DE69104250T2 - Device for driving rods into the ground, in particular for soil mechanics studies. - Google Patents

Description

The present invention relates to a device for driving rods, in particular for soil mechanics investigations, into the ground, according to the preamble of claim 1.

Known devices use straight rods, which are in particular tubular and made of metal so as to be able to withstand compressive and tensile stresses, and which are divided into sections with lengths ranging from one to several metres.

These sections are attached to one another at the end, generally by screwing, according to their depth of penetration into the ground. In order to electrically connect probes attached to the rod section that penetrates first with measuring instruments arranged on the ground surface, electrical cables of sufficient length must be provided, onto which the rod sections are pulled one after the other.

The rod sections must be stored on a suitable base, handled one after the other, screwed together at the end during the driving in process, then separated from one another and stored again during the pulling out process.

These devices have several disadvantages:

1) The preliminary threading of the sections onto the electrical cable is a long and laborious process, which which entails the risk of breakage or damage to the cable;

2) the screw connection of the pipe sections is relatively sensitive, especially in the case of the rod sections driven in last, which are subject to the maximum stress force when pulled out;

3) the automation of the various operations: removal from storage, screwing, driving, extraction, release and re-storage cannot practically be considered unless complex and expensive devices are developed;

4) all processes require several operations and considerable time, which is prolonged by numerous dead times that cannot be eliminated;

5) the operations of driving in or pulling out are necessarily discontinuous;

6) The starting points for fractures, generally at the screw connections, can practically not be detected early.

To mitigate these disadvantages, the use of a one-piece rod that can be stored on a drum has already been proposed.

European document EP 0 266 206 (see preamble of claim 1) proposes in particular a device for driving a one-piece rod into the ground, which is unwound from a drum mounted in a chassis frame.

The device comprises a device for straightening the rod and a driving device upstream of the straightening device. The rod used is a metallic rod coated with copper, which requires permanent deformation, i.e. high mechanical stress, for driving in. This document mentions that the operation of the driving device can be reversed to allow the rod to be extracted. However, this document does not mention how the rod is rewound onto the drum, which would require a reverse permanent deformation under high mechanical stress. These permanent deformations in one direction or the other are incompatible with the use of the rod at high cycle rates.

The aim of the present invention is to provide a device for driving and pulling provided with a rod which enables a high number of driving and pulling cycles to be carried out.

For this purpose, the object of the invention is a device for driving rods, in particular for soil mechanics investigations, into the ground, with a one-piece, tensile and compressive-resistant rod, a winding drum for the rod, a device for driving in/pulling out the rod and a frame which supports the winding drum and the device for driving in/pulling out, the drum being designed as an outwardly open, annular groove in which the rod is rolled up, the device being characterized in that the rod is designed as a tube which contains electrical and/or optical cables and/or electrical and/or pneumatic lines over its entire length, in that the rod is made of composite material which has highly stable fibers embedded in a binding agent and can be bent under reversible elastic deformation, and in that the device further comprises a winding motor which is carried by the frame and which applies a moment to the drum directed in the direction of rolling up the rod. wherein the motor is designed to compensate for the spring action of the rod during the driving and pulling out of the rod.

The diameter of the rod and its components are selected in dependence on the largest possible drum diameter so that no irreversible deformation of the rod can occur when it is rolled up onto the drum.

The free end of the rod is of course designed so that a probe or other measuring instrument can be accommodated.

Thanks to this pole structure, the pole can be used a large number of times. The device can be operated by a single person, since the winding motor enables the pole to be automatically unwound as it penetrates the ground and automatically rewound during the pole pulling phase.

The electrical cables or other means for transmitting information or driving energy are permanently mounted in the rod, either in a central channel machined into the rod, or by embedding it in its material.

In addition, one or more organs, e.g. electrical conductors, can be embedded in the rod in order to be able to quickly identify the starting points for rod breakages.

The further details and advantages of the device according to the invention will become clear from reading the following description with reference to the accompanying drawings, in which:

Fig. 1 is an oblique view of a device according to the invention,

Fig. 2 is a longitudinal sectional view,

Fig. 3 a view from behind,

Fig. 4 is an enlarged partial sectional view of the driving/pulling device according to line 4-4 in Fig. 3.

The rod driving device, designated in its entirety by 10 in Fig. 1, is mounted on a trailer 12 which is provided with wheels 14, 16 for its transport on roads or other surfaces and with a drawbar 18 for attachment to a towing vehicle (not shown).

In a variant not shown, the device can be mounted on an adapted self-propelled vehicle, which has devices for moving on the ground, such as wheels or tracks.

As will be seen, the trailer carries all the organs that are necessary for the independent functioning of the rod driving device.

The trailer 12 has a chassis frame of predominantly longitudinal extension, which is essentially formed by two slightly spaced longitudinal beams 20, 22, which are attached at the front to the drawbar 18 and at the rear to a transverse support structure 24. The two beams rest on the wheel shaft by any means known to those skilled in the art.

In order to bring the trailer into a horizontal position and to withstand the sinking forces, the trailer has three telescopic supports that are operated by working cylinders or as a variant, manually.

A front support 26 is arranged towards the centre of the chassis frame longitudinal members and two rear supports 28, 30, right and left respectively, are arranged under the lateral extensions of the transverse support structure which project beyond the beams 20, 22 on the right and left.

To counteract lifting forces of the trailer, the trailer has two ballast weights 32, 34, which are attached to the right and left side extensions of the support structure. These ballast weights are provided with lifting eyes 36, which enable the ballast weights or the trailer to be lifted using any suitable lifting device. In addition, the trailer can be held to the ground by anchor bolts 38, which are screwed into the ground and connected to the chassis frame by tensioned cables 40 or chains (Fig. 3).

The driving device essentially comprises a one-piece rod 42, a winding drum 44 and a driving/pulling device 46 for the rod, which will be described in detail sequentially.

The rod 42 is made of a composite material based on mechanically high-strength fibers, such as glass, carbon, metal or arylamide fibers, which are embedded in a binding agent, e.g. synthetic resin. Its cross-sectional shape can be arbitrary, in particular tubular.

The rod is manufactured in one piece with the required length of, for example, 40 m.

It is manufactured in such a way that it has excellent tensile and compressive strength, without noticeable stretching or contraction, while allowing it to be wound up by reversible elastic deformation to a radius of curvature of 1.50 to 2 m.

Its front end piece 48, which is to be driven vertically into the ground, is provided with a penetration head which is equipped with passive or active penetration elements and with suitable probes for measuring the soil parameters.

Inside the rod channel and along the entire length of the rod, there are electrical cables for connecting the probes to measuring devices (not shown). These devices can also be installed on the chassis frame or, if their sensitivity requires it, they can be transported to the work site by other means.

The winding drum 44 for the rod 42 is a narrow drum of large diameter, which is arranged on the trailer substantially vertically between the two longitudinal beams 20, 22, such that its axis XX is horizontal and transverse to the chassis frame.

The drum has a cylindrical rim 50 with two radial flanges 52, 54 on the side, thus forming a kind of annular groove open to the outside, in which the rod 42 is wound with several turns lying next to one another and/or one above the other. The cylindrical rim carries a rack 56 on the inside, which, as explained below, is intended to drive it in rotation.

The chassis frame also has two stabilizing cheeks 58, 60 which are firmly or integrally connected to the support structure 24 and which are aligned essentially vertically and are sufficiently spaced apart from one another to allow the drum to pass between them with lateral guidance.

The weight of the drum 44 is supported by two rollers held between the two cheeks (Fig. 2), namely an upper roller 62 which is substantially at the same height as the axis of the drum 44 and in abutment with the inside of the rim, such that the groove at this level is generally perpendicular to the transverse support structure, and a lower roller 64 arranged below the upper roller 62 and in abutment with the ends of the drum flanges 52, 54.

The lateral guidance of the drum 44 is also carried out in the area that separates the two longitudinal beams 20, 22 from each other.

In front of the lower roller 64, on the inside of the rim 50, the two cheeks carry a winding motor 66, which has at the end a gear 68 which engages with the rack 56 on the inside of the rim. It will be appreciated that this motor is only intended to ensure the winding of the rod 42 on the drum 44, compensating for the counter-torque that the wound rod exerts on the drum in the manner of a spring. The motor therefore exerts on the drum a torque that is always directed in the same direction, although it is caused to rotate in one direction or the other depending on whether the rod is unwound during driving or wound up during pulling. It is advantageous to choose a hydraulic motor adapted to these functions.

It should also be noted that the interaction between the rack 56 and the gear 68 is free from radial forces, which avoids wear and the occurrence of play and allows a correct dimensioning of these components solely for the purpose of transmitting the winding torque.

Substantially opposite the upper roller 62, on the outside of the drum, a set of rollers 70a, b, c, ..., q, arranged one behind the other on a line defined as the "bending line" of the rod.

More precisely, these rollers delimit for the rod 42 a rolling path whose curvature varies from a curvature close to the curvature of the drum rim 50 at the level of the first roller 70a arranged furthest up to a curvature of zero at the level of the last roller 70q arranged furthest down.

Thus, a transition zone is created for the rod 42 between a vertical straight configuration below the last roller and a certain curvature configuration above the last roller.

The exact arrangement of the rollers can be determined mathematically and/or through tests.

The other end 72 of the rod is securely fixed to the drum, for example to one of the flanges 52 on the outside of the latter, and the electric cable running through the entire rod extends beyond this end and terminates in a fixed connector (not shown) to which the measuring instruments can be connected. The cable extension is preferably of the spiral type so that it can undergo without damage variations in length and twist caused by the rotation of the drum. As a variant, the fixed connector can be of the rotary connector type.

The device 46 for driving/pulling the rod 42 is arranged in the transverse support structure 24 at the vertical straight rod section separating the last roller 70q from the ground.

As shown in Fig. 3, this device comprises two symmetrical parts which interact by friction on both sides of the rod 42.

Each part comprises a support guide 74a, 74b of predominantly longitudinal extension, which is arranged vertically parallel to the rod. An endless chain 76a, 76b runs around the support guide and is deflected at both ends of the support guide by deflection gears 78a, 78b.

Each chain link 80 (Fig. 4) has on its outside a receptacle 82 in which a plate 84 made of a material is fastened which is wear-resistant and has a high coefficient of friction compared to the material of the rod 42 or its coating material.

The plate has a recess on the outside forming a semi-cylindrical contact surface that is complementary to the cross-section of the rod.

At each support guide 74a, 74b, one of the chain deflection sprockets 78a, 78b is driven to rotate in one direction or the other by a motor 86a, 86b, which is also advantageously a hydraulic motor.

Both in order to release the rod 42 and to press the two endless chains 76a, 76b against the rod with great radial force, the two support guides have arms 88a, 88b that can pivot about a vertical axis Ya, Yb, such that the support guides and the chains can be moved away from or towards the rod via working cylinders 90a, 90b that are supported on the support structure 24.

To ensure that the two support guides 74a, 74b move symmetrically and hold the rod 42 without In order to displace them laterally, the arms 88a, 88b of the two support guides are provided with mutually engaging tooth sectors 82a, 92b.

The chassis frame carries a power source 94, advantageously an internal combustion engine, which drives a hydraulic pump which supplies a quantity of pressurized fluid to supply the various motors and working cylinders described above. Naturally, the distribution circuit includes the usual elements such as tanks, regulating and safety valves, pressure switches, control valves, as they appear necessary to the expert.

Finally, the chassis frame carries a control cabinet 96 with the electrical, electronic or electromechanical circuit arrangements and the associated switches necessary to control the operation of the various organs.

This working method is as follows:

- The trailer is pulled to the desired location and unhitched there;

- the stabilizer supports 26, 28, 30 are extended to level the trailer;

- if necessary, the anchoring screws 38 are drilled into the ground and the cables 40 are stretched between the screws and the chassis frame;

- the drive source 94 is switched on;

- pressure is applied to the working cylinders 90a, 90b of the driving/pulling device 46 in order to press the plates 84 of the endless chains firmly against the rod 42;

- the drive motors 86a, 86b of the driving/pulling device 46 are fed in the direction corresponding to the driving of the rod 42;

- during this time, an appropriate control of the winding motor 66 enables the rod 42 to be unwound from the drum 44;

- when the length of the rod 42 driven into the ground has reached a desired value, the drive motors of the driving/pulling device are stopped; the associated working cylinders can then be relieved of pressure.

The necessary measurements can be taken in two ways: continuously while driving the rod or at fixed points when the rod is stopped at a predetermined position.

If necessary, the drive source 94 can be switched off. Only the winding motor 66 then consumes some energy and it is sufficient to provide for this purpose a pressure fluid tank of sufficient capacity to maintain the torque preventing the rotation of the drum under the "spring" action of the rod.

After the measurements have been completed, the rod 42 is pulled out:

- Restart the power source;

- Pressurising the working cylinders of the driving/pulling device;

- powering the drive motors of this device in the direction corresponding to extraction;

- Switching off the same motors once the rod is completely pulled;

- then relieve the pressure on the working cylinders of the driving/pulling device;

- during the entire extraction period, the winding motor is supplied by the corresponding control to the extent necessary for correct winding of the rod.

The cables 40 can then be removed and the anchoring screws 38 loosened, then the stabilizer supports 26, 28, 30 can be retracted and the trailer can be towed to a new work location.

From the foregoing it is clear that the device according to the invention enables continuous driving of the rod, practically without manual intervention by the operator, in a considerably shorter time than with conventional techniques.

During towing and non-use periods, a mechanical locking device is provided for the drum to prevent accidental unwinding of the rod.

In order to also prevent damage to property and/or persons in the event of breakage of the rod and an abrupt release of the elastic energy stored by its winding, a covering 98 made of very thick sheet metal is provided, if not over the entire circumference of the drum, then at least over the entire lower area below the two longitudinal members (Fig. 2).

It is obvious that the inner channel of the rod 42 can accommodate not only electrical cables for the transmission of low-intensity signals from the probes, but also electrical cables for the power distribution to the active organs in the penetration head, hydraulic or compressed air lines in both directions, or even optical cables.

Finally, the invention advantageously provides that the rod itself has electrically conductive measuring wires embedded in its material over the length of the rod, which are connected to a suitable monitoring box.

If the local deformation experienced by the rod when it is pulled exceeds a permissible value and therefore causes the risk of the rod breaking, one or more of these measuring wires break and the monitoring box detects this break and generates a warning signal. In addition to this warning, the monitoring box can force the drive motors of the driving/pulling device to be switched off and force an operator to pull them out and switch them back on manually.

For practical reasons, dimensions are chosen for the trailer and the entire device that are compatible with the usual loading profiles in road traffic:

Height less than 4 m,

Width less than 2.50 m.

Claims (10)

1. Device for driving rods, in particular for soil mechanics investigations, into the ground, with a one-piece, tensile and compressive-resistant rod (42), a winding drum (44) for the rod (42), a device for driving in/pulling out (46) the rod and a frame (18,20,22,24) which carries the winding drum and the device for driving in/pulling out, wherein the drum is designed as an outwardly open annular groove in which the rod (42) is rolled up, characterized in that the rod is designed as a tube which contains electrical and/or optical cables and/or electrical and/or pneumatic lines over its entire length, in that the rod is made of composite material, which has highly stable fibers embedded in a binder and can be bent under reversible elastic deformation, and in that the device further comprises a winding motor (66) which is carried by the frame (18, 20, 22, 24) and exerts on the drum a moment directed in the direction of winding of the rod, the motor being intended to compensate for the spring action of the rod during the driving in and pulling out of the rod. 2. Device according to claim 1, characterized in that the rod contains measuring lines which are embedded in the material forming the rod, over the entire length of the rod. 3. Device according to one of claims 1 and 2, characterized in that the winding drum (44) is supported by the frame (18, 20, 22, 24) so that its axis (xx) is horizontal and transverse with respect to the frame, that the drum (44) is a large diameter drum and has a cylindrical rim (50) and two radial flanges, and that the drum is supported on the frame by two wheels (62, 64), an upper wheel (62) in contact with the inside of the rim (50) and a lower wheel (64) in contact with the edges of the flanges (52, 54). 4. Device according to claim 3, characterized in that the rim (50) of the drum carries a rack (56) on the inside, and in that the winding motor drives the drum through a gear (68) in engagement with the rack (56). 5. Device according to one of claims 1 to 4, characterized in that it comprises a series of wheels (70a, b, c ... 70q) arranged along a line called "curvature line" of the rod (42), so as to define for the rod a travel path of varying curvature, from a curvature similar to that of the rim (50) to a curvature equal to zero, at which the rod assumes a rectilinear shape oriented vertically. 6. Device according to one of claims 1 to 5, characterized in that the device for driving in/pulling out (46) contains two parts arranged on each side of the rod, each of which contains an endless chain (76a, 76b) driven by a motor (86a, 86b) and interacting by friction with the rod (42). 7. Device according to claim 6, characterized in that each part of the drive-in/out device (46) has an elongated support guide (74a, 74b) around which the endless chain (76a, 76b) runs and which is mounted so as to be pivotable about a vertical axis (Ya, Yb) under the action of pressure cylinders (90a, 90b) supported on the frame. 8. Device according to one of claims 6 or 7, characterized in that the links (80) of each endless chain carry segments (84) which are made of a wear-resistant material and have a higher coefficient of friction than the material of the rod. 9. Device according to one of claims 1 to 8, characterized in that it is mounted on a trailer (12) equipped with wheels for travel on the ground, and in that the trailer has a motor power source (94) and the control elements (96) necessary for its operation. 10. Device according to one of claims 1 to 9, characterized in that it is mounted on a self-propelled vehicle which is suitably equipped for travel on the ground and contains a motor power supply and the control elements necessary for its operation.