching valve 71 is located in the first operative position illustrated in Fig. 2.

[0025] Upon reaching the desired depth with the coupling of the required number of sequential rod sections, the rod is withdrawn out of the soil while being rotated. Extraction occurs with the simultaneous injection of air and consolidating liquid. During extraction, the rotation speed of rod 55 can be as high as 120 rpm, the air flow rate can be as high as 25000 lit/min with a pressure up to 25 bars, while the consolidating liquid flow rate can range between 10 and 1000 lit/min with a pressure ranging between 50 and 600 bars.

[0026] The consolidating liquid can consist of a mixture of water and cement, or a mixture of water, cement and bentonite; both mixtures may provide the addition of optional additives. Alternatively, the consolidating liquid can consist of suitable epoxy, phenolic, or acrylic resins, optionally diluted.

[0027] In the example, the rotation speed is 12 rpm, air is introduced with a flow rate of 8000 lit/min at a pressure of 12 bars, while consolidating liquid is introduced with a flow rate of 350 lit/min at a pressure of 400 bars. The consolidating liquid consists of a 1:1 mixture of water and cement.

[0028] The result of this operation is the injection of about 300 litres of mixture per meter of column being built, and the creation of a column having an average diameter ranging between 800 and 1000 mm.

[0029] If a column which does not have a circular irregular section, but instead an elliptic irregular section is desired to be created, the proximity sensor 8 is actuated, which for all the time in which it faces the wings 53, causes the shut-off valve 75 to switch to the open position.

[0030] Thereby, part of the pressurized fluid which runs in the first duct 72 is directly discharged to the auxiliary branch 74, thereby reducing the operative liquid flow rate which passes through the motor 6. The rotational speed of rod 55 proportionally decreases while the period of time for which the soil is exposed to the consolidating liquid jet increases, and so does also the penetration distance of the liquid into the soil.

[0031] Thereby, in the angular sector of the column corresponding to the reduced rotation speed, the liquid jet reaches a much greater distance than in the previous one, and a column is created having an elliptic section with its minor diameter equal to that of the cylindrical column, and its major diameter up to about twice. In particular, the speed reduction of rod 55, and hence the distance reached by the consolidating liquid jet, can be adjusted by a manual calibration of the adjusting device 76.

[0032] It is understood that, wishing to create a wall consisting of columns being in a side-by-side relationship and suitably oriented, the columns number is reduced to about half, thus greatly saving time and material.

[0033] By increasing the number of the wings 53 to three equidistant wings, and by proportionally reducing the circumferential extension, an approximately triangular section column is achieved. By adding a further wing 53, an approximately squared section is achieved, etc.

[0034] Although the example described and illustrated herein refers to a plant for air and liquid with dual rods and coaxial nozzles for injecting air and consolidating liquid, those skilled in the art will recognize that the principle underlying the invention is equally applicable to systems different from the cited one. For example, the invention is applicable to consolidating systems so-called "single-fluid", i.e. with rods intended to inject only one consolidating liquid but without the addition of air, and to other "two-fluid" combinations and to so-called "three-fluid" systems, where rods with coaxial nozzles for injecting air and water are used, with separate nozzles for injecting the consolidating fluid.

Claims

1. A plant for forming columns of consolidating material having a non-circular section in the soil, comprising:

- a vertically translatable head (5) connected to at least one hydraulic motor (6) for rotating it,

- at least one rod section (55) being outputted from the head, the rod section comprising at least one substantially radial nozzle for the injection of pressurized consolidating liquid,

- means for controlling the rotational speed of the perforating rods between a lowest speed and a highest speed,

characterized in that the means for varying the speed of the perforating rods comprise means (74, 75, 76) for varying the feeding flow rate of the hydraulic motor (6), these means for varying the flow rate comprising
a discharge pipe branch (74) which branches off a feeding duct (72) of the hydraulic motor (6),
the discharge pipe branch (74) being intercepted by a valve (75) controlled so as to reach two positions, open or closed,
valve control means comprising at least one horizontal surface (53) with a limited circumferential extension, secured to the rotating head (5), which surface (53) rotates with the head (5) in front of a proximity sensor (8) which, when it faces the surface (53), sends a signal which drives the valve (75) opening.

2. The plant according to claim 1, characterized in that said auxiliary branch (74) is intercepted by an adjusting device (76) for the stream flowing therein, which is located in series to said valve (75).

3. The plant according to claim 1, characterized in that the means for varying the rotational speed of the perforating rods act directly on a distributor for controlling the rotation function.

4. The plant according to claim 1, characterized in that the means for varying the rotational speed of the perforating rods act on the discharge pipe branch (74) by means of a counter-pressure.

5. The plant according to claim 1, characterized in that the means for varying the rotational speed of the perforating rods comprise means for controlling a feed pump (7).

Ansprüche

1. Anlage zur Bildung von Säulen aus verfestigtem Material mit nicht-kreisförmigem Querschnitt im Boden, umfassend:

- einen vertikal verschiebbaren Kopf (5), der mit mindestens einem hydraulischen Motor (6) verbunden ist, um ihn in eine Drehbewegung zu versetzen,

- mindestens einen Stangenabschnitt (55), der von dem Kopf aus hervorgebracht wird, wobei der Stangenabschnitt mindestens eine im Wesentlichen radiale Düse zum Einspritzen einer unter Druck stehenden Verfestigungsflüssigkeit umfasst,

- Mittel zur Steuerung der Drehgeschwindigkeit des Bohrgestänges zwischen einer Mindestgeschwindigkeit und einer Höchstgeschwindigkeit,

dadurch gekennzeichnet, dass die Mittel zum Variieren der Geschwindigkeit des Bohrgestänges Mittel (74, 75, 76) zum Variieren der Speiseflussrate des hydraulischen Motors (6) umfassen, wobei diese Mittel zum Variieren der Flussrate Folgendes umfassen
eine Ablassrohrverzweigung (74), die von einer Speiseleitung (72) des hydraulischen Motors (6) abzweigt, wobei die Ablassrohrverzweigung (74) auf ein Ventil (75) stößt, das derart gesteuert ist, dass es zwei Stellungen, offen und geschlossen, einnehmen kann, Ventilsteuerungsmittel einschließlich mindestens einer horizontalen Fläche (53), die eine begrenzte Ausdehnung in Richtung des Umfangs aufweist und sicher am Drehkopf (5) befestigt ist, wobei die Fläche (53) sich mit dem Kopf (5) vor einem Nahbereichssensor (8) dreht, wobei dieser, wenn sich ihm gegenüber die Fläche (53) befindet, ein Signal aussendet, welches die Öffnung des Ventils (75) betätigt.

2. Anlage nach Anspruch 1, dadurch gekennzeichnet, dass die Hilfsverzweigung (74) auf eine Vorrichtung (76) zur Anpassung des darin fließenden Stoffstroms stößt, wobei diese seriell zu dem Ventil (75) angeordnet ist.

3. Anlage nach Anspruch 1, dadurch gekennzeichnet, dass die Mittel zum Variieren der Drehgeschwindigkeit des Bohrgestänges direkt auf einen Verteiler zur Steuerung der Drehfunktion wirken.

4. Anlage nach Anspruch 1, dadurch gekennzeichnet, dass die Mittel zum Variieren der Drehgeschwindigkeit des Bohrgestänges mittels eines Gegendrucks auf die Ablassrohrverzweigung (74) wirken.

5. Anlage nach Anspruch 1, dadurch gekennzeichnet, dass die Mittel zum Variieren der Drehgeschwindigkeit des Bohrgestänges Mittel zur Steuerung einer Speisepumpe (7) umfassen.

Revendications

1. Installation pour former des colonnes de matériau de consolidation ayant une section non circulaire dans le sol, comprenant :

- une tête capable de translation verticalement (5) reliée à au moins un moteur hydraulique (6) pour la mettre en rotation,

- au moins un tronçon en forme de barre (55) qui sort de la tête, le tronçon en forme de barre comprenant au moins une buse sensiblement radiale pour l'injection de liquide de consolidation sous pression,

- des moyens pour commander la vitesse de rotation des barres de perforation entre une vitesse minimum et une vitesse maximum, caractérisée en ce que les moyens pour faire varier la vitesse des barres de perforation comprennent des moyens (74, 75, 76) pour faire varier le débit d'alimentation du moteur hydraulique (6), ces moyens pour faire varier le débit comprenant

une ramification (74) de tube de décharge qui est ramifiée depuis un conduit d'alimentation (72) du moteur hydraulique (6),
la ramification (74) de tube de décharge étant interceptée par une vanne (75) commandée de manière à atteindre deux positions, ouverte ou fermée,
des moyens de commande de vanne comprenant au moins une surface horizontale (53) avec une extension circonférentielle limitée, fixée sur la tête rotative (5) ladite surface (53) tournant avec la tête (5) en face d'un capteur de proximité (8) qui, lorsqu'il est en face de la surface (53), envoie un signal qui pilote l'ouverture de la vanne (75).

2. Installation selon la revendication 1, caractérisée en ce que ladite ramification auxiliaire (74) est interceptée par un dispositif d'ajustement (76) pour le flux qui s'écoule à travers elle-même, qui est situé en série par rapport à ladite vanne (75).

3. Installation selon la revendication 1, caractérisée en ce que les moyens pour faire varier la vitesse de rotation des barres de perforation agissent directement sur un distributeur pour commander la fonction de rotation.

4. Installation selon la revendication 1, caractérisée en ce que les moyens pour faire varier la vitesse de rotation des barres de perforation agissent sur la ramification (74) de tube de décharge au moyen d'une contrepression.

5. Installation selon la revendication 1, caractérisée en ce que les moyens pour faire varier la vitesse de rotation des barres de perforation comprennent des moyens pour commander une pompe d'alimentation (7).

Drawing